Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 3894 insertions, 0 deletions

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
new file mode 100644
index 000000000..3e59055aa
--- /dev/null
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -0,0 +1,3894 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * f_fs.c -- user mode file system API for USB composite function controllers
+ *
+ * Copyright (C) 2010 Samsung Electronics
+ * Author: Michal Nazarewicz <mina86@mina86.com>
+ *
+ * Based on inode.c (GadgetFS) which was:
+ * Copyright (C) 2003-2004 David Brownell
+ * Copyright (C) 2003 Agilent Technologies
+ */
+
+
+/* #define DEBUG */
+/* #define VERBOSE_DEBUG */
+
+#include <linux/blkdev.h>
+#include <linux/pagemap.h>
+#include <linux/export.h>
+#include <linux/fs_parser.h>
+#include <linux/hid.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/scatterlist.h>
+#include <linux/sched/signal.h>
+#include <linux/uio.h>
+#include <linux/vmalloc.h>
+#include <asm/unaligned.h>
+
+#include <linux/usb/ccid.h>
+#include <linux/usb/composite.h>
+#include <linux/usb/functionfs.h>
+
+#include <linux/aio.h>
+#include <linux/kthread.h>
+#include <linux/poll.h>
+#include <linux/eventfd.h>
+
+#include "u_fs.h"
+#include "u_f.h"
+#include "u_os_desc.h"
+#include "configfs.h"
+
+#define FUNCTIONFS_MAGIC	0xa647361 /* Chosen by a honest dice roll ;) */
+
+/* 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(const char *dev_name)
+	__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 ownership 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 inline enum ffs_setup_state
+ffs_setup_state_clear_cancelled(struct ffs_data *ffs)
+{
+	return (enum ffs_setup_state)
+		cmpxchg(&ffs->setup_state, FFS_SETUP_CANCELLED, FFS_NO_SETUP);
+}
+
+
+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 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 bool ffs_func_req_match(struct usb_function *,
+			       const struct usb_ctrlrequest *,
+			       bool config0);
+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, [2]: super speed */
+	struct usb_endpoint_descriptor	*descs[3];
+
+	u8				num;
+};
+
+struct ffs_epfile {
+	/* Protects ep->ep and ep->req. */
+	struct mutex			mutex;
+
+	struct ffs_data			*ffs;
+	struct ffs_ep			*ep;	/* P: ffs->eps_lock */
+
+	struct dentry			*dentry;
+
+	/*
+	 * Buffer for holding data from partial reads which may happen since
+	 * we’re rounding user read requests to a multiple of a max packet size.
+	 *
+	 * The pointer is initialised with NULL value and may be set by
+	 * __ffs_epfile_read_data function to point to a temporary buffer.
+	 *
+	 * In normal operation, calls to __ffs_epfile_read_buffered will consume
+	 * data from said buffer and eventually free it.  Importantly, while the
+	 * function is using the buffer, it sets the pointer to NULL.  This is
+	 * all right since __ffs_epfile_read_data and __ffs_epfile_read_buffered
+	 * can never run concurrently (they are synchronised by epfile->mutex)
+	 * so the latter will not assign a new value to the pointer.
+	 *
+	 * Meanwhile ffs_func_eps_disable frees the buffer (if the pointer is
+	 * valid) and sets the pointer to READ_BUFFER_DROP value.  This special
+	 * value is crux of the synchronisation between ffs_func_eps_disable and
+	 * __ffs_epfile_read_data.
+	 *
+	 * Once __ffs_epfile_read_data is about to finish it will try to set the
+	 * pointer back to its old value (as described above), but seeing as the
+	 * pointer is not-NULL (namely READ_BUFFER_DROP) it will instead free
+	 * the buffer.
+	 *
+	 * == State transitions ==
+	 *
+	 * • ptr == NULL:  (initial state)
+	 *   ◦ __ffs_epfile_read_buffer_free: go to ptr == DROP
+	 *   ◦ __ffs_epfile_read_buffered:    nop
+	 *   ◦ __ffs_epfile_read_data allocates temp buffer: go to ptr == buf
+	 *   ◦ reading finishes:              n/a, not in ‘and reading’ state
+	 * • ptr == DROP:
+	 *   ◦ __ffs_epfile_read_buffer_free: nop
+	 *   ◦ __ffs_epfile_read_buffered:    go to ptr == NULL
+	 *   ◦ __ffs_epfile_read_data allocates temp buffer: free buf, nop
+	 *   ◦ reading finishes:              n/a, not in ‘and reading’ state
+	 * • ptr == buf:
+	 *   ◦ __ffs_epfile_read_buffer_free: free buf, go to ptr == DROP
+	 *   ◦ __ffs_epfile_read_buffered:    go to ptr == NULL and reading
+	 *   ◦ __ffs_epfile_read_data:        n/a, __ffs_epfile_read_buffered
+	 *                                    is always called first
+	 *   ◦ reading finishes:              n/a, not in ‘and reading’ state
+	 * • ptr == NULL and reading:
+	 *   ◦ __ffs_epfile_read_buffer_free: go to ptr == DROP and reading
+	 *   ◦ __ffs_epfile_read_buffered:    n/a, mutex is held
+	 *   ◦ __ffs_epfile_read_data:        n/a, mutex is held
+	 *   ◦ reading finishes and …
+	 *     … all data read:               free buf, go to ptr == NULL
+	 *     … otherwise:                   go to ptr == buf and reading
+	 * • ptr == DROP and reading:
+	 *   ◦ __ffs_epfile_read_buffer_free: nop
+	 *   ◦ __ffs_epfile_read_buffered:    n/a, mutex is held
+	 *   ◦ __ffs_epfile_read_data:        n/a, mutex is held
+	 *   ◦ reading finishes:              free buf, go to ptr == DROP
+	 */
+	struct ffs_buffer		*read_buffer;
+#define READ_BUFFER_DROP ((struct ffs_buffer *)ERR_PTR(-ESHUTDOWN))
+
+	char				name[5];
+
+	unsigned char			in;	/* P: ffs->eps_lock */
+	unsigned char			isoc;	/* P: ffs->eps_lock */
+
+	unsigned char			_pad;
+};
+
+struct ffs_buffer {
+	size_t length;
+	char *data;
+	char storage[];
+};
+
+/*  ffs_io_data structure ***************************************************/
+
+struct ffs_io_data {
+	bool aio;
+	bool read;
+
+	struct kiocb *kiocb;
+	struct iov_iter data;
+	const void *to_free;
+	char *buf;
+
+	struct mm_struct *mm;
+	struct work_struct work;
+
+	struct usb_ep *ep;
+	struct usb_request *req;
+	struct sg_table sgt;
+	bool use_sg;
+
+	struct ffs_data *ffs;
+
+	int status;
+	struct completion done;
+};
+
+struct ffs_desc_helper {
+	struct ffs_data *ffs;
+	unsigned interfaces_count;
+	unsigned eps_count;
+};
+
+static int  __must_check ffs_epfiles_create(struct ffs_data *ffs);
+static void ffs_epfiles_destroy(struct ffs_epfile *epfiles, unsigned count);
+
+static struct dentry *
+ffs_sb_create_file(struct super_block *sb, const char *name, void *data,
+		   const struct file_operations *fops);
+
+/* Devices management *******************************************************/
+
+DEFINE_MUTEX(ffs_lock);
+EXPORT_SYMBOL_GPL(ffs_lock);
+
+static struct ffs_dev *_ffs_find_dev(const char *name);
+static struct ffs_dev *_ffs_alloc_dev(void);
+static void _ffs_free_dev(struct ffs_dev *dev);
+static int ffs_acquire_dev(const char *dev_name, struct ffs_data *ffs_data);
+static void ffs_release_dev(struct ffs_dev *ffs_dev);
+static int ffs_ready(struct ffs_data *ffs);
+static void ffs_closed(struct ffs_data *ffs);
+
+/* 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(&ffs->ep0req_completion);
+}
+
+static int __ffs_ep0_queue_wait(struct ffs_data *ffs, char *data, size_t len)
+	__releases(&ffs->ev.waitq.lock)
+{
+	struct usb_request *req = ffs->ep0req;
+	int ret;
+
+	if (!req) {
+		spin_unlock_irq(&ffs->ev.waitq.lock);
+		return -EINVAL;
+	}
+
+	req->zero     = len < le16_to_cpu(ffs->ev.setup.wLength);
+
+	spin_unlock_irq(&ffs->ev.waitq.lock);
+
+	req->buf      = data;
+	req->length   = len;
+
+	/*
+	 * UDC layer requires to provide a buffer even for ZLP, but should
+	 * not use it at all. Let's provide some poisoned pointer to catch
+	 * possible bug in the driver.
