storage_common.c

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/*
 * storage_common.c -- Common definitions for mass storage functionality
 *
 * Copyright (C) 2003-2008 Alan Stern
 * Copyeight (C) 2009 Samsung Electronics
 * Author: Michal Nazarewicz ([email protected])
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */


/*
 * This file requires the following identifiers used in USB strings to
 * be defined (each of type pointer to char):
 *  - fsg_string_manufacturer -- name of the manufacturer
 *  - fsg_string_product      -- name of the product
 *  - fsg_string_config       -- name of the configuration
 *  - fsg_string_interface    -- name of the interface
 * The first four are only needed when FSG_DESCRIPTORS_DEVICE_STRINGS
 * macro is defined prior to including this file.
 */

/*
 * When FSG_NO_INTR_EP is defined fsg_fs_intr_in_desc and
 * fsg_hs_intr_in_desc objects as well as
 * FSG_FS_FUNCTION_PRE_EP_ENTRIES and FSG_HS_FUNCTION_PRE_EP_ENTRIES
 * macros are not defined.
 *
 * When FSG_NO_DEVICE_STRINGS is defined FSG_STRING_MANUFACTURER,
 * FSG_STRING_PRODUCT, FSG_STRING_SERIAL and FSG_STRING_CONFIG are not
 * defined (as well as corresponding entries in string tables are
 * missing) and FSG_STRING_INTERFACE has value of zero.
 *
 * When FSG_NO_OTG is defined fsg_otg_desc won't be defined.
 */

/*
 * When USB_GADGET_DEBUG_FILES is defined the module param num_buffers
 * sets the number of pipeline buffers (length of the fsg_buffhd array).
 * The valid range of num_buffers is: num >= 2 && num <= 4.
 */


#include <linux/usb/storage.h>
#include <scsi/scsi.h>
#include <asm/unaligned.h>


/*
 * Thanks to NetChip Technologies for donating this product ID.
 *
 * DO NOT REUSE THESE IDs with any other driver!!  Ever!!
 * Instead:  allocate your own, using normal USB-IF procedures.
 */
#define FSG_VENDOR_ID   0x0525  /* NetChip */
#define FSG_PRODUCT_ID  0xa4a5  /* Linux-USB File-backed Storage Gadget */


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


#ifndef DEBUG
#undef VERBOSE_DEBUG
#undef DUMP_MSGS
#endif /* !DEBUG */

#ifdef VERBOSE_DEBUG
#define VLDBG   LDBG
#else
#define VLDBG(lun, fmt, args...) do { } while (0)
#endif /* VERBOSE_DEBUG */

#define LDBG(lun, fmt, args...)   dev_dbg (&(lun)->dev, fmt, ## args)
#define LERROR(lun, fmt, args...) dev_err (&(lun)->dev, fmt, ## args)
#define LWARN(lun, fmt, args...)  dev_warn(&(lun)->dev, fmt, ## args)
#define LINFO(lun, fmt, args...)  dev_info(&(lun)->dev, fmt, ## args)

/*
 * Keep those macros in sync with those in
 * include/linux/usb/composite.h or else GCC will complain.  If they
 * are identical (the same names of arguments, white spaces in the
 * same places) GCC will allow redefinition otherwise (even if some
 * white space is removed or added) warning will be issued.
 *
 * Those macros are needed here because File Storage Gadget does not
 * include the composite.h header.  For composite gadgets those macros
 * are redundant since composite.h is included any way.
 *
 * One could check whether those macros are already defined (which
 * would indicate composite.h had been included) or not (which would
 * indicate we were in FSG) but this is not done because a warning is
 * desired if definitions here differ from the ones in composite.h.
 *
 * We want the definitions to match and be the same in File Storage
 * Gadget as well as Mass Storage Function (and so composite gadgets
 * using MSF).  If someone changes them in composite.h it will produce
 * a warning in this file when building MSF.
 */
#define DBG(d, fmt, args...)     dev_dbg(&(d)->gadget->dev , fmt , ## args)
#define VDBG(d, fmt, args...)    dev_vdbg(&(d)->gadget->dev , fmt , ## args)
#define ERROR(d, fmt, args...)   dev_err(&(d)->gadget->dev , fmt , ## args)
#define WARNING(d, fmt, args...) dev_warn(&(d)->gadget->dev , fmt , ## args)
#define INFO(d, fmt, args...)    dev_info(&(d)->gadget->dev , fmt , ## args)



