file_storage.c

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/*
 * file_storage.c -- File-backed USB Storage Gadget, for USB development
 *
 * Copyright (C) 2003-2008 Alan Stern
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions, and the following disclaimer,
 *    without modification.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The names of the above-listed copyright holders may not be used
 *    to endorse or promote products derived from this software without
 *    specific prior written permission.
 *
 * ALTERNATIVELY, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") as published by the Free Software
 * Foundation, either version 2 of that License or (at your option) any
 * later version.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */


/*
 * The File-backed Storage Gadget acts as a USB Mass Storage device,
 * appearing to the host as a disk drive or as a CD-ROM drive.  In addition
 * to providing an example of a genuinely useful gadget driver for a USB
 * device, it also illustrates a technique of double-buffering for increased
 * throughput.  Last but not least, it gives an easy way to probe the
 * behavior of the Mass Storage drivers in a USB host.
 *
 * Backing storage is provided by a regular file or a block device, specified
 * by the "file" module parameter.  Access can be limited to read-only by
 * setting the optional "ro" module parameter.  (For CD-ROM emulation,
 * access is always read-only.)  The gadget will indicate that it has
 * removable media if the optional "removable" module parameter is set.
 *
 * The gadget supports the Control-Bulk (CB), Control-Bulk-Interrupt (CBI),
 * and Bulk-Only (also known as Bulk-Bulk-Bulk or BBB) transports, selected
 * by the optional "transport" module parameter.  It also supports the
 * following protocols: RBC (0x01), ATAPI or SFF-8020i (0x02), QIC-157 (0c03),
 * UFI (0x04), SFF-8070i (0x05), and transparent SCSI (0x06), selected by
 * the optional "protocol" module parameter.  In addition, the default
 * Vendor ID, Product ID, release number and serial number can be overridden.
 *
 * There is support for multiple logical units (LUNs), each of which has
 * its own backing file.  The number of LUNs can be set using the optional
 * "luns" module parameter (anywhere from 1 to 8), and the corresponding
 * files are specified using comma-separated lists for "file" and "ro".
 * The default number of LUNs is taken from the number of "file" elements;
 * it is 1 if "file" is not given.  If "removable" is not set then a backing
 * file must be specified for each LUN.  If it is set, then an unspecified
 * or empty backing filename means the LUN's medium is not loaded.  Ideally
 * each LUN would be settable independently as a disk drive or a CD-ROM
 * drive, but currently all LUNs have to be the same type.  The CD-ROM
 * emulation includes a single data track and no audio tracks; hence there
 * need be only one backing file per LUN.
 *
 * Requirements are modest; only a bulk-in and a bulk-out endpoint are
 * needed (an interrupt-out endpoint is also needed for CBI).  The memory
 * requirement amounts to two 16K buffers, size configurable by a parameter.
 * Support is included for both full-speed and high-speed operation.
 *
 * Note that the driver is slightly non-portable in that it assumes a
 * single memory/DMA buffer will be useable for bulk-in, bulk-out, and
 * interrupt-in endpoints.  With most device controllers this isn't an
 * issue, but there may be some with hardware restrictions that prevent
 * a buffer from being used by more than one endpoint.
 *
 * Module options:
 *
 *  file=filename[,filename...]
 *              Required if "removable" is not set, names of
 *                  the files or block devices used for
 *                  backing storage
 *  serial=HHHH...      Required serial number (string of hex chars)
 *  ro=b[,b...]     Default false, booleans for read-only access
 *  removable       Default false, boolean for removable media
 *  luns=N          Default N = number of filenames, number of
 *                  LUNs to support
 *  nofua=b[,b...]      Default false, booleans for ignore FUA flag
 *                  in SCSI WRITE(10,12) commands
 *  stall           Default determined according to the type of
 *                  USB device controller (usually true),
 *                  boolean to permit the driver to halt
 *                  bulk endpoints
 *  cdrom           Default false, boolean for whether to emulate
 *                  a CD-ROM drive
 *  transport=XXX       Default BBB, transport name (CB, CBI, or BBB)
 *  protocol=YYY        Default SCSI, protocol name (RBC, 8020 or
 *                  ATAPI, QIC, UFI, 8070, or SCSI;
 *                  also 1 - 6)
 *  vendor=0xVVVV       Default 0x0525 (NetChip), USB Vendor ID
 *  product=0xPPPP      Default 0xa4a5 (FSG), USB Product ID
 *  release=0xRRRR      Override the USB release number (bcdDevice)
 *  buflen=N        Default N=16384, buffer size used (will be
 *                  rounded down to a multiple of
 *                  PAGE_CACHE_SIZE)
 *
 * If CONFIG_USB_FILE_STORAGE_TEST is not set, only the "file", "serial", "ro",
 * "removable", "luns", "nofua", "stall", and "cdrom" options are available;
 * default values are used for everything else.
 *
 * The pathnames of the backing files and the ro settings are available in
 * the attribute files "file", "nofua", and "ro" in the lun<n> subdirectory of
 * the gadget's sysfs directory.  If the "removable" option is set, writing to
 * these files will simulate ejecting/loading the medium (writing an empty
 * line means eject) and adjusting a write-enable tab.  Changes to the ro
 * setting are not allowed when the medium is loaded or if CD-ROM emulation
 * is being used.
 *
 * This gadget driver is heavily based on "Gadget Zero" by David Brownell.
 * The driver's SCSI command interface was based on the "Information
 * technology - Small Computer System Interface - 2" document from
 * X3T9.2 Project 375D, Revision 10L, 7-SEP-93, available at
 * <http://www.t10.org/ftp/t10/drafts/s2/s2-r10l.pdf>.  The single exception
 * is opcode 0x23 (READ FORMAT CAPACITIES), which was based on the
 * "Universal Serial Bus Mass Storage Class UFI Command Specification"
 * document, Revision 1.0, December 14, 1998, available at
 * <http://www.usb.org/developers/devclass_docs/usbmass-ufi10.pdf>.
 */


/*
 *              Driver Design
 *
 * The FSG driver is fairly straightforward.  There is a main kernel
 * thread that handles most of the work.  Interrupt routines field
 * callbacks from the controller driver: bulk- and interrupt-request
 * completion notifications, endpoint-0 events, and disconnect events.
 * Completion events are passed to the main thread by wakeup calls.  Many
 * ep0 requests are handled at interrupt time, but SetInterface,
 * SetConfiguration, and device reset requests are forwarded to the
 * thread in the form of "exceptions" using SIGUSR1 signals (since they
 * should interrupt any ongoing file I/O operations).
 *
 * The thread's main routine implements the standard command/data/status
 * parts of a SCSI interaction.  It and its subroutines are full of tests
 * for pending signals/exceptions -- all this polling is necessary since
 * the kernel has no setjmp/longjmp equivalents.  (Maybe this is an
 * indication that the driver really wants to be running in userspace.)
 * An important point is that so long as the thread is alive it keeps an
 * open reference to the backing file.  This will prevent unmounting
 * the backing file's underlying filesystem and could cause problems
 * during system shutdown, for example.  To prevent such problems, the
 * thread catches INT, TERM, and KILL signals and converts them into
 * an EXIT exception.
 *
 * In normal operation the main thread is started during the gadget's
 * fsg_bind() callback and stopped during fsg_unbind().  But it can also
 * exit when it receives a signal, and there's no point leaving the
 * gadget running when the thread is dead.  So just before the thread
 * exits, it deregisters the gadget driver.  This makes things a little
 * tricky: The driver is deregistered at two places, and the exiting
 * thread can indirectly call fsg_unbind() which in turn can tell the
 * thread to exit.  The first problem is resolved through the use of the
 * REGISTERED atomic bitflag; the driver will only be deregistered once.
 * The second problem is resolved by having fsg_unbind() check
 * fsg->state; it won't try to stop the thread if the state is already
 * FSG_STATE_TERMINATED.
 *
 * To provide maximum throughput, the driver uses a circular pipeline of
 * buffer heads (struct fsg_buffhd).  In principle the pipeline can be
 * arbitrarily long; in practice the benefits don't justify having more
 * than 2 stages (i.e., double buffering).  But it helps to think of the
 * pipeline as being a long one.  Each buffer head contains a bulk-in and
 * a bulk-out request pointer (since the buffer can be used for both
 * output and input -- directions always are given from the host's
 * point of view) as well as a pointer to the buffer and various state
 * variables.
 *
 * Use of the pipeline follows a simple protocol.  There is a variable
 * (fsg->next_buffhd_to_fill) that points to the next buffer head to use.
 * At any time that buffer head may still be in use from an earlier
 * request, so each buffer head has a state variable indicating whether
 * it is EMPTY, FULL, or BUSY.  Typical use involves waiting for the
 * buffer head to be EMPTY, filling the buffer either by file I/O or by
 * USB I/O (during which the buffer head is BUSY), and marking the buffer
 * head FULL when the I/O is complete.  Then the buffer will be emptied
 * (again possibly by USB I/O, during which it is marked BUSY) and
 * finally marked EMPTY again (possibly by a completion routine).
 *
 * A module parameter tells the driver to avoid stalling the bulk
 * endpoints wherever the transport specification allows.  This is
 * necessary for some UDCs like the SuperH, which cannot reliably clear a
 * halt on a bulk endpoint.  However, under certain circumstances the
 * Bulk-only specification requires a stall.  In such cases the driver
 * will halt the endpoint and set a flag indicating that it should clear
 * the halt in software during the next device reset.  Hopefully this
 * will permit everything to work correctly.  Furthermore, although the
 * specification allows the bulk-out endpoint to halt when the host sends
 * too much data, implementing this would cause an unavoidable race.
 * The driver will always use the "no-stall" approach for OUT transfers.
 *
 * One subtle point concerns sending status-stage responses for ep0
 * requests.  Some of these requests, such as device reset, can involve
 * interrupting an ongoing file I/O operation, which might take an
 * arbitrarily long time.  During that delay the host might give up on
 * the original ep0 request and issue a new one.  When that happens the
 * driver should not notify the host about completion of the original
 * request, as the host will no longer be waiting for it.  So the driver
 * assigns to each ep0 request a unique tag, and it keeps track of the
 * tag value of the request associated with a long-running exception
 * (device-reset, interface-change, or configuration-change).  When the
 * exception handler is finished, the status-stage response is submitted
 * only if the current ep0 request tag is equal to the exception request
 * tag.  Thus only the most recently received ep0 request will get a
 * status-stage response.
 *
 * Warning: This driver source file is too long.  It ought to be split up
 * into a header file plus about 3 separate .c files, to handle the details
 * of the Gadget, USB Mass Storage, and SCSI protocols.
 */


/* #define VERBOSE_DEBUG */
/* #define DUMP_MSGS */


#include <linux/blkdev.h>
#include <linux/completion.h>
#include <linux/dcache.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/fcntl.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/kref.h>
#include <linux/kthread.h>
#include <linux/limits.h>
#include <linux/module.h>
#include <linux/rwsem.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/freezer.h>
#include <linux/utsname.h>

#include <linux/usb/composite.h>
#include <linux/usb/ch9.h>
#include <linux/usb/gadget.h>

#include "gadget_chips.h"

#define DRIVER_DESC     "File-backed Storage Gadget"
#define DRIVER_NAME     "g_file_storage"
#define DRIVER_VERSION      "1 September 2010"

static       char fsg_string_manufacturer[64];
static const char fsg_string_product[] = DRIVER_DESC;
static const char fsg_string_config[] = "Self-powered";
static const char fsg_string_interface[] = "Mass Storage";


#include "storage_common.c"


MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_AUTHOR("Alan Stern");
MODULE_LICENSE("Dual BSD/GPL");

/*
 * This driver assumes self-powered hardware and has no way for users to
 * trigger remote wakeup.  It uses autoconfiguration to select endpoints
 * and endpoint addresses.
 */


/*-------------------------------------------------------------------------*/


/* Encapsulate the module parameter settings */

static struct {
    char        *file[FSG_MAX_LUNS];
    char        *serial;
    bool        ro[FSG_MAX_LUNS];
    bool        nofua[FSG_MAX_LUNS];
    unsigned int    num_filenames;
    unsigned int    num_ros;
    unsigned int    num_nofuas;
    unsigned int    nluns;

    bool        removable;
    bool        can_stall;
    bool        cdrom;

    char        *transport_parm;
    char        *protocol_parm;
    unsigned short  vendor;
    unsigned short  product;
    unsigned short  release;
    unsigned int    buflen;

    int     transport_type;
    char        *transport_name;
    int     protocol_type;
    char        *protocol_name;

} mod_data = {                  // Default values
    .transport_parm     = "BBB",
    .protocol_parm      = "SCSI",
    .removable      = 0,
    .can_stall      = 1,
    .cdrom          = 0,
    .vendor         = FSG_VENDOR_ID,
    .product        = FSG_PRODUCT_ID,
    .release        = 0xffff,   // Use controller chip type
    .buflen         = 16384,
    };


module_param_array_named(file, mod_data.file, charp, &mod_data.num_filenames,
        S_IRUGO);
MODULE_PARM_DESC(file, "names of backing files or devices");

module_param_named(serial, mod_data.serial, charp, S_IRUGO);
MODULE_PARM_DESC(serial, "USB serial number");

module_param_array_named(ro, mod_data.ro, bool, &mod_data.num_ros, S_IRUGO);
MODULE_PARM_DESC(ro, "true to force read-only");

module_param_array_named(nofua, mod_data.nofua, bool, &mod_data.num_nofuas,
        S_IRUGO);
MODULE_PARM_DESC(nofua, "true to ignore SCSI WRITE(10,12) FUA bit");

module_param_named(luns, mod_data.nluns, uint, S_IRUGO);
MODULE_PARM_DESC(luns, "number of LUNs");

module_param_named(removable, mod_data.removable, bool, S_IRUGO);
MODULE_PARM_DESC(removable, "true to simulate removable media");

module_param_named(stall, mod_data.can_stall, bool, S_IRUGO);
MODULE_PARM_DESC(stall, "false to prevent bulk stalls");

module_param_named(cdrom, mod_data.cdrom, bool, S_IRUGO);
MODULE_PARM_DESC(cdrom, "true to emulate cdrom instead of disk");

/* In the non-TEST version, only the module parameters listed above
 * are available. */
#ifdef CONFIG_USB_FILE_STORAGE_TEST

module_param_named(transport, mod_data.transport_parm, charp, S_IRUGO);
MODULE_PARM_DESC(transport, "type of transport (BBB, CBI, or CB)");

module_param_named(protocol, mod_data.protocol_parm, charp, S_IRUGO);
MODULE_PARM_DESC(protocol, "type of protocol (RBC, 8020, QIC, UFI, "
        "8070, or SCSI)");

module_param_named(vendor, mod_data.vendor, ushort, S_IRUGO);
MODULE_PARM_DESC(vendor, "USB Vendor ID");

module_param_named(product, mod_data.product, ushort, S_IRUGO);
MODULE_PARM_DESC(product, "USB Product ID");

module_param_named(release, mod_data.release, ushort, S_IRUGO);
MODULE_PARM_DESC(release, "USB release number");

module_param_named(buflen, mod_data.buflen, uint, S_IRUGO);
MODULE_PARM_DESC(buflen, "I/O buffer size");

#endif /* CONFIG_USB_FILE_STORAGE_TEST */


/*
 * These definitions will permit the compiler to avoid generating code for
 * parts of the driver that aren't used in the non-TEST version.  Even gcc
 * can recognize when a test of a constant expression yields a dead code
 * path.
 */

#ifdef CONFIG_USB_FILE_STORAGE_TEST

#define transport_is_bbb()  (mod_data.transport_type == USB_PR_BULK)
#define transport_is_cbi()  (mod_data.transport_type == USB_PR_CBI)
#define protocol_is_scsi()  (mod_data.protocol_type == USB_SC_SCSI)

#else

#define transport_is_bbb()  1
#define transport_is_cbi()  0
#define protocol_is_scsi()  1

