USB: f_fs: the FunctionFS driver

The FunctionFS is a USB composite function that can be used
with the composite framework to create an USB gadget.

>From kernel point of view it is just a composite function with
some unique behaviour.  It may be added to an USB
configuration only after the user space driver has registered
by writing descriptors and strings (the user space program has
to provide the same information that kernel level composite
functions provide when they are added to the configuration).

>From user space point of view it is a file system which when
mounted provide an "ep0" file.  User space driver need to
write descriptors and strings to that file.  It does not need
to worry about endpoints, interfaces or strings numbers but
simply provide descriptors such as if the function was the
only one (endpoints and strings numbers starting from one and
interface numbers starting from core).  The FunctionFS changes
numbers of those as needed also handling situation when
numbers differ in different configurations.

When descriptors and strings are written "ep#" files appear
(one for each declared endpoint) which handle communication on
a single endpoint.  Again, FunctionFS takes care of the real
numbers and changing of the configuration (which means that
"ep1" file may be really mapped to (say) endpoint 3 (and when
configuration changes to (say) endpoint 2)).  "ep0" is used
for receiving events and handling setup requests.

When all files are closed the function disables itself.

Signed-off-by: Michal Nazarewicz <m.nazarewicz@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 2441 insertions, 0 deletions

diff --git a/drivers/usb/gadget/f_fs.c b/drivers/usb/gadget/f_fs.c
new file mode 100644
index 000000000000..af89ca672c60
--- /dev/null
+++ b/drivers/usb/gadget/f_fs.c
@@ -0,0 +1,2441 @@
+/*
+ * f_fs.c -- user mode filesystem api for usb composite funtcion controllers
+ *
+ * Copyright (C) 2010 Samsung Electronics
+ * Author: Michal Nazarewicz <m.nazarewicz@samsung.com>
+ *
+ * Based on inode.c (GadgetFS):
+ * Copyright (C) 2003-2004 David Brownell
+ * Copyright (C) 2003 Agilent Technologies
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+
+/* #define DEBUG */
+/* #define VERBOSE_DEBUG */
+
+#include <linux/blkdev.h>
+#include <asm/unaligned.h>
+#include <linux/smp_lock.h>
+
+#include <linux/usb/composite.h>
+#include <linux/usb/functionfs.h>
+
+
+#define FUNCTIONFS_MAGIC	0xa647361 /* Chosen by a honest dice roll ;) */
+
+
+/* Debuging *****************************************************************/
+
+#define ffs_printk(level, fmt, args...) printk(level "f_fs: " fmt "\n", ## args)
+
+#define FERR(...)  ffs_printk(KERN_ERR,  __VA_ARGS__)
+#define FINFO(...) ffs_printk(KERN_INFO, __VA_ARGS__)
+
+#ifdef DEBUG
+#  define FDBG(...) ffs_printk(KERN_DEBUG, __VA_ARGS__)
+#else
+#  define FDBG(...) do { } while (0)
+#endif /* DEBUG */
+
+#ifdef VERBOSE_DEBUG
+#  define FVDBG FDBG
+#else
+#  define FVDBG(...) do { } while (0)
+#endif /* VERBOSE_DEBUG */
+
+#define ENTER()    FVDBG("%s()", __func__)
+
+#ifdef VERBOSE_DEBUG
+#  define ffs_dump_mem(prefix, ptr, len) \
+	print_hex_dump_bytes("f_fs" prefix ": ", DUMP_PREFIX_NONE, ptr, len)
+#else
+#  define ffs_dump_mem(prefix, ptr, len) do { } while (0)
+#endif
+
+
+/* The data structure and setup file ****************************************/
+
+enum ffs_state {
+	/* Waiting for descriptors and strings. */
+	/* In this state no open(2), read(2) or write(2) on epfiles
+	 * may succeed (which should not be the problem as there
+	 * should be no such files opened in the firts place). */
+	FFS_READ_DESCRIPTORS,
+	FFS_READ_STRINGS,
+
+	/* We've got descriptors and strings.  We are or have called
+	 * functionfs_ready_callback().  functionfs_bind() may have
+	 * been called but we don't know. */
+	/* This is the only state in which operations on epfiles may
+	 * succeed. */
+	FFS_ACTIVE,
+
+	/* All endpoints have been closed.  This state is also set if
+	 * we encounter an unrecoverable error.  The only
+	 * unrecoverable error is situation when after reading strings
+	 * from user space we fail to initialise EP files or
+	 * functionfs_ready_callback() returns with error (<0). */
+	/* In this state no open(2), read(2) or write(2) (both on ep0
+	 * as well as epfile) may succeed (at this point epfiles are
+	 * unlinked and all closed so this is not a problem; ep0 is
+	 * also closed but ep0 file exists and so open(2) on ep0 must
+	 * fail). */
+	FFS_CLOSING
+};
+
+
+enum ffs_setup_state {
+	/* There is no setup request pending. */
+	FFS_NO_SETUP,
+	/* User has read events and there was a setup request event
+	 * there.  The next read/write on ep0 will handle the
+	 * request. */
+	FFS_SETUP_PENDING,
+	/* There was event pending but before user space handled it
+	 * some other event was introduced which canceled existing
+	 * setup.  If this state is set read/write on ep0 return
+	 * -EIDRM.  This state is only set when adding event. */
+	FFS_SETUP_CANCELED
+};
+
+
+
+struct ffs_epfile;
+struct ffs_function;
+
+struct ffs_data {
+	struct usb_gadget		*gadget;
+
+	/* Protect access read/write operations, only one read/write
+	 * at a time.  As a consequence protects ep0req and company.
+	 * While setup request is being processed (queued) this is
+	 * held. */
+	struct mutex			mutex;
+
+	/* Protect access to enpoint related structures (basically
+	 * usb_ep_queue(), usb_ep_dequeue(), etc. calls) except for
+	 * endpint zero. */
+	spinlock_t			eps_lock;
+
+	/* XXX REVISIT do we need our own request? Since we are not
+	 * handling setup requests immidiatelly user space may be so
+	 * slow that another setup will be sent to the gadget but this
+	 * time not to us but another function and then there could be
+	 * a race.  Is taht the case? Or maybe we can use cdev->req
+	 * after all, maybe we just need some spinlock for that? */
+	struct usb_request		*ep0req;		/* P: mutex */
+	struct completion		ep0req_completion;	/* P: mutex */
+	int				ep0req_status;		/* P: mutex */
+
+	/* reference counter */
+	atomic_t			ref;
+	/* how many files are opened (EP0 and others) */
+	atomic_t			opened;
+
+	/* EP0 state */
+	enum ffs_state			state;
+
+	/*
+	 * Possible transations:
+	 * + FFS_NO_SETUP       -> FFS_SETUP_PENDING  -- P: ev.waitq.lock
+	 *               happens only in ep0 read which is P: mutex
+	 * + FFS_SETUP_PENDING  -> FFS_NO_SETUP       -- P: ev.waitq.lock
+	 *               happens only in ep0 i/o  which is P: mutex
+	 * + FFS_SETUP_PENDING  -> FFS_SETUP_CANCELED -- P: ev.waitq.lock
+	 * + FFS_SETUP_CANCELED -> FFS_NO_SETUP       -- cmpxchg
+	 */
+	enum ffs_setup_state		setup_state;
+
+#define FFS_SETUP_STATE(ffs)					\
+	((enum ffs_setup_state)cmpxchg(&(ffs)->setup_state,	\
+				       FFS_SETUP_CANCELED, FFS_NO_SETUP))
+
+	/* Events & such. */
+	struct {
+		u8				types[4];
+		unsigned short			count;
+		/* XXX REVISIT need to update it in some places, or do we? */
+		unsigned short			can_stall;
+		struct usb_ctrlrequest		setup;
+
+		wait_queue_head_t		waitq;
+	} ev; /* the whole structure, P: ev.waitq.lock */
+
+	/* Flags */
+	unsigned long			flags;
+#define FFS_FL_CALL_CLOSED_CALLBACK 0
+#define FFS_FL_BOUND                1
+
+	/* Active function */
+	struct ffs_function		*func;
+
+	/* Device name, write once when file system is mounted.