#ifdef DUMP_MSGS

#  define dump_msg(fsg, /* const char * */ label,           \
           /* const u8 * */ buf, /* unsigned */ length) do {    \
    if (length < 512) {                     \
        DBG(fsg, "%s, length %u:\n", label, length);        \
        print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET,  \
                   16, 1, buf, length, 0);          \
    }                               \
} while (0)

#  define dump_cdb(fsg) do { } while (0)

#else

#  define dump_msg(fsg, /* const char * */ label, \
           /* const u8 * */ buf, /* unsigned */ length) do { } while (0)

#  ifdef VERBOSE_DEBUG

#    define dump_cdb(fsg)                       \
    print_hex_dump(KERN_DEBUG, "SCSI CDB: ", DUMP_PREFIX_NONE,  \
               16, 1, (fsg)->cmnd, (fsg)->cmnd_size, 0)     \

#  else

#    define dump_cdb(fsg) do { } while (0)

#  endif /* VERBOSE_DEBUG */

#endif /* DUMP_MSGS */

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

/* CBI Interrupt data structure */
struct interrupt_data {
    u8  bType;
    u8  bValue;
};

#define CBI_INTERRUPT_DATA_LEN      2

/* CBI Accept Device-Specific Command request */
#define USB_CBI_ADSC_REQUEST        0x00


/* Length of a SCSI Command Data Block */
#define MAX_COMMAND_SIZE    16

/* SCSI Sense Key/Additional Sense Code/ASC Qualifier values */
#define SS_NO_SENSE             0
#define SS_COMMUNICATION_FAILURE        0x040800
#define SS_INVALID_COMMAND          0x052000
#define SS_INVALID_FIELD_IN_CDB         0x052400
#define SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE   0x052100
#define SS_LOGICAL_UNIT_NOT_SUPPORTED       0x052500
#define SS_MEDIUM_NOT_PRESENT           0x023a00
#define SS_MEDIUM_REMOVAL_PREVENTED     0x055302
#define SS_NOT_READY_TO_READY_TRANSITION    0x062800
#define SS_RESET_OCCURRED           0x062900
#define SS_SAVING_PARAMETERS_NOT_SUPPORTED  0x053900
#define SS_UNRECOVERED_READ_ERROR       0x031100
#define SS_WRITE_ERROR              0x030c02
#define SS_WRITE_PROTECTED          0x072700

#define SK(x)       ((u8) ((x) >> 16))  /* Sense Key byte, etc. */
#define ASC(x)      ((u8) ((x) >> 8))
#define ASCQ(x)     ((u8) (x))


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


struct fsg_lun {
    struct file *filp;
    loff_t      file_length;
    loff_t      num_sectors;

    unsigned int    initially_ro:1;
    unsigned int    ro:1;
    unsigned int    removable:1;
    unsigned int    cdrom:1;
    unsigned int    prevent_medium_removal:1;
    unsigned int    registered:1;
    unsigned int    info_valid:1;
    unsigned int    nofua:1;

    u32     sense_data;
    u32     sense_data_info;
    u32     unit_attention_data;

    unsigned int    blkbits;    /* Bits of logical block size of bound block device */
    unsigned int    blksize;    /* logical block size of bound block device */
    struct device   dev;
};

#define fsg_lun_is_open(curlun) ((curlun)->filp != NULL)

static struct fsg_lun *fsg_lun_from_dev(struct device *dev)
{
    return container_of(dev, struct fsg_lun, dev);
}


/* Big enough to hold our biggest descriptor */
#define EP0_BUFSIZE 256
#define DELAYED_STATUS  (EP0_BUFSIZE + 999) /* An impossibly large value */