#endif /* CONFIG_USB_FILE_STORAGE_TEST */


/*-------------------------------------------------------------------------*/


struct fsg_dev {
    /* lock protects: state, all the req_busy's, and cbbuf_cmnd */
    spinlock_t      lock;
    struct usb_gadget   *gadget;

    /* filesem protects: backing files in use */
    struct rw_semaphore filesem;

    /* reference counting: wait until all LUNs are released */
    struct kref     ref;

    struct usb_ep       *ep0;       // Handy copy of gadget->ep0
    struct usb_request  *ep0req;    // For control responses
    unsigned int        ep0_req_tag;
    const char      *ep0req_name;

    struct usb_request  *intreq;    // For interrupt responses
    int         intreq_busy;
    struct fsg_buffhd   *intr_buffhd;

    unsigned int        bulk_out_maxpacket;
    enum fsg_state      state;      // For exception handling
    unsigned int        exception_req_tag;

    u8          config, new_config;

    unsigned int        running : 1;
    unsigned int        bulk_in_enabled : 1;
    unsigned int        bulk_out_enabled : 1;
    unsigned int        intr_in_enabled : 1;
    unsigned int        phase_error : 1;
    unsigned int        short_packet_received : 1;
    unsigned int        bad_lun_okay : 1;

    unsigned long       atomic_bitflags;
#define REGISTERED      0
#define IGNORE_BULK_OUT     1
#define SUSPENDED       2

    struct usb_ep       *bulk_in;
    struct usb_ep       *bulk_out;
    struct usb_ep       *intr_in;

    struct fsg_buffhd   *next_buffhd_to_fill;
    struct fsg_buffhd   *next_buffhd_to_drain;

    int         thread_wakeup_needed;
    struct completion   thread_notifier;
    struct task_struct  *thread_task;

    int         cmnd_size;
    u8          cmnd[MAX_COMMAND_SIZE];
    enum data_direction data_dir;
    u32         data_size;
    u32         data_size_from_cmnd;
    u32         tag;
    unsigned int        lun;
    u32         residue;
    u32         usb_amount_left;

    /* The CB protocol offers no way for a host to know when a command
     * has completed.  As a result the next command may arrive early,
     * and we will still have to handle it.  For that reason we need
     * a buffer to store new commands when using CB (or CBI, which
     * does not oblige a host to wait for command completion either). */
    int         cbbuf_cmnd_size;
    u8          cbbuf_cmnd[MAX_COMMAND_SIZE];

    unsigned int        nluns;
    struct fsg_lun      *luns;
    struct fsg_lun      *curlun;
    /* Must be the last entry */
    struct fsg_buffhd   buffhds[];
};

typedef void (*fsg_routine_t)(struct fsg_dev *);

static int exception_in_progress(struct fsg_dev *fsg)
{
    return (fsg->state > FSG_STATE_IDLE);
}

/* Make bulk-out requests be divisible by the maxpacket size */
static void set_bulk_out_req_length(struct fsg_dev *fsg,
        struct fsg_buffhd *bh, unsigned int length)
{
    unsigned int    rem;

    bh->bulk_out_intended_length = length;
    rem = length % fsg->bulk_out_maxpacket;
    if (rem > 0)
        length += fsg->bulk_out_maxpacket - rem;
    bh->outreq->length = length;
}

static struct fsg_dev           *the_fsg;
static struct usb_gadget_driver     fsg_driver;


/*-------------------------------------------------------------------------*/

static int fsg_set_halt(struct fsg_dev *fsg, struct usb_ep *ep)
{
    const char  *name;

    if (ep == fsg->bulk_in)
        name = "bulk-in";
    else if (ep == fsg->bulk_out)
        name = "bulk-out";
    else
        name = ep->name;
    DBG(fsg, "%s set halt\n", name);
    return usb_ep_set_halt(ep);
}


/*-------------------------------------------------------------------------*/

/*
 * DESCRIPTORS ... most are static, but strings and (full) configuration
 * descriptors are built on demand.  Also the (static) config and interface
 * descriptors are adjusted during fsg_bind().
 */

/* There is only one configuration. */
#define CONFIG_VALUE        1

static struct usb_device_descriptor
device_desc = {
    .bLength =      sizeof device_desc,
    .bDescriptorType =  USB_DT_DEVICE,

    .bcdUSB =       cpu_to_le16(0x0200),
    .bDeviceClass =     USB_CLASS_PER_INTERFACE,

    /* The next three values can be overridden by module parameters */
    .idVendor =     cpu_to_le16(FSG_VENDOR_ID),
    .idProduct =        cpu_to_le16(FSG_PRODUCT_ID),
    .bcdDevice =        cpu_to_le16(0xffff),

    .iManufacturer =    FSG_STRING_MANUFACTURER,
    .iProduct =     FSG_STRING_PRODUCT,
    .iSerialNumber =    FSG_STRING_SERIAL,
    .bNumConfigurations =   1,
};

static struct usb_config_descriptor
config_desc = {
    .bLength =      sizeof config_desc,
    .bDescriptorType =  USB_DT_CONFIG,

    /* wTotalLength computed by usb_gadget_config_buf() */
    .bNumInterfaces =   1,
    .bConfigurationValue =  CONFIG_VALUE,
    .iConfiguration =   FSG_STRING_CONFIG,
    .bmAttributes =     USB_CONFIG_ATT_ONE | USB_CONFIG_ATT_SELFPOWER,
    .bMaxPower =        CONFIG_USB_GADGET_VBUS_DRAW / 2,
};


static struct usb_qualifier_descriptor
dev_qualifier = {
    .bLength =      sizeof dev_qualifier,
    .bDescriptorType =  USB_DT_DEVICE_QUALIFIER,

    .bcdUSB =       cpu_to_le16(0x0200),
    .bDeviceClass =     USB_CLASS_PER_INTERFACE,

    .bNumConfigurations =   1,
};

static int populate_bos(struct fsg_dev *fsg, u8 *buf)
{
    memcpy(buf, &fsg_bos_desc, USB_DT_BOS_SIZE);
    buf += USB_DT_BOS_SIZE;

    memcpy(buf, &fsg_ext_cap_desc, USB_DT_USB_EXT_CAP_SIZE);
    buf += USB_DT_USB_EXT_CAP_SIZE;

    memcpy(buf, &fsg_ss_cap_desc, USB_DT_USB_SS_CAP_SIZE);

    return USB_DT_BOS_SIZE + USB_DT_USB_SS_CAP_SIZE
        + USB_DT_USB_EXT_CAP_SIZE;
}

/*
 * Config descriptors must agree with the code that sets configurations
 * and with code managing interfaces and their altsettings.  They must
 * also handle different speeds and other-speed requests.
 */
static int populate_config_buf(struct usb_gadget *gadget,
        u8 *buf, u8 type, unsigned index)
{
    enum usb_device_speed           speed = gadget->speed;
    int                 len;
    const struct usb_descriptor_header  **function;

    if (index > 0)
        return -EINVAL;

    if (gadget_is_dualspeed(gadget) && type == USB_DT_OTHER_SPEED_CONFIG)
        speed = (USB_SPEED_FULL + USB_SPEED_HIGH) - speed;
    function = gadget_is_dualspeed(gadget) && speed == USB_SPEED_HIGH
        ? (const struct usb_descriptor_header **)fsg_hs_function
        : (const struct usb_descriptor_header **)fsg_fs_function;

    /* for now, don't advertise srp-only devices */
    if (!gadget_is_otg(gadget))
        function++;

    len = usb_gadget_config_buf(&config_desc, buf, EP0_BUFSIZE, function);
    ((struct usb_config_descriptor *) buf)->bDescriptorType = type;
    return len;
}


/*-------------------------------------------------------------------------*/

/* These routines may be called in process context or in_irq */

/* Caller must hold fsg->lock */
static void wakeup_thread(struct fsg_dev *fsg)
{
    /* Tell the main thread that something has happened */
    fsg->thread_wakeup_needed = 1;
    if (fsg->thread_task)
        wake_up_process(fsg->thread_task);
}


static void raise_exception(struct fsg_dev *fsg, enum fsg_state new_state)
{
    unsigned long       flags;

    /* Do nothing if a higher-priority exception is already in progress.
     * If a lower-or-equal priority exception is in progress, preempt it
     * and notify the main thread by sending it a signal. */
    spin_lock_irqsave(&fsg->lock, flags);
    if (fsg->state <= new_state) {
        fsg->exception_req_tag = fsg->ep0_req_tag;
        fsg->state = new_state;
        if (fsg->thread_task)
            send_sig_info(SIGUSR1, SEND_SIG_FORCED,
                    fsg->thread_task);
    }
    spin_unlock_irqrestore(&fsg->lock, flags);
}


/*-------------------------------------------------------------------------*/

/* The disconnect callback and ep0 routines.  These always run in_irq,
 * except that ep0_queue() is called in the main thread to acknowledge
 * completion of various requests: set config, set interface, and
 * Bulk-only device reset. */

static void fsg_disconnect(struct usb_gadget *gadget)
{
    struct fsg_dev      *fsg = get_gadget_data(gadget);

    DBG(fsg, "disconnect or port reset\n");
    raise_exception(fsg, FSG_STATE_DISCONNECT);
}


static int ep0_queue(struct fsg_dev *fsg)
{
    int rc;

    rc = usb_ep_queue(fsg->ep0, fsg->ep0req, GFP_ATOMIC);
    if (rc != 0 && rc != -ESHUTDOWN) {

        /* We can't do much more than wait for a reset */
        WARNING(fsg, "error in submission: %s --> %d\n",
                fsg->ep0->name, rc);
    }
    return rc;
}

static void ep0_complete(struct usb_ep *ep, struct usb_request *req)
{
    struct fsg_dev      *fsg = ep->driver_data;

    if (req->actual > 0)
        dump_msg(fsg, fsg->ep0req_name, req->buf, req->actual);
    if (req->status || req->actual != req->length)
        DBG(fsg, "%s --> %d, %u/%u\n", __func__,
                req->status, req->actual, req->length);
    if (req->status == -ECONNRESET)     // Request was cancelled
        usb_ep_fifo_flush(ep);

    if (req->status == 0 && req->context)
        ((fsg_routine_t) (req->context))(fsg);
}


/*-------------------------------------------------------------------------*/

/* Bulk and interrupt endpoint completion handlers.
 * These always run in_irq. */

static void bulk_in_complete(struct usb_ep *ep, struct usb_request *req)
{
    struct fsg_dev      *fsg = ep->driver_data;
    struct fsg_buffhd   *bh = req->context;

    if (req->status || req->actual != req->length)
        DBG(fsg, "%s --> %d, %u/%u\n", __func__,
                req->status, req->actual, req->length);
    if (req->status == -ECONNRESET)     // Request was cancelled
        usb_ep_fifo_flush(ep);

    /* Hold the lock while we update the request and buffer states */
    smp_wmb();
    spin_lock(&fsg->lock);
    bh->inreq_busy = 0;
    bh->state = BUF_STATE_EMPTY;
    wakeup_thread(fsg);
    spin_unlock(&fsg->lock);
}

static void bulk_out_complete(struct usb_ep *ep, struct usb_request *req)
{
    struct fsg_dev      *fsg = ep->driver_data;
    struct fsg_buffhd   *bh = req->context;

    dump_msg(fsg, "bulk-out", req->buf, req->actual);
    if (req->status || req->actual != bh->bulk_out_intended_length)
        DBG(fsg, "%s --> %d, %u/%u\n", __func__,
                req->status, req->actual,
                bh->bulk_out_intended_length);
    if (req->status == -ECONNRESET)     // Request was cancelled
        usb_ep_fifo_flush(ep);

    /* Hold the lock while we update the request and buffer states */
    smp_wmb();
    spin_lock(&fsg->lock);
    bh->outreq_busy = 0;
    bh->state = BUF_STATE_FULL;
    wakeup_thread(fsg);
    spin_unlock(&fsg->lock);
}


#ifdef CONFIG_USB_FILE_STORAGE_TEST
static void intr_in_complete(struct usb_ep *ep, struct usb_request *req)
{
    struct fsg_dev      *fsg = ep->driver_data;
    struct fsg_buffhd   *bh = req->context;

    if (req->status || req->actual != req->length)
        DBG(fsg, "%s --> %d, %u/%u\n", __func__,
                req->status, req->actual, req->length);
    if (req->status == -ECONNRESET)     // Request was cancelled
        usb_ep_fifo_flush(ep);

    /* Hold the lock while we update the request and buffer states */
    smp_wmb();
    spin_lock(&fsg->lock);
    fsg->intreq_busy = 0;
    bh->state = BUF_STATE_EMPTY;
    wakeup_thread(fsg);
    spin_unlock(&fsg->lock);
}

#else
static void intr_in_complete(struct usb_ep *ep, struct usb_request *req)
{}
#endif /* CONFIG_USB_FILE_STORAGE_TEST */


/*-------------------------------------------------------------------------*/

/* Ep0 class-specific handlers.  These always run in_irq. */

#ifdef CONFIG_USB_FILE_STORAGE_TEST
static void received_cbi_adsc(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
    struct usb_request  *req = fsg->ep0req;
    static u8       cbi_reset_cmnd[6] = {
            SEND_DIAGNOSTIC, 4, 0xff, 0xff, 0xff, 0xff};

    /* Error in command transfer? */
    if (req->status || req->length != req->actual ||
            req->actual < 6 || req->actual > MAX_COMMAND_SIZE) {

        /* Not all controllers allow a protocol stall after
         * receiving control-out data, but we'll try anyway. */
        fsg_set_halt(fsg, fsg->ep0);
        return;         // Wait for reset
    }

    /* Is it the special reset command? */
    if (req->actual >= sizeof cbi_reset_cmnd &&
            memcmp(req->buf, cbi_reset_cmnd,
                sizeof cbi_reset_cmnd) == 0) {

        /* Raise an exception to stop the current operation
         * and reinitialize our state. */
        DBG(fsg, "cbi reset request\n");
        raise_exception(fsg, FSG_STATE_RESET);
        return;
    }

    VDBG(fsg, "CB[I] accept device-specific command\n");
    spin_lock(&fsg->lock);

    /* Save the command for later */
    if (fsg->cbbuf_cmnd_size)
        WARNING(fsg, "CB[I] overwriting previous command\n");
    fsg->cbbuf_cmnd_size = req->actual;
    memcpy(fsg->cbbuf_cmnd, req->buf, fsg->cbbuf_cmnd_size);

    wakeup_thread(fsg);
    spin_unlock(&fsg->lock);
}

#else
static void received_cbi_adsc(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{}
#endif /* CONFIG_USB_FILE_STORAGE_TEST */


static int class_setup_req(struct fsg_dev *fsg,
        const struct usb_ctrlrequest *ctrl)
{
    struct usb_request  *req = fsg->ep0req;
    int         value = -EOPNOTSUPP;
    u16         w_index = le16_to_cpu(ctrl->wIndex);
    u16                     w_value = le16_to_cpu(ctrl->wValue);
    u16         w_length = le16_to_cpu(ctrl->wLength);

    if (!fsg->config)
        return value;

    /* Handle Bulk-only class-specific requests */
    if (transport_is_bbb()) {
        switch (ctrl->bRequest) {

        case US_BULK_RESET_REQUEST:
            if (ctrl->bRequestType != (USB_DIR_OUT |
                    USB_TYPE_CLASS | USB_RECIP_INTERFACE))
                break;
            if (w_index != 0 || w_value != 0 || w_length != 0) {
                value = -EDOM;
                break;
            }

            /* Raise an exception to stop the current operation
             * and reinitialize our state. */
            DBG(fsg, "bulk reset request\n");
            raise_exception(fsg, FSG_STATE_RESET);
            value = DELAYED_STATUS;
            break;

        case US_BULK_GET_MAX_LUN:
            if (ctrl->bRequestType != (USB_DIR_IN |
                    USB_TYPE_CLASS | USB_RECIP_INTERFACE))
                break;
            if (w_index != 0 || w_value != 0 || w_length != 1) {
                value = -EDOM;
                break;
            }
            VDBG(fsg, "get max LUN\n");
            *(u8 *) req->buf = fsg->nluns - 1;
            value = 1;
            break;
        }
    }

