f_mass_storage.c

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/*
 * f_mass_storage.c -- Mass Storage USB Composite Function
 *
 * Copyright (C) 2003-2008 Alan Stern
 * Copyright (C) 2009 Samsung Electronics
 *                    Author: Michal Nazarewicz <[email protected]>
 * 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 Mass Storage Function 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 composite
 * function for a USB device, it also illustrates a technique of
 * double-buffering for increased throughput.
 *
 * For more information about MSF and in particular its module
 * parameters and sysfs interface read the
 * <Documentation/usb/mass-storage.txt> file.
 */

/*
 * MSF is configured by specifying a fsg_config structure.  It has the
 * following fields:
 *
 *  nluns       Number of LUNs function have (anywhere from 1
 *              to FSG_MAX_LUNS which is 8).
 *  luns        An array of LUN configuration values.  This
 *              should be filled for each LUN that
 *              function will include (ie. for "nluns"
 *              LUNs).  Each element of the array has
 *              the following fields:
 *  ->filename  The path to the backing file for the LUN.
 *              Required if LUN is not marked as
 *              removable.
 *  ->ro        Flag specifying access to the LUN shall be
 *              read-only.  This is implied if CD-ROM
 *              emulation is enabled as well as when
 *              it was impossible to open "filename"
 *              in R/W mode.
 *  ->removable Flag specifying that LUN shall be indicated as
 *              being removable.
 *  ->cdrom     Flag specifying that LUN shall be reported as
 *              being a CD-ROM.
 *  ->nofua     Flag specifying that FUA flag in SCSI WRITE(10,12)
 *              commands for this LUN shall be ignored.
 *
 *  vendor_name
 *  product_name
 *  release     Information used as a reply to INQUIRY
 *              request.  To use default set to NULL,
 *              NULL, 0xffff respectively.  The first
 *              field should be 8 and the second 16
 *              characters or less.
 *
 *  can_stall   Set to permit function to halt bulk endpoints.
 *              Disabled on some USB devices known not
 *              to work correctly.  You should set it
 *              to true.
 *
 * If "removable" is not set for a LUN then a backing file must be
 * specified.  If it is set, then NULL filename means the LUN's medium
 * is not loaded (an empty string as "filename" in the fsg_config
 * structure causes error).  The CD-ROM emulation includes a single
 * data track and no audio tracks; hence there need be only one
 * backing file per LUN.
 *
 * This function is heavily based on "File-backed Storage Gadget" by
 * Alan Stern which in turn 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 MSF 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.  As of this moment, MSF
 * provides no way to deregister the gadget when thread dies -- maybe
 * a callback functions is needed.
 *
 * 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/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/ch9.h>
#include <linux/usb/gadget.h>
#include <linux/usb/composite.h>

#include "gadget_chips.h"


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

#define FSG_DRIVER_DESC     "Mass Storage Function"
#define FSG_DRIVER_VERSION  "2009/09/11"

static const char fsg_string_interface[] = "Mass Storage";

#define FSG_NO_DEVICE_STRINGS    1
#define FSG_NO_OTG               1
#define FSG_NO_INTR_EP           1

#include "storage_common.c"


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

struct fsg_dev;
struct fsg_common;

/* FSF callback functions */
struct fsg_operations {
    /*
     * Callback function to call when thread exits.  If no
     * callback is set or it returns value lower then zero MSF
     * will force eject all LUNs it operates on (including those
     * marked as non-removable or with prevent_medium_removal flag
     * set).
     */
    int (*thread_exits)(struct fsg_common *common);

    /*
     * Called prior to ejection.  Negative return means error,
     * zero means to continue with ejection, positive means not to
     * eject.
     */
    int (*pre_eject)(struct fsg_common *common,
             struct fsg_lun *lun, int num);
    /*
     * Called after ejection.  Negative return means error, zero
     * or positive is just a success.
     */
    int (*post_eject)(struct fsg_common *common,
              struct fsg_lun *lun, int num);
};

/* Data shared by all the FSG instances. */
struct fsg_common {
    struct usb_gadget   *gadget;
    struct usb_composite_dev *cdev;
    struct fsg_dev      *fsg, *new_fsg;
    wait_queue_head_t   fsg_wait;

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

    /* lock protects: state, all the req_busy's */
    spinlock_t      lock;

    struct usb_ep       *ep0;       /* Copy of gadget->ep0 */
    struct usb_request  *ep0req;    /* Copy of cdev->req */
    unsigned int        ep0_req_tag;

    struct fsg_buffhd   *next_buffhd_to_fill;
    struct fsg_buffhd   *next_buffhd_to_drain;
    struct fsg_buffhd   *buffhds;

    int         cmnd_size;
    u8          cmnd[MAX_COMMAND_SIZE];

    unsigned int        nluns;
    unsigned int        lun;
    struct fsg_lun      *luns;
    struct fsg_lun      *curlun;

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

    enum data_direction data_dir;
    u32         data_size;
    u32         data_size_from_cmnd;
    u32         tag;
    u32         residue;
    u32         usb_amount_left;

    unsigned int        can_stall:1;
    unsigned int        free_storage_on_release:1;
    unsigned int        phase_error:1;
    unsigned int        short_packet_received:1;
    unsigned int        bad_lun_okay:1;
    unsigned int        running:1;

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

    /* Callback functions. */
    const struct fsg_operations *ops;
    /* Gadget's private data. */
    void            *private_data;

    /*
     * Vendor (8 chars), product (16 chars), release (4
     * hexadecimal digits) and NUL byte
     */
    char inquiry_string[8 + 16 + 4 + 1];

    struct kref     ref;
};

struct fsg_config {
    unsigned nluns;
    struct fsg_lun_config {
        const char *filename;
        char ro;
        char removable;
        char cdrom;
        char nofua;
    } luns[FSG_MAX_LUNS];

