[platform/adaptation/renesas_rcar/renesas_kernel.git] / drivers / usb / gadget / f_mass_storage.c

/*
 * f_mass_storage.c -- Mass Storage USB Composite Function
 *
 * Copyright (C) 2003-2008 Alan Stern
 * Copyright (C) 2009 Samsung Electronics
 *                    Author: Michal Nazarewicz <m.nazarewicz@samsung.com>
 * 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.
 *
 * Function supports multiple logical units (LUNs).  Backing storage
 * for each LUN is provided by a regular file or a block device.
 * Access for each LUN can be limited to read-only.  Moreover, the
 * function can indicate that LUN is removable and/or CD-ROM.  (The
 * later implies read-only access.)
 *
 * 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.
 *
 *      lun_name_format A printf-like format for names of the LUN
 *                              devices.  This determines how the
 *                              directory in sysfs will be named.
 *                              Unless you are using several MSFs in
 *                              a single gadget (as opposed to single
 *                              MSF in many configurations) you may
 *                              leave it as NULL (in which case
 *                              "lun%d" will be used).  In the format
 *                              you can use "%d" to index LUNs for
 *                              MSF's with more than one LUN.  (Beware
 *                              that there is only one integer given
 *                              as an argument for the format and
 *                              specifying invalid format may cause
 *                              unspecified behaviour.)
 *      thread_name     Name of the kernel thread process used by the
 *                              MSF.  You can safely set it to NULL
 *                              (in which case default "file-storage"
 *                              will be used).
 *
 *      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.  Note also that the CD-ROM block length is
 * set to 512 rather than the more common value 2048.
 *
 *
 * MSF includes support for module parameters.  If gadget using it
 * decides to use it, the following module parameters will be
 * available:
 *
 *      file=filename[,filename...]
 *                      Names of the files or block devices used for
 *                              backing storage.
 *      ro=b[,b...]     Default false, boolean for read-only access.
 *      removable=b[,b...]
 *                      Default true, boolean for removable media.
 *      cdrom=b[,b...]  Default false, boolean for whether to emulate
 *                              a CD-ROM drive.
 *      luns=N          Default N = number of filenames, number of
 *                              LUNs to support.
 *      stall           Default determined according to the type of
 *                              USB device controller (usually true),
 *                              boolean to permit the driver to halt
 *                              bulk endpoints.
 *
 * The module parameters may be prefixed with some string.  You need
 * to consult gadget's documentation or source to verify whether it is
 * using those module parameters and if it does what are the prefixes
 * (look for FSG_MODULE_PARAMETERS() macro usage, what's inside it is
 * the prefix).
 *
 *
 * Requirements are modest; only a bulk-in and a bulk-out endpoint are
 * needed.  The memory requirement amounts to two 16K buffers, size
 * configurable by a parameter.  Support is included for both
 * full-speed and high-speed operation.
 *
 * Note that the driver is slightly non-portable in that it assumes a
 * single memory/DMA buffer will be useable for bulk-in, bulk-out, and
 * interrupt-in endpoints.  With most device controllers this isn't an
 * issue, but there may be some with hardware restrictions that prevent
 * a buffer from being used by more than one endpoint.
 *
 *
 * The pathnames of the backing files and the ro settings are
 * available in the attribute files "file" and "ro" in the lun<n> (or
 * to be more precise in a directory which name comes from
 * "lun_name_format" option!) subdirectory of the gadget's sysfs
 * directory.  If the "removable" option is set, writing to these
 * files will simulate ejecting/loading the medium (writing an empty
 * line means eject) and adjusting a write-enable tab.  Changes to the
 * ro setting are not allowed when the medium is loaded or if CD-ROM
 * emulation is being used.
 *
 *
 * This 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.  At 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 "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_INTR_EP 1
#define FSG_BUFFHD_STATIC_BUFFER 1
#define FSG_NO_DEVICE_STRINGS    1
#define FSG_NO_OTG               1
#define FSG_NO_INTR_EP           1

#include "storage_common.c"


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


/* Data shared by all the FSG instances. */
struct fsg_common {
        struct usb_gadget       *gadget;