    /* Handle CBI class-specific requests */
    else {
        switch (ctrl->bRequest) {

        case USB_CBI_ADSC_REQUEST:
            if (ctrl->bRequestType != (USB_DIR_OUT |
                    USB_TYPE_CLASS | USB_RECIP_INTERFACE))
                break;
            if (w_index != 0 || w_value != 0) {
                value = -EDOM;
                break;
            }
            if (w_length > MAX_COMMAND_SIZE) {
                value = -EOVERFLOW;
                break;
            }
            value = w_length;
            fsg->ep0req->context = received_cbi_adsc;
            break;
        }
    }

    if (value == -EOPNOTSUPP)
        VDBG(fsg,
            "unknown class-specific control req "
            "%02x.%02x v%04x i%04x l%u\n",
            ctrl->bRequestType, ctrl->bRequest,
            le16_to_cpu(ctrl->wValue), w_index, w_length);
    return value;
}


/*-------------------------------------------------------------------------*/

/* Ep0 standard request handlers.  These always run in_irq. */

static int standard_setup_req(struct fsg_dev *fsg,
        const struct usb_ctrlrequest *ctrl)
{
    struct usb_request  *req = fsg->ep0req;
    int         value = -EOPNOTSUPP;
    u16         w_index = le16_to_cpu(ctrl->wIndex);
    u16         w_value = le16_to_cpu(ctrl->wValue);

    /* Usually this just stores reply data in the pre-allocated ep0 buffer,
     * but config change events will also reconfigure hardware. */
    switch (ctrl->bRequest) {

    case USB_REQ_GET_DESCRIPTOR:
        if (ctrl->bRequestType != (USB_DIR_IN | USB_TYPE_STANDARD |
                USB_RECIP_DEVICE))
            break;
        switch (w_value >> 8) {

        case USB_DT_DEVICE:
            VDBG(fsg, "get device descriptor\n");
            device_desc.bMaxPacketSize0 = fsg->ep0->maxpacket;
            value = sizeof device_desc;
            memcpy(req->buf, &device_desc, value);
            break;
        case USB_DT_DEVICE_QUALIFIER:
            VDBG(fsg, "get device qualifier\n");
            if (!gadget_is_dualspeed(fsg->gadget) ||
                    fsg->gadget->speed == USB_SPEED_SUPER)
                break;
            /*
             * Assume ep0 uses the same maxpacket value for both
             * speeds
             */
            dev_qualifier.bMaxPacketSize0 = fsg->ep0->maxpacket;
            value = sizeof dev_qualifier;
            memcpy(req->buf, &dev_qualifier, value);
            break;

        case USB_DT_OTHER_SPEED_CONFIG:
            VDBG(fsg, "get other-speed config descriptor\n");
            if (!gadget_is_dualspeed(fsg->gadget) ||
                    fsg->gadget->speed == USB_SPEED_SUPER)
                break;
            goto get_config;
        case USB_DT_CONFIG:
            VDBG(fsg, "get configuration descriptor\n");
get_config:
            value = populate_config_buf(fsg->gadget,
                    req->buf,
                    w_value >> 8,
                    w_value & 0xff);
            break;

        case USB_DT_STRING:
            VDBG(fsg, "get string descriptor\n");

            /* wIndex == language code */
            value = usb_gadget_get_string(&fsg_stringtab,
                    w_value & 0xff, req->buf);
            break;

        case USB_DT_BOS:
            VDBG(fsg, "get bos descriptor\n");

            if (gadget_is_superspeed(fsg->gadget))
                value = populate_bos(fsg, req->buf);
            break;
        }

        break;

    /* One config, two speeds */
    case USB_REQ_SET_CONFIGURATION:
        if (ctrl->bRequestType != (USB_DIR_OUT | USB_TYPE_STANDARD |
                USB_RECIP_DEVICE))
            break;
        VDBG(fsg, "set configuration\n");
        if (w_value == CONFIG_VALUE || w_value == 0) {
            fsg->new_config = w_value;

            /* Raise an exception to wipe out previous transaction
             * state (queued bufs, etc) and set the new config. */
            raise_exception(fsg, FSG_STATE_CONFIG_CHANGE);
            value = DELAYED_STATUS;
        }
        break;
    case USB_REQ_GET_CONFIGURATION:
        if (ctrl->bRequestType != (USB_DIR_IN | USB_TYPE_STANDARD |
                USB_RECIP_DEVICE))
            break;
        VDBG(fsg, "get configuration\n");
        *(u8 *) req->buf = fsg->config;
        value = 1;
        break;

    case USB_REQ_SET_INTERFACE:
        if (ctrl->bRequestType != (USB_DIR_OUT| USB_TYPE_STANDARD |
                USB_RECIP_INTERFACE))
            break;
        if (fsg->config && w_index == 0) {

            /* Raise an exception to wipe out previous transaction
             * state (queued bufs, etc) and install the new
             * interface altsetting. */
            raise_exception(fsg, FSG_STATE_INTERFACE_CHANGE);
            value = DELAYED_STATUS;
        }
        break;
    case USB_REQ_GET_INTERFACE:
        if (ctrl->bRequestType != (USB_DIR_IN | USB_TYPE_STANDARD |
                USB_RECIP_INTERFACE))
            break;
        if (!fsg->config)
            break;
        if (w_index != 0) {
            value = -EDOM;
            break;
        }
        VDBG(fsg, "get interface\n");
        *(u8 *) req->buf = 0;
        value = 1;
        break;

    default:
        VDBG(fsg,
            "unknown control req %02x.%02x v%04x i%04x l%u\n",
            ctrl->bRequestType, ctrl->bRequest,
            w_value, w_index, le16_to_cpu(ctrl->wLength));
    }

    return value;
}


static int fsg_setup(struct usb_gadget *gadget,
        const struct usb_ctrlrequest *ctrl)
{
    struct fsg_dev      *fsg = get_gadget_data(gadget);
    int         rc;
    int         w_length = le16_to_cpu(ctrl->wLength);

    ++fsg->ep0_req_tag;     // Record arrival of a new request
    fsg->ep0req->context = NULL;
    fsg->ep0req->length = 0;
    dump_msg(fsg, "ep0-setup", (u8 *) ctrl, sizeof(*ctrl));

    if ((ctrl->bRequestType & USB_TYPE_MASK) == USB_TYPE_CLASS)
        rc = class_setup_req(fsg, ctrl);
    else
        rc = standard_setup_req(fsg, ctrl);

    /* Respond with data/status or defer until later? */
    if (rc >= 0 && rc != DELAYED_STATUS) {
        rc = min(rc, w_length);
        fsg->ep0req->length = rc;
        fsg->ep0req->zero = rc < w_length;
        fsg->ep0req_name = (ctrl->bRequestType & USB_DIR_IN ?
                "ep0-in" : "ep0-out");
        rc = ep0_queue(fsg);
    }

    /* Device either stalls (rc < 0) or reports success */
    return rc;
}


/*-------------------------------------------------------------------------*/

/* All the following routines run in process context */


/* Use this for bulk or interrupt transfers, not ep0 */
static void start_transfer(struct fsg_dev *fsg, struct usb_ep *ep,
        struct usb_request *req, int *pbusy,
        enum fsg_buffer_state *state)
{
    int rc;

    if (ep == fsg->bulk_in)
        dump_msg(fsg, "bulk-in", req->buf, req->length);
    else if (ep == fsg->intr_in)
        dump_msg(fsg, "intr-in", req->buf, req->length);

    spin_lock_irq(&fsg->lock);
    *pbusy = 1;
    *state = BUF_STATE_BUSY;
    spin_unlock_irq(&fsg->lock);
    rc = usb_ep_queue(ep, req, GFP_KERNEL);
    if (rc != 0) {
        *pbusy = 0;
        *state = BUF_STATE_EMPTY;

        /* We can't do much more than wait for a reset */

        /* Note: currently the net2280 driver fails zero-length
         * submissions if DMA is enabled. */
        if (rc != -ESHUTDOWN && !(rc == -EOPNOTSUPP &&
                        req->length == 0))
            WARNING(fsg, "error in submission: %s --> %d\n",
                    ep->name, rc);
    }
}


static int sleep_thread(struct fsg_dev *fsg)
{
    int rc = 0;

    /* Wait until a signal arrives or we are woken up */
    for (;;) {
        try_to_freeze();
        set_current_state(TASK_INTERRUPTIBLE);
        if (signal_pending(current)) {
            rc = -EINTR;
            break;
        }
        if (fsg->thread_wakeup_needed)
            break;
        schedule();
    }
    __set_current_state(TASK_RUNNING);
    fsg->thread_wakeup_needed = 0;
    return rc;
}


/*-------------------------------------------------------------------------*/

static int do_read(struct fsg_dev *fsg)
{
    struct fsg_lun      *curlun = fsg->curlun;
    u32         lba;
    struct fsg_buffhd   *bh;
    int         rc;
    u32         amount_left;
    loff_t          file_offset, file_offset_tmp;
    unsigned int        amount;
    ssize_t         nread;

    /* Get the starting Logical Block Address and check that it's
     * not too big */
    if (fsg->cmnd[0] == READ_6)
        lba = get_unaligned_be24(&fsg->cmnd[1]);
    else {
        lba = get_unaligned_be32(&fsg->cmnd[2]);

        /* We allow DPO (Disable Page Out = don't save data in the
         * cache) and FUA (Force Unit Access = don't read from the
         * cache), but we don't implement them. */
        if ((fsg->cmnd[1] & ~0x18) != 0) {
            curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
            return -EINVAL;
        }
    }
    if (lba >= curlun->num_sectors) {
        curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
        return -EINVAL;
    }
    file_offset = ((loff_t) lba) << curlun->blkbits;

    /* Carry out the file reads */
    amount_left = fsg->data_size_from_cmnd;
    if (unlikely(amount_left == 0))
        return -EIO;        // No default reply

    for (;;) {

        /* Figure out how much we need to read:
         * Try to read the remaining amount.
         * But don't read more than the buffer size.
         * And don't try to read past the end of the file.
         */
        amount = min((unsigned int) amount_left, mod_data.buflen);
        amount = min((loff_t) amount,
                curlun->file_length - file_offset);

        /* Wait for the next buffer to become available */
        bh = fsg->next_buffhd_to_fill;
        while (bh->state != BUF_STATE_EMPTY) {
            rc = sleep_thread(fsg);
            if (rc)
                return rc;
        }

        /* If we were asked to read past the end of file,
         * end with an empty buffer. */
        if (amount == 0) {
            curlun->sense_data =
                    SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
            curlun->sense_data_info = file_offset >> curlun->blkbits;
            curlun->info_valid = 1;
            bh->inreq->length = 0;
            bh->state = BUF_STATE_FULL;
            break;
        }

        /* Perform the read */
        file_offset_tmp = file_offset;
        nread = vfs_read(curlun->filp,
                (char __user *) bh->buf,
                amount, &file_offset_tmp);
        VLDBG(curlun, "file read %u @ %llu -> %d\n", amount,
                (unsigned long long) file_offset,
                (int) nread);
        if (signal_pending(current))
            return -EINTR;

        if (nread < 0) {
            LDBG(curlun, "error in file read: %d\n",
                    (int) nread);
            nread = 0;
        } else if (nread < amount) {
            LDBG(curlun, "partial file read: %d/%u\n",
                    (int) nread, amount);
            nread = round_down(nread, curlun->blksize);
        }
        file_offset  += nread;
        amount_left  -= nread;
        fsg->residue -= nread;

        /* Except at the end of the transfer, nread will be
         * equal to the buffer size, which is divisible by the
         * bulk-in maxpacket size.
         */
        bh->inreq->length = nread;
        bh->state = BUF_STATE_FULL;

        /* If an error occurred, report it and its position */
        if (nread < amount) {
            curlun->sense_data = SS_UNRECOVERED_READ_ERROR;
            curlun->sense_data_info = file_offset >> curlun->blkbits;
            curlun->info_valid = 1;
            break;
        }

        if (amount_left == 0)
            break;      // No more left to read

        /* Send this buffer and go read some more */
        bh->inreq->zero = 0;
        start_transfer(fsg, fsg->bulk_in, bh->inreq,
                &bh->inreq_busy, &bh->state);
        fsg->next_buffhd_to_fill = bh->next;
    }

    return -EIO;        // No default reply
}


/*-------------------------------------------------------------------------*/

static int do_write(struct fsg_dev *fsg)
{
    struct fsg_lun      *curlun = fsg->curlun;
    u32         lba;
    struct fsg_buffhd   *bh;
    int         get_some_more;
    u32         amount_left_to_req, amount_left_to_write;
    loff_t          usb_offset, file_offset, file_offset_tmp;
    unsigned int        amount;
    ssize_t         nwritten;
    int         rc;

    if (curlun->ro) {
        curlun->sense_data = SS_WRITE_PROTECTED;
        return -EINVAL;
    }
    spin_lock(&curlun->filp->f_lock);
    curlun->filp->f_flags &= ~O_SYNC;   // Default is not to wait
    spin_unlock(&curlun->filp->f_lock);

    /* Get the starting Logical Block Address and check that it's
     * not too big */
    if (fsg->cmnd[0] == WRITE_6)
        lba = get_unaligned_be24(&fsg->cmnd[1]);
    else {
        lba = get_unaligned_be32(&fsg->cmnd[2]);

        /* We allow DPO (Disable Page Out = don't save data in the
         * cache) and FUA (Force Unit Access = write directly to the
         * medium).  We don't implement DPO; we implement FUA by
         * performing synchronous output. */
        if ((fsg->cmnd[1] & ~0x18) != 0) {
            curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
            return -EINVAL;
        }
        /* FUA */
        if (!curlun->nofua && (fsg->cmnd[1] & 0x08)) {
            spin_lock(&curlun->filp->f_lock);
            curlun->filp->f_flags |= O_DSYNC;
            spin_unlock(&curlun->filp->f_lock);
        }
    }
    if (lba >= curlun->num_sectors) {
        curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
        return -EINVAL;
    }

    /* Carry out the file writes */
    get_some_more = 1;
    file_offset = usb_offset = ((loff_t) lba) << curlun->blkbits;
    amount_left_to_req = amount_left_to_write = fsg->data_size_from_cmnd;

    while (amount_left_to_write > 0) {

        /* Queue a request for more data from the host */
        bh = fsg->next_buffhd_to_fill;
        if (bh->state == BUF_STATE_EMPTY && get_some_more) {

            /* Figure out how much we want to get:
             * Try to get the remaining amount,
             * but not more than the buffer size.
             */
            amount = min(amount_left_to_req, mod_data.buflen);

            /* Beyond the end of the backing file? */
            if (usb_offset >= curlun->file_length) {
                get_some_more = 0;
                curlun->sense_data =
                    SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                curlun->sense_data_info = usb_offset >> curlun->blkbits;
                curlun->info_valid = 1;
                continue;
            }

            /* Get the next buffer */
            usb_offset += amount;
            fsg->usb_amount_left -= amount;
            amount_left_to_req -= amount;
            if (amount_left_to_req == 0)
                get_some_more = 0;

            /* Except at the end of the transfer, amount will be
             * equal to the buffer size, which is divisible by
             * the bulk-out maxpacket size.
             */
            set_bulk_out_req_length(fsg, bh, amount);
            start_transfer(fsg, fsg->bulk_out, bh->outreq,
                    &bh->outreq_busy, &bh->state);
            fsg->next_buffhd_to_fill = bh->next;
            continue;
        }