+	 */
+	if (req->buf == NULL)
+		req->buf = (void *)0xDEADBABE;
+
+	reinit_completion(&ffs->ep0req_completion);
+
+	ret = usb_ep_queue(ffs->gadget->ep0, req, GFP_ATOMIC);
+	if (ret < 0)
+		return ret;
+
+	ret = wait_for_completion_interruptible(&ffs->ep0req_completion);
+	if (ret) {
+		usb_ep_dequeue(ffs->gadget->ep0, req);
+		return -EINTR;
+	}
+
+	ffs->setup_state = FFS_NO_SETUP;
+	return req->status ? req->status : req->actual;
+}
+
+static int __ffs_ep0_stall(struct ffs_data *ffs)
+{
+	if (ffs->ev.can_stall) {
+		pr_vdebug("ep0 stall\n");
+		usb_ep_set_halt(ffs->gadget->ep0);
+		ffs->setup_state = FFS_NO_SETUP;
+		return -EL2HLT;
+	} else {
+		pr_debug("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_clear_cancelled(ffs) == FFS_SETUP_CANCELLED)
+		return -EIDRM;
+
+	/* Acquire mutex */
+	ret = ffs_mutex_lock(&ffs->mutex, file->f_flags & O_NONBLOCK);
+	if (ret < 0)
+		return ret;
+
+	/* Check state */
+	switch (ffs->state) {
+	case FFS_READ_DESCRIPTORS:
+	case FFS_READ_STRINGS:
+		/* Copy data */
+		if (len < 16) {
+			ret = -EINVAL;
+			break;
+		}
+
+		data = ffs_prepare_buffer(buf, len);
+		if (IS_ERR(data)) {
+			ret = PTR_ERR(data);
+			break;
+		}
+
+		/* Handle data */
+		if (ffs->state == FFS_READ_DESCRIPTORS) {
+			pr_info("read descriptors\n");
+			ret = __ffs_data_got_descs(ffs, data, len);
+			if (ret < 0)
+				break;
+
+			ffs->state = FFS_READ_STRINGS;
+			ret = len;
+		} else {
+			pr_info("read strings\n");
+			ret = __ffs_data_got_strings(ffs, data, len);
+			if (ret < 0)
+				break;
+
+			ret = ffs_epfiles_create(ffs);
+			if (ret) {
+				ffs->state = FFS_CLOSING;
+				break;
+			}
+
+			ffs->state = FFS_ACTIVE;
+			mutex_unlock(&ffs->mutex);
+
+			ret = ffs_ready(ffs);
+			if (ret < 0) {
+				ffs->state = FFS_CLOSING;
+				return ret;
+			}
+
+			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_clear_cancelled(ffs)) {
+		case FFS_SETUP_CANCELLED:
+			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 (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_CANCELLED 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_clear_cancelled(ffs) ==
+		    FFS_SETUP_CANCELLED) {
+			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;
+}
+
+/* Called with ffs->ev.waitq.lock and ffs->mutex held, both released on exit. */
+static ssize_t __ffs_ep0_read_events(struct ffs_data *ffs, char __user *buf,
+				     size_t n)
+	__releases(&ffs->ev.waitq.lock)
+{
+	/*
+	 * n cannot be bigger than ffs->ev.count, which cannot be bigger than
+	 * size of ffs->ev.types array (which is four) so that's how much space
+	 * we reserve.
+	 */
+	struct usb_functionfs_event events[ARRAY_SIZE(ffs->ev.types)];
+	const size_t size = n * sizeof *events;
+	unsigned i = 0;
+
+	memset(events, 0, size);
+
+	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);
+
+	ffs->ev.count -= n;
+	if (ffs->ev.count)
+		memmove(ffs->ev.types, ffs->ev.types + n,
+			ffs->ev.count * sizeof *ffs->ev.types);
+
+	spin_unlock_irq(&ffs->ev.waitq.lock);
+	mutex_unlock(&ffs->mutex);
+
+	return copy_to_user(buf, events, size) ? -EFAULT : size;
+}
+
+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_clear_cancelled(ffs) == FFS_SETUP_CANCELLED)
+		return -EIDRM;
+
+	/* Acquire mutex */
+	ret = ffs_mutex_lock(&ffs->mutex, file->f_flags & O_NONBLOCK);
+	if (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_clear_cancelled(ffs)) {
+	case FFS_SETUP_CANCELLED:
+		ret = -EIDRM;
+		break;
+
+	case FFS_NO_SETUP:
+		n = len / sizeof(struct usb_functionfs_event);
+		if (!n) {
+			ret = -EINVAL;
+			break;
+		}
+
+		if ((file->f_flags & O_NONBLOCK) && !ffs->ev.count) {
+			ret = -EAGAIN;
+			break;
+		}
+
+		if (wait_event_interruptible_exclusive_locked_irq(ffs->ev.waitq,
+							ffs->ev.count)) {
+			ret = -EINTR;
+			break;
+		}
+
+		/* unlocks spinlock */
+		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 (len) {
+			data = kmalloc(len, GFP_KERNEL);
+			if (!data) {
+				ret = -ENOMEM;
+				goto done_mutex;
+			}
+		}
+
+		spin_lock_irq(&ffs->ev.waitq.lock);
+
+		/* See ffs_ep0_write() */
+		if (ffs_setup_state_clear_cancelled(ffs) ==
+		    FFS_SETUP_CANCELLED) {
+			ret = -EIDRM;
+			break;
+		}
+
+		/* unlocks spinlock */
+		ret = __ffs_ep0_queue_wait(ffs, data, len);
+		if ((ret > 0) && (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 (ffs->state == FFS_CLOSING)
+		return -EBUSY;
+
+	file->private_data = ffs;
+	ffs_data_opened(ffs);
+
+	return stream_open(inode, file);
+}
+
+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 && gadget->ops->ioctl) {
+		ret = gadget->ops->ioctl(gadget, code, value);
+	} else {
+		ret = -ENOTTY;
+	}
+
+	return ret;
+}
+
+static __poll_t ffs_ep0_poll(struct file *file, poll_table *wait)
+{
+	struct ffs_data *ffs = file->private_data;
+	__poll_t mask = EPOLLWRNORM;
+	int ret;
+
+	poll_wait(file, &ffs->ev.waitq, wait);
+
+	ret = ffs_mutex_lock(&ffs->mutex, file->f_flags & O_NONBLOCK);
+	if (ret < 0)
+		return mask;
+
+	switch (ffs->state) {
+	case FFS_READ_DESCRIPTORS:
+	case FFS_READ_STRINGS:
+		mask |= EPOLLOUT;
+		break;
+
+	case FFS_ACTIVE:
+		switch (ffs->setup_state) {
+		case FFS_NO_SETUP:
+			if (ffs->ev.count)
+				mask |= EPOLLIN;
+			break;
+
+		case FFS_SETUP_PENDING:
+		case FFS_SETUP_CANCELLED:
+			mask |= (EPOLLIN | EPOLLOUT);
+			break;
+		}
+		break;
+
+	case FFS_CLOSING:
+		break;
+	case FFS_DEACTIVATED:
+		break;
+	}
+
+	mutex_unlock(&ffs->mutex);
+
+	return mask;
+}
+
+static const struct file_operations ffs_ep0_operations = {
+	.llseek =	no_llseek,
+
+	.open =		ffs_ep0_open,
+	.write =	ffs_ep0_write,
+	.read =		ffs_ep0_read,
+	.release =	ffs_ep0_release,
+	.unlocked_ioctl =	ffs_ep0_ioctl,
+	.poll =		ffs_ep0_poll,
+};
+
+
+/* "Normal" endpoints operations ********************************************/
+
+static void ffs_epfile_io_complete(struct usb_ep *_ep, struct usb_request *req)
+{
+	struct ffs_io_data *io_data = req->context;
+
+	ENTER();
+	if (req->status)
+		io_data->status = req->status;
+	else
+		io_data->status = req->actual;
+
+	complete(&io_data->done);
+}
+
+static ssize_t ffs_copy_to_iter(void *data, int data_len, struct iov_iter *iter)
+{
+	ssize_t ret = copy_to_iter(data, data_len, iter);
+	if (ret == data_len)
+		return ret;
+
+	if (iov_iter_count(iter))
+		return -EFAULT;
+
+	/*
+	 * Dear user space developer!