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

        struct fsg_buffhd       *next_buffhd_to_fill;
        struct fsg_buffhd       *next_buffhd_to_drain;
        struct fsg_buffhd       buffhds[FSG_NUM_BUFFERS];

        int                     cmnd_size;
        u8                      cmnd[MAX_COMMAND_SIZE];

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

        unsigned int            can_stall:1;
        unsigned int            free_storage_on_release:1;

        const char              *thread_name;

        /* 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;
        } luns[FSG_MAX_LUNS];

        const char              *lun_name_format;
        const char              *thread_name;

        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_composite_dev *cdev;
        struct usb_gadget       *gadget;        /* Copy of cdev->gadget */
        struct fsg_common       *common;

        u16                     interface_number;

        /* 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;
        const char              *ep0req_name;

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

        u8                      config, new_config;

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

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

        struct usb_ep           *bulk_in;
        struct usb_ep           *bulk_out;

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

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


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_dev *fsg)
{
        return (fsg->state > FSG_STATE_IDLE);
}

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

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

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

static 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_dev *fsg)
{
        /* Tell the main thread that something has happened */
        fsg->thread_wakeup_needed = 1;
        if (fsg->thread_task)
                wake_up_process(fsg->thread_task);
}


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

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


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

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

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

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

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

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

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

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

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

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

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

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


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

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

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->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->config)
                return -EOPNOTSUPP;

        switch (ctrl->bRequest) {

        case USB_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)
                        return -EDOM;

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

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

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

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

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


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

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


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

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

        /* Get the starting Logical Block Address and check that it's
         * not too big */
        if (fsg->common->cmnd[0] == SC_READ_6)
                lba = get_unaligned_be24(&fsg->common->cmnd[1]);
        else {
                lba = get_unaligned_be32(&fsg->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 ((fsg->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) << 9;

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

        for (;;) {

                /* Figure out how much we need to read:
                 * Try to read the remaining amount.
                 * But don't read more than the buffer size.
                 * And don't try to read past the end of the file.
                 * Finally, if we're not at a page boundary, don't read past
                 *      the next page.
                 * If this means reading 0 then we were asked to read past
                 *      the end of file. */
                amount = min(amount_left, FSG_BUFLEN);
                amount = min((loff_t) amount,
                                curlun->file_length - file_offset);
                partial_page = file_offset & (PAGE_CACHE_SIZE - 1);
                if (partial_page > 0)
                        amount = min(amount, (unsigned int) PAGE_CACHE_SIZE -
                                        partial_page);

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

                /* If we were asked to read past the end of file,
                 * end with an empty buffer. */
                if (amount == 0) {
                        curlun->sense_data =
                                        SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                        curlun->sense_data_info = file_offset >> 9;
                        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 -= (nread & 511); /* Round down to a block */
                }
                file_offset  += nread;
                amount_left  -= nread;
                fsg->residue -= nread;
                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 >> 9;
                        curlun->info_valid = 1;
                        break;
                }

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

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

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


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

static int do_write(struct fsg_dev *fsg)
{
        struct fsg_lun          *curlun = fsg->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;
        unsigned int            partial_page;
        ssize_t                 nwritten;
        int                     rc;

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

        /* Get the starting Logical Block Address and check that it's
         * not too big */
        if (fsg->common->cmnd[0] == SC_WRITE_6)
                lba = get_unaligned_be24(&fsg->common->cmnd[1]);
        else {
                lba = get_unaligned_be32(&fsg->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 ((fsg->common->cmnd[1] & ~0x18) != 0) {
                        curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                        return -EINVAL;
                }
                if (fsg->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) << 9;
        amount_left_to_req = amount_left_to_write = fsg->data_size_from_cmnd;

        while (amount_left_to_write > 0) {

                /* Queue a request for more data from the host */
                bh = fsg->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 don't get more than the buffer size.
                         * And don't try to go past the end of the file.
                         * If we're not at a page boundary,
                         *      don't go past the next page.
                         * If this means getting 0, then we were asked
                         *      to write past the end of file.
                         * Finally, round down to a block boundary. */
                        amount = min(amount_left_to_req, FSG_BUFLEN);
                        amount = min((loff_t) amount, curlun->file_length -
                                        usb_offset);
                        partial_page = usb_offset & (PAGE_CACHE_SIZE - 1);
                        if (partial_page > 0)
                                amount = min(amount,
        (unsigned int) PAGE_CACHE_SIZE - partial_page);