    /* Callback functions. */
    const struct fsg_operations *ops;
    /* Gadget's private data. */
    void            *private_data;

    const char *vendor_name;        /*  8 characters or less */
    const char *product_name;       /* 16 characters or less */
    u16 release;

    char            can_stall;
};

struct fsg_dev {
    struct usb_function function;
    struct usb_gadget   *gadget;    /* Copy of cdev->gadget */
    struct fsg_common   *common;

    u16         interface_number;

    unsigned int        bulk_in_enabled:1;
    unsigned int        bulk_out_enabled:1;

    unsigned long       atomic_bitflags;
#define IGNORE_BULK_OUT     0

    struct usb_ep       *bulk_in;
    struct usb_ep       *bulk_out;
};

static inline int __fsg_is_set(struct fsg_common *common,
                   const char *func, unsigned line)
{
    if (common->fsg)
        return 1;
    ERROR(common, "common->fsg is NULL in %s at %u\n", func, line);
    WARN_ON(1);
    return 0;
}

#define fsg_is_set(common) likely(__fsg_is_set(common, __func__, __LINE__))

static inline struct fsg_dev *fsg_from_func(struct usb_function *f)
{
    return container_of(f, struct fsg_dev, function);
}

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

static int exception_in_progress(struct fsg_common *common)
{
    return common->state > FSG_STATE_IDLE;
}

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

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


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

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);
}


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

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

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

static void raise_exception(struct fsg_common *common, 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(&common->lock, flags);
    if (common->state <= new_state) {
        common->exception_req_tag = common->ep0_req_tag;
        common->state = new_state;
        if (common->thread_task)
            send_sig_info(SIGUSR1, SEND_SIG_FORCED,
                      common->thread_task);
    }
    spin_unlock_irqrestore(&common->lock, flags);
}


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

static int ep0_queue(struct fsg_common *common)
{
    int rc;

    rc = usb_ep_queue(common->ep0, common->ep0req, GFP_ATOMIC);
    common->ep0->driver_data = common;
    if (rc != 0 && rc != -ESHUTDOWN) {
        /* We can't do much more than wait for a reset */
        WARNING(common, "error in submission: %s --> %d\n",
            common->ep0->name, rc);
    }
    return rc;
}


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

/* Completion handlers. These always run in_irq. */

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

    if (req->status || req->actual != req->length)
        DBG(common, "%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(&common->lock);
    bh->inreq_busy = 0;
    bh->state = BUF_STATE_EMPTY;
    wakeup_thread(common);
    spin_unlock(&common->lock);
}

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

    dump_msg(common, "bulk-out", req->buf, req->actual);
    if (req->status || req->actual != bh->bulk_out_intended_length)
        DBG(common, "%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(&common->lock);
    bh->outreq_busy = 0;
    bh->state = BUF_STATE_FULL;
    wakeup_thread(common);
    spin_unlock(&common->lock);
}

static int fsg_setup(struct usb_function *f,
             const struct usb_ctrlrequest *ctrl)
{
    struct fsg_dev      *fsg = fsg_from_func(f);
    struct usb_request  *req = fsg->common->ep0req;
    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_is_set(fsg->common))
        return -EOPNOTSUPP;

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

    switch (ctrl->bRequest) {

    case US_BULK_RESET_REQUEST:
        if (ctrl->bRequestType !=
            (USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE))
            break;
        if (w_index != fsg->interface_number || w_value != 0 ||
                w_length != 0)
            return -EDOM;

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

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

        /* Respond with data/status */
        req->length = min((u16)1, w_length);
        return ep0_queue(fsg->common);
    }

    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 -EOPNOTSUPP;
}


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

/* 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);

    spin_lock_irq(&fsg->common->lock);
    *pbusy = 1;
    *state = BUF_STATE_BUSY;
    spin_unlock_irq(&fsg->common->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 bool start_in_transfer(struct fsg_common *common, struct fsg_buffhd *bh)
{
    if (!fsg_is_set(common))
        return false;
    start_transfer(common->fsg, common->fsg->bulk_in,
               bh->inreq, &bh->inreq_busy, &bh->state);
    return true;
}

static bool start_out_transfer(struct fsg_common *common, struct fsg_buffhd *bh)
{
    if (!fsg_is_set(common))
        return false;
    start_transfer(common->fsg, common->fsg->bulk_out,
               bh->outreq, &bh->outreq_busy, &bh->state);
    return true;
}

static int sleep_thread(struct fsg_common *common)
{
    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 (common->thread_wakeup_needed)
            break;
        schedule();
    }
    __set_current_state(TASK_RUNNING);
    common->thread_wakeup_needed = 0;
    return rc;
}


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

static int do_read(struct fsg_common *common)
{
    struct fsg_lun      *curlun = common->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 (common->cmnd[0] == READ_6)
        lba = get_unaligned_be24(&common->cmnd[1]);
    else {
        lba = get_unaligned_be32(&common->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 ((common->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 = common->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(amount_left, FSG_BUFLEN);
        amount = min((loff_t)amount,
                 curlun->file_length - file_offset);