+	 * Intendet for user to read if she wants. */
+	const char			*dev_name;
+	/* Private data for our user (ie. gadget).  Managed by
+	 * user. */
+	void				*private_data;
+
+	/* filled by __ffs_data_got_descs() */
+	/* real descriptors are 16 bytes after raw_descs (so you need
+	 * to skip 16 bytes (ie. ffs->raw_descs + 16) to get to the
+	 * first full speed descriptor).  raw_descs_length and
+	 * raw_fs_descs_length do not have those 16 bytes added. */
+	const void			*raw_descs;
+	unsigned			raw_descs_length;
+	unsigned			raw_fs_descs_length;
+	unsigned			fs_descs_count;
+	unsigned			hs_descs_count;
+
+	unsigned short			strings_count;
+	unsigned short			interfaces_count;
+	unsigned short			eps_count;
+	unsigned short			_pad1;
+
+	/* filled by __ffs_data_got_strings() */
+	/* ids in stringtabs are set in functionfs_bind() */
+	const void			*raw_strings;
+	struct usb_gadget_strings	**stringtabs;
+
+	/* File system's super block, write once when file system is mounted. */
+	struct super_block		*sb;
+
+	/* File permissions, written once when fs is mounted*/
+	struct ffs_file_perms {
+		umode_t				mode;
+		uid_t				uid;
+		gid_t				gid;
+	}				file_perms;
+
+	/* The endpoint files, filled by ffs_epfiles_create(),
+	 * destroyed by ffs_epfiles_destroy(). */
+	struct ffs_epfile		*epfiles;
+};
+
+/* Reference counter handling */
+static void ffs_data_get(struct ffs_data *ffs);
+static void ffs_data_put(struct ffs_data *ffs);
+/* Creates new ffs_data object. */
+static struct ffs_data *__must_check ffs_data_new(void) __attribute__((malloc));
+
+/* Opened counter handling. */
+static void ffs_data_opened(struct ffs_data *ffs);
+static void ffs_data_closed(struct ffs_data *ffs);
+
+/* Called with ffs->mutex held; take over ownerrship of data. */
+static int __must_check
+__ffs_data_got_descs(struct ffs_data *ffs, char *data, size_t len);
+static int __must_check
+__ffs_data_got_strings(struct ffs_data *ffs, char *data, size_t len);
+
+
+/* The function structure ***************************************************/
+
+struct ffs_ep;
+
+struct ffs_function {
+	struct usb_configuration	*conf;
+	struct usb_gadget		*gadget;
+	struct ffs_data			*ffs;
+
+	struct ffs_ep			*eps;
+	u8				eps_revmap[16];
+	short				*interfaces_nums;
+
+	struct usb_function		function;
+};
+
+
+static struct ffs_function *ffs_func_from_usb(struct usb_function *f)
+{
+	return container_of(f, struct ffs_function, function);
+}
+
+static void ffs_func_free(struct ffs_function *func);
+
+
+static void ffs_func_eps_disable(struct ffs_function *func);
+static int __must_check ffs_func_eps_enable(struct ffs_function *func);
+
+
+static int ffs_func_bind(struct usb_configuration *,
+			 struct usb_function *);
+static void ffs_func_unbind(struct usb_configuration *,
+			    struct usb_function *);
+static int ffs_func_set_alt(struct usb_function *, unsigned, unsigned);
+static void ffs_func_disable(struct usb_function *);
+static int ffs_func_setup(struct usb_function *,
+			  const struct usb_ctrlrequest *);
+static void ffs_func_suspend(struct usb_function *);
+static void ffs_func_resume(struct usb_function *);
+
+
+static int ffs_func_revmap_ep(struct ffs_function *func, u8 num);
+static int ffs_func_revmap_intf(struct ffs_function *func, u8 intf);
+
+
+
+/* The endpoints structures *************************************************/
+
+struct ffs_ep {
+	struct usb_ep			*ep;	/* P: ffs->eps_lock */
+	struct usb_request		*req;	/* P: epfile->mutex */
+
+	/* [0]: full speed, [1]: high speed */
+	struct usb_endpoint_descriptor	*descs[2];
+
+	u8				num;
+
+	int				status;	/* P: epfile->mutex */
+};
+
+struct ffs_epfile {
+	/* Protects ep->ep and ep->req. */
+	struct mutex			mutex;
+	wait_queue_head_t		wait;
+
+	struct ffs_data			*ffs;
+	struct ffs_ep			*ep;	/* P: ffs->eps_lock */
+
+	struct dentry			*dentry;
+
+	char				name[5];
+
+	unsigned char			in;	/* P: ffs->eps_lock */
+	unsigned char			isoc;	/* P: ffs->eps_lock */
+
+	unsigned char			_pad;
+};
+
+
+static int  __must_check ffs_epfiles_create(struct ffs_data *ffs);
+static void ffs_epfiles_destroy(struct ffs_epfile *epfiles, unsigned count);
+
+static struct inode *__must_check
+ffs_sb_create_file(struct super_block *sb, const char *name, void *data,
+		   const struct file_operations *fops,
+		   struct dentry **dentry_p);
+
+
+/* Misc helper functions ****************************************************/
+
+static int ffs_mutex_lock(struct mutex *mutex, unsigned nonblock)
+	__attribute__((warn_unused_result, nonnull));
+static char *ffs_prepare_buffer(const char * __user buf, size_t len)
+	__attribute__((warn_unused_result, nonnull));
+
+
+/* Control file aka ep0 *****************************************************/
+
+static void ffs_ep0_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	struct ffs_data *ffs = req->context;
+
+	complete_all(&ffs->ep0req_completion);
+}
+
+
+static int __ffs_ep0_queue_wait(struct ffs_data *ffs, char *data, size_t len)
+{
+	struct usb_request *req = ffs->ep0req;
+	int ret;
+
+	req->zero     = len < le16_to_cpu(ffs->ev.setup.wLength);
+
+	spin_unlock_irq(&ffs->ev.waitq.lock);
+
+	req->buf      = data;
+	req->length   = len;
+
+	INIT_COMPLETION(ffs->ep0req_completion);
+
+	ret = usb_ep_queue(ffs->gadget->ep0, req, GFP_ATOMIC);
+	if (unlikely(ret < 0))
+		return ret;
+
+	ret = wait_for_completion_interruptible(&ffs->ep0req_completion);
+	if (unlikely(ret)) {
+		usb_ep_dequeue(ffs->gadget->ep0, req);
+		return -EINTR;
+	}
+
+	ffs->setup_state = FFS_NO_SETUP;
+	return ffs->ep0req_status;
+}
+
+static int __ffs_ep0_stall(struct ffs_data *ffs)
+{
+	if (ffs->ev.can_stall) {
+		FVDBG("ep0 stall\n");
+		usb_ep_set_halt(ffs->gadget->ep0);
+		ffs->setup_state = FFS_NO_SETUP;
+		return -EL2HLT;
+	} else {
+		FDBG("bogus ep0 stall!\n");
+		return -ESRCH;
+	}
+}
+
+
+static ssize_t ffs_ep0_write(struct file *file, const char __user *buf,
+			     size_t len, loff_t *ptr)
+{
+	struct ffs_data *ffs = file->private_data;
+	ssize_t ret;
+	char *data;
+
+	ENTER();
+
+	/* Fast check if setup was canceled */
+	if (FFS_SETUP_STATE(ffs) == FFS_SETUP_CANCELED)
+		return -EIDRM;
+
+	/* Acquire mutex */
+	ret = ffs_mutex_lock(&ffs->mutex, file->f_flags & O_NONBLOCK);
+	if (unlikely(ret < 0))
+		return ret;
+
+
+	/* Check state */
+	switch (ffs->state) {
+	case FFS_READ_DESCRIPTORS:
+	case FFS_READ_STRINGS:
+		/* Copy data */
+		if (unlikely(len < 16)) {
+			ret = -EINVAL;
+			break;
+		}
+
+		data = ffs_prepare_buffer(buf, len);
+		if (unlikely(IS_ERR(data))) {
+			ret = PTR_ERR(data);
+			break;
+		}
+
+		/* Handle data */
+		if (ffs->state == FFS_READ_DESCRIPTORS) {
+			FINFO("read descriptors");
+			ret = __ffs_data_got_descs(ffs, data, len);
+			if (unlikely(ret < 0))
+				break;
+
+			ffs->state = FFS_READ_STRINGS;
+			ret = len;
+		} else {
+			FINFO("read strings");
+			ret = __ffs_data_got_strings(ffs, data, len);
+			if (unlikely(ret < 0))
+				break;
+
+			ret = ffs_epfiles_create(ffs);
+			if (unlikely(ret)) {
+				ffs->state = FFS_CLOSING;
+				break;
+			}
+
+			ffs->state = FFS_ACTIVE;
+			mutex_unlock(&ffs->mutex);
+
+			ret = functionfs_ready_callback(ffs);
+			if (unlikely(ret < 0)) {
+				ffs->state = FFS_CLOSING;
+				return ret;
+			}
+
+			set_bit(FFS_FL_CALL_CLOSED_CALLBACK, &ffs->flags);
+			return len;
+		}
+		break;
+
+
+	case FFS_ACTIVE:
+		data = NULL;
+		/* We're called from user space, we can use _irq