                        if (amount == 0) {
                                get_some_more = 0;
                                curlun->sense_data =
                                        SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                                curlun->sense_data_info = usb_offset >> 9;
                                curlun->info_valid = 1;
                                continue;
                        }
                        amount -= (amount & 511);
                        if (amount == 0) {

                                /* Why were we were asked to transfer a
                                 * partial block? */
                                get_some_more = 0;
                                continue;
                        }

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

                        /* amount is always divisible by 512, hence by
                         * the bulk-out maxpacket size */
                        bh->outreq->length = amount;
                        bh->bulk_out_intended_length = amount;
                        bh->outreq->short_not_ok = 1;
                        start_transfer(fsg, fsg->bulk_out, bh->outreq,
                                        &bh->outreq_busy, &bh->state);
                        fsg->common->next_buffhd_to_fill = bh->next;
                        continue;
                }

                /* Write the received data to the backing file */
                bh = fsg->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();
                        fsg->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 >> 9;
                                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;
                        }

                        /* 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 -= (nwritten & 511);
                                /* Round down to a block */
                        }
                        file_offset += nwritten;
                        amount_left_to_write -= nwritten;
                        fsg->residue -= nwritten;

                        /* If an error occurred, report it and its position */
                        if (nwritten < amount) {
                                curlun->sense_data = SS_WRITE_ERROR;
                                curlun->sense_data_info = file_offset >> 9;
                                curlun->info_valid = 1;
                                break;
                        }

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

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

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


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

static int do_synchronize_cache(struct fsg_dev *fsg)
{
        struct fsg_lun  *curlun = fsg->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_inode_pages -> %ld\n", rc);
}

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

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

        /* Prepare to carry out the file verify */
        amount_left = verification_length << 9;
        file_offset = ((loff_t) lba) << 9;

        /* 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.
                 * If this means reading 0 then we were asked to read
                 * past the end of 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 >> 9;
                        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 -= (nread & 511); /* Round down to a sector */
                }
                if (nread == 0) {
                        curlun->sense_data = SS_UNRECOVERED_READ_ERROR;
                        curlun->sense_data_info = file_offset >> 9;
                        curlun->info_valid = 1;
                        break;
                }
                file_offset += nread;
                amount_left -= nread;
        }
        return 0;
}


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

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

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

        buf[0] = curlun->cdrom ? TYPE_CDROM : 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, fsg->common->inquiry_string,
               sizeof fsg->common->inquiry_string);
        return 36;
}


static int do_request_sense(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = fsg->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 */
                fsg->bad_lun_okay = 1;
                sd = SS_LOGICAL_UNIT_NOT_SUPPORTED;
                sdinfo = 0;
                valid = 0;
        } else {
                sd = curlun->sense_data;
                sdinfo = curlun->sense_data_info;
                valid = curlun->info_valid << 7;
                curlun->sense_data = SS_NO_SENSE;
                curlun->sense_data_info = 0;
                curlun->info_valid = 0;
        }

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


static int do_read_capacity(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = fsg->common->curlun;
        u32             lba = get_unaligned_be32(&fsg->common->cmnd[2]);
        int             pmi = fsg->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(512, &buf[4]);       /* Block length */
        return 8;
}


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

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

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


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

        if ((fsg->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_dev *fsg, struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = fsg->common->curlun;
        int             mscmnd = fsg->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 ((fsg->common->cmnd[1] & ~0x08) != 0) {      /* Mask away DBD */
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }
        pc = fsg->common->cmnd[2] >> 6;
        page_code = fsg->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 == SC_MODE_SENSE_6) {
                buf[2] = (curlun->ro ? 0x80 : 0x00);            /* WP, DPOFUA */
                buf += 4;
                limit = 255;
        } else {                        /* SC_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 == SC_MODE_SENSE_6)
                buf0[0] = len - 1;
        else
                put_unaligned_be16(len - 2, buf0);
        return len;
}


static int do_start_stop(struct fsg_dev *fsg)
{
        if (!fsg->common->curlun) {
                return -EINVAL;
        } else if (!fsg->common->curlun->removable) {
                fsg->common->curlun->sense_data = SS_INVALID_COMMAND;
                return -EINVAL;
        }
        return 0;
}