        /* Wait for the next buffer to become available */
        bh = common->next_buffhd_to_fill;
        while (bh->state != BUF_STATE_EMPTY) {
            rc = sleep_thread(common);
            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;
        common->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;
        if (!start_in_transfer(common, bh))
            /* Don't know what to do if common->fsg is NULL */
            return -EIO;
        common->next_buffhd_to_fill = bh->next;
    }

    return -EIO;        /* No default reply */
}


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

static int do_write(struct fsg_common *common)
{
    struct fsg_lun      *curlun = common->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 (common->cmnd[0] == WRITE_6)
        lba = get_unaligned_be24(&common->cmnd[1]);
    else {
        lba = get_unaligned_be32(&common->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 (common->cmnd[1] & ~0x18) {
            curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
            return -EINVAL;
        }
        if (!curlun->nofua && (common->cmnd[1] & 0x08)) { /* FUA */
            spin_lock(&curlun->filp->f_lock);
            curlun->filp->f_flags |= O_SYNC;
            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 = common->data_size_from_cmnd;
    amount_left_to_write = common->data_size_from_cmnd;

    while (amount_left_to_write > 0) {

        /* Queue a request for more data from the host */
        bh = common->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, FSG_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;
            common->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(common, bh, amount);
            if (!start_out_transfer(common, bh))
                /* Dunno what to do if common->fsg is NULL */
                return -EIO;
            common->next_buffhd_to_fill = bh->next;
            continue;
        }

        /* Write the received data to the backing file */
        bh = common->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();
            common->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;
            common->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) {
                common->short_packet_received = 1;
                break;
            }
            continue;
        }

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

    return -EIO;        /* No default reply */
}


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

static int do_synchronize_cache(struct fsg_common *common)
{
    struct fsg_lun  *curlun = common->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_common *common)
{
    struct fsg_lun      *curlun = common->curlun;
    u32         lba;
    u32         verification_length;
    struct fsg_buffhd   *bh = common->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(&common->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 (common->cmnd[1] & ~0x10) {
        curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
        return -EINVAL;
    }

    verification_length = get_unaligned_be16(&common->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(amount_left, FSG_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_common *common, struct fsg_buffhd *bh)
{
    struct fsg_lun *curlun = common->curlun;
    u8  *buf = (u8 *) bh->buf;

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

    buf[0] = curlun->cdrom ? TYPE_ROM : TYPE_DISK;
    buf[1] = curlun->removable ? 0x80 : 0;
    buf[2] = 2;     /* ANSI SCSI level 2 */
    buf[3] = 2;     /* SCSI-2 INQUIRY data format */
    buf[4] = 31;        /* Additional length */
    buf[5] = 0;     /* No special options */
    buf[6] = 0;
    buf[7] = 0;
    memcpy(buf + 8, common->inquiry_string, sizeof common->inquiry_string);
    return 36;
}

static int do_request_sense(struct fsg_common *common, struct fsg_buffhd *bh)
{
    struct fsg_lun  *curlun = common->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 */
        common->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_common *common, struct fsg_buffhd *bh)
{
    struct fsg_lun  *curlun = common->curlun;
    u32     lba = get_unaligned_be32(&common->cmnd[2]);
    int     pmi = common->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_common *common, struct fsg_buffhd *bh)
{
    struct fsg_lun  *curlun = common->curlun;
    int     msf = common->cmnd[1] & 0x02;
    u32     lba = get_unaligned_be32(&common->cmnd[2]);
    u8      *buf = (u8 *)bh->buf;

    if (common->cmnd[1] & ~0x02) {      /* 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_common *common, struct fsg_buffhd *bh)
{
    struct fsg_lun  *curlun = common->curlun;
    int     msf = common->cmnd[1] & 0x02;
    int     start_track = common->cmnd[6];
    u8      *buf = (u8 *)bh->buf;

    if ((common->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_common *common, struct fsg_buffhd *bh)
{
    struct fsg_lun  *curlun = common->curlun;
    int     mscmnd = common->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 ((common->cmnd[1] & ~0x08) != 0) {   /* Mask away DBD */
        curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
        return -EINVAL;
    }
    pc = common->cmnd[2] >> 6;
    page_code = common->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 FSG_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_common *common)
{
    struct fsg_lun  *curlun = common->curlun;
    int     loej, start;

    if (!curlun) {
        return -EINVAL;
    } else if (!curlun->removable) {
        curlun->sense_data = SS_INVALID_COMMAND;
        return -EINVAL;
    } else if ((common->cmnd[1] & ~0x01) != 0 || /* Mask away Immed */
           (common->cmnd[4] & ~0x03) != 0) { /* Mask LoEj, Start */
        curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
        return -EINVAL;
    }

    loej  = common->cmnd[4] & 0x02;
    start = common->cmnd[4] & 0x01;

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

    /* 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)
        return 0;

    /* Simulate an unload/eject */
    if (common->ops && common->ops->pre_eject) {
        int r = common->ops->pre_eject(common, curlun,
                           curlun - common->luns);
        if (unlikely(r < 0))
            return r;
        else if (r)
            return 0;
    }

    up_read(&common->filesem);
    down_write(&common->filesem);
    fsg_lun_close(curlun);
    up_write(&common->filesem);
    down_read(&common->filesem);

    return common->ops && common->ops->post_eject
        ? min(0, common->ops->post_eject(common, curlun,
                         curlun - common->luns))
        : 0;
}

static int do_prevent_allow(struct fsg_common *common)
{
    struct fsg_lun  *curlun = common->curlun;
    int     prevent;

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

    prevent = common->cmnd[4] & 0x01;
    if ((common->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_common *common,
            struct fsg_buffhd *bh)
{
    struct fsg_lun  *curlun = common->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_common *common, struct fsg_buffhd *bh)
{
    struct fsg_lun  *curlun = common->curlun;

    /* We don't support MODE SELECT */
    if (curlun)
        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_common *common)
{
    struct fsg_buffhd   *bh;
    u32         amount;
    int         rc;

    for (bh = common->next_buffhd_to_drain;
         bh->state != BUF_STATE_EMPTY || common->usb_amount_left > 0;
         bh = common->next_buffhd_to_drain) {