+		 * rather then _irqsave */
+		spin_lock_irq(&ffs->ev.waitq.lock);
+		switch (FFS_SETUP_STATE(ffs)) {
+		case FFS_SETUP_CANCELED:
+			ret = -EIDRM;
+			goto done_spin;
+
+		case FFS_NO_SETUP:
+			ret = -ESRCH;
+			goto done_spin;
+
+		case FFS_SETUP_PENDING:
+			break;
+		}
+
+		/* FFS_SETUP_PENDING */
+		if (!(ffs->ev.setup.bRequestType & USB_DIR_IN)) {
+			spin_unlock_irq(&ffs->ev.waitq.lock);
+			ret = __ffs_ep0_stall(ffs);
+			break;
+		}
+
+		/* FFS_SETUP_PENDING and not stall */
+		len = min(len, (size_t)le16_to_cpu(ffs->ev.setup.wLength));
+
+		spin_unlock_irq(&ffs->ev.waitq.lock);
+
+		data = ffs_prepare_buffer(buf, len);
+		if (unlikely(IS_ERR(data))) {
+			ret = PTR_ERR(data);
+			break;
+		}
+
+		spin_lock_irq(&ffs->ev.waitq.lock);
+
+		/* We are guaranteed to be still in FFS_ACTIVE state
+		 * but the state of setup could have changed from
+		 * FFS_SETUP_PENDING to FFS_SETUP_CANCELED so we need
+		 * to check for that.  If that happened we copied data
+		 * from user space in vain but it's unlikely. */
+		/* For sure we are not in FFS_NO_SETUP since this is
+		 * the only place FFS_SETUP_PENDING -> FFS_NO_SETUP
+		 * transition can be performed and it's protected by
+		 * mutex. */
+
+		if (FFS_SETUP_STATE(ffs) == FFS_SETUP_CANCELED) {
+			ret = -EIDRM;
+done_spin:
+			spin_unlock_irq(&ffs->ev.waitq.lock);
+		} else {
+			/* unlocks spinlock */
+			ret = __ffs_ep0_queue_wait(ffs, data, len);
+		}
+		kfree(data);
+		break;
+
+
+	default:
+		ret = -EBADFD;
+		break;
+	}
+
+
+	mutex_unlock(&ffs->mutex);
+	return ret;
+}
+
+
+
+static ssize_t __ffs_ep0_read_events(struct ffs_data *ffs, char __user *buf,
+				     size_t n)
+{
+	/* We are holding ffs->ev.waitq.lock and ffs->mutex and we need
+	 * to release them. */
+
+	struct usb_functionfs_event events[n];
+	unsigned i = 0;
+
+	memset(events, 0, sizeof events);
+
+	do {
+		events[i].type = ffs->ev.types[i];
+		if (events[i].type == FUNCTIONFS_SETUP) {
+			events[i].u.setup = ffs->ev.setup;
+			ffs->setup_state = FFS_SETUP_PENDING;
+		}
+	} while (++i < n);
+
+	if (n < ffs->ev.count) {
+		ffs->ev.count -= n;
+		memmove(ffs->ev.types, ffs->ev.types + n,
+			ffs->ev.count * sizeof *ffs->ev.types);
+	} else {
+		ffs->ev.count = 0;
+	}
+
+	spin_unlock_irq(&ffs->ev.waitq.lock);
+	mutex_unlock(&ffs->mutex);
+
+	return unlikely(__copy_to_user(buf, events, sizeof events))
+		? -EFAULT : sizeof events;
+}
+
+
+static ssize_t ffs_ep0_read(struct file *file, char __user *buf,
+			    size_t len, loff_t *ptr)
+{
+	struct ffs_data *ffs = file->private_data;
+	char *data = NULL;
+	size_t n;
+	int ret;
+
+	ENTER();
+
+	/* Fast check if setup was canceled */
+	if (FFS_SETUP_STATE(ffs) == FFS_SETUP_CANCELED)
+		return -EIDRM;
+
+	/* Acquire mutex */
+	ret = ffs_mutex_lock(&ffs->mutex, file->f_flags & O_NONBLOCK);
+	if (unlikely(ret < 0))
+		return ret;
+
+
+	/* Check state */
+	if (ffs->state != FFS_ACTIVE) {
+		ret = -EBADFD;
+		goto done_mutex;
+	}
+
+
+	/* We're called from user space, we can use _irq rather then
+	 * _irqsave */
+	spin_lock_irq(&ffs->ev.waitq.lock);
+
+	switch (FFS_SETUP_STATE(ffs)) {
+	case FFS_SETUP_CANCELED:
+		ret = -EIDRM;
+		break;
+
+	case FFS_NO_SETUP:
+		n = len / sizeof(struct usb_functionfs_event);
+		if (unlikely(!n)) {
+			ret = -EINVAL;
+			break;
+		}
+
+		if ((file->f_flags & O_NONBLOCK) && !ffs->ev.count) {
+			ret = -EAGAIN;
+			break;
+		}
+
+		if (unlikely(wait_event_interruptible_exclusive_locked_irq(ffs->ev.waitq, ffs->ev.count))) {
+			ret = -EINTR;
+			break;
+		}
+
+		return __ffs_ep0_read_events(ffs, buf,
+					     min(n, (size_t)ffs->ev.count));
+
+
+	case FFS_SETUP_PENDING:
+		if (ffs->ev.setup.bRequestType & USB_DIR_IN) {
+			spin_unlock_irq(&ffs->ev.waitq.lock);
+			ret = __ffs_ep0_stall(ffs);
+			goto done_mutex;
+		}
+
+		len = min(len, (size_t)le16_to_cpu(ffs->ev.setup.wLength));
+
+		spin_unlock_irq(&ffs->ev.waitq.lock);
+
+		if (likely(len)) {
+			data = kmalloc(len, GFP_KERNEL);
+			if (unlikely(!data)) {
+				ret = -ENOMEM;
+				goto done_mutex;
+			}
+		}
+
+		spin_lock_irq(&ffs->ev.waitq.lock);
+
+		/* See ffs_ep0_write() */
+		if (FFS_SETUP_STATE(ffs) == FFS_SETUP_CANCELED) {
+			ret = -EIDRM;
+			break;
+		}
+
+		/* unlocks spinlock */
+		ret = __ffs_ep0_queue_wait(ffs, data, len);
+		if (likely(ret > 0) && unlikely(__copy_to_user(buf, data, len)))
+			ret = -EFAULT;
+		goto done_mutex;
+
+	default:
+		ret = -EBADFD;
+		break;
+	}
+
+	spin_unlock_irq(&ffs->ev.waitq.lock);
+done_mutex:
+	mutex_unlock(&ffs->mutex);
+	kfree(data);
+	return ret;
+}
+
+
+
+static int ffs_ep0_open(struct inode *inode, struct file *file)
+{
+	struct ffs_data *ffs = inode->i_private;
+
+	ENTER();
+
+	if (unlikely(ffs->state == FFS_CLOSING))
+		return -EBUSY;
+
+	file->private_data = ffs;
+	ffs_data_opened(ffs);
+
+	return 0;
+}
+
+
+static int ffs_ep0_release(struct inode *inode, struct file *file)
+{
+	struct ffs_data *ffs = file->private_data;
+
+	ENTER();
+
+	ffs_data_closed(ffs);
+
+	return 0;
+}
+
+
+static long ffs_ep0_ioctl(struct file *file, unsigned code, unsigned long value)
+{
+	struct ffs_data *ffs = file->private_data;
+	struct usb_gadget *gadget = ffs->gadget;
+	long ret;
+
+	ENTER();
+
+	if (code == FUNCTIONFS_INTERFACE_REVMAP) {
+		struct ffs_function *func = ffs->func;
+		ret = func ? ffs_func_revmap_intf(func, value) : -ENODEV;
+	} else if (gadget->ops->ioctl) {
+		lock_kernel();
+		ret = gadget->ops->ioctl(gadget, code, value);
+		unlock_kernel();
+	} else {
+		ret = -ENOTTY;
+	}
+
+	return ret;
+}
+
+
+static const struct file_operations ffs_ep0_operations = {
+	.owner =	THIS_MODULE,
+	.llseek =	no_llseek,
+
+	.open =		ffs_ep0_open,
+	.write =	ffs_ep0_write,
+	.read =		ffs_ep0_read,
+	.release =	ffs_ep0_release,
+	.unlocked_ioctl =	ffs_ep0_ioctl,
+};
+
+
+/* "Normal" endpoints operations ********************************************/
+
+
+static void ffs_epfile_io_complete(struct usb_ep *_ep, struct usb_request *req)
+{
+	ENTER();
+	if (likely(req->context)) {
+		struct ffs_ep *ep = _ep->driver_data;
+		ep->status = req->status ? req->status : req->actual;
+		complete(req->context);
+	}
+}
+
+
+static ssize_t ffs_epfile_io(struct file *file,
+			     char __user *buf, size_t len, int read)
+{
+	struct ffs_epfile *epfile = file->private_data;
+	struct ffs_ep *ep;
+	char *data = NULL;
+	ssize_t ret;
+	int halt;
+
+	goto first_try;
+	do {
+		spin_unlock_irq(&epfile->ffs->eps_lock);
+		mutex_unlock(&epfile->mutex);
+
+first_try:
+		/* Are we still active? */
+		if (WARN_ON(epfile->ffs->state != FFS_ACTIVE)) {
+			ret = -ENODEV;
+			goto error;
+		}
+
+		/* Wait for endpoint to be enabled */
+		ep = epfile->ep;
+		if (!ep) {
+			if (file->f_flags & O_NONBLOCK) {
+				ret = -EAGAIN;
+				goto error;
+			}
+
+			if (unlikely(wait_event_interruptible
+				     (epfile->wait, (ep = epfile->ep)))) {
+				ret = -EINTR;
+				goto error;
+			}
+		}
+
+		/* Do we halt? */
+		halt = !read == !epfile->in;
+		if (halt && epfile->isoc) {
+			ret = -EINVAL;
+			goto error;
+		}
+
+		/* Allocate & copy */
+		if (!halt && !data) {
+			data = kzalloc(len, GFP_KERNEL);
+			if (unlikely(!data))
+				return -ENOMEM;
+
+			if (!read &&
+			    unlikely(__copy_from_user(data, buf, len))) {
+				ret = -EFAULT;
+				goto error;
+			}
+		}
+
+		/* We will be using request */
+		ret = ffs_mutex_lock(&epfile->mutex,
+				     file->f_flags & O_NONBLOCK);
+		if (unlikely(ret))
+			goto error;
+