        /* Write the received data to the backing file */
        bh = fsg->next_buffhd_to_drain;
        if (bh->state == BUF_STATE_EMPTY && !get_some_more)
            break;          // We stopped early
        if (bh->state == BUF_STATE_FULL) {
            smp_rmb();
            fsg->next_buffhd_to_drain = bh->next;
            bh->state = BUF_STATE_EMPTY;

            /* Did something go wrong with the transfer? */
            if (bh->outreq->status != 0) {
                curlun->sense_data = SS_COMMUNICATION_FAILURE;
                curlun->sense_data_info = file_offset >> curlun->blkbits;
                curlun->info_valid = 1;
                break;
            }

            amount = bh->outreq->actual;
            if (curlun->file_length - file_offset < amount) {
                LERROR(curlun,
    "write %u @ %llu beyond end %llu\n",
    amount, (unsigned long long) file_offset,
    (unsigned long long) curlun->file_length);
                amount = curlun->file_length - file_offset;
            }

            /* Don't accept excess data.  The spec doesn't say
             * what to do in this case.  We'll ignore the error.
             */
            amount = min(amount, bh->bulk_out_intended_length);

            /* Don't write a partial block */
            amount = round_down(amount, curlun->blksize);
            if (amount == 0)
                goto empty_write;

            /* Perform the write */
            file_offset_tmp = file_offset;
            nwritten = vfs_write(curlun->filp,
                    (char __user *) bh->buf,
                    amount, &file_offset_tmp);
            VLDBG(curlun, "file write %u @ %llu -> %d\n", amount,
                    (unsigned long long) file_offset,
                    (int) nwritten);
            if (signal_pending(current))
                return -EINTR;      // Interrupted!

            if (nwritten < 0) {
                LDBG(curlun, "error in file write: %d\n",
                        (int) nwritten);
                nwritten = 0;
            } else if (nwritten < amount) {
                LDBG(curlun, "partial file write: %d/%u\n",
                        (int) nwritten, amount);
                nwritten = round_down(nwritten, curlun->blksize);
            }
            file_offset += nwritten;
            amount_left_to_write -= nwritten;
            fsg->residue -= nwritten;

            /* If an error occurred, report it and its position */
            if (nwritten < amount) {
                curlun->sense_data = SS_WRITE_ERROR;
                curlun->sense_data_info = file_offset >> curlun->blkbits;
                curlun->info_valid = 1;
                break;
            }

 empty_write:
            /* Did the host decide to stop early? */
            if (bh->outreq->actual < bh->bulk_out_intended_length) {
                fsg->short_packet_received = 1;
                break;
            }
            continue;
        }

        /* Wait for something to happen */
        rc = sleep_thread(fsg);
        if (rc)
            return rc;
    }

    return -EIO;        // No default reply
}


/*-------------------------------------------------------------------------*/

static int do_synchronize_cache(struct fsg_dev *fsg)
{
    struct fsg_lun  *curlun = fsg->curlun;
    int     rc;

    /* We ignore the requested LBA and write out all file's
     * dirty data buffers. */
    rc = fsg_lun_fsync_sub(curlun);
    if (rc)
        curlun->sense_data = SS_WRITE_ERROR;
    return 0;
}


/*-------------------------------------------------------------------------*/

static void invalidate_sub(struct fsg_lun *curlun)
{
    struct file *filp = curlun->filp;
    struct inode    *inode = filp->f_path.dentry->d_inode;
    unsigned long   rc;

    rc = invalidate_mapping_pages(inode->i_mapping, 0, -1);
    VLDBG(curlun, "invalidate_mapping_pages -> %ld\n", rc);
}

static int do_verify(struct fsg_dev *fsg)
{
    struct fsg_lun      *curlun = fsg->curlun;
    u32         lba;
    u32         verification_length;
    struct fsg_buffhd   *bh = fsg->next_buffhd_to_fill;
    loff_t          file_offset, file_offset_tmp;
    u32         amount_left;
    unsigned int        amount;
    ssize_t         nread;

    /* Get the starting Logical Block Address and check that it's
     * not too big */
    lba = get_unaligned_be32(&fsg->cmnd[2]);
    if (lba >= curlun->num_sectors) {
        curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
        return -EINVAL;
    }

    /* We allow DPO (Disable Page Out = don't save data in the
     * cache) but we don't implement it. */
    if ((fsg->cmnd[1] & ~0x10) != 0) {
        curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
        return -EINVAL;
    }

    verification_length = get_unaligned_be16(&fsg->cmnd[7]);
    if (unlikely(verification_length == 0))
        return -EIO;        // No default reply

    /* Prepare to carry out the file verify */
    amount_left = verification_length << curlun->blkbits;
    file_offset = ((loff_t) lba) << curlun->blkbits;

    /* Write out all the dirty buffers before invalidating them */
    fsg_lun_fsync_sub(curlun);
    if (signal_pending(current))
        return -EINTR;

    invalidate_sub(curlun);
    if (signal_pending(current))
        return -EINTR;

    /* Just try to read the requested blocks */
    while (amount_left > 0) {

        /* Figure out how much we need to read:
         * Try to read the remaining amount, but not more than
         * the buffer size.
         * And don't try to read past the end of the file.
         */
        amount = min((unsigned int) amount_left, mod_data.buflen);
        amount = min((loff_t) amount,
                curlun->file_length - file_offset);
        if (amount == 0) {
            curlun->sense_data =
                    SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
            curlun->sense_data_info = file_offset >> curlun->blkbits;
            curlun->info_valid = 1;
            break;
        }

        /* Perform the read */
        file_offset_tmp = file_offset;
        nread = vfs_read(curlun->filp,
                (char __user *) bh->buf,
                amount, &file_offset_tmp);
        VLDBG(curlun, "file read %u @ %llu -> %d\n", amount,
                (unsigned long long) file_offset,
                (int) nread);
        if (signal_pending(current))
            return -EINTR;

        if (nread < 0) {
            LDBG(curlun, "error in file verify: %d\n",
                    (int) nread);
            nread = 0;
        } else if (nread < amount) {
            LDBG(curlun, "partial file verify: %d/%u\n",
                    (int) nread, amount);
            nread = round_down(nread, curlun->blksize);
        }
        if (nread == 0) {
            curlun->sense_data = SS_UNRECOVERED_READ_ERROR;
            curlun->sense_data_info = file_offset >> curlun->blkbits;
            curlun->info_valid = 1;
            break;
        }
        file_offset += nread;
        amount_left -= nread;
    }
    return 0;
}


/*-------------------------------------------------------------------------*/

static int do_inquiry(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
    u8  *buf = (u8 *) bh->buf;

    static char vendor_id[] = "Linux   ";
    static char product_disk_id[] = "File-Stor Gadget";
    static char product_cdrom_id[] = "File-CD Gadget  ";

    if (!fsg->curlun) {     // Unsupported LUNs are okay
        fsg->bad_lun_okay = 1;
        memset(buf, 0, 36);
        buf[0] = 0x7f;      // Unsupported, no device-type
        buf[4] = 31;        // Additional length
        return 36;
    }

    memset(buf, 0, 8);
    buf[0] = (mod_data.cdrom ? TYPE_ROM : TYPE_DISK);
    if (mod_data.removable)
        buf[1] = 0x80;
    buf[2] = 2;     // ANSI SCSI level 2
    buf[3] = 2;     // SCSI-2 INQUIRY data format
    buf[4] = 31;        // Additional length
                // No special options
    sprintf(buf + 8, "%-8s%-16s%04x", vendor_id,
            (mod_data.cdrom ? product_cdrom_id :
                product_disk_id),
            mod_data.release);
    return 36;
}


static int do_request_sense(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
    struct fsg_lun  *curlun = fsg->curlun;
    u8      *buf = (u8 *) bh->buf;
    u32     sd, sdinfo;
    int     valid;

    /*
     * From the SCSI-2 spec., section 7.9 (Unit attention condition):
     *
     * If a REQUEST SENSE command is received from an initiator
     * with a pending unit attention condition (before the target
     * generates the contingent allegiance condition), then the
     * target shall either:
     *   a) report any pending sense data and preserve the unit
     *  attention condition on the logical unit, or,
     *   b) report the unit attention condition, may discard any
     *  pending sense data, and clear the unit attention
     *  condition on the logical unit for that initiator.
     *
     * FSG normally uses option a); enable this code to use option b).
     */
#if 0
    if (curlun && curlun->unit_attention_data != SS_NO_SENSE) {
        curlun->sense_data = curlun->unit_attention_data;
        curlun->unit_attention_data = SS_NO_SENSE;
    }
#endif

    if (!curlun) {      // Unsupported LUNs are okay
        fsg->bad_lun_okay = 1;
        sd = SS_LOGICAL_UNIT_NOT_SUPPORTED;
        sdinfo = 0;
        valid = 0;
    } else {
        sd = curlun->sense_data;
        sdinfo = curlun->sense_data_info;
        valid = curlun->info_valid << 7;
        curlun->sense_data = SS_NO_SENSE;
        curlun->sense_data_info = 0;
        curlun->info_valid = 0;
    }

    memset(buf, 0, 18);
    buf[0] = valid | 0x70;          // Valid, current error
    buf[2] = SK(sd);
    put_unaligned_be32(sdinfo, &buf[3]);    /* Sense information */
    buf[7] = 18 - 8;            // Additional sense length
    buf[12] = ASC(sd);
    buf[13] = ASCQ(sd);
    return 18;
}


static int do_read_capacity(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
    struct fsg_lun  *curlun = fsg->curlun;
    u32     lba = get_unaligned_be32(&fsg->cmnd[2]);
    int     pmi = fsg->cmnd[8];
    u8      *buf = (u8 *) bh->buf;

    /* Check the PMI and LBA fields */
    if (pmi > 1 || (pmi == 0 && lba != 0)) {
        curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
        return -EINVAL;
    }

    put_unaligned_be32(curlun->num_sectors - 1, &buf[0]);
                        /* Max logical block */
    put_unaligned_be32(curlun->blksize, &buf[4]);   /* Block length */
    return 8;
}


static int do_read_header(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
    struct fsg_lun  *curlun = fsg->curlun;
    int     msf = fsg->cmnd[1] & 0x02;
    u32     lba = get_unaligned_be32(&fsg->cmnd[2]);
    u8      *buf = (u8 *) bh->buf;

    if ((fsg->cmnd[1] & ~0x02) != 0) {      /* Mask away MSF */
        curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
        return -EINVAL;
    }
    if (lba >= curlun->num_sectors) {
        curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
        return -EINVAL;
    }

    memset(buf, 0, 8);
    buf[0] = 0x01;      /* 2048 bytes of user data, rest is EC */
    store_cdrom_address(&buf[4], msf, lba);
    return 8;
}


static int do_read_toc(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
    struct fsg_lun  *curlun = fsg->curlun;
    int     msf = fsg->cmnd[1] & 0x02;
    int     start_track = fsg->cmnd[6];
    u8      *buf = (u8 *) bh->buf;

    if ((fsg->cmnd[1] & ~0x02) != 0 ||      /* Mask away MSF */
            start_track > 1) {
        curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
        return -EINVAL;
    }

    memset(buf, 0, 20);
    buf[1] = (20-2);        /* TOC data length */
    buf[2] = 1;         /* First track number */
    buf[3] = 1;         /* Last track number */
    buf[5] = 0x16;          /* Data track, copying allowed */
    buf[6] = 0x01;          /* Only track is number 1 */
    store_cdrom_address(&buf[8], msf, 0);

    buf[13] = 0x16;         /* Lead-out track is data */
    buf[14] = 0xAA;         /* Lead-out track number */
    store_cdrom_address(&buf[16], msf, curlun->num_sectors);
    return 20;
}


static int do_mode_sense(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
    struct fsg_lun  *curlun = fsg->curlun;
    int     mscmnd = fsg->cmnd[0];
    u8      *buf = (u8 *) bh->buf;
    u8      *buf0 = buf;
    int     pc, page_code;
    int     changeable_values, all_pages;
    int     valid_page = 0;
    int     len, limit;

    if ((fsg->cmnd[1] & ~0x08) != 0) {      // Mask away DBD
        curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
        return -EINVAL;
    }
    pc = fsg->cmnd[2] >> 6;
    page_code = fsg->cmnd[2] & 0x3f;
    if (pc == 3) {
        curlun->sense_data = SS_SAVING_PARAMETERS_NOT_SUPPORTED;
        return -EINVAL;
    }
    changeable_values = (pc == 1);
    all_pages = (page_code == 0x3f);

    /* Write the mode parameter header.  Fixed values are: default
     * medium type, no cache control (DPOFUA), and no block descriptors.
     * The only variable value is the WriteProtect bit.  We will fill in
     * the mode data length later. */
    memset(buf, 0, 8);
    if (mscmnd == MODE_SENSE) {
        buf[2] = (curlun->ro ? 0x80 : 0x00);        // WP, DPOFUA
        buf += 4;
        limit = 255;
    } else {            // MODE_SENSE_10
        buf[3] = (curlun->ro ? 0x80 : 0x00);        // WP, DPOFUA
        buf += 8;
        limit = 65535;      // Should really be mod_data.buflen
    }

    /* No block descriptors */

    /* The mode pages, in numerical order.  The only page we support
     * is the Caching page. */
    if (page_code == 0x08 || all_pages) {
        valid_page = 1;
        buf[0] = 0x08;      // Page code
        buf[1] = 10;        // Page length
        memset(buf+2, 0, 10);   // None of the fields are changeable

        if (!changeable_values) {
            buf[2] = 0x04;  // Write cache enable,
                    // Read cache not disabled
                    // No cache retention priorities
            put_unaligned_be16(0xffff, &buf[4]);
                    /* Don't disable prefetch */
                    /* Minimum prefetch = 0 */
            put_unaligned_be16(0xffff, &buf[8]);
                    /* Maximum prefetch */
            put_unaligned_be16(0xffff, &buf[10]);
                    /* Maximum prefetch ceiling */
        }
        buf += 12;
    }

    /* Check that a valid page was requested and the mode data length
     * isn't too long. */
    len = buf - buf0;
    if (!valid_page || len > limit) {
        curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
        return -EINVAL;
    }

    /*  Store the mode data length */
    if (mscmnd == MODE_SENSE)
        buf0[0] = len - 1;
    else
        put_unaligned_be16(len - 2, buf0);
    return len;
}


static int do_start_stop(struct fsg_dev *fsg)
{
    struct fsg_lun  *curlun = fsg->curlun;
    int     loej, start;

    if (!mod_data.removable) {
        curlun->sense_data = SS_INVALID_COMMAND;
        return -EINVAL;
    }

    // int immed = fsg->cmnd[1] & 0x01;
    loej = fsg->cmnd[4] & 0x02;
    start = fsg->cmnd[4] & 0x01;

#ifdef CONFIG_USB_FILE_STORAGE_TEST
    if ((fsg->cmnd[1] & ~0x01) != 0 ||      // Mask away Immed
            (fsg->cmnd[4] & ~0x03) != 0) {  // Mask LoEj, Start
        curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
        return -EINVAL;
    }

    if (!start) {

        /* Are we allowed to unload the media? */
        if (curlun->prevent_medium_removal) {
            LDBG(curlun, "unload attempt prevented\n");
            curlun->sense_data = SS_MEDIUM_REMOVAL_PREVENTED;
            return -EINVAL;
        }
        if (loej) {     // Simulate an unload/eject
            up_read(&fsg->filesem);
            down_write(&fsg->filesem);
            fsg_lun_close(curlun);
            up_write(&fsg->filesem);
            down_read(&fsg->filesem);
        }
    } else {