#ifdef CONFIG_USB_GADGET_DEBUG_FILES

static unsigned int fsg_num_buffers = CONFIG_USB_GADGET_STORAGE_NUM_BUFFERS;
module_param_named(num_buffers, fsg_num_buffers, uint, S_IRUGO);
MODULE_PARM_DESC(num_buffers, "Number of pipeline buffers");

#else

/*
 * Number of buffers we will use.
 * 2 is usually enough for good buffering pipeline
 */
#define fsg_num_buffers CONFIG_USB_GADGET_STORAGE_NUM_BUFFERS

#endif /* CONFIG_USB_DEBUG */

/* check if fsg_num_buffers is within a valid range */
static inline int fsg_num_buffers_validate(void)
{
    if (fsg_num_buffers >= 2 && fsg_num_buffers <= 4)
        return 0;
    pr_err("fsg_num_buffers %u is out of range (%d to %d)\n",
           fsg_num_buffers, 2 ,4);
    return -EINVAL;
}

/* Default size of buffer length. */
#define FSG_BUFLEN  ((u32)16384)

/* Maximal number of LUNs supported in mass storage function */
#define FSG_MAX_LUNS    8

enum fsg_buffer_state {
    BUF_STATE_EMPTY = 0,
    BUF_STATE_FULL,
    BUF_STATE_BUSY
};

struct fsg_buffhd {
    void                *buf;
    enum fsg_buffer_state       state;
    struct fsg_buffhd       *next;

    /*
     * The NetChip 2280 is faster, and handles some protocol faults
     * better, if we don't submit any short bulk-out read requests.
     * So we will record the intended request length here.
     */
    unsigned int            bulk_out_intended_length;

    struct usb_request      *inreq;
    int             inreq_busy;
    struct usb_request      *outreq;
    int             outreq_busy;
};

enum fsg_state {
    /* This one isn't used anywhere */
    FSG_STATE_COMMAND_PHASE = -10,
    FSG_STATE_DATA_PHASE,
    FSG_STATE_STATUS_PHASE,

    FSG_STATE_IDLE = 0,
    FSG_STATE_ABORT_BULK_OUT,
    FSG_STATE_RESET,
    FSG_STATE_INTERFACE_CHANGE,
    FSG_STATE_CONFIG_CHANGE,
    FSG_STATE_DISCONNECT,
    FSG_STATE_EXIT,
    FSG_STATE_TERMINATED
};

enum data_direction {
    DATA_DIR_UNKNOWN = 0,
    DATA_DIR_FROM_HOST,
    DATA_DIR_TO_HOST,
    DATA_DIR_NONE
};


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


static inline u32 get_unaligned_be24(u8 *buf)
{
    return 0xffffff & (u32) get_unaligned_be32(buf - 1);
}


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


enum {
#ifndef FSG_NO_DEVICE_STRINGS
    FSG_STRING_MANUFACTURER = 1,
    FSG_STRING_PRODUCT,
    FSG_STRING_SERIAL,
    FSG_STRING_CONFIG,
#endif
    FSG_STRING_INTERFACE
};


#ifndef FSG_NO_OTG
static struct usb_otg_descriptor
fsg_otg_desc = {
    .bLength =      sizeof fsg_otg_desc,
    .bDescriptorType =  USB_DT_OTG,

    .bmAttributes =     USB_OTG_SRP,
};
#endif

/* There is only one interface. */

static struct usb_interface_descriptor
fsg_intf_desc = {
    .bLength =      sizeof fsg_intf_desc,
    .bDescriptorType =  USB_DT_INTERFACE,

    .bNumEndpoints =    2,      /* Adjusted during fsg_bind() */
    .bInterfaceClass =  USB_CLASS_MASS_STORAGE,
    .bInterfaceSubClass =   USB_SC_SCSI,    /* Adjusted during fsg_bind() */
    .bInterfaceProtocol =   USB_PR_BULK,    /* Adjusted during fsg_bind() */
    .iInterface =       FSG_STRING_INTERFACE,
};