+		/* We're called from user space, we can use _irq rather then
+		 * _irqsave */
+		spin_lock_irq(&epfile->ffs->eps_lock);
+
+		/* While we were acquiring mutex endpoint got disabled
+		 * or changed? */
+	} while (unlikely(epfile->ep != ep));
+
+	/* Halt */
+	if (unlikely(halt)) {
+		if (likely(epfile->ep == ep) && !WARN_ON(!ep->ep))
+			usb_ep_set_halt(ep->ep);
+		spin_unlock_irq(&epfile->ffs->eps_lock);
+		ret = -EBADMSG;
+	} else {
+		/* Fire the request */
+		DECLARE_COMPLETION_ONSTACK(done);
+
+		struct usb_request *req = ep->req;
+		req->context  = &done;
+		req->complete = ffs_epfile_io_complete;
+		req->buf      = data;
+		req->length   = len;
+
+		ret = usb_ep_queue(ep->ep, req, GFP_ATOMIC);
+
+		spin_unlock_irq(&epfile->ffs->eps_lock);
+
+		if (unlikely(ret < 0)) {
+			/* nop */
+		} else if (unlikely(wait_for_completion_interruptible(&done))) {
+			ret = -EINTR;
+			usb_ep_dequeue(ep->ep, req);
+		} else {
+			ret = ep->status;
+			if (read && ret > 0 &&
+			    unlikely(copy_to_user(buf, data, ret)))
+				ret = -EFAULT;
+		}
+	}
+
+	mutex_unlock(&epfile->mutex);
+error:
+	kfree(data);
+	return ret;
+}
+
+
+static ssize_t
+ffs_epfile_write(struct file *file, const char __user *buf, size_t len,
+		 loff_t *ptr)
+{
+	ENTER();
+
+	return ffs_epfile_io(file, (char __user *)buf, len, 0);
+}
+
+static ssize_t
+ffs_epfile_read(struct file *file, char __user *buf, size_t len, loff_t *ptr)
+{
+	ENTER();
+
+	return ffs_epfile_io(file, buf, len, 1);
+}
+
+static int
+ffs_epfile_open(struct inode *inode, struct file *file)
+{
+	struct ffs_epfile *epfile = inode->i_private;
+
+	ENTER();
+
+	if (WARN_ON(epfile->ffs->state != FFS_ACTIVE))
+		return -ENODEV;
+
+	file->private_data = epfile;
+	ffs_data_opened(epfile->ffs);
+
+	return 0;
+}
+
+static int
+ffs_epfile_release(struct inode *inode, struct file *file)
+{
+	struct ffs_epfile *epfile = inode->i_private;
+
+	ENTER();
+
+	ffs_data_closed(epfile->ffs);
+
+	return 0;
+}
+
+
+static long ffs_epfile_ioctl(struct file *file, unsigned code,
+			     unsigned long value)
+{
+	struct ffs_epfile *epfile = file->private_data;
+	int ret;
+
+	ENTER();
+
+	if (WARN_ON(epfile->ffs->state != FFS_ACTIVE))
+		return -ENODEV;
+
+	spin_lock_irq(&epfile->ffs->eps_lock);
+	if (likely(epfile->ep)) {
+		switch (code) {
+		case FUNCTIONFS_FIFO_STATUS:
+			ret = usb_ep_fifo_status(epfile->ep->ep);
+			break;
+		case FUNCTIONFS_FIFO_FLUSH:
+			usb_ep_fifo_flush(epfile->ep->ep);
+			ret = 0;
+			break;
+		case FUNCTIONFS_CLEAR_HALT:
+			ret = usb_ep_clear_halt(epfile->ep->ep);
+			break;
+		case FUNCTIONFS_ENDPOINT_REVMAP:
+			ret = epfile->ep->num;
+			break;
+		default:
+			ret = -ENOTTY;
+		}
+	} else {
+		ret = -ENODEV;
+	}
+	spin_unlock_irq(&epfile->ffs->eps_lock);
+
+	return ret;
+}
+
+
+static const struct file_operations ffs_epfile_operations = {
+	.owner =	THIS_MODULE,
+	.llseek =	no_llseek,
+
+	.open =		ffs_epfile_open,
+	.write =	ffs_epfile_write,
+	.read =		ffs_epfile_read,
+	.release =	ffs_epfile_release,
+	.unlocked_ioctl =	ffs_epfile_ioctl,
+};
+
+
+
+/* File system and super block operations ***********************************/
+
+/*
+ * Mounting the filesystem creates a controller file, used first for
+ * function configuration then later for event monitoring.
+ */
+
+
+static struct inode *__must_check
+ffs_sb_make_inode(struct super_block *sb, void *data,
+		  const struct file_operations *fops,
+		  const struct inode_operations *iops,
+		  struct ffs_file_perms *perms)
+{
+	struct inode *inode;
+
+	ENTER();
+
+	inode = new_inode(sb);
+
+	if (likely(inode)) {
+		struct timespec current_time = CURRENT_TIME;
+
+		inode->i_mode    = perms->mode;
+		inode->i_uid     = perms->uid;
+		inode->i_gid     = perms->gid;
+		inode->i_atime   = current_time;
+		inode->i_mtime   = current_time;
+		inode->i_ctime   = current_time;
+		inode->i_private = data;
+		if (fops)
+			inode->i_fop = fops;
+		if (iops)
+			inode->i_op  = iops;
+	}
+
+	return inode;
+}
+
+
+/* Create "regular" file */
+
+static struct inode *ffs_sb_create_file(struct super_block *sb,
+					const char *name, void *data,
+					const struct file_operations *fops,
+					struct dentry **dentry_p)
+{
+	struct ffs_data	*ffs = sb->s_fs_info;
+	struct dentry	*dentry;
+	struct inode	*inode;
+
+	ENTER();
+
+	dentry = d_alloc_name(sb->s_root, name);
+	if (unlikely(!dentry))
+		return NULL;
+
+	inode = ffs_sb_make_inode(sb, data, fops, NULL, &ffs->file_perms);
+	if (unlikely(!inode)) {
+		dput(dentry);
+		return NULL;
+	}
+
+	d_add(dentry, inode);
+	if (dentry_p)
+		*dentry_p = dentry;
+
+	return inode;
+}
+
+
+/* Super block */
+
+static const struct super_operations ffs_sb_operations = {
+	.statfs =	simple_statfs,
+	.drop_inode =	generic_delete_inode,
+};
+
+struct ffs_sb_fill_data {
+	struct ffs_file_perms perms;
+	umode_t root_mode;
+	const char *dev_name;
+};
+
+static int ffs_sb_fill(struct super_block *sb, void *_data, int silent)
+{
+	struct ffs_sb_fill_data *data = _data;
+	struct inode	*inode;
+	struct dentry	*d;
+	struct ffs_data	*ffs;
+
+	ENTER();
+
+	/* Initialize data */
+	ffs = ffs_data_new();
+	if (unlikely(!ffs))
+		goto enomem0;
+
+	ffs->sb              = sb;
+	ffs->dev_name        = data->dev_name;
+	ffs->file_perms      = data->perms;
+
+	sb->s_fs_info        = ffs;
+	sb->s_blocksize      = PAGE_CACHE_SIZE;
+	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
+	sb->s_magic          = FUNCTIONFS_MAGIC;
+	sb->s_op             = &ffs_sb_operations;
+	sb->s_time_gran      = 1;
+
+	/* Root inode */
+	data->perms.mode = data->root_mode;
+	inode = ffs_sb_make_inode(sb, NULL,
+				  &simple_dir_operations,
+				  &simple_dir_inode_operations,
+				  &data->perms);
+	if (unlikely(!inode))
+		goto enomem1;
+	d = d_alloc_root(inode);
+	if (unlikely(!d))
+		goto enomem2;
+	sb->s_root = d;
+
+	/* EP0 file */
+	if (unlikely(!ffs_sb_create_file(sb, "ep0", ffs,
+					 &ffs_ep0_operations, NULL)))
+		goto enomem3;
+
+	return 0;
+
+enomem3:
+	dput(d);
+enomem2:
+	iput(inode);
+enomem1:
+	ffs_data_put(ffs);
+enomem0:
+	return -ENOMEM;
+}
+
+
+static int ffs_fs_parse_opts(struct ffs_sb_fill_data *data, char *opts)
+{
+	ENTER();
+
+	if (!opts || !*opts)
+		return 0;
+
+	for (;;) {
+		char *end, *eq, *comma;
+		unsigned long value;
+
+		/* Option limit */
+		comma = strchr(opts, ',');
+		if (comma)
+			*comma = 0;
+
+		/* Value limit */
+		eq = strchr(opts, '=');
+		if (unlikely(!eq)) {
+			FERR("'=' missing in %s", opts);
+			return -EINVAL;
+		}
+		*eq = 0;
+
+		/* Parse value */
+		value = simple_strtoul(eq + 1, &end, 0);
+		if (unlikely(*end != ',' && *end != 0)) {
+			FERR("%s: invalid value: %s", opts, eq + 1);
+			return -EINVAL;
+		}
+
+		/* Interpret option */
+		switch (eq - opts) {
+		case 5:
+			if (!memcmp(opts, "rmode", 5))
+				data->root_mode  = (value & 0555) | S_IFDIR;
+			else if (!memcmp(opts, "fmode", 5))
+				data->perms.mode = (value & 0666) | S_IFREG;
+			else
+				goto invalid;
+			break;
+
+		case 4:
+			if (!memcmp(opts, "mode", 4)) {
+				data->root_mode  = (value & 0555) | S_IFDIR;
+				data->perms.mode = (value & 0666) | S_IFREG;
+			} else {
+				goto invalid;
+			}
+			break;
+
+		case 3:
+			if (!memcmp(opts, "uid", 3))
+				data->perms.uid = value;
+			else if (!memcmp(opts, "gid", 3))
+				data->perms.gid = value;
+			else
+				goto invalid;
+			break;
+
+		default:
+invalid:
+			FERR("%s: invalid option", opts);
+			return -EINVAL;
+		}
+