        /* Throw away the data in a filled buffer */
        if (bh->state == BUF_STATE_FULL) {
            smp_rmb();
            bh->state = BUF_STATE_EMPTY;
            common->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(common,
                        FSG_STATE_ABORT_BULK_OUT);
                return -EINTR;
            }
            continue;
        }

        /* Try to submit another request if we need one */
        bh = common->next_buffhd_to_fill;
        if (bh->state == BUF_STATE_EMPTY
         && common->usb_amount_left > 0) {
            amount = min(common->usb_amount_left, FSG_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(common, bh, amount);
            if (!start_out_transfer(common, bh))
                /* Dunno what to do if common->fsg is NULL */
                return -EIO;
            common->next_buffhd_to_fill = bh->next;
            common->usb_amount_left -= amount;
            continue;
        }

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

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

    switch (common->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 (!common->can_stall) {
            /* Nothing */
        } else if (fsg_is_set(common)) {
            fsg_set_halt(common->fsg, common->fsg->bulk_out);
            rc = halt_bulk_in_endpoint(common->fsg);
        } else {
            /* Don't know what to do if common->fsg is NULL */
            rc = -EIO;
        }
        break;

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

        /* Don't know what to do if common->fsg is NULL */
        } else if (!fsg_is_set(common)) {
            rc = -EIO;

        /* If there's no residue, simply send the last buffer */
        } else if (common->residue == 0) {
            bh->inreq->zero = 0;
            if (!start_in_transfer(common, bh))
                return -EIO;
            common->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;
            if (!start_in_transfer(common, bh))
                rc = -EIO;
            common->next_buffhd_to_fill = bh->next;
            if (common->can_stall)
                rc = halt_bulk_in_endpoint(common->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 (common->residue == 0) {
            /* Nothing to receive */

        /* Did the host stop sending unexpectedly early? */
        } else if (common->short_packet_received) {
            raise_exception(common, 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 (common->can_stall) {
            if (fsg_is_set(common))
                fsg_set_halt(common->fsg,
                         common->fsg->bulk_out);
            raise_exception(common, 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(common);
        }
        break;
    }
    return rc;
}

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

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

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

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

    /* Store and send the Bulk-only CSW */
    csw = (void *)bh->buf;

    csw->Signature = cpu_to_le32(US_BULK_CS_SIGN);
    csw->Tag = common->tag;
    csw->Residue = cpu_to_le32(common->residue);
    csw->Status = status;

    bh->inreq->length = US_BULK_CS_WRAP_LEN;
    bh->inreq->zero = 0;
    if (!start_in_transfer(common, bh))
        /* Don't know what to do if common->fsg is NULL */
        return -EIO;

    common->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_common *common, int cmnd_size,
             enum data_direction data_dir, unsigned int mask,
             int needs_medium, const char *name)
{
    int         i;
    int         lun = common->cmnd[1] >> 5;
    static const char   dirletter[4] = {'u', 'o', 'i', 'n'};
    char            hdlen[20];
    struct fsg_lun      *curlun;

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

    /*
     * We can't reply at all until we know the correct data direction
     * and size.
     */
    if (common->data_size_from_cmnd == 0)
        data_dir = DATA_DIR_NONE;
    if (common->data_size < common->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.
         */
        common->data_size_from_cmnd = common->data_size;
        common->phase_error = 1;
    }
    common->residue = common->data_size;
    common->usb_amount_left = common->data_size;

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

    /* Verify the length of the command itself */
    if (cmnd_size != common->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 <= common->cmnd_size) {
            DBG(common, "%s is buggy! Expected length %d "
                "but we got %d\n", name,
                cmnd_size, common->cmnd_size);
            cmnd_size = common->cmnd_size;
        } else {
            common->phase_error = 1;
            return -EINVAL;
        }
    }

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

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

        /*
         * INQUIRY and REQUEST SENSE commands are explicitly allowed
         * to use unsupported LUNs; all others may not.
         */
        if (common->cmnd[0] != INQUIRY &&
            common->cmnd[0] != REQUEST_SENSE) {
            DBG(common, "unsupported LUN %d\n", common->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 &&
        common->cmnd[0] != INQUIRY &&
        common->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 */
    common->cmnd[1] &= 0x1f;            /* Mask away the LUN */
    for (i = 1; i < cmnd_size; ++i) {
        if (common->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_common *common,
        int cmnd_size, enum data_direction data_dir,
        unsigned int mask, int needs_medium, const char *name)
{
    if (common->curlun)
        common->data_size_from_cmnd <<= common->curlun->blkbits;
    return check_command(common, cmnd_size, data_dir,
            mask, needs_medium, name);
}

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

    dump_cdb(common);

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

    case TEST_UNIT_READY:
        common->data_size_from_cmnd = 0;
        reply = check_command(common, 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:
        common->data_size_from_cmnd = 0;
        reply = check_command(common, 10, DATA_DIR_NONE,
                      (1<<1) | (0xf<<2) | (3<<7), 1,
                      "VERIFY");
        if (reply == 0)
            reply = do_verify(common);
        break;

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

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

    case WRITE_12:
        common->data_size_from_cmnd =
                get_unaligned_be32(&common->cmnd[6]);
        reply = check_command_size_in_blocks(common, 12,
                      DATA_DIR_FROM_HOST,
                      (1<<1) | (0xf<<2) | (0xf<<6), 1,
                      "WRITE(12)");
        if (reply == 0)
            reply = do_write(common);
        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:
        common->data_size_from_cmnd = 0;
        sprintf(unknown, "Unknown x%02x", common->cmnd[0]);
        reply = check_command(common, common->cmnd_size,
                      DATA_DIR_UNKNOWN, ~0, 0, unknown);
        if (reply == 0) {
            common->curlun->sense_data = SS_INVALID_COMMAND;
            reply = -EINVAL;
        }
        break;
    }
    up_read(&common->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 && common->data_dir == DATA_DIR_TO_HOST) {
        reply = min((u32)reply, common->data_size_from_cmnd);
        bh->inreq->length = reply;
        bh->state = BUF_STATE_FULL;
        common->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;
    struct fsg_common   *common = fsg->common;