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

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

        prevent = fsg->common->cmnd[4] & 0x01;
        if ((fsg->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_dev *fsg,
                        struct fsg_buffhd *bh)
{
        struct fsg_lun  *curlun = fsg->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(512, &buf[4]);       /* Block length */
        buf[4] = 0x02;                          /* Current capacity */
        return 12;
}


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

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


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

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

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

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

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

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

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

static int pad_with_zeros(struct fsg_dev *fsg)
{
        struct fsg_buffhd       *bh = fsg->common->next_buffhd_to_fill;
        u32                     nkeep = bh->inreq->length;
        u32                     nsend;
        int                     rc;

        bh->state = BUF_STATE_EMPTY;            /* For the first iteration */
        fsg->usb_amount_left = nkeep + fsg->residue;
        while (fsg->usb_amount_left > 0) {

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

                nsend = min(fsg->usb_amount_left, FSG_BUFLEN);
                memset(bh->buf + nkeep, 0, nsend - nkeep);
                bh->inreq->length = nsend;
                bh->inreq->zero = 0;
                start_transfer(fsg, fsg->bulk_in, bh->inreq,
                                &bh->inreq_busy, &bh->state);
                bh = fsg->common->next_buffhd_to_fill = bh->next;
                fsg->usb_amount_left -= nsend;
                nkeep = 0;
        }
        return 0;
}

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

        for (bh = fsg->common->next_buffhd_to_drain;
             bh->state != BUF_STATE_EMPTY || fsg->usb_amount_left > 0;
             bh = fsg->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;
                        fsg->common->next_buffhd_to_drain = bh->next;

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

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

                        /* amount is always divisible by 512, hence by
                         * the bulk-out maxpacket size */
                        bh->outreq->length = amount;
                        bh->bulk_out_intended_length = amount;
                        bh->outreq->short_not_ok = 1;
                        start_transfer(fsg, fsg->bulk_out, bh->outreq,
                                        &bh->outreq_busy, &bh->state);
                        fsg->common->next_buffhd_to_fill = bh->next;
                        fsg->usb_amount_left -= amount;
                        continue;
                }

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


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

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

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

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

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

                /* For Bulk-only, if we're allowed to stall then send the
                 * short packet and halt the bulk-in endpoint.  If we can't
                 * stall, pad out the remaining data with 0's. */
                } else if (fsg->can_stall) {
                        bh->inreq->zero = 1;
                        start_transfer(fsg, fsg->bulk_in, bh->inreq,
                                       &bh->inreq_busy, &bh->state);
                        fsg->common->next_buffhd_to_fill = bh->next;
                        rc = halt_bulk_in_endpoint(fsg);
                } else {
                        rc = pad_with_zeros(fsg);
                }
                break;

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

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

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

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


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

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

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

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

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

        csw->Signature = cpu_to_le32(USB_BULK_CS_SIG);
        csw->Tag = fsg->tag;
        csw->Residue = cpu_to_le32(fsg->residue);
        csw->Status = status;

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

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

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

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

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

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

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

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

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

        /* Check the LUN */
        if (fsg->common->lun >= 0 && fsg->common->lun < fsg->common->nluns) {
                curlun = &fsg->common->luns[fsg->common->lun];
                fsg->common->curlun = curlun;
                if (fsg->common->cmnd[0] != SC_REQUEST_SENSE) {
                        curlun->sense_data = SS_NO_SENSE;
                        curlun->sense_data_info = 0;
                        curlun->info_valid = 0;
                }
        } else {
                fsg->common->curlun = curlun = NULL;
                fsg->bad_lun_okay = 0;

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

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


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

        dump_cdb(fsg->common);