+		/* Next iteration */
+		if (!comma)
+			break;
+		opts = comma + 1;
+	}
+
+	return 0;
+}
+
+
+/* "mount -t functionfs dev_name /dev/function" ends up here */
+
+static int
+ffs_fs_get_sb(struct file_system_type *t, int flags,
+	      const char *dev_name, void *opts, struct vfsmount *mnt)
+{
+	struct ffs_sb_fill_data data = {
+		.perms = {
+			.mode = S_IFREG | 0600,
+			.uid = 0,
+			.gid = 0
+		},
+		.root_mode = S_IFDIR | 0500,
+	};
+	int ret;
+
+	ENTER();
+
+	ret = functionfs_check_dev_callback(dev_name);
+	if (unlikely(ret < 0))
+		return ret;
+
+	ret = ffs_fs_parse_opts(&data, opts);
+	if (unlikely(ret < 0))
+		return ret;
+
+	data.dev_name = dev_name;
+	return get_sb_single(t, flags, &data, ffs_sb_fill, mnt);
+}
+
+static void
+ffs_fs_kill_sb(struct super_block *sb)
+{
+	void *ptr;
+
+	ENTER();
+
+	kill_litter_super(sb);
+	ptr = xchg(&sb->s_fs_info, NULL);
+	if (ptr)
+		ffs_data_put(ptr);
+}
+
+static struct file_system_type ffs_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "functionfs",
+	.get_sb		= ffs_fs_get_sb,
+	.kill_sb	= ffs_fs_kill_sb,
+};
+
+
+
+/* Driver's main init/cleanup functions *************************************/
+
+
+static int functionfs_init(void)
+{
+	int ret;
+
+	ENTER();
+
+	ret = register_filesystem(&ffs_fs_type);
+	if (likely(!ret))
+		FINFO("file system registered");
+	else
+		FERR("failed registering file system (%d)", ret);
+
+	return ret;
+}
+
+static void functionfs_cleanup(void)
+{
+	ENTER();
+
+	FINFO("unloading");
+	unregister_filesystem(&ffs_fs_type);
+}
+
+
+
+/* ffs_data and ffs_function construction and destruction code **************/
+
+static void ffs_data_clear(struct ffs_data *ffs);
+static void ffs_data_reset(struct ffs_data *ffs);
+
+
+static void ffs_data_get(struct ffs_data *ffs)
+{
+	ENTER();
+
+	atomic_inc(&ffs->ref);
+}
+
+static void ffs_data_opened(struct ffs_data *ffs)
+{
+	ENTER();
+
+	atomic_inc(&ffs->ref);
+	atomic_inc(&ffs->opened);
+}
+
+static void ffs_data_put(struct ffs_data *ffs)
+{
+	ENTER();
+
+	if (unlikely(atomic_dec_and_test(&ffs->ref))) {
+		FINFO("%s(): freeing", __func__);
+		ffs_data_clear(ffs);
+		BUG_ON(mutex_is_locked(&ffs->mutex) ||
+		       spin_is_locked(&ffs->ev.waitq.lock) ||
+		       waitqueue_active(&ffs->ev.waitq) ||
+		       waitqueue_active(&ffs->ep0req_completion.wait));
+		kfree(ffs);
+	}
+}
+
+
+
+static void ffs_data_closed(struct ffs_data *ffs)
+{
+	ENTER();
+
+	if (atomic_dec_and_test(&ffs->opened)) {
+		ffs->state = FFS_CLOSING;
+		ffs_data_reset(ffs);
+	}
+
+	ffs_data_put(ffs);
+}
+
+
+static struct ffs_data *ffs_data_new(void)
+{
+	struct ffs_data *ffs = kzalloc(sizeof *ffs, GFP_KERNEL);
+	if (unlikely(!ffs))
+		return 0;
+
+	ENTER();
+
+	atomic_set(&ffs->ref, 1);
+	atomic_set(&ffs->opened, 0);
+	ffs->state = FFS_READ_DESCRIPTORS;
+	mutex_init(&ffs->mutex);
+	spin_lock_init(&ffs->eps_lock);
+	init_waitqueue_head(&ffs->ev.waitq);
+	init_completion(&ffs->ep0req_completion);
+
+	/* XXX REVISIT need to update it in some places, or do we? */
+	ffs->ev.can_stall = 1;
+
+	return ffs;
+}
+
+
+static void ffs_data_clear(struct ffs_data *ffs)
+{
+	ENTER();
+
+	if (test_and_clear_bit(FFS_FL_CALL_CLOSED_CALLBACK, &ffs->flags))
+		functionfs_closed_callback(ffs);
+
+	BUG_ON(ffs->gadget);
+
+	if (ffs->epfiles)
+		ffs_epfiles_destroy(ffs->epfiles, ffs->eps_count);
+
+	kfree(ffs->raw_descs);
+	kfree(ffs->raw_strings);
+	kfree(ffs->stringtabs);
+}
+
+
+static void ffs_data_reset(struct ffs_data *ffs)
+{
+	ENTER();
+
+	ffs_data_clear(ffs);
+
+	ffs->epfiles = NULL;
+	ffs->raw_descs = NULL;
+	ffs->raw_strings = NULL;
+	ffs->stringtabs = NULL;
+
+	ffs->raw_descs_length = 0;
+	ffs->raw_fs_descs_length = 0;
+	ffs->fs_descs_count = 0;
+	ffs->hs_descs_count = 0;
+
+	ffs->strings_count = 0;
+	ffs->interfaces_count = 0;
+	ffs->eps_count = 0;
+
+	ffs->ev.count = 0;
+
+	ffs->state = FFS_READ_DESCRIPTORS;
+	ffs->setup_state = FFS_NO_SETUP;
+	ffs->flags = 0;
+}
+
+
+static int functionfs_bind(struct ffs_data *ffs, struct usb_composite_dev *cdev)
+{
+	unsigned i, count;
+
+	ENTER();
+
+	if (WARN_ON(ffs->state != FFS_ACTIVE
+		 || test_and_set_bit(FFS_FL_BOUND, &ffs->flags)))
+		return -EBADFD;
+
+	ffs_data_get(ffs);
+
+	ffs->ep0req = usb_ep_alloc_request(cdev->gadget->ep0, GFP_KERNEL);
+	if (unlikely(!ffs->ep0req))
+		return -ENOMEM;
+	ffs->ep0req->complete = ffs_ep0_complete;
+	ffs->ep0req->context = ffs;
+
+	/* Get strings identifiers */
+	for (count = ffs->strings_count, i = 0; i < count; ++i) {
+		struct usb_gadget_strings **lang;
+
+		int id = usb_string_id(cdev);
+		if (unlikely(id < 0)) {
+			usb_ep_free_request(cdev->gadget->ep0, ffs->ep0req);
+			ffs->ep0req = NULL;
+			return id;
+		}
+
+		lang = ffs->stringtabs;
+		do {
+			(*lang)->strings[i].id = id;
+			++lang;
+		} while (*lang);
+	}
+
+	ffs->gadget = cdev->gadget;
+	return 0;
+}
+
+
+static void functionfs_unbind(struct ffs_data *ffs)
+{
+	ENTER();
+
+	if (!WARN_ON(!ffs->gadget)) {
+		usb_ep_free_request(ffs->gadget->ep0, ffs->ep0req);
+		ffs->ep0req = NULL;
+		ffs->gadget = NULL;
+		ffs_data_put(ffs);
+	}
+}
+
+
+static int ffs_epfiles_create(struct ffs_data *ffs)
+{
+	struct ffs_epfile *epfile, *epfiles;
+	unsigned i, count;
+
+	ENTER();
+
+	count = ffs->eps_count;
+	epfiles = kzalloc(count * sizeof *epfiles, GFP_KERNEL);
+	if (!epfiles)
+		return -ENOMEM;
+
+	epfile = epfiles;
+	for (i = 1; i <= count; ++i, ++epfile) {
+		epfile->ffs = ffs;
+		mutex_init(&epfile->mutex);
+		init_waitqueue_head(&epfile->wait);
+		sprintf(epfiles->name, "ep%u",  i);
+		if (!unlikely(ffs_sb_create_file(ffs->sb, epfiles->name, epfile,
+						 &ffs_epfile_operations,
+						 &epfile->dentry))) {
+			ffs_epfiles_destroy(epfiles, i - 1);
+			return -ENOMEM;
+		}
+	}
+
+	ffs->epfiles = epfiles;
+	return 0;
+}
+
+
+static void ffs_epfiles_destroy(struct ffs_epfile *epfiles, unsigned count)
+{
+	struct ffs_epfile *epfile = epfiles;
+
+	ENTER();
+
+	for (; count; --count, ++epfile) {
+		BUG_ON(mutex_is_locked(&epfile->mutex) ||
+		       waitqueue_active(&epfile->wait));
+		if (epfile->dentry) {
+			d_delete(epfile->dentry);
+			dput(epfile->dentry);
+			epfile->dentry = NULL;
+		}
+	}
+
+	kfree(epfiles);
+}
+
+
+static int functionfs_add(struct usb_composite_dev *cdev,
+			  struct usb_configuration *c,
+			  struct ffs_data *ffs)
+{
+	struct ffs_function *func;
+	int ret;
+
+	ENTER();
+
+	func = kzalloc(sizeof *func, GFP_KERNEL);
+	if (unlikely(!func))
+		return -ENOMEM;
+
+	func->function.name    = "Function FS Gadget";
+	func->function.strings = ffs->stringtabs;
+
+	func->function.bind    = ffs_func_bind;
+	func->function.unbind  = ffs_func_unbind;
+	func->function.set_alt = ffs_func_set_alt;
+	/*func->function.get_alt = ffs_func_get_alt;*/
+	func->function.disable = ffs_func_disable;
+	func->function.setup   = ffs_func_setup;
+	func->function.suspend = ffs_func_suspend;
+	func->function.resume  = ffs_func_resume;
+
+	func->conf   = c;
+	func->gadget = cdev->gadget;
+	func->ffs = ffs;
+	ffs_data_get(ffs);
+
+	ret = usb_add_function(c, &func->function);
+	if (unlikely(ret))
+		ffs_func_free(func);
+
+	return ret;
+}
+
+static void ffs_func_free(struct ffs_function *func)
+{
+	ENTER();
+
+	ffs_data_put(func->ffs);
+
+	kfree(func->eps);
+	/* eps and interfaces_nums are allocated in the same chunk so
+	 * only one free is required.  Descriptors are also allocated
+	 * in the same chunk. */
+
+	kfree(func);
+}
+
+
+static void ffs_func_eps_disable(struct ffs_function *func)