/*
 * Three full-speed endpoint descriptors: bulk-in, bulk-out, and
 * interrupt-in.
 */

static struct usb_endpoint_descriptor
fsg_fs_bulk_in_desc = {
    .bLength =      USB_DT_ENDPOINT_SIZE,
    .bDescriptorType =  USB_DT_ENDPOINT,

    .bEndpointAddress = USB_DIR_IN,
    .bmAttributes =     USB_ENDPOINT_XFER_BULK,
    /* wMaxPacketSize set by autoconfiguration */
};

static struct usb_endpoint_descriptor
fsg_fs_bulk_out_desc = {
    .bLength =      USB_DT_ENDPOINT_SIZE,
    .bDescriptorType =  USB_DT_ENDPOINT,

    .bEndpointAddress = USB_DIR_OUT,
    .bmAttributes =     USB_ENDPOINT_XFER_BULK,
    /* wMaxPacketSize set by autoconfiguration */
};

#ifndef FSG_NO_INTR_EP

static struct usb_endpoint_descriptor
fsg_fs_intr_in_desc = {
    .bLength =      USB_DT_ENDPOINT_SIZE,
    .bDescriptorType =  USB_DT_ENDPOINT,

    .bEndpointAddress = USB_DIR_IN,
    .bmAttributes =     USB_ENDPOINT_XFER_INT,
    .wMaxPacketSize =   cpu_to_le16(2),
    .bInterval =        32, /* frames -> 32 ms */
};

#ifndef FSG_NO_OTG
#  define FSG_FS_FUNCTION_PRE_EP_ENTRIES    2
#else
#  define FSG_FS_FUNCTION_PRE_EP_ENTRIES    1
#endif

#endif

static struct usb_descriptor_header *fsg_fs_function[] = {
#ifndef FSG_NO_OTG
    (struct usb_descriptor_header *) &fsg_otg_desc,
#endif
    (struct usb_descriptor_header *) &fsg_intf_desc,
    (struct usb_descriptor_header *) &fsg_fs_bulk_in_desc,
    (struct usb_descriptor_header *) &fsg_fs_bulk_out_desc,
#ifndef FSG_NO_INTR_EP
    (struct usb_descriptor_header *) &fsg_fs_intr_in_desc,
#endif
    NULL,
};


/*
 * USB 2.0 devices need to expose both high speed and full speed
 * descriptors, unless they only run at full speed.
 *
 * That means alternate endpoint descriptors (bigger packets)
 * and a "device qualifier" ... plus more construction options
 * for the configuration descriptor.
 */
static struct usb_endpoint_descriptor
fsg_hs_bulk_in_desc = {
    .bLength =      USB_DT_ENDPOINT_SIZE,
    .bDescriptorType =  USB_DT_ENDPOINT,

    /* bEndpointAddress copied from fs_bulk_in_desc during fsg_bind() */
    .bmAttributes =     USB_ENDPOINT_XFER_BULK,
    .wMaxPacketSize =   cpu_to_le16(512),
};

static struct usb_endpoint_descriptor
fsg_hs_bulk_out_desc = {
    .bLength =      USB_DT_ENDPOINT_SIZE,
    .bDescriptorType =  USB_DT_ENDPOINT,

    /* bEndpointAddress copied from fs_bulk_out_desc during fsg_bind() */
    .bmAttributes =     USB_ENDPOINT_XFER_BULK,
    .wMaxPacketSize =   cpu_to_le16(512),
    .bInterval =        1,  /* NAK every 1 uframe */
};

#ifndef FSG_NO_INTR_EP

static struct usb_endpoint_descriptor
fsg_hs_intr_in_desc = {
    .bLength =      USB_DT_ENDPOINT_SIZE,
    .bDescriptorType =  USB_DT_ENDPOINT,

    /* bEndpointAddress copied from fs_intr_in_desc during fsg_bind() */
    .bmAttributes =     USB_ENDPOINT_XFER_INT,
    .wMaxPacketSize =   cpu_to_le16(2),
    .bInterval =        9,  /* 2**(9-1) = 256 uframes -> 32 ms */
};