        /* Our emulation doesn't support mounting; the medium is
         * available for use as soon as it is loaded. */
        if (!fsg_lun_is_open(curlun)) {
            curlun->sense_data = SS_MEDIUM_NOT_PRESENT;
            return -EINVAL;
        }
    }
#endif
    return 0;
}


static int do_prevent_allow(struct fsg_dev *fsg)
{
    struct fsg_lun  *curlun = fsg->curlun;
    int     prevent;

    if (!mod_data.removable) {
        curlun->sense_data = SS_INVALID_COMMAND;
        return -EINVAL;
    }

    prevent = fsg->cmnd[4] & 0x01;
    if ((fsg->cmnd[4] & ~0x01) != 0) {      // Mask away Prevent
        curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
        return -EINVAL;
    }

    if (curlun->prevent_medium_removal && !prevent)
        fsg_lun_fsync_sub(curlun);
    curlun->prevent_medium_removal = prevent;
    return 0;
}


static int do_read_format_capacities(struct fsg_dev *fsg,
            struct fsg_buffhd *bh)
{
    struct fsg_lun  *curlun = fsg->curlun;
    u8      *buf = (u8 *) bh->buf;

    buf[0] = buf[1] = buf[2] = 0;
    buf[3] = 8;     // Only the Current/Maximum Capacity Descriptor
    buf += 4;

    put_unaligned_be32(curlun->num_sectors, &buf[0]);
                        /* Number of blocks */
    put_unaligned_be32(curlun->blksize, &buf[4]);   /* Block length */
    buf[4] = 0x02;              /* Current capacity */
    return 12;
}


static int do_mode_select(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
    struct fsg_lun  *curlun = fsg->curlun;

    /* We don't support MODE SELECT */
    curlun->sense_data = SS_INVALID_COMMAND;
    return -EINVAL;
}


/*-------------------------------------------------------------------------*/

static int halt_bulk_in_endpoint(struct fsg_dev *fsg)
{
    int rc;

    rc = fsg_set_halt(fsg, fsg->bulk_in);
    if (rc == -EAGAIN)
        VDBG(fsg, "delayed bulk-in endpoint halt\n");
    while (rc != 0) {
        if (rc != -EAGAIN) {
            WARNING(fsg, "usb_ep_set_halt -> %d\n", rc);
            rc = 0;
            break;
        }

        /* Wait for a short time and then try again */
        if (msleep_interruptible(100) != 0)
            return -EINTR;
        rc = usb_ep_set_halt(fsg->bulk_in);
    }
    return rc;
}

static int wedge_bulk_in_endpoint(struct fsg_dev *fsg)
{
    int rc;

    DBG(fsg, "bulk-in set wedge\n");
    rc = usb_ep_set_wedge(fsg->bulk_in);
    if (rc == -EAGAIN)
        VDBG(fsg, "delayed bulk-in endpoint wedge\n");
    while (rc != 0) {
        if (rc != -EAGAIN) {
            WARNING(fsg, "usb_ep_set_wedge -> %d\n", rc);
            rc = 0;
            break;
        }

        /* Wait for a short time and then try again */
        if (msleep_interruptible(100) != 0)
            return -EINTR;
        rc = usb_ep_set_wedge(fsg->bulk_in);
    }
    return rc;
}

static int throw_away_data(struct fsg_dev *fsg)
{
    struct fsg_buffhd   *bh;
    u32         amount;
    int         rc;

    while ((bh = fsg->next_buffhd_to_drain)->state != BUF_STATE_EMPTY ||
            fsg->usb_amount_left > 0) {

        /* Throw away the data in a filled buffer */
        if (bh->state == BUF_STATE_FULL) {
            smp_rmb();
            bh->state = BUF_STATE_EMPTY;
            fsg->next_buffhd_to_drain = bh->next;

            /* A short packet or an error ends everything */
            if (bh->outreq->actual < bh->bulk_out_intended_length ||
                    bh->outreq->status != 0) {
                raise_exception(fsg, FSG_STATE_ABORT_BULK_OUT);
                return -EINTR;
            }
            continue;
        }

        /* Try to submit another request if we need one */
        bh = fsg->next_buffhd_to_fill;
        if (bh->state == BUF_STATE_EMPTY && fsg->usb_amount_left > 0) {
            amount = min(fsg->usb_amount_left,
                    (u32) mod_data.buflen);

            /* Except at the end of the transfer, amount will be
             * equal to the buffer size, which is divisible by
             * the bulk-out maxpacket size.
             */
            set_bulk_out_req_length(fsg, bh, amount);
            start_transfer(fsg, fsg->bulk_out, bh->outreq,
                    &bh->outreq_busy, &bh->state);
            fsg->next_buffhd_to_fill = bh->next;
            fsg->usb_amount_left -= amount;
            continue;
        }

        /* Otherwise wait for something to happen */
        rc = sleep_thread(fsg);
        if (rc)
            return rc;
    }
    return 0;
}


static int finish_reply(struct fsg_dev *fsg)
{
    struct fsg_buffhd   *bh = fsg->next_buffhd_to_fill;
    int         rc = 0;

    switch (fsg->data_dir) {
    case DATA_DIR_NONE:
        break;          // Nothing to send

    /* If we don't know whether the host wants to read or write,
     * this must be CB or CBI with an unknown command.  We mustn't
     * try to send or receive any data.  So stall both bulk pipes
     * if we can and wait for a reset. */
    case DATA_DIR_UNKNOWN:
        if (mod_data.can_stall) {
            fsg_set_halt(fsg, fsg->bulk_out);
            rc = halt_bulk_in_endpoint(fsg);
        }
        break;

    /* All but the last buffer of data must have already been sent */
    case DATA_DIR_TO_HOST:
        if (fsg->data_size == 0)
            ;       // Nothing to send

        /* If there's no residue, simply send the last buffer */
        else if (fsg->residue == 0) {
            bh->inreq->zero = 0;
            start_transfer(fsg, fsg->bulk_in, bh->inreq,
                    &bh->inreq_busy, &bh->state);
            fsg->next_buffhd_to_fill = bh->next;
        }

        /* There is a residue.  For CB and CBI, simply mark the end
         * of the data with a short packet.  However, if we are
         * allowed to stall, there was no data at all (residue ==
         * data_size), and the command failed (invalid LUN or
         * sense data is set), then halt the bulk-in endpoint
         * instead. */
        else if (!transport_is_bbb()) {
            if (mod_data.can_stall &&
                    fsg->residue == fsg->data_size &&
    (!fsg->curlun || fsg->curlun->sense_data != SS_NO_SENSE)) {
                bh->state = BUF_STATE_EMPTY;
                rc = halt_bulk_in_endpoint(fsg);
            } else {
                bh->inreq->zero = 1;
                start_transfer(fsg, fsg->bulk_in, bh->inreq,
                        &bh->inreq_busy, &bh->state);
                fsg->next_buffhd_to_fill = bh->next;
            }
        }

        /*
         * For Bulk-only, mark the end of the data with a short
         * packet.  If we are allowed to stall, halt the bulk-in
         * endpoint.  (Note: This violates the Bulk-Only Transport
         * specification, which requires us to pad the data if we
         * don't halt the endpoint.  Presumably nobody will mind.)
         */
        else {
            bh->inreq->zero = 1;
            start_transfer(fsg, fsg->bulk_in, bh->inreq,
                    &bh->inreq_busy, &bh->state);
            fsg->next_buffhd_to_fill = bh->next;
            if (mod_data.can_stall)
                rc = halt_bulk_in_endpoint(fsg);
        }
        break;

    /* We have processed all we want from the data the host has sent.
     * There may still be outstanding bulk-out requests. */
    case DATA_DIR_FROM_HOST:
        if (fsg->residue == 0)
            ;       // Nothing to receive

        /* Did the host stop sending unexpectedly early? */
        else if (fsg->short_packet_received) {
            raise_exception(fsg, FSG_STATE_ABORT_BULK_OUT);
            rc = -EINTR;
        }

        /* We haven't processed all the incoming data.  Even though
         * we may be allowed to stall, doing so would cause a race.
         * The controller may already have ACK'ed all the remaining
         * bulk-out packets, in which case the host wouldn't see a
         * STALL.  Not realizing the endpoint was halted, it wouldn't
         * clear the halt -- leading to problems later on. */
#if 0
        else if (mod_data.can_stall) {
            fsg_set_halt(fsg, fsg->bulk_out);
            raise_exception(fsg, FSG_STATE_ABORT_BULK_OUT);
            rc = -EINTR;
        }
#endif

        /* We can't stall.  Read in the excess data and throw it
         * all away. */
        else
            rc = throw_away_data(fsg);
        break;
    }
    return rc;
}


static int send_status(struct fsg_dev *fsg)
{
    struct fsg_lun      *curlun = fsg->curlun;
    struct fsg_buffhd   *bh;
    int         rc;
    u8          status = US_BULK_STAT_OK;
    u32         sd, sdinfo = 0;

    /* Wait for the next buffer to become available */
    bh = fsg->next_buffhd_to_fill;
    while (bh->state != BUF_STATE_EMPTY) {
        rc = sleep_thread(fsg);
        if (rc)
            return rc;
    }

    if (curlun) {
        sd = curlun->sense_data;
        sdinfo = curlun->sense_data_info;
    } else if (fsg->bad_lun_okay)
        sd = SS_NO_SENSE;
    else
        sd = SS_LOGICAL_UNIT_NOT_SUPPORTED;

    if (fsg->phase_error) {
        DBG(fsg, "sending phase-error status\n");
        status = US_BULK_STAT_PHASE;
        sd = SS_INVALID_COMMAND;
    } else if (sd != SS_NO_SENSE) {
        DBG(fsg, "sending command-failure status\n");
        status = US_BULK_STAT_FAIL;
        VDBG(fsg, "  sense data: SK x%02x, ASC x%02x, ASCQ x%02x;"
                "  info x%x\n",
                SK(sd), ASC(sd), ASCQ(sd), sdinfo);
    }

    if (transport_is_bbb()) {
        struct bulk_cs_wrap *csw = bh->buf;

        /* Store and send the Bulk-only CSW */
        csw->Signature = cpu_to_le32(US_BULK_CS_SIGN);
        csw->Tag = fsg->tag;
        csw->Residue = cpu_to_le32(fsg->residue);
        csw->Status = status;

        bh->inreq->length = US_BULK_CS_WRAP_LEN;
        bh->inreq->zero = 0;
        start_transfer(fsg, fsg->bulk_in, bh->inreq,
                &bh->inreq_busy, &bh->state);

    } else if (mod_data.transport_type == USB_PR_CB) {

        /* Control-Bulk transport has no status phase! */
        return 0;

    } else {            // USB_PR_CBI
        struct interrupt_data   *buf = bh->buf;

        /* Store and send the Interrupt data.  UFI sends the ASC
         * and ASCQ bytes.  Everything else sends a Type (which
         * is always 0) and the status Value. */
        if (mod_data.protocol_type == USB_SC_UFI) {
            buf->bType = ASC(sd);
            buf->bValue = ASCQ(sd);
        } else {
            buf->bType = 0;
            buf->bValue = status;
        }
        fsg->intreq->length = CBI_INTERRUPT_DATA_LEN;

        fsg->intr_buffhd = bh;      // Point to the right buffhd
        fsg->intreq->buf = bh->inreq->buf;
        fsg->intreq->context = bh;
        start_transfer(fsg, fsg->intr_in, fsg->intreq,
                &fsg->intreq_busy, &bh->state);
    }

    fsg->next_buffhd_to_fill = bh->next;
    return 0;
}


/*-------------------------------------------------------------------------*/

/* Check whether the command is properly formed and whether its data size
 * and direction agree with the values we already have. */
static int check_command(struct fsg_dev *fsg, int cmnd_size,
        enum data_direction data_dir, unsigned int mask,
        int needs_medium, const char *name)
{
    int         i;
    int         lun = fsg->cmnd[1] >> 5;
    static const char   dirletter[4] = {'u', 'o', 'i', 'n'};
    char            hdlen[20];
    struct fsg_lun      *curlun;

    /* Adjust the expected cmnd_size for protocol encapsulation padding.
     * Transparent SCSI doesn't pad. */
    if (protocol_is_scsi())
        ;

    /* There's some disagreement as to whether RBC pads commands or not.
     * We'll play it safe and accept either form. */
    else if (mod_data.protocol_type == USB_SC_RBC) {
        if (fsg->cmnd_size == 12)
            cmnd_size = 12;

    /* All the other protocols pad to 12 bytes */
    } else
        cmnd_size = 12;

    hdlen[0] = 0;
    if (fsg->data_dir != DATA_DIR_UNKNOWN)
        sprintf(hdlen, ", H%c=%u", dirletter[(int) fsg->data_dir],
                fsg->data_size);
    VDBG(fsg, "SCSI command: %s;  Dc=%d, D%c=%u;  Hc=%d%s\n",
            name, cmnd_size, dirletter[(int) data_dir],
            fsg->data_size_from_cmnd, fsg->cmnd_size, hdlen);

    /* We can't reply at all until we know the correct data direction
     * and size. */
    if (fsg->data_size_from_cmnd == 0)
        data_dir = DATA_DIR_NONE;
    if (fsg->data_dir == DATA_DIR_UNKNOWN) {    // CB or CBI
        fsg->data_dir = data_dir;
        fsg->data_size = fsg->data_size_from_cmnd;

    } else {                    // Bulk-only
        if (fsg->data_size < fsg->data_size_from_cmnd) {

            /* Host data size < Device data size is a phase error.
             * Carry out the command, but only transfer as much
             * as we are allowed. */
            fsg->data_size_from_cmnd = fsg->data_size;
            fsg->phase_error = 1;
        }
    }
    fsg->residue = fsg->usb_amount_left = fsg->data_size;

    /* Conflicting data directions is a phase error */
    if (fsg->data_dir != data_dir && fsg->data_size_from_cmnd > 0) {
        fsg->phase_error = 1;
        return -EINVAL;
    }

    /* Verify the length of the command itself */
    if (cmnd_size != fsg->cmnd_size) {

        /* Special case workaround: There are plenty of buggy SCSI
         * implementations. Many have issues with cbw->Length
         * field passing a wrong command size. For those cases we
         * always try to work around the problem by using the length
         * sent by the host side provided it is at least as large
         * as the correct command length.
         * Examples of such cases would be MS-Windows, which issues
         * REQUEST SENSE with cbw->Length == 12 where it should
         * be 6, and xbox360 issuing INQUIRY, TEST UNIT READY and
         * REQUEST SENSE with cbw->Length == 10 where it should
         * be 6 as well.
         */
        if (cmnd_size <= fsg->cmnd_size) {
            DBG(fsg, "%s is buggy! Expected length %d "
                    "but we got %d\n", name,
                    cmnd_size, fsg->cmnd_size);
            cmnd_size = fsg->cmnd_size;
        } else {
            fsg->phase_error = 1;
            return -EINVAL;
        }
    }

    /* Check that the LUN values are consistent */
    if (transport_is_bbb()) {
        if (fsg->lun != lun)
            DBG(fsg, "using LUN %d from CBW, "
                    "not LUN %d from CDB\n",
                    fsg->lun, lun);
    }

    /* Check the LUN */
    curlun = fsg->curlun;
    if (curlun) {
        if (fsg->cmnd[0] != REQUEST_SENSE) {
            curlun->sense_data = SS_NO_SENSE;
            curlun->sense_data_info = 0;
            curlun->info_valid = 0;
        }
    } else {
        fsg->bad_lun_okay = 0;

        /* INQUIRY and REQUEST SENSE commands are explicitly allowed
         * to use unsupported LUNs; all others may not. */
        if (fsg->cmnd[0] != INQUIRY &&
                fsg->cmnd[0] != REQUEST_SENSE) {
            DBG(fsg, "unsupported LUN %d\n", fsg->lun);
            return -EINVAL;
        }
    }

    /* If a unit attention condition exists, only INQUIRY and
     * REQUEST SENSE commands are allowed; anything else must fail. */
    if (curlun && curlun->unit_attention_data != SS_NO_SENSE &&
            fsg->cmnd[0] != INQUIRY &&
            fsg->cmnd[0] != REQUEST_SENSE) {
        curlun->sense_data = curlun->unit_attention_data;
        curlun->unit_attention_data = SS_NO_SENSE;
        return -EINVAL;
    }