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

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

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

        case SC_MODE_SELECT_6:
                fsg->data_size_from_cmnd = fsg->common->cmnd[4];
                reply = check_command(fsg, 6, DATA_DIR_FROM_HOST,
                                      (1<<1) | (1<<4), 0,
                                      "MODE SELECT(6)");
                if (reply == 0)
                        reply = do_mode_select(fsg, bh);
                break;

        case SC_MODE_SELECT_10:
                fsg->data_size_from_cmnd =
                        get_unaligned_be16(&fsg->common->cmnd[7]);
                reply = check_command(fsg, 10, DATA_DIR_FROM_HOST,
                                      (1<<1) | (3<<7), 0,
                                      "MODE SELECT(10)");
                if (reply == 0)
                        reply = do_mode_select(fsg, bh);
                break;

        case SC_MODE_SENSE_6:
                fsg->data_size_from_cmnd = fsg->common->cmnd[4];
                reply = check_command(fsg, 6, DATA_DIR_TO_HOST,
                                      (1<<1) | (1<<2) | (1<<4), 0,
                                      "MODE SENSE(6)");
                if (reply == 0)
                        reply = do_mode_sense(fsg, bh);
                break;

        case SC_MODE_SENSE_10:
                fsg->data_size_from_cmnd =
                        get_unaligned_be16(&fsg->common->cmnd[7]);
                reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
                                      (1<<1) | (1<<2) | (3<<7), 0,
                                      "MODE SENSE(10)");
                if (reply == 0)
                        reply = do_mode_sense(fsg, bh);
                break;

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

        case SC_READ_6:
                i = fsg->common->cmnd[4];
                fsg->data_size_from_cmnd = (i == 0 ? 256 : i) << 9;
                reply = check_command(fsg, 6, DATA_DIR_TO_HOST,
                                      (7<<1) | (1<<4), 1,
                                      "READ(6)");
                if (reply == 0)
                        reply = do_read(fsg);
                break;

        case SC_READ_10:
                fsg->data_size_from_cmnd =
                                get_unaligned_be16(&fsg->common->cmnd[7]) << 9;
                reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
                                      (1<<1) | (0xf<<2) | (3<<7), 1,
                                      "READ(10)");
                if (reply == 0)
                        reply = do_read(fsg);
                break;

        case SC_READ_12:
                fsg->data_size_from_cmnd =
                                get_unaligned_be32(&fsg->common->cmnd[6]) << 9;
                reply = check_command(fsg, 12, DATA_DIR_TO_HOST,
                                      (1<<1) | (0xf<<2) | (0xf<<6), 1,
                                      "READ(12)");
                if (reply == 0)
                        reply = do_read(fsg);
                break;

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

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

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

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

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

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

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

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

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

        case SC_WRITE_6:
                i = fsg->common->cmnd[4];
                fsg->data_size_from_cmnd = (i == 0 ? 256 : i) << 9;
                reply = check_command(fsg, 6, DATA_DIR_FROM_HOST,
                                      (7<<1) | (1<<4), 1,
                                      "WRITE(6)");
                if (reply == 0)
                        reply = do_write(fsg);
                break;

        case SC_WRITE_10:
                fsg->data_size_from_cmnd =
                                get_unaligned_be16(&fsg->common->cmnd[7]) << 9;
                reply = check_command(fsg, 10, DATA_DIR_FROM_HOST,
                                      (1<<1) | (0xf<<2) | (3<<7), 1,
                                      "WRITE(10)");
                if (reply == 0)
                        reply = do_write(fsg);
                break;

        case SC_WRITE_12:
                fsg->data_size_from_cmnd =
                                get_unaligned_be32(&fsg->common->cmnd[6]) << 9;
                reply = check_command(fsg, 12, DATA_DIR_FROM_HOST,
                                      (1<<1) | (0xf<<2) | (0xf<<6), 1,
                                      "WRITE(12)");
                if (reply == 0)
                        reply = do_write(fsg);
                break;