    /* 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 (common->can_stall) {
            fsg_set_halt(fsg, fsg->bulk_out);
            halt_bulk_in_endpoint(fsg);
        }
        return -EINVAL;
    }

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

static int get_next_command(struct fsg_common *common)
{
    struct fsg_buffhd   *bh;
    int         rc = 0;

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

    /* Queue a request to read a Bulk-only CBW */
    set_bulk_out_req_length(common, bh, US_BULK_CB_WRAP_LEN);
    if (!start_out_transfer(common, bh))
        /* Don't know what to do if common->fsg is NULL */
        return -EIO;

    /*
     * 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(common);
        if (rc)
            return rc;
    }
    smp_rmb();
    rc = fsg_is_set(common) ? received_cbw(common->fsg, bh) : -EIO;
    bh->state = BUF_STATE_EMPTY;

    return rc;
}


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

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

/* Reset interface setting and re-init endpoint state (toggle etc). */
static int do_set_interface(struct fsg_common *common, struct fsg_dev *new_fsg)
{
    struct fsg_dev *fsg;
    int i, rc = 0;

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

reset:
    /* Deallocate the requests */
    if (common->fsg) {
        fsg = common->fsg;

        for (i = 0; i < fsg_num_buffers; ++i) {
            struct fsg_buffhd *bh = &common->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;
            }
        }

        /* 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;
        }

        common->fsg = NULL;
        wake_up(&common->fsg_wait);
    }

    common->running = 0;
    if (!new_fsg || rc)
        return rc;

    common->fsg = new_fsg;
    fsg = common->fsg;

    /* Enable the endpoints */
    rc = config_ep_by_speed(common->gadget, &(fsg->function), fsg->bulk_in);
    if (rc)
        goto reset;
    rc = usb_ep_enable(fsg->bulk_in);
    if (rc)
        goto reset;
    fsg->bulk_in->driver_data = common;
    fsg->bulk_in_enabled = 1;

    rc = config_ep_by_speed(common->gadget, &(fsg->function),
                fsg->bulk_out);
    if (rc)
        goto reset;
    rc = usb_ep_enable(fsg->bulk_out);
    if (rc)
        goto reset;
    fsg->bulk_out->driver_data = common;
    fsg->bulk_out_enabled = 1;
    common->bulk_out_maxpacket = usb_endpoint_maxp(fsg->bulk_out->desc);
    clear_bit(IGNORE_BULK_OUT, &fsg->atomic_bitflags);

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

        rc = alloc_request(common, fsg->bulk_in, &bh->inreq);
        if (rc)
            goto reset;
        rc = alloc_request(common, fsg->bulk_out, &bh->outreq);
        if (rc)
            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;
    }

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


/****************************** ALT CONFIGS ******************************/

static int fsg_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
{
    struct fsg_dev *fsg = fsg_from_func(f);
    fsg->common->new_fsg = fsg;
    raise_exception(fsg->common, FSG_STATE_CONFIG_CHANGE);
    return USB_GADGET_DELAYED_STATUS;
}

static void fsg_disable(struct usb_function *f)
{
    struct fsg_dev *fsg = fsg_from_func(f);
    fsg->common->new_fsg = NULL;
    raise_exception(fsg->common, FSG_STATE_CONFIG_CHANGE);
}


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

static void handle_exception(struct fsg_common *common)
{
    siginfo_t       info;
    int         i;
    struct fsg_buffhd   *bh;
    enum fsg_state      old_state;
    struct fsg_lun      *curlun;
    unsigned int        exception_req_tag;

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

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

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

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

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

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

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

    /* Carry out any extra actions required for the exception */
    switch (old_state) {
    case FSG_STATE_ABORT_BULK_OUT:
        send_status(common);
        spin_lock_irq(&common->lock);
        if (common->state == FSG_STATE_STATUS_PHASE)
            common->state = FSG_STATE_IDLE;
        spin_unlock_irq(&common->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 (!fsg_is_set(common))
            break;
        if (test_and_clear_bit(IGNORE_BULK_OUT,
                       &common->fsg->atomic_bitflags))
            usb_ep_clear_halt(common->fsg->bulk_in);

        if (common->ep0_req_tag == exception_req_tag)
            ep0_queue(common);  /* Complete the status stage */

        /*
         * 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 < common->nluns; ++i) */
        /*  common->luns[i].unit_attention_data = */
        /*      SS_RESET_OCCURRED;  */
        break;

    case FSG_STATE_CONFIG_CHANGE:
        do_set_interface(common, common->new_fsg);
        if (common->new_fsg)
            usb_composite_setup_continue(common->cdev);
        break;

    case FSG_STATE_EXIT:
    case FSG_STATE_TERMINATED:
        do_set_interface(common, NULL);     /* Free resources */
        spin_lock_irq(&common->lock);
        common->state = FSG_STATE_TERMINATED;   /* Stop the thread */
        spin_unlock_irq(&common->lock);
        break;

    case FSG_STATE_INTERFACE_CHANGE:
    case FSG_STATE_DISCONNECT:
    case FSG_STATE_COMMAND_PHASE:
    case FSG_STATE_DATA_PHASE:
    case FSG_STATE_STATUS_PHASE:
    case FSG_STATE_IDLE:
        break;
    }
}