+	 *
+	 * TL;DR: To stop getting below error message in your kernel log, change
+	 * user space code using functionfs to align read buffers to a max
+	 * packet size.
+	 *
+	 * Some UDCs (e.g. dwc3) require request sizes to be a multiple of a max
+	 * packet size.  When unaligned buffer is passed to functionfs, it
+	 * internally uses a larger, aligned buffer so that such UDCs are happy.
+	 *
+	 * Unfortunately, this means that host may send more data than was
+	 * requested in read(2) system call.  f_fs doesn’t know what to do with
+	 * that excess data so it simply drops it.
+	 *
+	 * Was the buffer aligned in the first place, no such problem would
+	 * happen.
+	 *
+	 * Data may be dropped only in AIO reads.  Synchronous reads are handled
+	 * by splitting a request into multiple parts.  This splitting may still
+	 * be a problem though so it’s likely best to align the buffer
+	 * regardless of it being AIO or not..
+	 *
+	 * This only affects OUT endpoints, i.e. reading data with a read(2),
+	 * aio_read(2) etc. system calls.  Writing data to an IN endpoint is not
+	 * affected.
+	 */
+	pr_err("functionfs read size %d > requested size %zd, dropping excess data. "
+	       "Align read buffer size to max packet size to avoid the problem.\n",
+	       data_len, ret);
+
+	return ret;
+}
+
+/*
+ * allocate a virtually contiguous buffer and create a scatterlist describing it
+ * @sg_table	- pointer to a place to be filled with sg_table contents
+ * @size	- required buffer size
+ */
+static void *ffs_build_sg_list(struct sg_table *sgt, size_t sz)
+{
+	struct page **pages;
+	void *vaddr, *ptr;
+	unsigned int n_pages;
+	int i;
+
+	vaddr = vmalloc(sz);
+	if (!vaddr)
+		return NULL;
+
+	n_pages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
+	pages = kvmalloc_array(n_pages, sizeof(struct page *), GFP_KERNEL);
+	if (!pages) {
+		vfree(vaddr);
+
+		return NULL;
+	}
+	for (i = 0, ptr = vaddr; i < n_pages; ++i, ptr += PAGE_SIZE)
+		pages[i] = vmalloc_to_page(ptr);
+
+	if (sg_alloc_table_from_pages(sgt, pages, n_pages, 0, sz, GFP_KERNEL)) {
+		kvfree(pages);
+		vfree(vaddr);
+
+		return NULL;
+	}
+	kvfree(pages);
+
+	return vaddr;
+}
+
+static inline void *ffs_alloc_buffer(struct ffs_io_data *io_data,
+	size_t data_len)
+{
+	if (io_data->use_sg)
+		return ffs_build_sg_list(&io_data->sgt, data_len);
+
+	return kmalloc(data_len, GFP_KERNEL);
+}
+
+static inline void ffs_free_buffer(struct ffs_io_data *io_data)
+{
+	if (!io_data->buf)
+		return;
+
+	if (io_data->use_sg) {
+		sg_free_table(&io_data->sgt);
+		vfree(io_data->buf);
+	} else {
+		kfree(io_data->buf);
+	}
+}
+
+static void ffs_user_copy_worker(struct work_struct *work)
+{
+	struct ffs_io_data *io_data = container_of(work, struct ffs_io_data,
+						   work);
+	int ret = io_data->req->status ? io_data->req->status :
+					 io_data->req->actual;
+	bool kiocb_has_eventfd = io_data->kiocb->ki_flags & IOCB_EVENTFD;
+
+	if (io_data->read && ret > 0) {
+		kthread_use_mm(io_data->mm);
+		ret = ffs_copy_to_iter(io_data->buf, ret, &io_data->data);
+		kthread_unuse_mm(io_data->mm);
+	}
+
+	io_data->kiocb->ki_complete(io_data->kiocb, ret);
+
+	if (io_data->ffs->ffs_eventfd && !kiocb_has_eventfd)
+		eventfd_signal(io_data->ffs->ffs_eventfd, 1);
+
+	usb_ep_free_request(io_data->ep, io_data->req);
+
+	if (io_data->read)
+		kfree(io_data->to_free);
+	ffs_free_buffer(io_data);
+	kfree(io_data);
+}
+
+static void ffs_epfile_async_io_complete(struct usb_ep *_ep,
+					 struct usb_request *req)
+{
+	struct ffs_io_data *io_data = req->context;
+	struct ffs_data *ffs = io_data->ffs;
+
+	ENTER();
+
+	INIT_WORK(&io_data->work, ffs_user_copy_worker);
+	queue_work(ffs->io_completion_wq, &io_data->work);
+}
+
+static void __ffs_epfile_read_buffer_free(struct ffs_epfile *epfile)
+{
+	/*
+	 * See comment in struct ffs_epfile for full read_buffer pointer
+	 * synchronisation story.
+	 */
+	struct ffs_buffer *buf = xchg(&epfile->read_buffer, READ_BUFFER_DROP);
+	if (buf && buf != READ_BUFFER_DROP)
+		kfree(buf);
+}
+
+/* Assumes epfile->mutex is held. */
+static ssize_t __ffs_epfile_read_buffered(struct ffs_epfile *epfile,
+					  struct iov_iter *iter)
+{
+	/*
+	 * Null out epfile->read_buffer so ffs_func_eps_disable does not free
+	 * the buffer while we are using it.  See comment in struct ffs_epfile
+	 * for full read_buffer pointer synchronisation story.
+	 */
+	struct ffs_buffer *buf = xchg(&epfile->read_buffer, NULL);
+	ssize_t ret;
+	if (!buf || buf == READ_BUFFER_DROP)
+		return 0;
+
+	ret = copy_to_iter(buf->data, buf->length, iter);
+	if (buf->length == ret) {
+		kfree(buf);
+		return ret;
+	}
+
+	if (iov_iter_count(iter)) {
+		ret = -EFAULT;
+	} else {
+		buf->length -= ret;
+		buf->data += ret;
+	}
+
+	if (cmpxchg(&epfile->read_buffer, NULL, buf))
+		kfree(buf);
+
+	return ret;
+}
+
+/* Assumes epfile->mutex is held. */
+static ssize_t __ffs_epfile_read_data(struct ffs_epfile *epfile,
+				      void *data, int data_len,
+				      struct iov_iter *iter)
+{
+	struct ffs_buffer *buf;
+
+	ssize_t ret = copy_to_iter(data, data_len, iter);
+	if (data_len == ret)
+		return ret;
+
+	if (iov_iter_count(iter))
+		return -EFAULT;
+
+	/* See ffs_copy_to_iter for more context. */
+	pr_warn("functionfs read size %d > requested size %zd, splitting request into multiple reads.",
+		data_len, ret);
+
+	data_len -= ret;
+	buf = kmalloc(struct_size(buf, storage, data_len), GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+	buf->length = data_len;
+	buf->data = buf->storage;
+	memcpy(buf->storage, data + ret, flex_array_size(buf, storage, data_len));
+
+	/*
+	 * At this point read_buffer is NULL or READ_BUFFER_DROP (if
+	 * ffs_func_eps_disable has been called in the meanwhile).  See comment
+	 * in struct ffs_epfile for full read_buffer pointer synchronisation
+	 * story.