+{
+	struct ffs_ep *ep         = func->eps;
+	struct ffs_epfile *epfile = func->ffs->epfiles;
+	unsigned count            = func->ffs->eps_count;
+	unsigned long flags;
+
+	spin_lock_irqsave(&func->ffs->eps_lock, flags);
+	do {
+		/* pending requests get nuked */
+		if (likely(ep->ep))
+			usb_ep_disable(ep->ep);
+		epfile->ep = NULL;
+
+		++ep;
+		++epfile;
+	} while (--count);
+	spin_unlock_irqrestore(&func->ffs->eps_lock, flags);
+}
+
+static int ffs_func_eps_enable(struct ffs_function *func)
+{
+	struct ffs_data *ffs      = func->ffs;
+	struct ffs_ep *ep         = func->eps;
+	struct ffs_epfile *epfile = ffs->epfiles;
+	unsigned count            = ffs->eps_count;
+	unsigned long flags;
+	int ret = 0;
+
+	spin_lock_irqsave(&func->ffs->eps_lock, flags);
+	do {
+		struct usb_endpoint_descriptor *ds;
+		ds = ep->descs[ep->descs[1] ? 1 : 0];
+
+		ep->ep->driver_data = ep;
+		ret = usb_ep_enable(ep->ep, ds);
+		if (likely(!ret)) {
+			epfile->ep = ep;
+			epfile->in = usb_endpoint_dir_in(ds);
+			epfile->isoc = usb_endpoint_xfer_isoc(ds);
+		} else {
+			break;
+		}
+
+		wake_up(&epfile->wait);
+
+		++ep;
+		++epfile;
+	} while (--count);
+	spin_unlock_irqrestore(&func->ffs->eps_lock, flags);
+
+	return ret;
+}
+
+
+/* Parsing and building descriptors and strings *****************************/
+
+
+/* This validates if data pointed by data is a valid USB descriptor as
+ * well as record how many interfaces, endpoints and strings are
+ * required by given configuration.  Returns address afther the
+ * descriptor or NULL if data is invalid. */
+
+enum ffs_entity_type {
+	FFS_DESCRIPTOR, FFS_INTERFACE, FFS_STRING, FFS_ENDPOINT
+};
+
+typedef int (*ffs_entity_callback)(enum ffs_entity_type entity,
+				   u8 *valuep,
+				   struct usb_descriptor_header *desc,
+				   void *priv);
+
+static int __must_check ffs_do_desc(char *data, unsigned len,
+				    ffs_entity_callback entity, void *priv)
+{
+	struct usb_descriptor_header *_ds = (void *)data;
+	u8 length;
+	int ret;
+
+	ENTER();
+
+	/* At least two bytes are required: length and type */
+	if (len < 2) {
+		FVDBG("descriptor too short");
+		return -EINVAL;
+	}
+
+	/* If we have at least as many bytes as the descriptor takes? */
+	length = _ds->bLength;
+	if (len < length) {
+		FVDBG("descriptor longer then available data");
+		return -EINVAL;
+	}
+
+#define __entity_check_INTERFACE(val)  1
+#define __entity_check_STRING(val)     (val)
+#define __entity_check_ENDPOINT(val)   ((val) & USB_ENDPOINT_NUMBER_MASK)
+#define __entity(type, val) do {					\
+		FVDBG("entity " #type "(%02x)", (val));			\
+		if (unlikely(!__entity_check_ ##type(val))) {		\
+			FVDBG("invalid entity's value");		\
+			return -EINVAL;					\
+		}							\
+		ret = entity(FFS_ ##type, &val, _ds, priv);		\
+		if (unlikely(ret < 0)) {				\
+			FDBG("entity " #type "(%02x); ret = %d",	\
+			     (val), ret);				\
+			return ret;					\
+		}							\
+	} while (0)
+
+	/* Parse descriptor depending on type. */
+	switch (_ds->bDescriptorType) {
+	case USB_DT_DEVICE:
+	case USB_DT_CONFIG:
+	case USB_DT_STRING:
+	case USB_DT_DEVICE_QUALIFIER:
+		/* function can't have any of those */
+		FVDBG("descriptor reserved for gadget: %d", _ds->bDescriptorType);
+		return -EINVAL;
+
+	case USB_DT_INTERFACE: {
+		struct usb_interface_descriptor *ds = (void *)_ds;
+		FVDBG("interface descriptor");
+		if (length != sizeof *ds)
+			goto inv_length;
+
+		__entity(INTERFACE, ds->bInterfaceNumber);
+		if (ds->iInterface)
+			__entity(STRING, ds->iInterface);
+	}
+		break;
+
+	case USB_DT_ENDPOINT: {
+		struct usb_endpoint_descriptor *ds = (void *)_ds;
+		FVDBG("endpoint descriptor");
+		if (length != USB_DT_ENDPOINT_SIZE &&
+		    length != USB_DT_ENDPOINT_AUDIO_SIZE)
+			goto inv_length;
+		__entity(ENDPOINT, ds->bEndpointAddress);
+	}
+		break;
+
+	case USB_DT_OTG:
+		if (length != sizeof(struct usb_otg_descriptor))
+			goto inv_length;
+		break;
+
+	case USB_DT_INTERFACE_ASSOCIATION: {
+		struct usb_interface_assoc_descriptor *ds = (void *)_ds;
+		FVDBG("interface association descriptor");
+		if (length != sizeof *ds)
+			goto inv_length;
+		if (ds->iFunction)
+			__entity(STRING, ds->iFunction);
+	}
+		break;
+
+	case USB_DT_OTHER_SPEED_CONFIG:
+	case USB_DT_INTERFACE_POWER:
+	case USB_DT_DEBUG:
+	case USB_DT_SECURITY:
+	case USB_DT_CS_RADIO_CONTROL:
+		/* TODO */
+		FVDBG("unimplemented descriptor: %d", _ds->bDescriptorType);
+		return -EINVAL;
+
+	default:
+		/* We should never be here */
+		FVDBG("unknown descriptor: %d", _ds->bDescriptorType);
+		return -EINVAL;
+
+	inv_length:
+		FVDBG("invalid length: %d (descriptor %d)",
+		      _ds->bLength, _ds->bDescriptorType);
+		return -EINVAL;
+	}
+
+#undef __entity
+#undef __entity_check_DESCRIPTOR
+#undef __entity_check_INTERFACE
+#undef __entity_check_STRING
+#undef __entity_check_ENDPOINT
+
+	return length;
+}
+
+
+static int __must_check ffs_do_descs(unsigned count, char *data, unsigned len,
+				     ffs_entity_callback entity, void *priv)
+{
+	const unsigned _len = len;
+	unsigned long num = 0;
+
+	ENTER();
+
+	for (;;) {
+		int ret;
+
+		if (num == count)
+			data = NULL;
+
+		/* Record "descriptor" entitny */
+		ret = entity(FFS_DESCRIPTOR, (u8 *)num, (void *)data, priv);
+		if (unlikely(ret < 0)) {
+			FDBG("entity DESCRIPTOR(%02lx); ret = %d", num, ret);
+			return ret;
+		}
+
+		if (!data)
+			return _len - len;
+
+		ret = ffs_do_desc(data, len, entity, priv);
+		if (unlikely(ret < 0)) {
+			FDBG("%s returns %d", __func__, ret);
+			return ret;
+		}
+
+		len -= ret;
+		data += ret;
+		++num;
+	}
+}
+
+
+static int __ffs_data_do_entity(enum ffs_entity_type type,
+				u8 *valuep, struct usb_descriptor_header *desc,
+				void *priv)
+{
+	struct ffs_data *ffs = priv;
+
+	ENTER();
+
+	switch (type) {
+	case FFS_DESCRIPTOR:
+		break;
+
+	case FFS_INTERFACE:
+		/* Interfaces are indexed from zero so if we
+		 * encountered interface "n" then there are at least
+		 * "n+1" interfaces. */
+		if (*valuep >= ffs->interfaces_count)
+			ffs->interfaces_count = *valuep + 1;
+		break;
+
+	case FFS_STRING:
+		/* Strings are indexed from 1 (0 is magic ;) reserved
+		 * for languages list or some such) */
+		if (*valuep > ffs->strings_count)
+			ffs->strings_count = *valuep;
+		break;
+
+	case FFS_ENDPOINT:
+		/* Endpoints are indexed from 1 as well. */
+		if ((*valuep & USB_ENDPOINT_NUMBER_MASK) > ffs->eps_count)
+			ffs->eps_count = (*valuep & USB_ENDPOINT_NUMBER_MASK);
+		break;
+	}
+
+	return 0;
+}
+
+
+static int __ffs_data_got_descs(struct ffs_data *ffs,
+				char *const _data, size_t len)
+{
+	unsigned fs_count, hs_count;
+	int fs_len, ret = -EINVAL;
+	char *data = _data;
+
+	ENTER();
+
+	if (unlikely(get_unaligned_le32(data) != FUNCTIONFS_DESCRIPTORS_MAGIC ||
+		     get_unaligned_le32(data + 4) != len))
+		goto error;
+	fs_count = get_unaligned_le32(data +  8);
+	hs_count = get_unaligned_le32(data + 12);
+
+	if (!fs_count && !hs_count)
+		goto einval;
+
+	data += 16;
+	len  -= 16;
+
+	if (likely(fs_count)) {
+		fs_len = ffs_do_descs(fs_count, data, len,
+				      __ffs_data_do_entity, ffs);
+		if (unlikely(fs_len < 0)) {
+			ret = fs_len;
+			goto error;
+		}
+
+		data += fs_len;
+		len  -= fs_len;
+	} else {
+		fs_len = 0;
+	}
+
+	if (likely(hs_count)) {
+		ret = ffs_do_descs(hs_count, data, len,
+				   __ffs_data_do_entity, ffs);
+		if (unlikely(ret < 0))
+			goto error;
+	} else {