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

static int fsg_main_thread(void *common_)
{
    struct fsg_common   *common = common_;

    /*
     * 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 (common->state != FSG_STATE_TERMINATED) {
        if (exception_in_progress(common) || signal_pending(current)) {
            handle_exception(common);
            continue;
        }

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

        if (get_next_command(common))
            continue;

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

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

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

        if (send_status(common))
            continue;

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

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

    if (!common->ops || !common->ops->thread_exits
     || common->ops->thread_exits(common) < 0) {
        struct fsg_lun *curlun = common->luns;
        unsigned i = common->nluns;

        down_write(&common->filesem);
        for (; i--; ++curlun) {
            if (!fsg_lun_is_open(curlun))
                continue;

            fsg_lun_close(curlun);
            curlun->unit_attention_data = SS_MEDIUM_NOT_PRESENT;
        }
        up_write(&common->filesem);
    }

    /* Let fsg_unbind() know the thread has exited */
    complete_and_exit(&common->thread_notifier, 0);
}


/*************************** DEVICE ATTRIBUTES ***************************/

static DEVICE_ATTR(ro, 0644, fsg_show_ro, fsg_store_ro);
static DEVICE_ATTR(nofua, 0644, fsg_show_nofua, fsg_store_nofua);
static DEVICE_ATTR(file, 0644, fsg_show_file, fsg_store_file);

static struct device_attribute dev_attr_ro_cdrom =
    __ATTR(ro, 0444, fsg_show_ro, NULL);
static struct device_attribute dev_attr_file_nonremovable =
    __ATTR(file, 0444, fsg_show_file, NULL);


/****************************** FSG COMMON ******************************/

static void fsg_common_release(struct kref *ref);

static void fsg_lun_release(struct device *dev)
{
    /* Nothing needs to be done */
}

static inline void fsg_common_get(struct fsg_common *common)
{
    kref_get(&common->ref);
}

static inline void fsg_common_put(struct fsg_common *common)
{
    kref_put(&common->ref, fsg_common_release);
}

static struct fsg_common *fsg_common_init(struct fsg_common *common,
                      struct usb_composite_dev *cdev,
                      struct fsg_config *cfg)
{
    struct usb_gadget *gadget = cdev->gadget;
    struct fsg_buffhd *bh;
    struct fsg_lun *curlun;
    struct fsg_lun_config *lcfg;
    int nluns, i, rc;
    char *pathbuf;

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

    /* Find out how many LUNs there should be */
    nluns = cfg->nluns;
    if (nluns < 1 || nluns > FSG_MAX_LUNS) {
        dev_err(&gadget->dev, "invalid number of LUNs: %u\n", nluns);
        return ERR_PTR(-EINVAL);
    }

    /* Allocate? */
    if (!common) {
        common = kzalloc(sizeof *common, GFP_KERNEL);
        if (!common)
            return ERR_PTR(-ENOMEM);
        common->free_storage_on_release = 1;
    } else {
        memset(common, 0, sizeof *common);
        common->free_storage_on_release = 0;
    }

    common->buffhds = kcalloc(fsg_num_buffers,
                  sizeof *(common->buffhds), GFP_KERNEL);
    if (!common->buffhds) {
        if (common->free_storage_on_release)
            kfree(common);
        return ERR_PTR(-ENOMEM);
    }

    common->ops = cfg->ops;
    common->private_data = cfg->private_data;

    common->gadget = gadget;
    common->ep0 = gadget->ep0;
    common->ep0req = cdev->req;
    common->cdev = cdev;

    /* Maybe allocate device-global string IDs, and patch descriptors */
    if (fsg_strings[FSG_STRING_INTERFACE].id == 0) {
        rc = usb_string_id(cdev);
        if (unlikely(rc < 0))
            goto error_release;
        fsg_strings[FSG_STRING_INTERFACE].id = rc;
        fsg_intf_desc.iInterface = rc;
    }

    /*
     * Create the LUNs, open their backing files, and register the
     * LUN devices in sysfs.
     */
    curlun = kcalloc(nluns, sizeof(*curlun), GFP_KERNEL);
    if (unlikely(!curlun)) {
        rc = -ENOMEM;
        goto error_release;
    }
    common->luns = curlun;

    init_rwsem(&common->filesem);

    for (i = 0, lcfg = cfg->luns; i < nluns; ++i, ++curlun, ++lcfg) {
        curlun->cdrom = !!lcfg->cdrom;
        curlun->ro = lcfg->cdrom || lcfg->ro;
        curlun->initially_ro = curlun->ro;
        curlun->removable = lcfg->removable;
        curlun->dev.release = fsg_lun_release;
        curlun->dev.parent = &gadget->dev;
        /* curlun->dev.driver = &fsg_driver.driver; XXX */
        dev_set_drvdata(&curlun->dev, &common->filesem);
        dev_set_name(&curlun->dev, "lun%d", i);

        rc = device_register(&curlun->dev);
        if (rc) {
            INFO(common, "failed to register LUN%d: %d\n", i, rc);
            common->nluns = i;
            put_device(&curlun->dev);
            goto error_release;
        }

        rc = device_create_file(&curlun->dev,
                    curlun->cdrom
                      ? &dev_attr_ro_cdrom
                      : &dev_attr_ro);
        if (rc)
            goto error_luns;
        rc = device_create_file(&curlun->dev,
                    curlun->removable
                      ? &dev_attr_file
                      : &dev_attr_file_nonremovable);
        if (rc)
            goto error_luns;
        rc = device_create_file(&curlun->dev, &dev_attr_nofua);
        if (rc)
            goto error_luns;

        if (lcfg->filename) {
            rc = fsg_lun_open(curlun, lcfg->filename);
            if (rc)
                goto error_luns;
        } else if (!curlun->removable) {
            ERROR(common, "no file given for LUN%d\n", i);
            rc = -EINVAL;
            goto error_luns;
        }
    }
    common->nluns = nluns;