+	 */
+	if (cmpxchg(&epfile->read_buffer, NULL, buf))
+		kfree(buf);
+
+	return ret;
+}
+
+static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
+{
+	struct ffs_epfile *epfile = file->private_data;
+	struct usb_request *req;
+	struct ffs_ep *ep;
+	char *data = NULL;
+	ssize_t ret, data_len = -EINVAL;
+	int halt;
+
+	/* Are we still active? */
+	if (WARN_ON(epfile->ffs->state != FFS_ACTIVE))
+		return -ENODEV;
+
+	/* Wait for endpoint to be enabled */
+	ep = epfile->ep;
+	if (!ep) {
+		if (file->f_flags & O_NONBLOCK)
+			return -EAGAIN;
+
+		ret = wait_event_interruptible(
+				epfile->ffs->wait, (ep = epfile->ep));
+		if (ret)
+			return -EINTR;
+	}
+
+	/* Do we halt? */
+	halt = (!io_data->read == !epfile->in);
+	if (halt && epfile->isoc)
+		return -EINVAL;
+
+	/* We will be using request and read_buffer */
+	ret = ffs_mutex_lock(&epfile->mutex, file->f_flags & O_NONBLOCK);
+	if (ret)
+		goto error;
+
+	/* Allocate & copy */
+	if (!halt) {
+		struct usb_gadget *gadget;
+
+		/*
+		 * Do we have buffered data from previous partial read?  Check
+		 * that for synchronous case only because we do not have
+		 * facility to ‘wake up’ a pending asynchronous read and push
+		 * buffered data to it which we would need to make things behave
+		 * consistently.
+		 */
+		if (!io_data->aio && io_data->read) {
+			ret = __ffs_epfile_read_buffered(epfile, &io_data->data);
+			if (ret)
+				goto error_mutex;
+		}
+
+		/*
+		 * if we _do_ wait above, the epfile->ffs->gadget might be NULL
+		 * before the waiting completes, so do not assign to 'gadget'
+		 * earlier
+		 */
+		gadget = epfile->ffs->gadget;
+
+		spin_lock_irq(&epfile->ffs->eps_lock);
+		/* In the meantime, endpoint got disabled or changed. */
+		if (epfile->ep != ep) {
+			ret = -ESHUTDOWN;
+			goto error_lock;
+		}
+		data_len = iov_iter_count(&io_data->data);
+		/*
+		 * Controller may require buffer size to be aligned to
+		 * maxpacketsize of an out endpoint.
+		 */
+		if (io_data->read)
+			data_len = usb_ep_align_maybe(gadget, ep->ep, data_len);
+
+		io_data->use_sg = gadget->sg_supported && data_len > PAGE_SIZE;
+		spin_unlock_irq(&epfile->ffs->eps_lock);
+
+		data = ffs_alloc_buffer(io_data, data_len);
+		if (!data) {
+			ret = -ENOMEM;
+			goto error_mutex;
+		}
+		if (!io_data->read &&
+		    !copy_from_iter_full(data, data_len, &io_data->data)) {
+			ret = -EFAULT;
+			goto error_mutex;
+		}
+	}
+
+	spin_lock_irq(&epfile->ffs->eps_lock);
+
+	if (epfile->ep != ep) {
+		/* In the meantime, endpoint got disabled or changed. */
+		ret = -ESHUTDOWN;
+	} else if (halt) {
+		ret = usb_ep_set_halt(ep->ep);
+		if (!ret)
+			ret = -EBADMSG;
+	} else if (data_len == -EINVAL) {
+		/*
+		 * Sanity Check: even though data_len can't be used
+		 * uninitialized at the time I write this comment, some
+		 * compilers complain about this situation.
+		 * In order to keep the code clean from warnings, data_len is
+		 * being initialized to -EINVAL during its declaration, which
+		 * means we can't rely on compiler anymore to warn no future
+		 * changes won't result in data_len being used uninitialized.
+		 * For such reason, we're adding this redundant sanity check
+		 * here.
+		 */
+		WARN(1, "%s: data_len == -EINVAL\n", __func__);
+		ret = -EINVAL;
+	} else if (!io_data->aio) {
+		bool interrupted = false;
+
+		req = ep->req;
+		if (io_data->use_sg) {
+			req->buf = NULL;
+			req->sg	= io_data->sgt.sgl;
+			req->num_sgs = io_data->sgt.nents;
+		} else {
+			req->buf = data;
+			req->num_sgs = 0;
+		}
+		req->length = data_len;
+
+		io_data->buf = data;
+
+		init_completion(&io_data->done);
+		req->context  = io_data;
+		req->complete = ffs_epfile_io_complete;
+
+		ret = usb_ep_queue(ep->ep, req, GFP_ATOMIC);
+		if (ret < 0)
+			goto error_lock;
+
+		spin_unlock_irq(&epfile->ffs->eps_lock);
+
+		if (wait_for_completion_interruptible(&io_data->done)) {
+			spin_lock_irq(&epfile->ffs->eps_lock);
+			if (epfile->ep != ep) {
+				ret = -ESHUTDOWN;
+				goto error_lock;
+			}
+			/*
+			 * To avoid race condition with ffs_epfile_io_complete,
+			 * dequeue the request first then check
+			 * status. usb_ep_dequeue API should guarantee no race
+			 * condition with req->complete callback.
+			 */
+			usb_ep_dequeue(ep->ep, req);
+			spin_unlock_irq(&epfile->ffs->eps_lock);
+			wait_for_completion(&io_data->done);
+			interrupted = io_data->status < 0;
+		}
+
+		if (interrupted)
+			ret = -EINTR;
+		else if (io_data->read && io_data->status > 0)
+			ret = __ffs_epfile_read_data(epfile, data, io_data->status,
+						     &io_data->data);
+		else
+			ret = io_data->status;
+		goto error_mutex;
+	} else if (!(req = usb_ep_alloc_request(ep->ep, GFP_ATOMIC))) {
+		ret = -ENOMEM;
+	} else {
+		if (io_data->use_sg) {
+			req->buf = NULL;
+			req->sg	= io_data->sgt.sgl;
+			req->num_sgs = io_data->sgt.nents;
+		} else {
+			req->buf = data;
+			req->num_sgs = 0;
+		}
+		req->length = data_len;
+
+		io_data->buf = data;
+		io_data->ep = ep->ep;
+		io_data->req = req;
+		io_data->ffs = epfile->ffs;
+
+		req->context  = io_data;
+		req->complete = ffs_epfile_async_io_complete;
+
+		ret = usb_ep_queue(ep->ep, req, GFP_ATOMIC);
+		if (ret) {
+			io_data->req = NULL;
+			usb_ep_free_request(ep->ep, req);
+			goto error_lock;
+		}
+
+		ret = -EIOCBQUEUED;
+		/*
+		 * Do not kfree the buffer in this function.  It will be freed
+		 * by ffs_user_copy_worker.