    /* Check that only command bytes listed in the mask are non-zero */
    fsg->cmnd[1] &= 0x1f;           // Mask away the LUN
    for (i = 1; i < cmnd_size; ++i) {
        if (fsg->cmnd[i] && !(mask & (1 << i))) {
            if (curlun)
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
            return -EINVAL;
        }
    }

    /* If the medium isn't mounted and the command needs to access
     * it, return an error. */
    if (curlun && !fsg_lun_is_open(curlun) && needs_medium) {
        curlun->sense_data = SS_MEDIUM_NOT_PRESENT;
        return -EINVAL;
    }

    return 0;
}

/* wrapper of check_command for data size in blocks handling */
static int check_command_size_in_blocks(struct fsg_dev *fsg, int cmnd_size,
        enum data_direction data_dir, unsigned int mask,
        int needs_medium, const char *name)
{
    if (fsg->curlun)
        fsg->data_size_from_cmnd <<= fsg->curlun->blkbits;
    return check_command(fsg, cmnd_size, data_dir,
            mask, needs_medium, name);
}

static int do_scsi_command(struct fsg_dev *fsg)
{
    struct fsg_buffhd   *bh;
    int         rc;
    int         reply = -EINVAL;
    int         i;
    static char     unknown[16];

    dump_cdb(fsg);

    /* Wait for the next buffer to become available for data or status */
    bh = fsg->next_buffhd_to_drain = fsg->next_buffhd_to_fill;
    while (bh->state != BUF_STATE_EMPTY) {
        rc = sleep_thread(fsg);
        if (rc)
            return rc;
    }
    fsg->phase_error = 0;
    fsg->short_packet_received = 0;

    down_read(&fsg->filesem);   // We're using the backing file
    switch (fsg->cmnd[0]) {

    case INQUIRY:
        fsg->data_size_from_cmnd = fsg->cmnd[4];
        if ((reply = check_command(fsg, 6, DATA_DIR_TO_HOST,
                (1<<4), 0,
                "INQUIRY")) == 0)
            reply = do_inquiry(fsg, bh);
        break;

    case MODE_SELECT:
        fsg->data_size_from_cmnd = fsg->cmnd[4];
        if ((reply = check_command(fsg, 6, DATA_DIR_FROM_HOST,
                (1<<1) | (1<<4), 0,
                "MODE SELECT(6)")) == 0)
            reply = do_mode_select(fsg, bh);
        break;

    case MODE_SELECT_10:
        fsg->data_size_from_cmnd = get_unaligned_be16(&fsg->cmnd[7]);
        if ((reply = check_command(fsg, 10, DATA_DIR_FROM_HOST,
                (1<<1) | (3<<7), 0,
                "MODE SELECT(10)")) == 0)
            reply = do_mode_select(fsg, bh);
        break;

    case MODE_SENSE:
        fsg->data_size_from_cmnd = fsg->cmnd[4];
        if ((reply = check_command(fsg, 6, DATA_DIR_TO_HOST,
                (1<<1) | (1<<2) | (1<<4), 0,
                "MODE SENSE(6)")) == 0)
            reply = do_mode_sense(fsg, bh);
        break;

    case MODE_SENSE_10:
        fsg->data_size_from_cmnd = get_unaligned_be16(&fsg->cmnd[7]);
        if ((reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
                (1<<1) | (1<<2) | (3<<7), 0,
                "MODE SENSE(10)")) == 0)
            reply = do_mode_sense(fsg, bh);
        break;

    case ALLOW_MEDIUM_REMOVAL:
        fsg->data_size_from_cmnd = 0;
        if ((reply = check_command(fsg, 6, DATA_DIR_NONE,
                (1<<4), 0,
                "PREVENT-ALLOW MEDIUM REMOVAL")) == 0)
            reply = do_prevent_allow(fsg);
        break;

    case READ_6:
        i = fsg->cmnd[4];
        fsg->data_size_from_cmnd = (i == 0) ? 256 : i;
        if ((reply = check_command_size_in_blocks(fsg, 6,
                DATA_DIR_TO_HOST,
                (7<<1) | (1<<4), 1,
                "READ(6)")) == 0)
            reply = do_read(fsg);
        break;

    case READ_10:
        fsg->data_size_from_cmnd = get_unaligned_be16(&fsg->cmnd[7]);
        if ((reply = check_command_size_in_blocks(fsg, 10,
                DATA_DIR_TO_HOST,
                (1<<1) | (0xf<<2) | (3<<7), 1,
                "READ(10)")) == 0)
            reply = do_read(fsg);
        break;

    case READ_12:
        fsg->data_size_from_cmnd = get_unaligned_be32(&fsg->cmnd[6]);
        if ((reply = check_command_size_in_blocks(fsg, 12,
                DATA_DIR_TO_HOST,
                (1<<1) | (0xf<<2) | (0xf<<6), 1,
                "READ(12)")) == 0)
            reply = do_read(fsg);
        break;

    case READ_CAPACITY:
        fsg->data_size_from_cmnd = 8;
        if ((reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
                (0xf<<2) | (1<<8), 1,
                "READ CAPACITY")) == 0)
            reply = do_read_capacity(fsg, bh);
        break;

    case READ_HEADER:
        if (!mod_data.cdrom)
            goto unknown_cmnd;
        fsg->data_size_from_cmnd = get_unaligned_be16(&fsg->cmnd[7]);
        if ((reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
                (3<<7) | (0x1f<<1), 1,
                "READ HEADER")) == 0)
            reply = do_read_header(fsg, bh);
        break;

    case READ_TOC:
        if (!mod_data.cdrom)
            goto unknown_cmnd;
        fsg->data_size_from_cmnd = get_unaligned_be16(&fsg->cmnd[7]);
        if ((reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
                (7<<6) | (1<<1), 1,
                "READ TOC")) == 0)
            reply = do_read_toc(fsg, bh);
        break;

    case READ_FORMAT_CAPACITIES:
        fsg->data_size_from_cmnd = get_unaligned_be16(&fsg->cmnd[7]);
        if ((reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
                (3<<7), 1,
                "READ FORMAT CAPACITIES")) == 0)
            reply = do_read_format_capacities(fsg, bh);
        break;

    case REQUEST_SENSE:
        fsg->data_size_from_cmnd = fsg->cmnd[4];
        if ((reply = check_command(fsg, 6, DATA_DIR_TO_HOST,
                (1<<4), 0,
                "REQUEST SENSE")) == 0)
            reply = do_request_sense(fsg, bh);
        break;

    case START_STOP:
        fsg->data_size_from_cmnd = 0;
        if ((reply = check_command(fsg, 6, DATA_DIR_NONE,
                (1<<1) | (1<<4), 0,
                "START-STOP UNIT")) == 0)
            reply = do_start_stop(fsg);
        break;

    case SYNCHRONIZE_CACHE:
        fsg->data_size_from_cmnd = 0;
        if ((reply = check_command(fsg, 10, DATA_DIR_NONE,
                (0xf<<2) | (3<<7), 1,
                "SYNCHRONIZE CACHE")) == 0)
            reply = do_synchronize_cache(fsg);
        break;

    case TEST_UNIT_READY:
        fsg->data_size_from_cmnd = 0;
        reply = check_command(fsg, 6, DATA_DIR_NONE,
                0, 1,
                "TEST UNIT READY");
        break;

    /* Although optional, this command is used by MS-Windows.  We
     * support a minimal version: BytChk must be 0. */
    case VERIFY:
        fsg->data_size_from_cmnd = 0;
        if ((reply = check_command(fsg, 10, DATA_DIR_NONE,
                (1<<1) | (0xf<<2) | (3<<7), 1,
                "VERIFY")) == 0)
            reply = do_verify(fsg);
        break;

    case WRITE_6:
        i = fsg->cmnd[4];
        fsg->data_size_from_cmnd = (i == 0) ? 256 : i;
        if ((reply = check_command_size_in_blocks(fsg, 6,
                DATA_DIR_FROM_HOST,
                (7<<1) | (1<<4), 1,
                "WRITE(6)")) == 0)
            reply = do_write(fsg);
        break;

    case WRITE_10:
        fsg->data_size_from_cmnd = get_unaligned_be16(&fsg->cmnd[7]);
        if ((reply = check_command_size_in_blocks(fsg, 10,
                DATA_DIR_FROM_HOST,
                (1<<1) | (0xf<<2) | (3<<7), 1,
                "WRITE(10)")) == 0)
            reply = do_write(fsg);
        break;

    case WRITE_12:
        fsg->data_size_from_cmnd = get_unaligned_be32(&fsg->cmnd[6]);
        if ((reply = check_command_size_in_blocks(fsg, 12,
                DATA_DIR_FROM_HOST,
                (1<<1) | (0xf<<2) | (0xf<<6), 1,
                "WRITE(12)")) == 0)
            reply = do_write(fsg);
        break;

    /* Some mandatory commands that we recognize but don't implement.
     * They don't mean much in this setting.  It's left as an exercise
     * for anyone interested to implement RESERVE and RELEASE in terms
     * of Posix locks. */
    case FORMAT_UNIT:
    case RELEASE:
    case RESERVE:
    case SEND_DIAGNOSTIC:
        // Fall through

    default:
 unknown_cmnd:
        fsg->data_size_from_cmnd = 0;
        sprintf(unknown, "Unknown x%02x", fsg->cmnd[0]);
        if ((reply = check_command(fsg, fsg->cmnd_size,
                DATA_DIR_UNKNOWN, ~0, 0, unknown)) == 0) {
            fsg->curlun->sense_data = SS_INVALID_COMMAND;
            reply = -EINVAL;
        }
        break;
    }
    up_read(&fsg->filesem);

    if (reply == -EINTR || signal_pending(current))
        return -EINTR;

    /* Set up the single reply buffer for finish_reply() */
    if (reply == -EINVAL)
        reply = 0;      // Error reply length
    if (reply >= 0 && fsg->data_dir == DATA_DIR_TO_HOST) {
        reply = min((u32) reply, fsg->data_size_from_cmnd);
        bh->inreq->length = reply;
        bh->state = BUF_STATE_FULL;
        fsg->residue -= reply;
    }               // Otherwise it's already set

    return 0;
}


/*-------------------------------------------------------------------------*/

static int received_cbw(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
    struct usb_request      *req = bh->outreq;
    struct bulk_cb_wrap *cbw = req->buf;

    /* Was this a real packet?  Should it be ignored? */
    if (req->status || test_bit(IGNORE_BULK_OUT, &fsg->atomic_bitflags))
        return -EINVAL;

    /* Is the CBW valid? */
    if (req->actual != US_BULK_CB_WRAP_LEN ||
            cbw->Signature != cpu_to_le32(
                US_BULK_CB_SIGN)) {
        DBG(fsg, "invalid CBW: len %u sig 0x%x\n",
                req->actual,
                le32_to_cpu(cbw->Signature));

        /* The Bulk-only spec says we MUST stall the IN endpoint
         * (6.6.1), so it's unavoidable.  It also says we must
         * retain this state until the next reset, but there's
         * no way to tell the controller driver it should ignore
         * Clear-Feature(HALT) requests.
         *
         * We aren't required to halt the OUT endpoint; instead
         * we can simply accept and discard any data received
         * until the next reset. */
        wedge_bulk_in_endpoint(fsg);
        set_bit(IGNORE_BULK_OUT, &fsg->atomic_bitflags);
        return -EINVAL;
    }

    /* Is the CBW meaningful? */
    if (cbw->Lun >= FSG_MAX_LUNS || cbw->Flags & ~US_BULK_FLAG_IN ||
            cbw->Length <= 0 || cbw->Length > MAX_COMMAND_SIZE) {
        DBG(fsg, "non-meaningful CBW: lun = %u, flags = 0x%x, "
                "cmdlen %u\n",
                cbw->Lun, cbw->Flags, cbw->Length);

        /* We can do anything we want here, so let's stall the
         * bulk pipes if we are allowed to. */
        if (mod_data.can_stall) {
            fsg_set_halt(fsg, fsg->bulk_out);
            halt_bulk_in_endpoint(fsg);
        }
        return -EINVAL;
    }

    /* Save the command for later */
    fsg->cmnd_size = cbw->Length;
    memcpy(fsg->cmnd, cbw->CDB, fsg->cmnd_size);
    if (cbw->Flags & US_BULK_FLAG_IN)
        fsg->data_dir = DATA_DIR_TO_HOST;
    else
        fsg->data_dir = DATA_DIR_FROM_HOST;
    fsg->data_size = le32_to_cpu(cbw->DataTransferLength);
    if (fsg->data_size == 0)
        fsg->data_dir = DATA_DIR_NONE;
    fsg->lun = cbw->Lun;
    fsg->tag = cbw->Tag;
    return 0;
}


static int get_next_command(struct fsg_dev *fsg)
{
    struct fsg_buffhd   *bh;
    int         rc = 0;

    if (transport_is_bbb()) {

        /* Wait for the next buffer to become available */
        bh = fsg->next_buffhd_to_fill;
        while (bh->state != BUF_STATE_EMPTY) {
            rc = sleep_thread(fsg);
            if (rc)
                return rc;
        }

        /* Queue a request to read a Bulk-only CBW */
        set_bulk_out_req_length(fsg, bh, US_BULK_CB_WRAP_LEN);
        start_transfer(fsg, fsg->bulk_out, bh->outreq,
                &bh->outreq_busy, &bh->state);

        /* We will drain the buffer in software, which means we
         * can reuse it for the next filling.  No need to advance
         * next_buffhd_to_fill. */

        /* Wait for the CBW to arrive */
        while (bh->state != BUF_STATE_FULL) {
            rc = sleep_thread(fsg);
            if (rc)
                return rc;
        }
        smp_rmb();
        rc = received_cbw(fsg, bh);
        bh->state = BUF_STATE_EMPTY;

    } else {        // USB_PR_CB or USB_PR_CBI

        /* Wait for the next command to arrive */
        while (fsg->cbbuf_cmnd_size == 0) {
            rc = sleep_thread(fsg);
            if (rc)
                return rc;
        }

        /* Is the previous status interrupt request still busy?
         * The host is allowed to skip reading the status,
         * so we must cancel it. */
        if (fsg->intreq_busy)
            usb_ep_dequeue(fsg->intr_in, fsg->intreq);

        /* Copy the command and mark the buffer empty */
        fsg->data_dir = DATA_DIR_UNKNOWN;
        spin_lock_irq(&fsg->lock);
        fsg->cmnd_size = fsg->cbbuf_cmnd_size;
        memcpy(fsg->cmnd, fsg->cbbuf_cmnd, fsg->cmnd_size);
        fsg->cbbuf_cmnd_size = 0;
        spin_unlock_irq(&fsg->lock);

        /* Use LUN from the command */
        fsg->lun = fsg->cmnd[1] >> 5;
    }

    /* Update current lun */
    if (fsg->lun >= 0 && fsg->lun < fsg->nluns)
        fsg->curlun = &fsg->luns[fsg->lun];
    else
        fsg->curlun = NULL;

    return rc;
}


/*-------------------------------------------------------------------------*/

static int enable_endpoint(struct fsg_dev *fsg, struct usb_ep *ep,
        const struct usb_endpoint_descriptor *d)
{
    int rc;

    ep->driver_data = fsg;
    ep->desc = d;
    rc = usb_ep_enable(ep);
    if (rc)
        ERROR(fsg, "can't enable %s, result %d\n", ep->name, rc);
    return rc;
}

static int alloc_request(struct fsg_dev *fsg, struct usb_ep *ep,
        struct usb_request **preq)
{
    *preq = usb_ep_alloc_request(ep, GFP_ATOMIC);
    if (*preq)
        return 0;
    ERROR(fsg, "can't allocate request for %s\n", ep->name);
    return -ENOMEM;
}