#ifndef FSG_NO_OTG
#  define FSG_HS_FUNCTION_PRE_EP_ENTRIES    2
#else
#  define FSG_HS_FUNCTION_PRE_EP_ENTRIES    1
#endif

#endif

static struct usb_descriptor_header *fsg_hs_function[] = {
#ifndef FSG_NO_OTG
    (struct usb_descriptor_header *) &fsg_otg_desc,
#endif
    (struct usb_descriptor_header *) &fsg_intf_desc,
    (struct usb_descriptor_header *) &fsg_hs_bulk_in_desc,
    (struct usb_descriptor_header *) &fsg_hs_bulk_out_desc,
#ifndef FSG_NO_INTR_EP
    (struct usb_descriptor_header *) &fsg_hs_intr_in_desc,
#endif
    NULL,
};

static struct usb_endpoint_descriptor
fsg_ss_bulk_in_desc = {
    .bLength =      USB_DT_ENDPOINT_SIZE,
    .bDescriptorType =  USB_DT_ENDPOINT,

    /* bEndpointAddress copied from fs_bulk_in_desc during fsg_bind() */
    .bmAttributes =     USB_ENDPOINT_XFER_BULK,
    .wMaxPacketSize =   cpu_to_le16(1024),
};

static struct usb_ss_ep_comp_descriptor fsg_ss_bulk_in_comp_desc = {
    .bLength =      sizeof(fsg_ss_bulk_in_comp_desc),
    .bDescriptorType =  USB_DT_SS_ENDPOINT_COMP,

    /*.bMaxBurst =      DYNAMIC, */
};

static struct usb_endpoint_descriptor
fsg_ss_bulk_out_desc = {
    .bLength =      USB_DT_ENDPOINT_SIZE,
    .bDescriptorType =  USB_DT_ENDPOINT,

    /* bEndpointAddress copied from fs_bulk_out_desc during fsg_bind() */
    .bmAttributes =     USB_ENDPOINT_XFER_BULK,
    .wMaxPacketSize =   cpu_to_le16(1024),
};

static struct usb_ss_ep_comp_descriptor fsg_ss_bulk_out_comp_desc = {
    .bLength =      sizeof(fsg_ss_bulk_in_comp_desc),
    .bDescriptorType =  USB_DT_SS_ENDPOINT_COMP,

    /*.bMaxBurst =      DYNAMIC, */
};

#ifndef FSG_NO_INTR_EP

static struct usb_endpoint_descriptor
fsg_ss_intr_in_desc = {
    .bLength =      USB_DT_ENDPOINT_SIZE,
    .bDescriptorType =  USB_DT_ENDPOINT,

    /* bEndpointAddress copied from fs_intr_in_desc during fsg_bind() */
    .bmAttributes =     USB_ENDPOINT_XFER_INT,
    .wMaxPacketSize =   cpu_to_le16(2),
    .bInterval =        9,  /* 2**(9-1) = 256 uframes -> 32 ms */
};

static struct usb_ss_ep_comp_descriptor fsg_ss_intr_in_comp_desc = {
    .bLength =      sizeof(fsg_ss_bulk_in_comp_desc),
    .bDescriptorType =  USB_DT_SS_ENDPOINT_COMP,

    .wBytesPerInterval =    cpu_to_le16(2),
};

#ifndef FSG_NO_OTG
#  define FSG_SS_FUNCTION_PRE_EP_ENTRIES    2
#else
#  define FSG_SS_FUNCTION_PRE_EP_ENTRIES    1
#endif

#endif

static __maybe_unused struct usb_ext_cap_descriptor fsg_ext_cap_desc = {
    .bLength =      USB_DT_USB_EXT_CAP_SIZE,
    .bDescriptorType =  USB_DT_DEVICE_CAPABILITY,
    .bDevCapabilityType =   USB_CAP_TYPE_EXT,