+		 */
+		data = NULL;
+	}
+
+error_lock:
+	spin_unlock_irq(&epfile->ffs->eps_lock);
+error_mutex:
+	mutex_unlock(&epfile->mutex);
+error:
+	if (ret != -EIOCBQUEUED) /* don't free if there is iocb queued */
+		ffs_free_buffer(io_data);
+	return ret;
+}
+
+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 stream_open(inode, file);
+}
+
+static int ffs_aio_cancel(struct kiocb *kiocb)
+{
+	struct ffs_io_data *io_data = kiocb->private;
+	struct ffs_epfile *epfile = kiocb->ki_filp->private_data;
+	unsigned long flags;
+	int value;
+
+	ENTER();
+
+	spin_lock_irqsave(&epfile->ffs->eps_lock, flags);
+
+	if (io_data && io_data->ep && io_data->req)
+		value = usb_ep_dequeue(io_data->ep, io_data->req);
+	else
+		value = -EINVAL;
+
+	spin_unlock_irqrestore(&epfile->ffs->eps_lock, flags);
+
+	return value;
+}
+
+static ssize_t ffs_epfile_write_iter(struct kiocb *kiocb, struct iov_iter *from)
+{
+	struct ffs_io_data io_data, *p = &io_data;
+	ssize_t res;
+
+	ENTER();
+
+	if (!is_sync_kiocb(kiocb)) {
+		p = kzalloc(sizeof(io_data), GFP_KERNEL);
+		if (!p)
+			return -ENOMEM;
+		p->aio = true;
+	} else {
+		memset(p, 0, sizeof(*p));
+		p->aio = false;
+	}
+
+	p->read = false;
+	p->kiocb = kiocb;
+	p->data = *from;
+	p->mm = current->mm;
+
+	kiocb->private = p;
+
+	if (p->aio)
+		kiocb_set_cancel_fn(kiocb, ffs_aio_cancel);
+
+	res = ffs_epfile_io(kiocb->ki_filp, p);
+	if (res == -EIOCBQUEUED)
+		return res;
+	if (p->aio)
+		kfree(p);
+	else
+		*from = p->data;
+	return res;
+}
+
+static ssize_t ffs_epfile_read_iter(struct kiocb *kiocb, struct iov_iter *to)
+{
+	struct ffs_io_data io_data, *p = &io_data;
+	ssize_t res;
+
+	ENTER();
+
+	if (!is_sync_kiocb(kiocb)) {
+		p = kzalloc(sizeof(io_data), GFP_KERNEL);
+		if (!p)
+			return -ENOMEM;
+		p->aio = true;
+	} else {
+		memset(p, 0, sizeof(*p));
+		p->aio = false;
+	}
+
+	p->read = true;
+	p->kiocb = kiocb;
+	if (p->aio) {
+		p->to_free = dup_iter(&p->data, to, GFP_KERNEL);
+		if (!p->to_free) {
+			kfree(p);
+			return -ENOMEM;
+		}
+	} else {
+		p->data = *to;
+		p->to_free = NULL;
+	}
+	p->mm = current->mm;
+
+	kiocb->private = p;
+
+	if (p->aio)
+		kiocb_set_cancel_fn(kiocb, ffs_aio_cancel);
+
+	res = ffs_epfile_io(kiocb->ki_filp, p);
+	if (res == -EIOCBQUEUED)
+		return res;
+
+	if (p->aio) {
+		kfree(p->to_free);
+		kfree(p);
+	} else {
+		*to = p->data;
+	}
+	return res;
+}
+
+static int
+ffs_epfile_release(struct inode *inode, struct file *file)
+{
+	struct ffs_epfile *epfile = inode->i_private;
+
+	ENTER();
+
+	__ffs_epfile_read_buffer_free(epfile);
+	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;
+	struct ffs_ep *ep;
+	int ret;
+
+	ENTER();
+
+	if (WARN_ON(epfile->ffs->state != FFS_ACTIVE))
+		return -ENODEV;
+
+	/* Wait for endpoint to be enabled */
+	ep = epfile->ep;
+	if (!ep) {
+		if (file->f_flags & O_NONBLOCK)
+			return -EAGAIN;
+
+		ret = wait_event_interruptible(
+				epfile->ffs->wait, (ep = epfile->ep));
+		if (ret)
+			return -EINTR;
+	}
+
+	spin_lock_irq(&epfile->ffs->eps_lock);
+
+	/* In the meantime, endpoint got disabled or changed. */
+	if (epfile->ep != ep) {
+		spin_unlock_irq(&epfile->ffs->eps_lock);
+		return -ESHUTDOWN;
+	}
+
+	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;
+	case FUNCTIONFS_ENDPOINT_DESC:
+	{
+		int desc_idx;
+		struct usb_endpoint_descriptor desc1, *desc;
+
+		switch (epfile->ffs->gadget->speed) {
+		case USB_SPEED_SUPER:
+		case USB_SPEED_SUPER_PLUS:
+			desc_idx = 2;
+			break;
+		case USB_SPEED_HIGH:
+			desc_idx = 1;
+			break;
+		default:
+			desc_idx = 0;
+		}
+
+		desc = epfile->ep->descs[desc_idx];
+		memcpy(&desc1, desc, desc->bLength);
+
+		spin_unlock_irq(&epfile->ffs->eps_lock);
+		ret = copy_to_user((void __user *)value, &desc1, desc1.bLength);
+		if (ret)
+			ret = -EFAULT;
+		return ret;
+	}
+	default:
+		ret = -ENOTTY;
+	}
+	spin_unlock_irq(&epfile->ffs->eps_lock);
+
+	return ret;
+}
+
+static const struct file_operations ffs_epfile_operations = {
+	.llseek =	no_llseek,
+
+	.open =		ffs_epfile_open,
+	.write_iter =	ffs_epfile_write_iter,
+	.read_iter =	ffs_epfile_read_iter,
+	.release =	ffs_epfile_release,
+	.unlocked_ioctl =	ffs_epfile_ioctl,
+	.compat_ioctl = compat_ptr_ioctl,
+};
+
+
+/* File system and super block operations ***********************************/
+
+/*
+ * Mounting the file system 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 (inode) {
+		struct timespec64 ts = current_time(inode);
+
+		inode->i_ino	 = get_next_ino();
+		inode->i_mode    = perms->mode;
+		inode->i_uid     = perms->uid;
+		inode->i_gid     = perms->gid;
+		inode->i_atime   = ts;
+		inode->i_mtime   = ts;
+		inode->i_ctime   = ts;
+		inode->i_private = data;
+		if (fops)
+			inode->i_fop = fops;
+		if (iops)
+			inode->i_op  = iops;
+	}
+
+	return inode;
+}
+
+/* Create "regular" file */
+static struct dentry *ffs_sb_create_file(struct super_block *sb,
+					const char *name, void *data,
+					const struct file_operations *fops)
+{
+	struct ffs_data	*ffs = sb->s_fs_info;
+	struct dentry	*dentry;
+	struct inode	*inode;
+
+	ENTER();
+
+	dentry = d_alloc_name(sb->s_root, name);
+	if (!dentry)
+		return NULL;
+
+	inode = ffs_sb_make_inode(sb, data, fops, NULL, &ffs->file_perms);
+	if (!inode) {
+		dput(dentry);
+		return NULL;
+	}
+
+	d_add(dentry, inode);
+	return dentry;
+}
+
+/* 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;
+	bool no_disconnect;
+	struct ffs_data *ffs_data;
+};
+
+static int ffs_sb_fill(struct super_block *sb, struct fs_context *fc)
+{
+	struct ffs_sb_fill_data *data = fc->fs_private;
+	struct inode	*inode;
+	struct ffs_data	*ffs = data->ffs_data;
+
+	ENTER();
+
+	ffs->sb              = sb;
+	data->ffs_data       = NULL;
+	sb->s_fs_info        = ffs;
+	sb->s_blocksize      = PAGE_SIZE;
+	sb->s_blocksize_bits = PAGE_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);
+	sb->s_root = d_make_root(inode);
+	if (!sb->s_root)
+		return -ENOMEM;
+
+	/* EP0 file */
+	if (!ffs_sb_create_file(sb, "ep0", ffs, &ffs_ep0_operations))
+		return -ENOMEM;
+
+	return 0;
+}
+
+enum {
+	Opt_no_disconnect,
+	Opt_rmode,
+	Opt_fmode,
+	Opt_mode,
+	Opt_uid,
+	Opt_gid,
+};
+
+static const struct fs_parameter_spec ffs_fs_fs_parameters[] = {
+	fsparam_bool	("no_disconnect",	Opt_no_disconnect),
+	fsparam_u32	("rmode",		Opt_rmode),
+	fsparam_u32	("fmode",		Opt_fmode),
+	fsparam_u32	("mode",		Opt_mode),
+	fsparam_u32	("uid",			Opt_uid),
+	fsparam_u32	("gid",			Opt_gid),
+	{}
+};
+
+static int ffs_fs_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+	struct ffs_sb_fill_data *data = fc->fs_private;
+	struct fs_parse_result result;
+	int opt;
+
+	ENTER();
+
+	opt = fs_parse(fc, ffs_fs_fs_parameters, param, &result);
+	if (opt < 0)
+		return opt;
+
+	switch (opt) {
+	case Opt_no_disconnect:
+		data->no_disconnect = result.boolean;
+		break;
+	case Opt_rmode:
+		data->root_mode  = (result.uint_32 & 0555) | S_IFDIR;
+		break;
+	case Opt_fmode:
+		data->perms.mode = (result.uint_32 & 0666) | S_IFREG;
+		break;
+	case Opt_mode:
+		data->root_mode  = (result.uint_32 & 0555) | S_IFDIR;
+		data->perms.mode = (result.uint_32 & 0666) | S_IFREG;
+		break;
+
+	case Opt_uid:
+		data->perms.uid = make_kuid(current_user_ns(), result.uint_32);
+		if (!uid_valid(data->perms.uid))
+			goto unmapped_value;
+		break;
+	case Opt_gid:
+		data->perms.gid = make_kgid(current_user_ns(), result.uint_32);
+		if (!gid_valid(data->perms.gid))
+			goto unmapped_value;
+		break;
+
+	default:
+		return -ENOPARAM;
+	}
+
+	return 0;
+
+unmapped_value:
+	return invalf(fc, "%s: unmapped value: %u", param->key, result.uint_32);
+}
+
+/*
+ * Set up the superblock for a mount.