/*
 * Reset interface setting and re-init endpoint state (toggle etc).
 * Call with altsetting < 0 to disable the interface.  The only other
 * available altsetting is 0, which enables the interface.
 */
static int do_set_interface(struct fsg_dev *fsg, int altsetting)
{
    int rc = 0;
    int i;
    const struct usb_endpoint_descriptor    *d;

    if (fsg->running)
        DBG(fsg, "reset interface\n");

reset:
    /* Deallocate the requests */
    for (i = 0; i < fsg_num_buffers; ++i) {
        struct fsg_buffhd *bh = &fsg->buffhds[i];

        if (bh->inreq) {
            usb_ep_free_request(fsg->bulk_in, bh->inreq);
            bh->inreq = NULL;
        }
        if (bh->outreq) {
            usb_ep_free_request(fsg->bulk_out, bh->outreq);
            bh->outreq = NULL;
        }
    }
    if (fsg->intreq) {
        usb_ep_free_request(fsg->intr_in, fsg->intreq);
        fsg->intreq = NULL;
    }

    /* Disable the endpoints */
    if (fsg->bulk_in_enabled) {
        usb_ep_disable(fsg->bulk_in);
        fsg->bulk_in_enabled = 0;
    }
    if (fsg->bulk_out_enabled) {
        usb_ep_disable(fsg->bulk_out);
        fsg->bulk_out_enabled = 0;
    }
    if (fsg->intr_in_enabled) {
        usb_ep_disable(fsg->intr_in);
        fsg->intr_in_enabled = 0;
    }

    fsg->running = 0;
    if (altsetting < 0 || rc != 0)
        return rc;

    DBG(fsg, "set interface %d\n", altsetting);

    /* Enable the endpoints */
    d = fsg_ep_desc(fsg->gadget,
            &fsg_fs_bulk_in_desc, &fsg_hs_bulk_in_desc,
            &fsg_ss_bulk_in_desc);
    if ((rc = enable_endpoint(fsg, fsg->bulk_in, d)) != 0)
        goto reset;
    fsg->bulk_in_enabled = 1;

    d = fsg_ep_desc(fsg->gadget,
            &fsg_fs_bulk_out_desc, &fsg_hs_bulk_out_desc,
            &fsg_ss_bulk_out_desc);
    if ((rc = enable_endpoint(fsg, fsg->bulk_out, d)) != 0)
        goto reset;
    fsg->bulk_out_enabled = 1;
    fsg->bulk_out_maxpacket = usb_endpoint_maxp(d);
    clear_bit(IGNORE_BULK_OUT, &fsg->atomic_bitflags);

    if (transport_is_cbi()) {
        d = fsg_ep_desc(fsg->gadget,
                &fsg_fs_intr_in_desc, &fsg_hs_intr_in_desc,
                &fsg_ss_intr_in_desc);
        if ((rc = enable_endpoint(fsg, fsg->intr_in, d)) != 0)
            goto reset;
        fsg->intr_in_enabled = 1;
    }

    /* Allocate the requests */
    for (i = 0; i < fsg_num_buffers; ++i) {
        struct fsg_buffhd   *bh = &fsg->buffhds[i];

        if ((rc = alloc_request(fsg, fsg->bulk_in, &bh->inreq)) != 0)
            goto reset;
        if ((rc = alloc_request(fsg, fsg->bulk_out, &bh->outreq)) != 0)
            goto reset;
        bh->inreq->buf = bh->outreq->buf = bh->buf;
        bh->inreq->context = bh->outreq->context = bh;
        bh->inreq->complete = bulk_in_complete;
        bh->outreq->complete = bulk_out_complete;
    }
    if (transport_is_cbi()) {
        if ((rc = alloc_request(fsg, fsg->intr_in, &fsg->intreq)) != 0)
            goto reset;
        fsg->intreq->complete = intr_in_complete;
    }

    fsg->running = 1;
    for (i = 0; i < fsg->nluns; ++i)
        fsg->luns[i].unit_attention_data = SS_RESET_OCCURRED;
    return rc;
}


/*
 * Change our operational configuration.  This code must agree with the code
 * that returns config descriptors, and with interface altsetting code.
 *
 * It's also responsible for power management interactions.  Some
 * configurations might not work with our current power sources.
 * For now we just assume the gadget is always self-powered.
 */
static int do_set_config(struct fsg_dev *fsg, u8 new_config)
{
    int rc = 0;

    /* Disable the single interface */
    if (fsg->config != 0) {
        DBG(fsg, "reset config\n");
        fsg->config = 0;
        rc = do_set_interface(fsg, -1);
    }

    /* Enable the interface */
    if (new_config != 0) {
        fsg->config = new_config;
        if ((rc = do_set_interface(fsg, 0)) != 0)
            fsg->config = 0;    // Reset on errors
        else
            INFO(fsg, "%s config #%d\n",
                 usb_speed_string(fsg->gadget->speed),
                 fsg->config);
    }
    return rc;
}


/*-------------------------------------------------------------------------*/

static void handle_exception(struct fsg_dev *fsg)
{
    siginfo_t       info;
    int         sig;
    int         i;
    int         num_active;
    struct fsg_buffhd   *bh;
    enum fsg_state      old_state;
    u8          new_config;
    struct fsg_lun      *curlun;
    unsigned int        exception_req_tag;
    int         rc;

    /* Clear the existing signals.  Anything but SIGUSR1 is converted
     * into a high-priority EXIT exception. */
    for (;;) {
        sig = dequeue_signal_lock(current, &current->blocked, &info);
        if (!sig)
            break;
        if (sig != SIGUSR1) {
            if (fsg->state < FSG_STATE_EXIT)
                DBG(fsg, "Main thread exiting on signal\n");
            raise_exception(fsg, FSG_STATE_EXIT);
        }
    }

    /* Cancel all the pending transfers */
    if (fsg->intreq_busy)
        usb_ep_dequeue(fsg->intr_in, fsg->intreq);
    for (i = 0; i < fsg_num_buffers; ++i) {
        bh = &fsg->buffhds[i];
        if (bh->inreq_busy)
            usb_ep_dequeue(fsg->bulk_in, bh->inreq);
        if (bh->outreq_busy)
            usb_ep_dequeue(fsg->bulk_out, bh->outreq);
    }

    /* Wait until everything is idle */
    for (;;) {
        num_active = fsg->intreq_busy;
        for (i = 0; i < fsg_num_buffers; ++i) {
            bh = &fsg->buffhds[i];
            num_active += bh->inreq_busy + bh->outreq_busy;
        }
        if (num_active == 0)
            break;
        if (sleep_thread(fsg))
            return;
    }

    /* Clear out the controller's fifos */
    if (fsg->bulk_in_enabled)
        usb_ep_fifo_flush(fsg->bulk_in);
    if (fsg->bulk_out_enabled)
        usb_ep_fifo_flush(fsg->bulk_out);
    if (fsg->intr_in_enabled)
        usb_ep_fifo_flush(fsg->intr_in);

    /* Reset the I/O buffer states and pointers, the SCSI
     * state, and the exception.  Then invoke the handler. */
    spin_lock_irq(&fsg->lock);

    for (i = 0; i < fsg_num_buffers; ++i) {
        bh = &fsg->buffhds[i];
        bh->state = BUF_STATE_EMPTY;
    }
    fsg->next_buffhd_to_fill = fsg->next_buffhd_to_drain =
            &fsg->buffhds[0];

    exception_req_tag = fsg->exception_req_tag;
    new_config = fsg->new_config;
    old_state = fsg->state;

    if (old_state == FSG_STATE_ABORT_BULK_OUT)
        fsg->state = FSG_STATE_STATUS_PHASE;
    else {
        for (i = 0; i < fsg->nluns; ++i) {
            curlun = &fsg->luns[i];
            curlun->prevent_medium_removal = 0;
            curlun->sense_data = curlun->unit_attention_data =
                    SS_NO_SENSE;
            curlun->sense_data_info = 0;
            curlun->info_valid = 0;
        }
        fsg->state = FSG_STATE_IDLE;
    }
    spin_unlock_irq(&fsg->lock);

    /* Carry out any extra actions required for the exception */
    switch (old_state) {
    default:
        break;

    case FSG_STATE_ABORT_BULK_OUT:
        send_status(fsg);
        spin_lock_irq(&fsg->lock);
        if (fsg->state == FSG_STATE_STATUS_PHASE)
            fsg->state = FSG_STATE_IDLE;
        spin_unlock_irq(&fsg->lock);
        break;

    case FSG_STATE_RESET:
        /* In case we were forced against our will to halt a
         * bulk endpoint, clear the halt now.  (The SuperH UDC
         * requires this.) */
        if (test_and_clear_bit(IGNORE_BULK_OUT, &fsg->atomic_bitflags))
            usb_ep_clear_halt(fsg->bulk_in);

        if (transport_is_bbb()) {
            if (fsg->ep0_req_tag == exception_req_tag)
                ep0_queue(fsg); // Complete the status stage

        } else if (transport_is_cbi())
            send_status(fsg);   // Status by interrupt pipe

        /* Technically this should go here, but it would only be
         * a waste of time.  Ditto for the INTERFACE_CHANGE and
         * CONFIG_CHANGE cases. */
        // for (i = 0; i < fsg->nluns; ++i)
        //  fsg->luns[i].unit_attention_data = SS_RESET_OCCURRED;
        break;

    case FSG_STATE_INTERFACE_CHANGE:
        rc = do_set_interface(fsg, 0);
        if (fsg->ep0_req_tag != exception_req_tag)
            break;
        if (rc != 0)            // STALL on errors
            fsg_set_halt(fsg, fsg->ep0);
        else                // Complete the status stage
            ep0_queue(fsg);
        break;

    case FSG_STATE_CONFIG_CHANGE:
        rc = do_set_config(fsg, new_config);
        if (fsg->ep0_req_tag != exception_req_tag)
            break;
        if (rc != 0)            // STALL on errors
            fsg_set_halt(fsg, fsg->ep0);
        else                // Complete the status stage
            ep0_queue(fsg);
        break;

    case FSG_STATE_DISCONNECT:
        for (i = 0; i < fsg->nluns; ++i)
            fsg_lun_fsync_sub(fsg->luns + i);
        do_set_config(fsg, 0);      // Unconfigured state
        break;

    case FSG_STATE_EXIT:
    case FSG_STATE_TERMINATED:
        do_set_config(fsg, 0);          // Free resources
        spin_lock_irq(&fsg->lock);
        fsg->state = FSG_STATE_TERMINATED;  // Stop the thread
        spin_unlock_irq(&fsg->lock);
        break;
    }
}


/*-------------------------------------------------------------------------*/

static int fsg_main_thread(void *fsg_)
{
    struct fsg_dev      *fsg = fsg_;

    /* Allow the thread to be killed by a signal, but set the signal mask
     * to block everything but INT, TERM, KILL, and USR1. */
    allow_signal(SIGINT);
    allow_signal(SIGTERM);
    allow_signal(SIGKILL);
    allow_signal(SIGUSR1);

    /* Allow the thread to be frozen */
    set_freezable();

    /* Arrange for userspace references to be interpreted as kernel
     * pointers.  That way we can pass a kernel pointer to a routine
     * that expects a __user pointer and it will work okay. */
    set_fs(get_ds());

    /* The main loop */
    while (fsg->state != FSG_STATE_TERMINATED) {
        if (exception_in_progress(fsg) || signal_pending(current)) {
            handle_exception(fsg);
            continue;
        }

        if (!fsg->running) {
            sleep_thread(fsg);
            continue;
        }

        if (get_next_command(fsg))
            continue;

        spin_lock_irq(&fsg->lock);
        if (!exception_in_progress(fsg))
            fsg->state = FSG_STATE_DATA_PHASE;
        spin_unlock_irq(&fsg->lock);

        if (do_scsi_command(fsg) || finish_reply(fsg))
            continue;

        spin_lock_irq(&fsg->lock);
        if (!exception_in_progress(fsg))
            fsg->state = FSG_STATE_STATUS_PHASE;
        spin_unlock_irq(&fsg->lock);

        if (send_status(fsg))
            continue;

        spin_lock_irq(&fsg->lock);
        if (!exception_in_progress(fsg))
            fsg->state = FSG_STATE_IDLE;
        spin_unlock_irq(&fsg->lock);
        }

    spin_lock_irq(&fsg->lock);
    fsg->thread_task = NULL;
    spin_unlock_irq(&fsg->lock);

    /* If we are exiting because of a signal, unregister the
     * gadget driver. */
    if (test_and_clear_bit(REGISTERED, &fsg->atomic_bitflags))
        usb_gadget_unregister_driver(&fsg_driver);

    /* Let the unbind and cleanup routines know the thread has exited */
    complete_and_exit(&fsg->thread_notifier, 0);
}


/*-------------------------------------------------------------------------*/


/* The write permissions and store_xxx pointers are set in fsg_bind() */
static DEVICE_ATTR(ro, 0444, fsg_show_ro, NULL);
static DEVICE_ATTR(nofua, 0644, fsg_show_nofua, NULL);
static DEVICE_ATTR(file, 0444, fsg_show_file, NULL);


/*-------------------------------------------------------------------------*/

static void fsg_release(struct kref *ref)
{
    struct fsg_dev  *fsg = container_of(ref, struct fsg_dev, ref);

    kfree(fsg->luns);
    kfree(fsg);
}

static void lun_release(struct device *dev)
{
    struct rw_semaphore *filesem = dev_get_drvdata(dev);
    struct fsg_dev      *fsg =
        container_of(filesem, struct fsg_dev, filesem);

    kref_put(&fsg->ref, fsg_release);
}

static void /* __init_or_exit */ fsg_unbind(struct usb_gadget *gadget)
{
    struct fsg_dev      *fsg = get_gadget_data(gadget);
    int         i;
    struct fsg_lun      *curlun;
    struct usb_request  *req = fsg->ep0req;

    DBG(fsg, "unbind\n");
    clear_bit(REGISTERED, &fsg->atomic_bitflags);

    /* If the thread isn't already dead, tell it to exit now */
    if (fsg->state != FSG_STATE_TERMINATED) {
        raise_exception(fsg, FSG_STATE_EXIT);
        wait_for_completion(&fsg->thread_notifier);

        /* The cleanup routine waits for this completion also */
        complete(&fsg->thread_notifier);
    }

    /* Unregister the sysfs attribute files and the LUNs */
    for (i = 0; i < fsg->nluns; ++i) {
        curlun = &fsg->luns[i];
        if (curlun->registered) {
            device_remove_file(&curlun->dev, &dev_attr_nofua);
            device_remove_file(&curlun->dev, &dev_attr_ro);
            device_remove_file(&curlun->dev, &dev_attr_file);
            fsg_lun_close(curlun);
            device_unregister(&curlun->dev);
            curlun->registered = 0;
        }
    }

    /* Free the data buffers */
    for (i = 0; i < fsg_num_buffers; ++i)
        kfree(fsg->buffhds[i].buf);

    /* Free the request and buffer for endpoint 0 */
    if (req) {
        kfree(req->buf);
        usb_ep_free_request(fsg->ep0, req);
    }

    set_gadget_data(gadget, NULL);
}


static int __init check_parameters(struct fsg_dev *fsg)
{
    int prot;

    /* Store the default values */
    mod_data.transport_type = USB_PR_BULK;
    mod_data.transport_name = "Bulk-only";
    mod_data.protocol_type = USB_SC_SCSI;
    mod_data.protocol_name = "Transparent SCSI";

    /* Some peripheral controllers are known not to be able to
     * halt bulk endpoints correctly.  If one of them is present,
     * disable stalls.
     */
    if (gadget_is_at91(fsg->gadget))
        mod_data.can_stall = 0;

    if (mod_data.release == 0xffff)
        mod_data.release = get_default_bcdDevice();

    prot = simple_strtol(mod_data.protocol_parm, NULL, 0);

