/*
 * 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.
 *	->nofua		Flag specifying that FUA flag in SCSI WRITE(10,12)
 *				commands for this LUN shall be ignored.
 *
 *	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.
 *	nofua=b[,b...]	Default false, booleans for ignore FUA flag
 *				in SCSI WRITE(10,12) commands
 *	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.
 *
 * When a LUN receive an "eject" SCSI request (Start/Stop Unit),
 * if the LUN is removable, the backing file is released to simulate
 * ejection.
 *
 *
 * 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 <linux/usb/composite.h>

#include "gadget_chips.h"


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

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

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

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

#include "storage_common.c"


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

struct fsg_dev;
struct fsg_common;

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

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

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

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

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

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

	struct fsg_buffhd	*next_buffhd_to_fill;
	struct fsg_buffhd	*next_buffhd_to_drain;
	struct fsg_buffhd	buffhds[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		bulk_out_maxpacket;
	enum fsg_state		state;		/* For exception handling */
	unsigned int		exception_req_tag;

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

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

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

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

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

	struct kref		ref;
};

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

	const char		*lun_name_format;
	const char		*thread_name;

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

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

	char			can_stall;
};

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

	u16			interface_number;

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

	unsigned long		atomic_bitflags;
#define IGNORE_BULK_OUT		0

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

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

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

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

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

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

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

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


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

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

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


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

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

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

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

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


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

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

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


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

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

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

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

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

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

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

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

static int fsg_setup(struct usb_function *f,
		     const struct usb_ctrlrequest *ctrl)
{
	struct fsg_dev		*fsg = fsg_from_func(f);
	struct usb_request	*req = fsg->common->ep0req;
	u16			w_index = le16_to_cpu(ctrl->wIndex);
	u16			w_value = le16_to_cpu(ctrl->wValue);
	u16			w_length = le16_to_cpu(ctrl->wLength);

	if (!fsg_is_set(fsg->common))
		return -EOPNOTSUPP;

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

	switch (ctrl->bRequest) {

	case 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->common, 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;

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

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


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

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

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

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

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

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

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

static bool start_in_transfer(struct fsg_common *common, struct fsg_buffhd *bh)
{
	if (!fsg_is_set(common))
		return false;
	start_transfer(common->fsg, common->fsg->bulk_in,
		       bh->inreq, &bh->inreq_busy, &bh->state);
	return true;
}

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

static int sleep_thread(struct fsg_common *common)
{
	int	rc = 0;

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


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

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

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

		/*
		 * We allow DPO (Disable Page Out = don't save data in the
		 * cache) and FUA (Force Unit Access = don't read from the
		 * cache), but we don't implement them.
		 */
		if ((common->cmnd[1] & ~0x18) != 0) {
			curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
			return -EINVAL;
		}
	}
	if (lba >= curlun->num_sectors) {
		curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
		return -EINVAL;
	}
	file_offset = ((loff_t) lba) << 9;

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

	for (;;) {
		/*
		 * Figure out how much we need to read:
		 * Try to read the remaining amount.
		 * But don't read more than the buffer size.
		 * And don't try to read past the end of the file.
		 * 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 = common->next_buffhd_to_fill;
		while (bh->state != BUF_STATE_EMPTY) {
			rc = sleep_thread(common);
			if (rc)
				return rc;
		}

		/*
		 * If we were asked to read past the end of file,
		 * end with an empty buffer.
		 */
		if (amount == 0) {
			curlun->sense_data =
					SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
			curlun->sense_data_info = file_offset >> 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;
		common->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;
		if (!start_in_transfer(common, bh))
			/* Don't know what to do if common->fsg is NULL */
			return -EIO;
		common->next_buffhd_to_fill = bh->next;
	}

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


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

static int do_write(struct fsg_common *common)
{
	struct fsg_lun		*curlun = common->curlun;
	u32			lba;
	struct fsg_buffhd	*bh;
	int			get_some_more;
	u32			amount_left_to_req, amount_left_to_write;
	loff_t			usb_offset, file_offset, file_offset_tmp;
	unsigned int		amount;
	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 (common->cmnd[0] == WRITE_6)
		lba = get_unaligned_be24(&common->cmnd[1]);
	else {
		lba = get_unaligned_be32(&common->cmnd[2]);

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

	/* Carry out the file writes */
	get_some_more = 1;
	file_offset = usb_offset = ((loff_t) lba) << 9;
	amount_left_to_req = common->data_size_from_cmnd;
	amount_left_to_write = common->data_size_from_cmnd;

	while (amount_left_to_write > 0) {

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

			/*
			 * Figure out how much we want to get:
			 * Try to get the remaining amount.
			 * But 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;
			common->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;
			if (!start_out_transfer(common, bh))
				/* Dunno what to do if common->fsg is NULL */
				return -EIO;
			common->next_buffhd_to_fill = bh->next;
			continue;
		}

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

			/* Did something go wrong with the transfer? */
			if (bh->outreq->status != 0) {
				curlun->sense_data = SS_COMMUNICATION_FAILURE;
				curlun->sense_data_info = file_offset >> 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;
			common->residue -= nwritten;

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

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

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

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


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

static int do_synchronize_cache(struct fsg_common *common)
{
	struct fsg_lun	*curlun = common->curlun;
	int		rc;

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


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

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

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

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

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

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

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

	/* Prepare to carry out the file verify */
	amount_left = verification_length << 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_common *common, struct fsg_buffhd *bh)
{
	struct fsg_lun *curlun = common->curlun;
	u8	*buf = (u8 *) bh->buf;

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

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

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

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

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

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

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

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

	put_unaligned_be32(curlun->num_sectors - 1, &buf[0]);
						/* Max logical block */
	put_unaligned_be32(512, &buf[4]);	/* Block length */
	return 8;
}

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

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

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

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

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

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

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

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

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

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

	/* No block descriptors */

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

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

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

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

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

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

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

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

	/* Are we allowed to unload the media? */
	if (curlun->prevent_medium_removal) {
		LDBG(curlun, "unload attempt prevented\n");
		curlun->sense_data = SS_MEDIUM_REMOVAL_PREVENTED;
		return -EINVAL;
	}

	if (!loej)
		return 0;

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

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

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

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

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

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

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

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

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

	put_unaligned_be32(curlun->num_sectors, &buf[0]);
						/* Number of blocks */
	put_unaligned_be32(512, &buf[4]);	/* Block length */
	buf[4] = 0x02;				/* Current capacity */
	return 12;
}

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

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


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

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

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

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

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

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

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

static int throw_away_data(struct fsg_common *common)
{
	struct fsg_buffhd	*bh;
	u32			amount;
	int			rc;

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

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

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

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

			/*
			 * 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;
			if (!start_out_transfer(common, bh))
				/* Dunno what to do if common->fsg is NULL */
				return -EIO;
			common->next_buffhd_to_fill = bh->next;
			common->usb_amount_left -= amount;
			continue;
		}

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

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

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

	/*
	 * If we don't know whether the host wants to read or write,
	 * this must be CB or CBI with an unknown command.  We…