+ */
+static int ffs_fs_get_tree(struct fs_context *fc)
+{
+	struct ffs_sb_fill_data *ctx = fc->fs_private;
+	struct ffs_data	*ffs;
+	int ret;
+
+	ENTER();
+
+	if (!fc->source)
+		return invalf(fc, "No source specified");
+
+	ffs = ffs_data_new(fc->source);
+	if (!ffs)
+		return -ENOMEM;
+	ffs->file_perms = ctx->perms;
+	ffs->no_disconnect = ctx->no_disconnect;
+
+	ffs->dev_name = kstrdup(fc->source, GFP_KERNEL);
+	if (!ffs->dev_name) {
+		ffs_data_put(ffs);
+		return -ENOMEM;
+	}
+
+	ret = ffs_acquire_dev(ffs->dev_name, ffs);
+	if (ret) {
+		ffs_data_put(ffs);
+		return ret;
+	}
+
+	ctx->ffs_data = ffs;
+	return get_tree_nodev(fc, ffs_sb_fill);
+}
+
+static void ffs_fs_free_fc(struct fs_context *fc)
+{
+	struct ffs_sb_fill_data *ctx = fc->fs_private;
+
+	if (ctx) {
+		if (ctx->ffs_data) {
+			ffs_data_put(ctx->ffs_data);
+		}
+
+		kfree(ctx);
+	}
+}
+
+static const struct fs_context_operations ffs_fs_context_ops = {
+	.free		= ffs_fs_free_fc,
+	.parse_param	= ffs_fs_parse_param,
+	.get_tree	= ffs_fs_get_tree,
+};
+
+static int ffs_fs_init_fs_context(struct fs_context *fc)
+{
+	struct ffs_sb_fill_data *ctx;
+
+	ctx = kzalloc(sizeof(struct ffs_sb_fill_data), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	ctx->perms.mode = S_IFREG | 0600;
+	ctx->perms.uid = GLOBAL_ROOT_UID;
+	ctx->perms.gid = GLOBAL_ROOT_GID;
+	ctx->root_mode = S_IFDIR | 0500;
+	ctx->no_disconnect = false;
+
+	fc->fs_private = ctx;
+	fc->ops = &ffs_fs_context_ops;
+	return 0;
+}
+
+static void
+ffs_fs_kill_sb(struct super_block *sb)
+{
+	ENTER();
+
+	kill_litter_super(sb);
+	if (sb->s_fs_info)
+		ffs_data_closed(sb->s_fs_info);
+}
+
+static struct file_system_type ffs_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "functionfs",
+	.init_fs_context = ffs_fs_init_fs_context,
+	.parameters	= ffs_fs_fs_parameters,
+	.kill_sb	= ffs_fs_kill_sb,
+};
+MODULE_ALIAS_FS("functionfs");
+
+
+/* Driver's main init/cleanup functions *************************************/
+
+static int functionfs_init(void)
+{
+	int ret;
+
+	ENTER();
+
+	ret = register_filesystem(&ffs_fs_type);
+	if (!ret)
+		pr_info("file system registered\n");
+	else
+		pr_err("failed registering file system (%d)\n", ret);
+
+	return ret;
+}
+
+static void functionfs_cleanup(void)
+{
+	ENTER();
+
+	pr_info("unloading\n");
+	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();
+
+	refcount_inc(&ffs->ref);
+}
+
+static void ffs_data_opened(struct ffs_data *ffs)
+{
+	ENTER();
+
+	refcount_inc(&ffs->ref);
+	if (atomic_add_return(1, &ffs->opened) == 1 &&
+			ffs->state == FFS_DEACTIVATED) {
+		ffs->state = FFS_CLOSING;
+		ffs_data_reset(ffs);
+	}
+}
+
+static void ffs_data_put(struct ffs_data *ffs)
+{
+	ENTER();
+
+	if (refcount_dec_and_test(&ffs->ref)) {
+		pr_info("%s(): freeing\n", __func__);
+		ffs_data_clear(ffs);
+		ffs_release_dev(ffs->private_data);
+		BUG_ON(waitqueue_active(&ffs->ev.waitq) ||
+		       swait_active(&ffs->ep0req_completion.wait) ||
+		       waitqueue_active(&ffs->wait));
+		destroy_workqueue(ffs->io_completion_wq);
+		kfree(ffs->dev_name);
+		kfree(ffs);
+	}
+}
+
+static void ffs_data_closed(struct ffs_data *ffs)
+{
+	struct ffs_epfile *epfiles;
+	unsigned long flags;
+
+	ENTER();
+
+	if (atomic_dec_and_test(&ffs->opened)) {
+		if (ffs->no_disconnect) {
+			ffs->state = FFS_DEACTIVATED;
+			spin_lock_irqsave(&ffs->eps_lock, flags);
+			epfiles = ffs->epfiles;
+			ffs->epfiles = NULL;
+			spin_unlock_irqrestore(&ffs->eps_lock,
+							flags);
+
+			if (epfiles)
+				ffs_epfiles_destroy(epfiles,
+						 ffs->eps_count);
+
+			if (ffs->setup_state == FFS_SETUP_PENDING)
+				__ffs_ep0_stall(ffs);
+		} else {
+			ffs->state = FFS_CLOSING;
+			ffs_data_reset(ffs);
+		}
+	}
+	if (atomic_read(&ffs->opened) < 0) {
+		ffs->state = FFS_CLOSING;
+		ffs_data_reset(ffs);
+	}
+
+	ffs_data_put(ffs);
+}
+
+static struct ffs_data *ffs_data_new(const char *dev_name)
+{
+	struct ffs_data *ffs = kzalloc(sizeof *ffs, GFP_KERNEL);
+	if (!ffs)
+		return NULL;
+
+	ENTER();
+
+	ffs->io_completion_wq = alloc_ordered_workqueue("%s", 0, dev_name);
+	if (!ffs->io_completion_wq) {
+		kfree(ffs);
+		return NULL;
+	}
+
+	refcount_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_waitqueue_head(&ffs->wait);
+	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)
+{
+	struct ffs_epfile *epfiles;
+	unsigned long flags;
+
+	ENTER();
+
+	ffs_closed(ffs);
+
+	BUG_ON(ffs->gadget);
+
+	spin_lock_irqsave(&ffs->eps_lock, flags);
+	epfiles = ffs->epfiles;
+	ffs->epfiles = NULL;
+	spin_unlock_irqrestore(&ffs->eps_lock, flags);
+
+	/*
+	 * potential race possible between ffs_func_eps_disable
+	 * & ffs_epfile_release therefore maintaining a local
+	 * copy of epfile will save us from use-after-free.