+		ret = 0;
+	}
+
+	if (unlikely(len != ret))
+		goto einval;
+
+	ffs->raw_fs_descs_length = fs_len;
+	ffs->raw_descs_length    = fs_len + ret;
+	ffs->raw_descs           = _data;
+	ffs->fs_descs_count      = fs_count;
+	ffs->hs_descs_count      = hs_count;
+
+	return 0;
+
+einval:
+	ret = -EINVAL;
+error:
+	kfree(_data);
+	return ret;
+}
+
+
+
+static int __ffs_data_got_strings(struct ffs_data *ffs,
+				  char *const _data, size_t len)
+{
+	u32 str_count, needed_count, lang_count;
+	struct usb_gadget_strings **stringtabs, *t;
+	struct usb_string *strings, *s;
+	const char *data = _data;
+
+	ENTER();
+
+	if (unlikely(get_unaligned_le32(data) != FUNCTIONFS_STRINGS_MAGIC ||
+		     get_unaligned_le32(data + 4) != len))
+		goto error;
+	str_count  = get_unaligned_le32(data + 8);
+	lang_count = get_unaligned_le32(data + 12);
+
+	/* if one is zero the other must be zero */
+	if (unlikely(!str_count != !lang_count))
+		goto error;
+
+	/* Do we have at least as many strings as descriptors need? */
+	needed_count = ffs->strings_count;
+	if (unlikely(str_count < needed_count))
+		goto error;
+
+	/* If we don't need any strings just return and free all
+	 * memory */
+	if (!needed_count) {
+		kfree(_data);
+		return 0;
+	}
+
+	/* Allocate */
+	{
+		/* Allocate everything in one chunk so there's less
+		 * maintanance. */
+		struct {
+			struct usb_gadget_strings *stringtabs[lang_count + 1];
+			struct usb_gadget_strings stringtab[lang_count];
+			struct usb_string strings[lang_count*(needed_count+1)];
+		} *d;
+		unsigned i = 0;
+
+		d = kmalloc(sizeof *d, GFP_KERNEL);
+		if (unlikely(!d)) {
+			kfree(_data);
+			return -ENOMEM;
+		}
+
+		stringtabs = d->stringtabs;
+		t = d->stringtab;
+		i = lang_count;
+		do {
+			*stringtabs++ = t++;
+		} while (--i);
+		*stringtabs = NULL;
+
+		stringtabs = d->stringtabs;
+		t = d->stringtab;
+		s = d->strings;
+		strings = s;
+	}
+
+	/* For each language */
+	data += 16;
+	len -= 16;
+
+	do { /* lang_count > 0 so we can use do-while */
+		unsigned needed = needed_count;
+
+		if (unlikely(len < 3))
+			goto error_free;
+		t->language = get_unaligned_le16(data);
+		t->strings  = s;
+		++t;
+
+		data += 2;
+		len -= 2;
+
+		/* For each string */
+		do { /* str_count > 0 so we can use do-while */
+			size_t length = strnlen(data, len);
+
+			if (unlikely(length == len))
+				goto error_free;
+
+			/* user may provide more strings then we need,
+			 * if that's the case we simply ingore the
+			 * rest */
+			if (likely(needed)) {
+				/* s->id will be set while adding
+				 * function to configuration so for
+				 * now just leave garbage here. */
+				s->s = data;
+				--needed;
+				++s;
+			}
+
+			data += length + 1;
+			len -= length + 1;
+		} while (--str_count);
+
+		s->id = 0;   /* terminator */
+		s->s = NULL;
+		++s;
+
+	} while (--lang_count);
+
+	/* Some garbage left? */
+	if (unlikely(len))
+		goto error_free;
+
+	/* Done! */
+	ffs->stringtabs = stringtabs;
+	ffs->raw_strings = _data;
+
+	return 0;
+
+error_free:
+	kfree(stringtabs);
+error:
+	kfree(_data);
+	return -EINVAL;
+}
+
+
+
+
+/* Events handling and management *******************************************/
+
+static void __ffs_event_add(struct ffs_data *ffs,
+			    enum usb_functionfs_event_type type)
+{
+	enum usb_functionfs_event_type rem_type1, rem_type2 = type;
+	int neg = 0;
+
+	/* Abort any unhandled setup */
+	/* We do not need to worry about some cmpxchg() changing value
+	 * of ffs->setup_state without holding the lock because when
+	 * state is FFS_SETUP_PENDING cmpxchg() in several places in
+	 * the source does nothing. */
+	if (ffs->setup_state == FFS_SETUP_PENDING)
+		ffs->setup_state = FFS_SETUP_CANCELED;
+
+	switch (type) {
+	case FUNCTIONFS_RESUME:
+		rem_type2 = FUNCTIONFS_SUSPEND;
+		/* FALL THGOUTH */
+	case FUNCTIONFS_SUSPEND:
+	case FUNCTIONFS_SETUP:
+		rem_type1 = type;
+		/* discard all similar events */
+		break;
+
+	case FUNCTIONFS_BIND:
+	case FUNCTIONFS_UNBIND:
+	case FUNCTIONFS_DISABLE:
+	case FUNCTIONFS_ENABLE:
+		/* discard everything other then power management. */
+		rem_type1 = FUNCTIONFS_SUSPEND;
+		rem_type2 = FUNCTIONFS_RESUME;
+		neg = 1;
+		break;
+
+	default:
+		BUG();
+	}
+
+	{
+		u8 *ev  = ffs->ev.types, *out = ev;
+		unsigned n = ffs->ev.count;
+		for (; n; --n, ++ev)
+			if ((*ev == rem_type1 || *ev == rem_type2) == neg)
+				*out++ = *ev;
+			else
+				FVDBG("purging event %d", *ev);
+		ffs->ev.count = out - ffs->ev.types;
+	}
+
+	FVDBG("adding event %d", type);
+	ffs->ev.types[ffs->ev.count++] = type;
+	wake_up_locked(&ffs->ev.waitq);
+}
+
+static void ffs_event_add(struct ffs_data *ffs,
+			  enum usb_functionfs_event_type type)
+{
+	unsigned long flags;
+	spin_lock_irqsave(&ffs->ev.waitq.lock, flags);
+	__ffs_event_add(ffs, type);
+	spin_unlock_irqrestore(&ffs->ev.waitq.lock, flags);
+}
+
+
+/* Bind/unbind USB function hooks *******************************************/
+
+static int __ffs_func_bind_do_descs(enum ffs_entity_type type, u8 *valuep,
+				    struct usb_descriptor_header *desc,
+				    void *priv)
+{
+	struct usb_endpoint_descriptor *ds = (void *)desc;
+	struct ffs_function *func = priv;
+	struct ffs_ep *ffs_ep;
+
+	/* If hs_descriptors is not NULL then we are reading hs
+	 * descriptors now */
+	const int isHS = func->function.hs_descriptors != NULL;
+	unsigned idx;
+
+	if (type != FFS_DESCRIPTOR)
+		return 0;
+
+	if (isHS)
+		func->function.hs_descriptors[(long)valuep] = desc;
+	else
+		func->function.descriptors[(long)valuep]    = desc;
+
+	if (!desc || desc->bDescriptorType != USB_DT_ENDPOINT)
+		return 0;
+
+	idx = (ds->bEndpointAddress & USB_ENDPOINT_NUMBER_MASK) - 1;
+	ffs_ep = func->eps + idx;
+
+	if (unlikely(ffs_ep->descs[isHS])) {
+		FVDBG("two %sspeed descriptors for EP %d",
+		      isHS ? "high" : "full",
+		      ds->bEndpointAddress & USB_ENDPOINT_NUMBER_MASK);
+		return -EINVAL;
+	}
+	ffs_ep->descs[isHS] = ds;
+
+	ffs_dump_mem(": Original  ep desc", ds, ds->bLength);
+	if (ffs_ep->ep) {
+		ds->bEndpointAddress = ffs_ep->descs[0]->bEndpointAddress;
+		if (!ds->wMaxPacketSize)
+			ds->wMaxPacketSize = ffs_ep->descs[0]->wMaxPacketSize;
+	} else {
+		struct usb_request *req;
+		struct usb_ep *ep;
+
+		FVDBG("autoconfig");
+		ep = usb_ep_autoconfig(func->gadget, ds);
+		if (unlikely(!ep))
+			return -ENOTSUPP;
+		ep->driver_data = func->eps + idx;;
+
+		req = usb_ep_alloc_request(ep, GFP_KERNEL);
+		if (unlikely(!req))
+			return -ENOMEM;
+
+		ffs_ep->ep  = ep;
+		ffs_ep->req = req;
+		func->eps_revmap[ds->bEndpointAddress &
+				 USB_ENDPOINT_NUMBER_MASK] = idx + 1;
+	}
+	ffs_dump_mem(": Rewritten ep desc", ds, ds->bLength);
+
+	return 0;
+}
+
+
+static int __ffs_func_bind_do_nums(enum ffs_entity_type type, u8 *valuep,
+				   struct usb_descriptor_header *desc,
+				   void *priv)
+{
+	struct ffs_function *func = priv;
+	unsigned idx;
+	u8 newValue;
+
+	switch (type) {
+	default:
+	case FFS_DESCRIPTOR:
+		/* Handled in previous pass by __ffs_func_bind_do_descs() */
+		return 0;
+
+	case FFS_INTERFACE:
+		idx = *valuep;
+		if (func->interfaces_nums[idx] < 0) {
+			int id = usb_interface_id(func->conf, &func->function);
+			if (unlikely(id < 0))
+				return id;
+			func->interfaces_nums[idx] = id;
+		}
+		newValue = func->interfaces_nums[idx];
+		break;
+
+	case FFS_STRING:
+		/* String' IDs are allocated when fsf_data is bound to cdev */
+		newValue = func->ffs->stringtabs[0]->strings[*valuep - 1].id;