    .bmAttributes =     cpu_to_le32(USB_LPM_SUPPORT),
};

static __maybe_unused struct usb_ss_cap_descriptor fsg_ss_cap_desc = {
    .bLength =      USB_DT_USB_SS_CAP_SIZE,
    .bDescriptorType =  USB_DT_DEVICE_CAPABILITY,
    .bDevCapabilityType =   USB_SS_CAP_TYPE,

    /* .bmAttributes = LTM is not supported yet */

    .wSpeedSupported =  cpu_to_le16(USB_LOW_SPEED_OPERATION
        | USB_FULL_SPEED_OPERATION
        | USB_HIGH_SPEED_OPERATION
        | USB_5GBPS_OPERATION),
    .bFunctionalitySupport = USB_LOW_SPEED_OPERATION,
    .bU1devExitLat =    USB_DEFAULT_U1_DEV_EXIT_LAT,
    .bU2DevExitLat =    cpu_to_le16(USB_DEFAULT_U2_DEV_EXIT_LAT),
};

static __maybe_unused struct usb_bos_descriptor fsg_bos_desc = {
    .bLength =      USB_DT_BOS_SIZE,
    .bDescriptorType =  USB_DT_BOS,

    .wTotalLength =     cpu_to_le16(USB_DT_BOS_SIZE
                + USB_DT_USB_EXT_CAP_SIZE
                + USB_DT_USB_SS_CAP_SIZE),

    .bNumDeviceCaps =   2,
};

static struct usb_descriptor_header *fsg_ss_function[] = {
#ifndef FSG_NO_OTG
    (struct usb_descriptor_header *) &fsg_otg_desc,
#endif
    (struct usb_descriptor_header *) &fsg_intf_desc,
    (struct usb_descriptor_header *) &fsg_ss_bulk_in_desc,
    (struct usb_descriptor_header *) &fsg_ss_bulk_in_comp_desc,
    (struct usb_descriptor_header *) &fsg_ss_bulk_out_desc,
    (struct usb_descriptor_header *) &fsg_ss_bulk_out_comp_desc,
#ifndef FSG_NO_INTR_EP
    (struct usb_descriptor_header *) &fsg_ss_intr_in_desc,
    (struct usb_descriptor_header *) &fsg_ss_intr_in_comp_desc,
#endif
    NULL,
};

/* Maxpacket and other transfer characteristics vary by speed. */
static __maybe_unused struct usb_endpoint_descriptor *
fsg_ep_desc(struct usb_gadget *g, struct usb_endpoint_descriptor *fs,
        struct usb_endpoint_descriptor *hs,
        struct usb_endpoint_descriptor *ss)
{
    if (gadget_is_superspeed(g) && g->speed == USB_SPEED_SUPER)
        return ss;
    else if (gadget_is_dualspeed(g) && g->speed == USB_SPEED_HIGH)
        return hs;
    return fs;
}


/* Static strings, in UTF-8 (for simplicity we use only ASCII characters) */
static struct usb_string        fsg_strings[] = {
#ifndef FSG_NO_DEVICE_STRINGS
    {FSG_STRING_MANUFACTURER,   fsg_string_manufacturer},
    {FSG_STRING_PRODUCT,        fsg_string_product},
    {FSG_STRING_SERIAL,     ""},
    {FSG_STRING_CONFIG,     fsg_string_config},
#endif
    {FSG_STRING_INTERFACE,      fsg_string_interface},
    {}
};

static struct usb_gadget_strings    fsg_stringtab = {
    .language   = 0x0409,       /* en-us */
    .strings    = fsg_strings,
};


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

/*
 * If the next two routines are called while the gadget is registered,
 * the caller must own fsg->filesem for writing.
 */

static void fsg_lun_close(struct fsg_lun *curlun)
{
    if (curlun->filp) {
        LDBG(curlun, "close backing file\n");
        fput(curlun->filp);
        curlun->filp = NULL;
    }
}


static int fsg_lun_open(struct fsg_lun *curlun, const char *filename)
{
    int             ro;
    struct file         *filp = NULL;
    int             rc = -EINVAL;
    struct inode            *inode = NULL;
    loff_t              size;
    loff_t              num_sectors;
    loff_t              min_sectors;
    unsigned int            blkbits;
    unsigned int            blksize;