#ifdef CONFIG_USB_FILE_STORAGE_TEST
    if (strnicmp(mod_data.transport_parm, "BBB", 10) == 0) {
        ;       // Use default setting
    } else if (strnicmp(mod_data.transport_parm, "CB", 10) == 0) {
        mod_data.transport_type = USB_PR_CB;
        mod_data.transport_name = "Control-Bulk";
    } else if (strnicmp(mod_data.transport_parm, "CBI", 10) == 0) {
        mod_data.transport_type = USB_PR_CBI;
        mod_data.transport_name = "Control-Bulk-Interrupt";
    } else {
        ERROR(fsg, "invalid transport: %s\n", mod_data.transport_parm);
        return -EINVAL;
    }

    if (strnicmp(mod_data.protocol_parm, "SCSI", 10) == 0 ||
            prot == USB_SC_SCSI) {
        ;       // Use default setting
    } else if (strnicmp(mod_data.protocol_parm, "RBC", 10) == 0 ||
            prot == USB_SC_RBC) {
        mod_data.protocol_type = USB_SC_RBC;
        mod_data.protocol_name = "RBC";
    } else if (strnicmp(mod_data.protocol_parm, "8020", 4) == 0 ||
            strnicmp(mod_data.protocol_parm, "ATAPI", 10) == 0 ||
            prot == USB_SC_8020) {
        mod_data.protocol_type = USB_SC_8020;
        mod_data.protocol_name = "8020i (ATAPI)";
    } else if (strnicmp(mod_data.protocol_parm, "QIC", 3) == 0 ||
            prot == USB_SC_QIC) {
        mod_data.protocol_type = USB_SC_QIC;
        mod_data.protocol_name = "QIC-157";
    } else if (strnicmp(mod_data.protocol_parm, "UFI", 10) == 0 ||
            prot == USB_SC_UFI) {
        mod_data.protocol_type = USB_SC_UFI;
        mod_data.protocol_name = "UFI";
    } else if (strnicmp(mod_data.protocol_parm, "8070", 4) == 0 ||
            prot == USB_SC_8070) {
        mod_data.protocol_type = USB_SC_8070;
        mod_data.protocol_name = "8070i";
    } else {
        ERROR(fsg, "invalid protocol: %s\n", mod_data.protocol_parm);
        return -EINVAL;
    }

    mod_data.buflen &= PAGE_CACHE_MASK;
    if (mod_data.buflen <= 0) {
        ERROR(fsg, "invalid buflen\n");
        return -ETOOSMALL;
    }

#endif /* CONFIG_USB_FILE_STORAGE_TEST */

    /* Serial string handling.
     * On a real device, the serial string would be loaded
     * from permanent storage. */
    if (mod_data.serial) {
        const char *ch;
        unsigned len = 0;

        /* Sanity check :
         * The CB[I] specification limits the serial string to
         * 12 uppercase hexadecimal characters.
         * BBB need at least 12 uppercase hexadecimal characters,
         * with a maximum of 126. */
        for (ch = mod_data.serial; *ch; ++ch) {
            ++len;
            if ((*ch < '0' || *ch > '9') &&
                (*ch < 'A' || *ch > 'F')) { /* not uppercase hex */
                WARNING(fsg,
                    "Invalid serial string character: %c\n",
                    *ch);
                goto no_serial;
            }
        }
        if (len > 126 ||
            (mod_data.transport_type == USB_PR_BULK && len < 12) ||
            (mod_data.transport_type != USB_PR_BULK && len > 12)) {
            WARNING(fsg, "Invalid serial string length!\n");
            goto no_serial;
        }
        fsg_strings[FSG_STRING_SERIAL - 1].s = mod_data.serial;
    } else {
        WARNING(fsg, "No serial-number string provided!\n");
 no_serial:
        device_desc.iSerialNumber = 0;
    }

    return 0;
}


static int __init fsg_bind(struct usb_gadget *gadget,
        struct usb_gadget_driver *driver)
{
    struct fsg_dev      *fsg = the_fsg;
    int         rc;
    int         i;
    struct fsg_lun      *curlun;
    struct usb_ep       *ep;
    struct usb_request  *req;
    char            *pathbuf, *p;

    fsg->gadget = gadget;
    set_gadget_data(gadget, fsg);
    fsg->ep0 = gadget->ep0;
    fsg->ep0->driver_data = fsg;

    if ((rc = check_parameters(fsg)) != 0)
        goto out;

    if (mod_data.removable) {   // Enable the store_xxx attributes
        dev_attr_file.attr.mode = 0644;
        dev_attr_file.store = fsg_store_file;
        if (!mod_data.cdrom) {
            dev_attr_ro.attr.mode = 0644;
            dev_attr_ro.store = fsg_store_ro;
        }
    }

    /* Only for removable media? */
    dev_attr_nofua.attr.mode = 0644;
    dev_attr_nofua.store = fsg_store_nofua;

    /* Find out how many LUNs there should be */
    i = mod_data.nluns;
    if (i == 0)
        i = max(mod_data.num_filenames, 1u);
    if (i > FSG_MAX_LUNS) {
        ERROR(fsg, "invalid number of LUNs: %d\n", i);
        rc = -EINVAL;
        goto out;
    }

    /* Create the LUNs, open their backing files, and register the
     * LUN devices in sysfs. */
    fsg->luns = kzalloc(i * sizeof(struct fsg_lun), GFP_KERNEL);
    if (!fsg->luns) {
        rc = -ENOMEM;
        goto out;
    }
    fsg->nluns = i;

    for (i = 0; i < fsg->nluns; ++i) {
        curlun = &fsg->luns[i];
        curlun->cdrom = !!mod_data.cdrom;
        curlun->ro = mod_data.cdrom || mod_data.ro[i];
        curlun->initially_ro = curlun->ro;
        curlun->removable = mod_data.removable;
        curlun->nofua = mod_data.nofua[i];
        curlun->dev.release = lun_release;
        curlun->dev.parent = &gadget->dev;
        curlun->dev.driver = &fsg_driver.driver;
        dev_set_drvdata(&curlun->dev, &fsg->filesem);
        dev_set_name(&curlun->dev,"%s-lun%d",
                 dev_name(&gadget->dev), i);

        kref_get(&fsg->ref);
        rc = device_register(&curlun->dev);
        if (rc) {
            INFO(fsg, "failed to register LUN%d: %d\n", i, rc);
            put_device(&curlun->dev);
            goto out;
        }
        curlun->registered = 1;

        rc = device_create_file(&curlun->dev, &dev_attr_ro);
        if (rc)
            goto out;
        rc = device_create_file(&curlun->dev, &dev_attr_nofua);
        if (rc)
            goto out;
        rc = device_create_file(&curlun->dev, &dev_attr_file);
        if (rc)
            goto out;

        if (mod_data.file[i] && *mod_data.file[i]) {
            rc = fsg_lun_open(curlun, mod_data.file[i]);
            if (rc)
                goto out;
        } else if (!mod_data.removable) {
            ERROR(fsg, "no file given for LUN%d\n", i);
            rc = -EINVAL;
            goto out;
        }
    }

    /* Find all the endpoints we will use */
    usb_ep_autoconfig_reset(gadget);
    ep = usb_ep_autoconfig(gadget, &fsg_fs_bulk_in_desc);
    if (!ep)
        goto autoconf_fail;
    ep->driver_data = fsg;      // claim the endpoint
    fsg->bulk_in = ep;

    ep = usb_ep_autoconfig(gadget, &fsg_fs_bulk_out_desc);
    if (!ep)
        goto autoconf_fail;
    ep->driver_data = fsg;      // claim the endpoint
    fsg->bulk_out = ep;

    if (transport_is_cbi()) {
        ep = usb_ep_autoconfig(gadget, &fsg_fs_intr_in_desc);
        if (!ep)
            goto autoconf_fail;
        ep->driver_data = fsg;      // claim the endpoint
        fsg->intr_in = ep;
    }

    /* Fix up the descriptors */
    device_desc.idVendor = cpu_to_le16(mod_data.vendor);
    device_desc.idProduct = cpu_to_le16(mod_data.product);
    device_desc.bcdDevice = cpu_to_le16(mod_data.release);

    i = (transport_is_cbi() ? 3 : 2);   // Number of endpoints
    fsg_intf_desc.bNumEndpoints = i;
    fsg_intf_desc.bInterfaceSubClass = mod_data.protocol_type;
    fsg_intf_desc.bInterfaceProtocol = mod_data.transport_type;
    fsg_fs_function[i + FSG_FS_FUNCTION_PRE_EP_ENTRIES] = NULL;

    if (gadget_is_dualspeed(gadget)) {
        fsg_hs_function[i + FSG_HS_FUNCTION_PRE_EP_ENTRIES] = NULL;

        /* Assume endpoint addresses are the same for both speeds */
        fsg_hs_bulk_in_desc.bEndpointAddress =
            fsg_fs_bulk_in_desc.bEndpointAddress;
        fsg_hs_bulk_out_desc.bEndpointAddress =
            fsg_fs_bulk_out_desc.bEndpointAddress;
        fsg_hs_intr_in_desc.bEndpointAddress =
            fsg_fs_intr_in_desc.bEndpointAddress;
    }

    if (gadget_is_superspeed(gadget)) {
        unsigned        max_burst;

        fsg_ss_function[i + FSG_SS_FUNCTION_PRE_EP_ENTRIES] = NULL;

        /* Calculate bMaxBurst, we know packet size is 1024 */
        max_burst = min_t(unsigned, mod_data.buflen / 1024, 15);

        /* Assume endpoint addresses are the same for both speeds */
        fsg_ss_bulk_in_desc.bEndpointAddress =
            fsg_fs_bulk_in_desc.bEndpointAddress;
        fsg_ss_bulk_in_comp_desc.bMaxBurst = max_burst;

        fsg_ss_bulk_out_desc.bEndpointAddress =
            fsg_fs_bulk_out_desc.bEndpointAddress;
        fsg_ss_bulk_out_comp_desc.bMaxBurst = max_burst;
    }

    if (gadget_is_otg(gadget))
        fsg_otg_desc.bmAttributes |= USB_OTG_HNP;

    rc = -ENOMEM;

    /* Allocate the request and buffer for endpoint 0 */
    fsg->ep0req = req = usb_ep_alloc_request(fsg->ep0, GFP_KERNEL);
    if (!req)
        goto out;
    req->buf = kmalloc(EP0_BUFSIZE, GFP_KERNEL);
    if (!req->buf)
        goto out;
    req->complete = ep0_complete;

    /* Allocate the data buffers */
    for (i = 0; i < fsg_num_buffers; ++i) {
        struct fsg_buffhd   *bh = &fsg->buffhds[i];

        /* Allocate for the bulk-in endpoint.  We assume that
         * the buffer will also work with the bulk-out (and
         * interrupt-in) endpoint. */
        bh->buf = kmalloc(mod_data.buflen, GFP_KERNEL);
        if (!bh->buf)
            goto out;
        bh->next = bh + 1;
    }
    fsg->buffhds[fsg_num_buffers - 1].next = &fsg->buffhds[0];

    /* This should reflect the actual gadget power source */
    usb_gadget_set_selfpowered(gadget);

    snprintf(fsg_string_manufacturer, sizeof fsg_string_manufacturer,
            "%s %s with %s",
            init_utsname()->sysname, init_utsname()->release,
            gadget->name);

    fsg->thread_task = kthread_create(fsg_main_thread, fsg,
            "file-storage-gadget");
    if (IS_ERR(fsg->thread_task)) {
        rc = PTR_ERR(fsg->thread_task);
        goto out;
    }

    INFO(fsg, DRIVER_DESC ", version: " DRIVER_VERSION "\n");
    INFO(fsg, "NOTE: This driver is deprecated.  "
            "Consider using g_mass_storage instead.\n");
    INFO(fsg, "Number of LUNs=%d\n", fsg->nluns);

    pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
    for (i = 0; i < fsg->nluns; ++i) {
        curlun = &fsg->luns[i];
        if (fsg_lun_is_open(curlun)) {
            p = NULL;
            if (pathbuf) {
                p = d_path(&curlun->filp->f_path,
                       pathbuf, PATH_MAX);
                if (IS_ERR(p))
                    p = NULL;
            }
            LINFO(curlun, "ro=%d, nofua=%d, file: %s\n",
                  curlun->ro, curlun->nofua, (p ? p : "(error)"));
        }
    }
    kfree(pathbuf);

    DBG(fsg, "transport=%s (x%02x)\n",
            mod_data.transport_name, mod_data.transport_type);
    DBG(fsg, "protocol=%s (x%02x)\n",
            mod_data.protocol_name, mod_data.protocol_type);
    DBG(fsg, "VendorID=x%04x, ProductID=x%04x, Release=x%04x\n",
            mod_data.vendor, mod_data.product, mod_data.release);
    DBG(fsg, "removable=%d, stall=%d, cdrom=%d, buflen=%u\n",
            mod_data.removable, mod_data.can_stall,
            mod_data.cdrom, mod_data.buflen);
    DBG(fsg, "I/O thread pid: %d\n", task_pid_nr(fsg->thread_task));

    set_bit(REGISTERED, &fsg->atomic_bitflags);

    /* Tell the thread to start working */
    wake_up_process(fsg->thread_task);
    return 0;

autoconf_fail:
    ERROR(fsg, "unable to autoconfigure all endpoints\n");
    rc = -ENOTSUPP;

out:
    fsg->state = FSG_STATE_TERMINATED;  // The thread is dead
    fsg_unbind(gadget);
    complete(&fsg->thread_notifier);
    return rc;
}


/*-------------------------------------------------------------------------*/

static void fsg_suspend(struct usb_gadget *gadget)
{
    struct fsg_dev      *fsg = get_gadget_data(gadget);

    DBG(fsg, "suspend\n");
    set_bit(SUSPENDED, &fsg->atomic_bitflags);
}

static void fsg_resume(struct usb_gadget *gadget)
{
    struct fsg_dev      *fsg = get_gadget_data(gadget);

    DBG(fsg, "resume\n");
    clear_bit(SUSPENDED, &fsg->atomic_bitflags);
}


/*-------------------------------------------------------------------------*/

static __refdata struct usb_gadget_driver       fsg_driver = {
    .max_speed  = USB_SPEED_SUPER,
    .function   = (char *) fsg_string_product,
    .bind       = fsg_bind,
    .unbind     = fsg_unbind,
    .disconnect = fsg_disconnect,
    .setup      = fsg_setup,
    .suspend    = fsg_suspend,
    .resume     = fsg_resume,

    .driver     = {
        .name       = DRIVER_NAME,
        .owner      = THIS_MODULE,
        // .release = ...
        // .suspend = ...
        // .resume = ...
    },
};


static int __init fsg_alloc(void)
{
    struct fsg_dev      *fsg;

    fsg = kzalloc(sizeof *fsg +
              fsg_num_buffers * sizeof *(fsg->buffhds), GFP_KERNEL);

    if (!fsg)
        return -ENOMEM;
    spin_lock_init(&fsg->lock);
    init_rwsem(&fsg->filesem);
    kref_init(&fsg->ref);
    init_completion(&fsg->thread_notifier);

    the_fsg = fsg;
    return 0;
}


static int __init fsg_init(void)
{
    int     rc;
    struct fsg_dev  *fsg;

    rc = fsg_num_buffers_validate();
    if (rc != 0)
        return rc;

    if ((rc = fsg_alloc()) != 0)
        return rc;
    fsg = the_fsg;
    rc = usb_gadget_probe_driver(&fsg_driver);
    if (rc != 0)
        kref_put(&fsg->ref, fsg_release);
    return rc;
}
module_init(fsg_init);


static void __exit fsg_cleanup(void)
{
    struct fsg_dev  *fsg = the_fsg;

    /* Unregister the driver iff the thread hasn't already done so */
    if (test_and_clear_bit(REGISTERED, &fsg->atomic_bitflags))
        usb_gadget_unregister_driver(&fsg_driver);

    /* Wait for the thread to finish up */
    wait_for_completion(&fsg->thread_notifier);

    kref_put(&fsg->ref, fsg_release);
}
module_exit(fsg_cleanup);