+		break;
+
+	case FFS_ENDPOINT:
+		/* USB_DT_ENDPOINT are handled in
+		 * __ffs_func_bind_do_descs(). */
+		if (desc->bDescriptorType == USB_DT_ENDPOINT)
+			return 0;
+
+		idx = (*valuep & USB_ENDPOINT_NUMBER_MASK) - 1;
+		if (unlikely(!func->eps[idx].ep))
+			return -EINVAL;
+
+		{
+			struct usb_endpoint_descriptor **descs;
+			descs = func->eps[idx].descs;
+			newValue = descs[descs[0] ? 0 : 1]->bEndpointAddress;
+		}
+		break;
+	}
+
+	FVDBG("%02x -> %02x", *valuep, newValue);
+	*valuep = newValue;
+	return 0;
+}
+
+static int ffs_func_bind(struct usb_configuration *c,
+			 struct usb_function *f)
+{
+	struct ffs_function *func = ffs_func_from_usb(f);
+	struct ffs_data *ffs = func->ffs;
+
+	const int full = !!func->ffs->fs_descs_count;
+	const int high = gadget_is_dualspeed(func->gadget) &&
+		func->ffs->hs_descs_count;
+
+	int ret;
+
+	/* Make it a single chunk, less management later on */
+	struct {
+		struct ffs_ep eps[ffs->eps_count];
+		struct usb_descriptor_header
+			*fs_descs[full ? ffs->fs_descs_count + 1 : 0];
+		struct usb_descriptor_header
+			*hs_descs[high ? ffs->hs_descs_count + 1 : 0];
+		short inums[ffs->interfaces_count];
+		char raw_descs[high ? ffs->raw_descs_length
+				    : ffs->raw_fs_descs_length];
+	} *data;
+
+	ENTER();
+
+	/* Only high speed but not supported by gadget? */
+	if (unlikely(!(full | high)))
+		return -ENOTSUPP;
+
+	/* Allocate */
+	data = kmalloc(sizeof *data, GFP_KERNEL);
+	if (unlikely(!data))
+		return -ENOMEM;
+
+	/* Zero */
+	memset(data->eps, 0, sizeof data->eps);
+	memcpy(data->raw_descs, ffs->raw_descs + 16, sizeof data->raw_descs);
+	memset(data->inums, 0xff, sizeof data->inums);
+	for (ret = ffs->eps_count; ret; --ret)
+		data->eps[ret].num = -1;
+
+	/* Save pointers */
+	func->eps             = data->eps;
+	func->interfaces_nums = data->inums;
+
+	/* Go throught all the endpoint descriptors and allocate
+	 * endpoints first, so that later we can rewrite the endpoint
+	 * numbers without worying that it may be described later on. */
+	if (likely(full)) {
+		func->function.descriptors = data->fs_descs;
+		ret = ffs_do_descs(ffs->fs_descs_count,
+				   data->raw_descs,
+				   sizeof data->raw_descs,
+				   __ffs_func_bind_do_descs, func);
+		if (unlikely(ret < 0))
+			goto error;
+	} else {
+		ret = 0;
+	}
+
+	if (likely(high)) {
+		func->function.hs_descriptors = data->hs_descs;
+		ret = ffs_do_descs(ffs->hs_descs_count,
+				   data->raw_descs + ret,
+				   (sizeof data->raw_descs) - ret,
+				   __ffs_func_bind_do_descs, func);
+	}
+
+	/* Now handle interface numbers allocation and interface and
+	 * enpoint numbers rewritting.  We can do that in one go
+	 * now. */
+	ret = ffs_do_descs(ffs->fs_descs_count +
+			   (high ? ffs->hs_descs_count : 0),
+			   data->raw_descs, sizeof data->raw_descs,
+			   __ffs_func_bind_do_nums, func);
+	if (unlikely(ret < 0))
+		goto error;
+
+	/* And we're done */
+	ffs_event_add(ffs, FUNCTIONFS_BIND);
+	return 0;
+
+error:
+	/* XXX Do we need to release all claimed endpoints here? */
+	return ret;
+}
+
+
+/* Other USB function hooks *************************************************/
+
+static void ffs_func_unbind(struct usb_configuration *c,
+			    struct usb_function *f)
+{
+	struct ffs_function *func = ffs_func_from_usb(f);
+	struct ffs_data *ffs = func->ffs;
+
+	ENTER();
+
+	if (ffs->func == func) {
+		ffs_func_eps_disable(func);
+		ffs->func = NULL;
+	}
+
+	ffs_event_add(ffs, FUNCTIONFS_UNBIND);
+
+	ffs_func_free(func);
+}
+
+
+static int ffs_func_set_alt(struct usb_function *f,
+			    unsigned interface, unsigned alt)
+{
+	struct ffs_function *func = ffs_func_from_usb(f);
+	struct ffs_data *ffs = func->ffs;
+	int ret = 0, intf;
+
+	if (alt != (unsigned)-1) {
+		intf = ffs_func_revmap_intf(func, interface);
+		if (unlikely(intf < 0))
+			return intf;
+	}
+
+	if (ffs->func)
+		ffs_func_eps_disable(ffs->func);
+
+	if (ffs->state != FFS_ACTIVE)
+		return -ENODEV;
+
+	if (alt == (unsigned)-1) {
+		ffs->func = NULL;
+		ffs_event_add(ffs, FUNCTIONFS_DISABLE);
+		return 0;
+	}
+
+	ffs->func = func;
+	ret = ffs_func_eps_enable(func);
+	if (likely(ret >= 0))
+		ffs_event_add(ffs, FUNCTIONFS_ENABLE);
+	return ret;
+}
+
+static void ffs_func_disable(struct usb_function *f)
+{
+	ffs_func_set_alt(f, 0, (unsigned)-1);
+}
+
+static int ffs_func_setup(struct usb_function *f,
+			  const struct usb_ctrlrequest *creq)
+{
+	struct ffs_function *func = ffs_func_from_usb(f);
+	struct ffs_data *ffs = func->ffs;
+	unsigned long flags;
+	int ret;
+
+	ENTER();
+
+	FVDBG("creq->bRequestType = %02x", creq->bRequestType);
+	FVDBG("creq->bRequest     = %02x", creq->bRequest);
+	FVDBG("creq->wValue       = %04x", le16_to_cpu(creq->wValue));
+	FVDBG("creq->wIndex       = %04x", le16_to_cpu(creq->wIndex));
+	FVDBG("creq->wLength      = %04x", le16_to_cpu(creq->wLength));
+
+	/* Most requests directed to interface go throught here
+	 * (notable exceptions are set/get interface) so we need to
+	 * handle them.  All other either handled by composite or
+	 * passed to usb_configuration->setup() (if one is set).  No
+	 * matter, we will handle requests directed to endpoint here
+	 * as well (as it's straightforward) but what to do with any
+	 * other request? */
+
+	if (ffs->state != FFS_ACTIVE)
+		return -ENODEV;
+
+	switch (creq->bRequestType & USB_RECIP_MASK) {
+	case USB_RECIP_INTERFACE:
+		ret = ffs_func_revmap_intf(func, le16_to_cpu(creq->wIndex));
+		if (unlikely(ret < 0))
+			return ret;
+		break;
+
+	case USB_RECIP_ENDPOINT:
+		ret = ffs_func_revmap_ep(func, le16_to_cpu(creq->wIndex));
+		if (unlikely(ret < 0))
+			return ret;
+		break;
+
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	spin_lock_irqsave(&ffs->ev.waitq.lock, flags);
+	ffs->ev.setup = *creq;
+	ffs->ev.setup.wIndex = cpu_to_le16(ret);
+	__ffs_event_add(ffs, FUNCTIONFS_SETUP);
+	spin_unlock_irqrestore(&ffs->ev.waitq.lock, flags);
+
+	return 0;
+}
+
+static void ffs_func_suspend(struct usb_function *f)
+{
+	ENTER();
+	ffs_event_add(ffs_func_from_usb(f)->ffs, FUNCTIONFS_SUSPEND);
+}
+
+static void ffs_func_resume(struct usb_function *f)
+{
+	ENTER();
+	ffs_event_add(ffs_func_from_usb(f)->ffs, FUNCTIONFS_RESUME);
+}
+
+
+
+/* Enpoint and interface numbers reverse mapping ****************************/
+
+static int ffs_func_revmap_ep(struct ffs_function *func, u8 num)
+{
+	num = func->eps_revmap[num & USB_ENDPOINT_NUMBER_MASK];
+	return num ? num : -EDOM;
+}
+
+static int ffs_func_revmap_intf(struct ffs_function *func, u8 intf)
+{
+	short *nums = func->interfaces_nums;
+	unsigned count = func->ffs->interfaces_count;
+
+	for (; count; --count, ++nums) {
+		if (*nums >= 0 && *nums == intf)
+			return nums - func->interfaces_nums;
+	}
+
+	return -EDOM;
+}
+
+
+/* Misc helper functions ****************************************************/
+
+static int ffs_mutex_lock(struct mutex *mutex, unsigned nonblock)
+{
+	return nonblock
+		? likely(mutex_trylock(mutex)) ? 0 : -EAGAIN
+		: mutex_lock_interruptible(mutex);
+}
+
+
+static char *ffs_prepare_buffer(const char * __user buf, size_t len)
+{
+	char *data;
+
+	if (unlikely(!len))
+		return NULL;
+
+	data = kmalloc(len, GFP_KERNEL);
+	if (unlikely(!data))
+		return ERR_PTR(-ENOMEM);
+
+	if (unlikely(__copy_from_user(data, buf, len))) {
+		kfree(data);
+		return ERR_PTR(-EFAULT);
+	}
+
+	FVDBG("Buffer from user space:");
+	ffs_dump_mem("", data, len);
+
+	return data;
+}