    /* Data buffers cyclic list */
    bh = common->buffhds;
    i = fsg_num_buffers;
    goto buffhds_first_it;
    do {
        bh->next = bh + 1;
        ++bh;
buffhds_first_it:
        bh->buf = kmalloc(FSG_BUFLEN, GFP_KERNEL);
        if (unlikely(!bh->buf)) {
            rc = -ENOMEM;
            goto error_release;
        }
    } while (--i);
    bh->next = common->buffhds;

    /* Prepare inquiryString */
    if (cfg->release != 0xffff) {
        i = cfg->release;
    } else {
        i = usb_gadget_controller_number(gadget);
        if (i >= 0) {
            i = 0x0300 + i;
        } else {
            WARNING(common, "controller '%s' not recognized\n",
                gadget->name);
            i = 0x0399;
        }
    }
    snprintf(common->inquiry_string, sizeof common->inquiry_string,
         "%-8s%-16s%04x", cfg->vendor_name ?: "Linux",
         /* Assume product name dependent on the first LUN */
         cfg->product_name ?: (common->luns->cdrom
                     ? "File-Stor Gadget"
                     : "File-CD Gadget"),
         i);

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

    spin_lock_init(&common->lock);
    kref_init(&common->ref);

    /* Tell the thread to start working */
    common->thread_task =
        kthread_create(fsg_main_thread, common, "file-storage");
    if (IS_ERR(common->thread_task)) {
        rc = PTR_ERR(common->thread_task);
        goto error_release;
    }
    init_completion(&common->thread_notifier);
    init_waitqueue_head(&common->fsg_wait);

    /* Information */
    INFO(common, FSG_DRIVER_DESC ", version: " FSG_DRIVER_VERSION "\n");
    INFO(common, "Number of LUNs=%d\n", common->nluns);

    pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
    for (i = 0, nluns = common->nluns, curlun = common->luns;
         i < nluns;
         ++curlun, ++i) {
        char *p = "(no medium)";
        if (fsg_lun_is_open(curlun)) {
            p = "(error)";
            if (pathbuf) {
                p = d_path(&curlun->filp->f_path,
                       pathbuf, PATH_MAX);
                if (IS_ERR(p))
                    p = "(error)";
            }
        }
        LINFO(curlun, "LUN: %s%s%sfile: %s\n",
              curlun->removable ? "removable " : "",
              curlun->ro ? "read only " : "",
              curlun->cdrom ? "CD-ROM " : "",
              p);
    }
    kfree(pathbuf);

    DBG(common, "I/O thread pid: %d\n", task_pid_nr(common->thread_task));

    wake_up_process(common->thread_task);

    return common;

error_luns:
    common->nluns = i + 1;
error_release:
    common->state = FSG_STATE_TERMINATED;   /* The thread is dead */
    /* Call fsg_common_release() directly, ref might be not initialised. */
    fsg_common_release(&common->ref);
    return ERR_PTR(rc);
}

static void fsg_common_release(struct kref *ref)
{
    struct fsg_common *common = container_of(ref, struct fsg_common, ref);

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

    if (likely(common->luns)) {
        struct fsg_lun *lun = common->luns;
        unsigned i = common->nluns;

        /* In error recovery common->nluns may be zero. */
        for (; i; --i, ++lun) {
            device_remove_file(&lun->dev, &dev_attr_nofua);
            device_remove_file(&lun->dev,
                       lun->cdrom
                     ? &dev_attr_ro_cdrom
                     : &dev_attr_ro);
            device_remove_file(&lun->dev,
                       lun->removable
                     ? &dev_attr_file
                     : &dev_attr_file_nonremovable);
            fsg_lun_close(lun);
            device_unregister(&lun->dev);
        }

        kfree(common->luns);
    }

    {
        struct fsg_buffhd *bh = common->buffhds;
        unsigned i = fsg_num_buffers;
        do {
            kfree(bh->buf);
        } while (++bh, --i);
    }

    kfree(common->buffhds);
    if (common->free_storage_on_release)
        kfree(common);
}


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

static void fsg_unbind(struct usb_configuration *c, struct usb_function *f)
{
    struct fsg_dev      *fsg = fsg_from_func(f);
    struct fsg_common   *common = fsg->common;

    DBG(fsg, "unbind\n");
    if (fsg->common->fsg == fsg) {
        fsg->common->new_fsg = NULL;
        raise_exception(fsg->common, FSG_STATE_CONFIG_CHANGE);
        /* FIXME: make interruptible or killable somehow? */
        wait_event(common->fsg_wait, common->fsg != fsg);
    }

    fsg_common_put(common);
    usb_free_descriptors(fsg->function.descriptors);
    usb_free_descriptors(fsg->function.hs_descriptors);
    usb_free_descriptors(fsg->function.ss_descriptors);
    kfree(fsg);
}

static int fsg_bind(struct usb_configuration *c, struct usb_function *f)
{
    struct fsg_dev      *fsg = fsg_from_func(f);
    struct usb_gadget   *gadget = c->cdev->gadget;
    int         i;
    struct usb_ep       *ep;

    fsg->gadget = gadget;

    /* New interface */
    i = usb_interface_id(c, f);
    if (i < 0)
        return i;
    fsg_intf_desc.bInterfaceNumber = i;
    fsg->interface_number = i;