    /* R/W if we can, R/O if we must */
    ro = curlun->initially_ro;
    if (!ro) {
        filp = filp_open(filename, O_RDWR | O_LARGEFILE, 0);
        if (PTR_ERR(filp) == -EROFS || PTR_ERR(filp) == -EACCES)
            ro = 1;
    }
    if (ro)
        filp = filp_open(filename, O_RDONLY | O_LARGEFILE, 0);
    if (IS_ERR(filp)) {
        LINFO(curlun, "unable to open backing file: %s\n", filename);
        return PTR_ERR(filp);
    }

    if (!(filp->f_mode & FMODE_WRITE))
        ro = 1;

    inode = filp->f_path.dentry->d_inode;
    if ((!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))) {
        LINFO(curlun, "invalid file type: %s\n", filename);
        goto out;
    }

    /*
     * If we can't read the file, it's no good.
     * If we can't write the file, use it read-only.
     */
    if (!(filp->f_op->read || filp->f_op->aio_read)) {
        LINFO(curlun, "file not readable: %s\n", filename);
        goto out;
    }
    if (!(filp->f_op->write || filp->f_op->aio_write))
        ro = 1;

    size = i_size_read(inode->i_mapping->host);
    if (size < 0) {
        LINFO(curlun, "unable to find file size: %s\n", filename);
        rc = (int) size;
        goto out;
    }

    if (curlun->cdrom) {
        blksize = 2048;
        blkbits = 11;
    } else if (inode->i_bdev) {
        blksize = bdev_logical_block_size(inode->i_bdev);
        blkbits = blksize_bits(blksize);
    } else {
        blksize = 512;
        blkbits = 9;
    }

    num_sectors = size >> blkbits; /* File size in logic-block-size blocks */
    min_sectors = 1;
    if (curlun->cdrom) {
        min_sectors = 300;  /* Smallest track is 300 frames */
        if (num_sectors >= 256*60*75) {
            num_sectors = 256*60*75 - 1;
            LINFO(curlun, "file too big: %s\n", filename);
            LINFO(curlun, "using only first %d blocks\n",
                    (int) num_sectors);
        }
    }
    if (num_sectors < min_sectors) {
        LINFO(curlun, "file too small: %s\n", filename);
        rc = -ETOOSMALL;
        goto out;
    }

    if (fsg_lun_is_open(curlun))
        fsg_lun_close(curlun);

    curlun->blksize = blksize;
    curlun->blkbits = blkbits;
    curlun->ro = ro;
    curlun->filp = filp;
    curlun->file_length = size;
    curlun->num_sectors = num_sectors;
    LDBG(curlun, "open backing file: %s\n", filename);
    return 0;

out:
    fput(filp);
    return rc;
}


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

/*
 * Sync the file data, don't bother with the metadata.
 * This code was copied from fs/buffer.c:sys_fdatasync().
 */
static int fsg_lun_fsync_sub(struct fsg_lun *curlun)
{
    struct file *filp = curlun->filp;

    if (curlun->ro || !filp)
        return 0;
    return vfs_fsync(filp, 1);
}

static void store_cdrom_address(u8 *dest, int msf, u32 addr)
{
    if (msf) {
        /* Convert to Minutes-Seconds-Frames */
        addr >>= 2;     /* Convert to 2048-byte frames */
        addr += 2*75;       /* Lead-in occupies 2 seconds */
        dest[3] = addr % 75;    /* Frames */
        addr /= 75;
        dest[2] = addr % 60;    /* Seconds */
        addr /= 60;
        dest[1] = addr;     /* Minutes */
        dest[0] = 0;        /* Reserved */
    } else {
        /* Absolute sector */
        put_unaligned_be32(addr, dest);
    }
}