+	 */
+	if (epfiles) {
+		ffs_epfiles_destroy(epfiles, ffs->eps_count);
+		ffs->epfiles = NULL;
+	}
+
+	if (ffs->ffs_eventfd) {
+		eventfd_ctx_put(ffs->ffs_eventfd);
+		ffs->ffs_eventfd = NULL;
+	}
+
+	kfree(ffs->raw_descs_data);
+	kfree(ffs->raw_strings);
+	kfree(ffs->stringtabs);
+}
+
+static void ffs_data_reset(struct ffs_data *ffs)
+{
+	ENTER();
+
+	ffs_data_clear(ffs);
+
+	ffs->raw_descs_data = NULL;
+	ffs->raw_descs = NULL;
+	ffs->raw_strings = NULL;
+	ffs->stringtabs = NULL;
+
+	ffs->raw_descs_length = 0;
+	ffs->fs_descs_count = 0;
+	ffs->hs_descs_count = 0;
+	ffs->ss_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;
+
+	ffs->ms_os_descs_ext_prop_count = 0;
+	ffs->ms_os_descs_ext_prop_name_len = 0;
+	ffs->ms_os_descs_ext_prop_data_len = 0;
+}
+
+
+static int functionfs_bind(struct ffs_data *ffs, struct usb_composite_dev *cdev)
+{
+	struct usb_gadget_strings **lang;
+	int first_id;
+
+	ENTER();
+
+	if (WARN_ON(ffs->state != FFS_ACTIVE
+		 || test_and_set_bit(FFS_FL_BOUND, &ffs->flags)))
+		return -EBADFD;
+
+	first_id = usb_string_ids_n(cdev, ffs->strings_count);
+	if (first_id < 0)
+		return first_id;
+
+	ffs->ep0req = usb_ep_alloc_request(cdev->gadget->ep0, GFP_KERNEL);
+	if (!ffs->ep0req)
+		return -ENOMEM;
+	ffs->ep0req->complete = ffs_ep0_complete;
+	ffs->ep0req->context = ffs;
+
+	lang = ffs->stringtabs;
+	if (lang) {
+		for (; *lang; ++lang) {
+			struct usb_string *str = (*lang)->strings;
+			int id = first_id;
+			for (; str->s; ++id, ++str)
+				str->id = id;
+		}
+	}
+
+	ffs->gadget = cdev->gadget;
+	ffs_data_get(ffs);
+	return 0;
+}
+
+static void functionfs_unbind(struct ffs_data *ffs)
+{
+	ENTER();
+
+	if (!WARN_ON(!ffs->gadget)) {
+		/* dequeue before freeing ep0req */
+		usb_ep_dequeue(ffs->gadget->ep0, ffs->ep0req);
+		mutex_lock(&ffs->mutex);
+		usb_ep_free_request(ffs->gadget->ep0, ffs->ep0req);
+		ffs->ep0req = NULL;
+		ffs->gadget = NULL;
+		clear_bit(FFS_FL_BOUND, &ffs->flags);
+		mutex_unlock(&ffs->mutex);
+		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 = kcalloc(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);
+		if (ffs->user_flags & FUNCTIONFS_VIRTUAL_ADDR)
+			sprintf(epfile->name, "ep%02x", ffs->eps_addrmap[i]);
+		else
+			sprintf(epfile->name, "ep%u", i);
+		epfile->dentry = ffs_sb_create_file(ffs->sb, epfile->name,
+						 epfile,
+						 &ffs_epfile_operations);
+		if (!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));
+		if (epfile->dentry) {
+			d_delete(epfile->dentry);
+			dput(epfile->dentry);
+			epfile->dentry = NULL;
+		}
+	}
+
+	kfree(epfiles);
+}
+
+static void ffs_func_eps_disable(struct ffs_function *func)
+{
+	struct ffs_ep *ep;
+	struct ffs_epfile *epfile;
+	unsigned short count;
+	unsigned long flags;
+
+	spin_lock_irqsave(&func->ffs->eps_lock, flags);
+	count = func->ffs->eps_count;
+	epfile = func->ffs->epfiles;
+	ep = func->eps;
+	while (count--) {
+		/* pending requests get nuked */
+		if (ep->ep)
+			usb_ep_disable(ep->ep);
+		++ep;
+
+		if (epfile) {
+			epfile->ep = NULL;
+			__ffs_epfile_read_buffer_free(epfile);
+			++epfile;
+		}
+	}
+	spin_unlock_irqrestore(&func->ffs->eps_lock, flags);
+}
+
+static int ffs_func_eps_enable(struct ffs_function *func)
+{
+	struct ffs_data *ffs;
+	struct ffs_ep *ep;
+	struct ffs_epfile *epfile;
+	unsigned short count;
+	unsigned long flags;
+	int ret = 0;
+
+	spin_lock_irqsave(&func->ffs->eps_lock, flags);
+	ffs = func->ffs;
+	ep = func->eps;
+	epfile = ffs->epfiles;
+	count = ffs->eps_count;
+	while(count--) {
+		ep->ep->driver_data = ep;
+
+		ret = config_ep_by_speed(func->gadget, &func->function, ep->ep);
+		if (ret) {
+			pr_err("%s: config_ep_by_speed(%s) returned %d\n",
+					__func__, ep->ep->name, ret);
+			break;
+		}
+
+		ret = usb_ep_enable(ep->ep);
+		if (!ret) {
+			epfile->ep = ep;
+			epfile->in = usb_endpoint_dir_in(ep->ep->desc);
+			epfile->isoc = usb_endpoint_xfer_isoc(ep->ep->desc);
+		} else {
+			break;
+		}
+
+		++ep;
+		++epfile;
+	}
+
+	wake_up_interruptible(&ffs->wait);
+	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 after the
+ * descriptor or NULL if data is invalid.