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

        default:
unknown_cmnd:
                fsg->data_size_from_cmnd = 0;
                sprintf(unknown, "Unknown x%02x", fsg->common->cmnd[0]);
                reply = check_command(fsg, fsg->common->cmnd_size,
                                      DATA_DIR_UNKNOWN, 0xff, 0, unknown);
                if (reply == 0) {
                        fsg->common->curlun->sense_data = SS_INVALID_COMMAND;
                        reply = -EINVAL;
                }
                break;
        }
        up_read(&fsg->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 && fsg->data_dir == DATA_DIR_TO_HOST) {
                reply = min((u32) reply, fsg->data_size_from_cmnd);
                bh->inreq->length = reply;
                bh->state = BUF_STATE_FULL;
                fsg->residue -= reply;
        }                               /* Otherwise it's already set */

        return 0;
}


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

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

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

        /* Is the CBW valid? */
        if (req->actual != USB_BULK_CB_WRAP_LEN ||
                        cbw->Signature != cpu_to_le32(
                                USB_BULK_CB_SIG)) {
                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 & ~USB_BULK_IN_FLAG ||
                        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 (fsg->can_stall) {
                        fsg_set_halt(fsg, fsg->bulk_out);
                        halt_bulk_in_endpoint(fsg);
                }
                return -EINVAL;
        }

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


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

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

        /* Queue a request to read a Bulk-only CBW */
        set_bulk_out_req_length(fsg, bh, USB_BULK_CB_WRAP_LEN);
        bh->outreq->short_not_ok = 1;
        start_transfer(fsg, fsg->bulk_out, bh->outreq,
                       &bh->outreq_busy, &bh->state);

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

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

        return rc;
}


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

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

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

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

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

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

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

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

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

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

        d = fsg_ep_desc(fsg->gadget,
                        &fsg_fs_bulk_out_desc, &fsg_hs_bulk_out_desc);
        rc = enable_endpoint(fsg, fsg->bulk_out, d);
        if (rc != 0)
                goto reset;
        fsg->bulk_out_enabled = 1;
        fsg->bulk_out_maxpacket = le16_to_cpu(d->wMaxPacketSize);
        clear_bit(IGNORE_BULK_OUT, &fsg->atomic_bitflags);

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

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

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


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

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

        /* Enable the interface */
        if (new_config != 0) {
                fsg->config = new_config;
                rc = do_set_interface(fsg, 0);
                if (rc != 0)
                        fsg->config = 0;        /* Reset on errors */
        }
        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->new_config = 1;
        raise_exception(fsg, FSG_STATE_CONFIG_CHANGE);
        return 0;
}

static void fsg_disable(struct usb_function *f)
{
        struct fsg_dev *fsg = fsg_from_func(f);
        fsg->new_config = 0;
        raise_exception(fsg, FSG_STATE_CONFIG_CHANGE);
}


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

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

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

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

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

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

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

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

        if (old_state == FSG_STATE_ABORT_BULK_OUT)
                fsg->state = FSG_STATE_STATUS_PHASE;
        else {
                for (i = 0; i < fsg->common->nluns; ++i) {
                        curlun = &fsg->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;
                }
                fsg->state = FSG_STATE_IDLE;
        }
        spin_unlock_irq(&fsg->lock);

        /* Carry out any extra actions required for the exception */
        switch (old_state) {
        case FSG_STATE_ABORT_BULK_OUT:
                send_status(fsg);
                spin_lock_irq(&fsg->lock);
                if (fsg->state == FSG_STATE_STATUS_PHASE)
                        fsg->state = FSG_STATE_IDLE;
                spin_unlock_irq(&fsg->lock);
                break;

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

                if (fsg->ep0_req_tag == exception_req_tag)
                        ep0_queue(fsg); /* 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 < fsg->common->nluns; ++i) */
                /*      fsg->common->luns[i].unit_attention_data = */
                /*              SS_RESET_OCCURRED;  */
                break;

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

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

        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 *fsg_)
{
        struct fsg_dev          *fsg = fsg_;

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

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

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

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

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

                if (get_next_command(fsg))
                        continue;

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

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

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

                if (send_status(fsg))
                        continue;

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

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

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

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


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

/* Write permission is checked per LUN in store_*() functions. */
static DEVICE_ATTR(ro, 0644, fsg_show_ro, fsg_store_ro);
static DEVICE_ATTR(file, 0644, fsg_show_file, fsg_store_file);


/****************************** 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;

        /* 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->gadget = gadget;

        /* Create the LUNs, open their backing files, and register the
         * LUN devices in sysfs. */
        curlun = kzalloc(nluns * sizeof *curlun, GFP_KERNEL);
        if (!curlun) {
                kfree(common);
                return ERR_PTR(-ENOMEM);
        }
        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->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,
                             cfg->lun_name_format
                           ? cfg->lun_name_format
                           : "lun%d",
                             i);