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

    /* Copy descriptors */
    f->descriptors = usb_copy_descriptors(fsg_fs_function);
    if (unlikely(!f->descriptors))
        return -ENOMEM;

    if (gadget_is_dualspeed(gadget)) {
        /* 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;
        f->hs_descriptors = usb_copy_descriptors(fsg_hs_function);
        if (unlikely(!f->hs_descriptors)) {
            usb_free_descriptors(f->descriptors);
            return -ENOMEM;
        }
    }

    if (gadget_is_superspeed(gadget)) {
        unsigned    max_burst;

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

        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;

        f->ss_descriptors = usb_copy_descriptors(fsg_ss_function);
        if (unlikely(!f->ss_descriptors)) {
            usb_free_descriptors(f->hs_descriptors);
            usb_free_descriptors(f->descriptors);
            return -ENOMEM;
        }
    }

    return 0;

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


/****************************** ADD FUNCTION ******************************/

static struct usb_gadget_strings *fsg_strings_array[] = {
    &fsg_stringtab,
    NULL,
};

static int fsg_bind_config(struct usb_composite_dev *cdev,
               struct usb_configuration *c,
               struct fsg_common *common)
{
    struct fsg_dev *fsg;
    int rc;

    fsg = kzalloc(sizeof *fsg, GFP_KERNEL);
    if (unlikely(!fsg))
        return -ENOMEM;

    fsg->function.name        = FSG_DRIVER_DESC;
    fsg->function.strings     = fsg_strings_array;
    fsg->function.bind        = fsg_bind;
    fsg->function.unbind      = fsg_unbind;
    fsg->function.setup       = fsg_setup;
    fsg->function.set_alt     = fsg_set_alt;
    fsg->function.disable     = fsg_disable;

    fsg->common               = common;
    /*
     * Our caller holds a reference to common structure so we
     * don't have to be worry about it being freed until we return
     * from this function.  So instead of incrementing counter now
     * and decrement in error recovery we increment it only when
     * call to usb_add_function() was successful.
     */

    rc = usb_add_function(c, &fsg->function);
    if (unlikely(rc))
        kfree(fsg);
    else
        fsg_common_get(fsg->common);
    return rc;
}


/************************* Module parameters *************************/

struct fsg_module_parameters {
    char        *file[FSG_MAX_LUNS];
    bool        ro[FSG_MAX_LUNS];
    bool        removable[FSG_MAX_LUNS];
    bool        cdrom[FSG_MAX_LUNS];
    bool        nofua[FSG_MAX_LUNS];

    unsigned int    file_count, ro_count, removable_count, cdrom_count;
    unsigned int    nofua_count;
    unsigned int    luns;   /* nluns */
    bool        stall;  /* can_stall */
};

#define _FSG_MODULE_PARAM_ARRAY(prefix, params, name, type, desc)   \
    module_param_array_named(prefix ## name, params.name, type, \
                 &prefix ## params.name ## _count,  \
                 S_IRUGO);              \
    MODULE_PARM_DESC(prefix ## name, desc)

#define _FSG_MODULE_PARAM(prefix, params, name, type, desc)     \
    module_param_named(prefix ## name, params.name, type,       \
               S_IRUGO);                    \
    MODULE_PARM_DESC(prefix ## name, desc)

#define FSG_MODULE_PARAMETERS(prefix, params)               \
    _FSG_MODULE_PARAM_ARRAY(prefix, params, file, charp,        \
                "names of backing files or devices");   \
    _FSG_MODULE_PARAM_ARRAY(prefix, params, ro, bool,       \
                "true to force read-only");     \
    _FSG_MODULE_PARAM_ARRAY(prefix, params, removable, bool,    \
                "true to simulate removable media");    \
    _FSG_MODULE_PARAM_ARRAY(prefix, params, cdrom, bool,        \
                "true to simulate CD-ROM instead of disk"); \
    _FSG_MODULE_PARAM_ARRAY(prefix, params, nofua, bool,        \
                "true to ignore SCSI WRITE(10,12) FUA bit"); \
    _FSG_MODULE_PARAM(prefix, params, luns, uint,           \
              "number of LUNs");                \
    _FSG_MODULE_PARAM(prefix, params, stall, bool,          \
              "false to prevent bulk stalls")

static void
fsg_config_from_params(struct fsg_config *cfg,
               const struct fsg_module_parameters *params)
{
    struct fsg_lun_config *lun;
    unsigned i;

    /* Configure LUNs */
    cfg->nluns =
        min(params->luns ?: (params->file_count ?: 1u),
            (unsigned)FSG_MAX_LUNS);
    for (i = 0, lun = cfg->luns; i < cfg->nluns; ++i, ++lun) {
        lun->ro = !!params->ro[i];
        lun->cdrom = !!params->cdrom[i];
        lun->removable = !!params->removable[i];
        lun->filename =
            params->file_count > i && params->file[i][0]
            ? params->file[i]
            : 0;
    }

    /* Let MSF use defaults */
    cfg->vendor_name = 0;
    cfg->product_name = 0;
    cfg->release = 0xffff;

    cfg->ops = NULL;
    cfg->private_data = NULL;

    /* Finalise */
    cfg->can_stall = params->stall;
}

static inline struct fsg_common *
fsg_common_from_params(struct fsg_common *common,
               struct usb_composite_dev *cdev,
               const struct fsg_module_parameters *params)
    __attribute__((unused));
static inline struct fsg_common *
fsg_common_from_params(struct fsg_common *common,
               struct usb_composite_dev *cdev,
               const struct fsg_module_parameters *params)
{
    struct fsg_config cfg;
    fsg_config_from_params(&cfg, params);
    return fsg_common_init(common, cdev, &cfg);
}