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


static ssize_t fsg_show_ro(struct device *dev, struct device_attribute *attr,
               char *buf)
{
    struct fsg_lun  *curlun = fsg_lun_from_dev(dev);

    return sprintf(buf, "%d\n", fsg_lun_is_open(curlun)
                  ? curlun->ro
                  : curlun->initially_ro);
}

static ssize_t fsg_show_nofua(struct device *dev, struct device_attribute *attr,
                  char *buf)
{
    struct fsg_lun  *curlun = fsg_lun_from_dev(dev);

    return sprintf(buf, "%u\n", curlun->nofua);
}

static ssize_t fsg_show_file(struct device *dev, struct device_attribute *attr,
                 char *buf)
{
    struct fsg_lun  *curlun = fsg_lun_from_dev(dev);
    struct rw_semaphore *filesem = dev_get_drvdata(dev);
    char        *p;
    ssize_t     rc;

    down_read(filesem);
    if (fsg_lun_is_open(curlun)) {  /* Get the complete pathname */
        p = d_path(&curlun->filp->f_path, buf, PAGE_SIZE - 1);
        if (IS_ERR(p))
            rc = PTR_ERR(p);
        else {
            rc = strlen(p);
            memmove(buf, p, rc);
            buf[rc] = '\n';     /* Add a newline */
            buf[++rc] = 0;
        }
    } else {                /* No file, return 0 bytes */
        *buf = 0;
        rc = 0;
    }
    up_read(filesem);
    return rc;
}


static ssize_t fsg_store_ro(struct device *dev, struct device_attribute *attr,
                const char *buf, size_t count)
{
    ssize_t     rc;
    struct fsg_lun  *curlun = fsg_lun_from_dev(dev);
    struct rw_semaphore *filesem = dev_get_drvdata(dev);
    unsigned    ro;

    rc = kstrtouint(buf, 2, &ro);
    if (rc)
        return rc;

    /*
     * Allow the write-enable status to change only while the
     * backing file is closed.
     */
    down_read(filesem);
    if (fsg_lun_is_open(curlun)) {
        LDBG(curlun, "read-only status change prevented\n");
        rc = -EBUSY;
    } else {
        curlun->ro = ro;
        curlun->initially_ro = ro;
        LDBG(curlun, "read-only status set to %d\n", curlun->ro);
        rc = count;
    }
    up_read(filesem);
    return rc;
}

static ssize_t fsg_store_nofua(struct device *dev,
                   struct device_attribute *attr,
                   const char *buf, size_t count)
{
    struct fsg_lun  *curlun = fsg_lun_from_dev(dev);
    unsigned    nofua;
    int     ret;

    ret = kstrtouint(buf, 2, &nofua);
    if (ret)
        return ret;

    /* Sync data when switching from async mode to sync */
    if (!nofua && curlun->nofua)
        fsg_lun_fsync_sub(curlun);

    curlun->nofua = nofua;

    return count;
}

static ssize_t fsg_store_file(struct device *dev, struct device_attribute *attr,
                  const char *buf, size_t count)
{
    struct fsg_lun  *curlun = fsg_lun_from_dev(dev);
    struct rw_semaphore *filesem = dev_get_drvdata(dev);
    int     rc = 0;

    if (curlun->prevent_medium_removal && fsg_lun_is_open(curlun)) {
        LDBG(curlun, "eject attempt prevented\n");
        return -EBUSY;              /* "Door is locked" */
    }

    /* Remove a trailing newline */
    if (count > 0 && buf[count-1] == '\n')
        ((char *) buf)[count-1] = 0;        /* Ugh! */

    /* Load new medium */
    down_write(filesem);
    if (count > 0 && buf[0]) {
        /* fsg_lun_open() will close existing file if any. */
        rc = fsg_lun_open(curlun, buf);
        if (rc == 0)
            curlun->unit_attention_data =
                    SS_NOT_READY_TO_READY_TRANSITION;
    } else if (fsg_lun_is_open(curlun)) {
        fsg_lun_close(curlun);
        curlun->unit_attention_data = SS_MEDIUM_NOT_PRESENT;
    }
    up_write(filesem);
    return (rc < 0 ? rc : count);
}