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

                rc = device_create_file(&curlun->dev, &dev_attr_ro);
                if (rc)
                        goto error_luns;
                rc = device_create_file(&curlun->dev, &dev_attr_file);
                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 */
        /* Buffers in buffhds are static -- no need for additional
         * allocation. */
        bh = common->buffhds;
        i = FSG_NUM_BUFFERS - 1;
        do {
                bh->next = bh + 1;
        } while (++bh, --i);
        bh->next = common->buffhds;


        /* Prepare inquiryString */
        if (cfg->release != 0xffff) {
                i = cfg->release;
        } else {
                /* The sa1100 controller is not supported */
                i = gadget_is_sa1100(gadget)
                        ? -1
                        : usb_gadget_controller_number(gadget);
                if (i >= 0) {
                        i = 0x0300 + i;
                } else {
                        WARNING(common, "controller '%s' not recognized\n",
                                gadget->name);
                        i = 0x0399;
                }
        }
#define OR(x, y) ((x) ? (x) : (y))
        snprintf(common->inquiry_string, sizeof common->inquiry_string,
                 "%-8s%-16s%04x",
                 OR(cfg->vendor_name, "Linux   "),
                 /* Assume product name dependent on the first LUN */
                 OR(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_sh(fsg->gadget) || gadget_is_at91(fsg->gadget));


        common->thread_name = OR(cfg->thread_name, "file-storage");
        kref_init(&common->ref);
#undef OR


        /* 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);

        return common;


error_luns:
        common->nluns = i + 1;
error_release:
        /* 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);
        unsigned i = common->nluns;
        struct fsg_lun *lun = common->luns;

        /* Beware tempting for -> do-while optimization: when in error
         * recovery nluns may be zero. */

        for (; i; --i, ++lun) {
                device_remove_file(&lun->dev, &dev_attr_ro);
                device_remove_file(&lun->dev, &dev_attr_file);
                fsg_lun_close(lun);
                device_unregister(&lun->dev);
        }

        kfree(common->luns);
        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);

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

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

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

        fsg_common_put(fsg->common);
        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                     rc;
        int                     i;
        struct usb_ep           *ep;

        fsg->gadget = gadget;
        fsg->ep0 = gadget->ep0;
        fsg->ep0req = c->cdev->req;

        /* 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;          /* claim the endpoint */
        fsg->bulk_in = ep;

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

        if (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 = fsg_hs_function;
        }


        /* maybe allocate device-global string IDs, and patch descriptors */
        if (fsg_strings[FSG_STRING_INTERFACE].id == 0) {
                i = usb_string_id(c->cdev);
                if (i < 0)
                        return i;
                fsg_strings[FSG_STRING_INTERFACE].id = i;
                fsg_intf_desc.iInterface = i;
        }


        fsg->thread_task = kthread_create(fsg_main_thread, fsg,
                                          fsg->common->thread_name);
        if (IS_ERR(fsg->thread_task)) {
                rc = PTR_ERR(fsg->thread_task);
                goto out;
        }

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

        set_bit(REGISTERED, &fsg->atomic_bitflags);

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

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

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


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

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

static int fsg_add(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;

        spin_lock_init(&fsg->lock);
        init_completion(&fsg->thread_notifier);

        fsg->cdev                 = cdev;
        fsg->function.name        = FSG_DRIVER_DESC;
        fsg->function.strings     = fsg_strings_array;
        fsg->function.descriptors = fsg_fs_function;
        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. */
        fsg->can_stall = common->can_stall;

        rc = usb_add_function(c, &fsg->function);

        if (likely(rc == 0))
                fsg_common_get(fsg->common);
        else
                kfree(fsg);

        return rc;
}



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


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

        unsigned int    file_count, ro_count, removable_count, cdrom_count;
        unsigned int    luns;   /* nluns */
        int             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(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 = /* Removable by default */
                        params->removable_count <= i || params->removable[i];
                lun->filename =
                        params->file_count > i && params->file[i][0]
                        ? params->file[i]
                        : 0;
        }

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

        /* 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);
}