+ */
+
+enum ffs_entity_type {
+	FFS_DESCRIPTOR, FFS_INTERFACE, FFS_STRING, FFS_ENDPOINT
+};
+
+enum ffs_os_desc_type {
+	FFS_OS_DESC, FFS_OS_DESC_EXT_COMPAT, FFS_OS_DESC_EXT_PROP
+};
+
+typedef int (*ffs_entity_callback)(enum ffs_entity_type entity,
+				   u8 *valuep,
+				   struct usb_descriptor_header *desc,
+				   void *priv);
+
+typedef int (*ffs_os_desc_callback)(enum ffs_os_desc_type entity,
+				    struct usb_os_desc_header *h, void *data,
+				    unsigned len, void *priv);
+
+static int __must_check ffs_do_single_desc(char *data, unsigned len,
+					   ffs_entity_callback entity,
+					   void *priv, int *current_class)
+{
+	struct usb_descriptor_header *_ds = (void *)data;
+	u8 length;
+	int ret;
+
+	ENTER();
+
+	/* At least two bytes are required: length and type */
+	if (len < 2) {
+		pr_vdebug("descriptor too short\n");
+		return -EINVAL;
+	}
+
+	/* If we have at least as many bytes as the descriptor takes? */
+	length = _ds->bLength;
+	if (len < length) {
+		pr_vdebug("descriptor longer then available data\n");
+		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 {					\
+		pr_vdebug("entity " #type "(%02x)\n", (val));		\
+		if (!__entity_check_ ##type(val)) {			\
+			pr_vdebug("invalid entity's value\n");		\
+			return -EINVAL;					\
+		}							\
+		ret = entity(FFS_ ##type, &val, _ds, priv);		\
+		if (ret < 0) {						\
+			pr_debug("entity " #type "(%02x); ret = %d\n",	\
+				 (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 */
+		pr_vdebug("descriptor reserved for gadget: %d\n",
+		      _ds->bDescriptorType);
+		return -EINVAL;
+
+	case USB_DT_INTERFACE: {
+		struct usb_interface_descriptor *ds = (void *)_ds;
+		pr_vdebug("interface descriptor\n");
+		if (length != sizeof *ds)
+			goto inv_length;
+
+		__entity(INTERFACE, ds->bInterfaceNumber);
+		if (ds->iInterface)
+			__entity(STRING, ds->iInterface);
+		*current_class = ds->bInterfaceClass;
+	}
+		break;
+
+	case USB_DT_ENDPOINT: {
+		struct usb_endpoint_descriptor *ds = (void *)_ds;
+		pr_vdebug("endpoint descriptor\n");
+		if (length != USB_DT_ENDPOINT_SIZE &&
+		    length != USB_DT_ENDPOINT_AUDIO_SIZE)
+			goto inv_length;
+		__entity(ENDPOINT, ds->bEndpointAddress);
+	}
+		break;
+
+	case USB_TYPE_CLASS | 0x01:
+		if (*current_class == USB_INTERFACE_CLASS_HID) {
+			pr_vdebug("hid descriptor\n");
+			if (length != sizeof(struct hid_descriptor))
+				goto inv_length;
+			break;
+		} else if (*current_class == USB_INTERFACE_CLASS_CCID) {
+			pr_vdebug("ccid descriptor\n");
+			if (length != sizeof(struct ccid_descriptor))
+				goto inv_length;
+			break;
+		} else {
+			pr_vdebug("unknown descriptor: %d for class %d\n",
+			      _ds->bDescriptorType, *current_class);
+			return -EINVAL;
+		}
+
+	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;
+		pr_vdebug("interface association descriptor\n");
+		if (length != sizeof *ds)
+			goto inv_length;
+		if (ds->iFunction)
+			__entity(STRING, ds->iFunction);
+	}
+		break;
+
+	case USB_DT_SS_ENDPOINT_COMP:
+		pr_vdebug("EP SS companion descriptor\n");
+		if (length != sizeof(struct usb_ss_ep_comp_descriptor))
+			goto inv_length;
+		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 */
+		pr_vdebug("unimplemented descriptor: %d\n", _ds->bDescriptorType);
+		return -EINVAL;
+
+	default:
+		/* We should never be here */
+		pr_vdebug("unknown descriptor: %d\n", _ds->bDescriptorType);
+		return -EINVAL;
+
+inv_length:
+		pr_vdebug("invalid length: %d (descriptor %d)\n",
+			  _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;
+	int current_class = -1;
+
+	ENTER();
+
+	for (;;) {
+		int ret;
+
+		if (num == count)
+			data = NULL;
+
+		/* Record "descriptor" entity */
+		ret = entity(FFS_DESCRIPTOR, (u8 *)num, (void *)data, priv);
+		if (ret < 0) {
+			pr_debug("entity DESCRIPTOR(%02lx); ret = %d\n",
+				 num, ret);
+			return ret;
+		}
+
+		if (!data)
+			return _len - len;
+
+		ret = ffs_do_single_desc(data, len, entity, priv,
+			&current_class);
+		if (ret < 0) {
+			pr_debug("%s returns %d\n", __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_desc_helper *helper = priv;
+	struct usb_endpoint_descriptor *d;
+
+	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 >= helper->interfaces_count)
+			helper->interfaces_count = *valuep + 1;
+		break;
+
+	case FFS_STRING:
+		/*
+		 * Strings are indexed from 1 (0 is reserved
+		 * for languages list)
+		 */
+		if (*valuep > helper->ffs->strings_count)
+			helper->ffs->strings_count = *valuep;
+		break;
+
+	case FFS_ENDPOINT:
+		d = (void *)desc;
+		helper->eps_count++;
+		if (helper->eps_count >= FFS_MAX_EPS_COUNT)
+			return -EINVAL;
+		/* Check if descriptors for any speed were already parsed */
+		if (!helper->ffs->eps_count && !helper->ffs->interfaces_count)
+			helper->ffs->eps_addrmap[helper->eps_count] =
+				d->bEndpointAddress;
+		else if (helper->ffs->eps_addrmap[helper->eps_count] !=
+				d->bEndpointAddress)
+			return -EINVAL;
+		break;
+	}
+
+	return 0;
+}
+
+static int __ffs_do_os_desc_header(enum ffs_os_desc_type *next_type,
+				   struct usb_os_desc_header *desc)
+{
+	u16 bcd_version = le16_to_cpu(desc->bcdVersion);
+	u16 w_index = le16_to_cpu(desc->wIndex);
+
+	if (bcd_version != 1) {
+		pr_vdebug("unsupported os descriptors version: %d",
+			  bcd_version);
+		return -EINVAL;
+	}
+	switch (w_index) {
+	case 0x4:
+		*next_type = FFS_OS_DESC_EXT_COMPAT;
+		break;
+	case 0x5:
+		*next_type = FFS_OS_DESC_EXT_PROP;
+		break;
+	default:
+		pr_vdebug("unsupported os descriptor type: %d", w_index);
+		return -EINVAL;
+	}
+
+	return sizeof(*desc);
+}
+
+/*
+ * Process all extended compatibility/extended property descriptors
+ * of a feature descriptor
+ */
+static int __must_check ffs_do_single_os_desc(char *data, unsigned len,
+					      enum ffs_os_desc_type type,
+					      u16 feature_count,
+					      ffs_os_desc_callback entity,
+					      void *priv,
+					      struct usb_os_desc_header *h)
+{
+	int ret;
+	const unsigned _len = len;
+
+	ENTER();
+
+	/* loop over all ext compat/ext prop descriptors */
+	while (feature_count--) {
+		ret = entity(type, h, data, len, priv);
+		if (ret < 0) {
+			pr_debug("bad OS descriptor, type: %d\n", type);
+			return ret;
+		}
+		data += ret;
+		len -= ret;
+	}
+	return _len - len;
+}
+
+/* Process a number of complete Feature Descriptors (Ext Compat or Ext Prop) */
+static int __must_check ffs_do_os_descs(unsigned count,
+					char *data, unsigned len,
+					ffs_os_desc_callback entity, void *priv)
+{
+	const unsigned _len = len;
+	unsigned long num = 0;
+
+	ENTER();
+
+	for (num = 0; num < count; ++num) {
+		int ret;
+		enum ffs_os_desc_type type;
+		u16 feature_count;
+		struct usb_os_desc_header *desc = (void *)data;
+
+		if (len < sizeof(*desc))
+			return -EINVAL;
+
+		/*
+		 * Record "descriptor" entity.
+		 * Process dwLength, bcdVersion, wIndex, get b/wCount.
+		 * Move the data pointer to the beginning of extended
+		 * compatibilities proper or extended properties proper
+		 * portions of the data
+		 */
+		if (le32_to_cpu(desc->dwLength) > len)
+			return -EINVAL;
+
+		ret = __ffs_do_os_desc_header(&type, desc);
+		if (ret < 0) {
+			pr_debug("entity OS_DESCRIPTOR(%02lx); ret = %d\n",
+				 num, ret);
+			return ret;
+		}
+		/*
+		 * 16-bit hex "?? 00" Little Endian looks like 8-bit hex "??"
+		 */
+		feature_count = le16_to_cpu(desc->wCount);
+		if (type == FFS_OS_DESC_EXT_COMPAT &&
+		    (feature_count > 255 || desc->Reserved))
+				return -EINVAL;
+		len -= ret;
+		data += ret;
+
+		/*
+		 * Process all function/property descriptors
+		 * of this Feature Descriptor
+		 */
+		ret = ffs_do_single_os_desc(data, len, type,
+					    feature_count, entity, priv, desc);
+		if (ret < 0) {
+			pr_debug("%s returns %d\n", __func__, ret);
+			return ret;
+		}
+
+		len -= ret;
+		data += ret;
+	}
+	return _len - len;
+}
+
+/*
+ * Validate contents of the buffer from userspace related to OS descriptors.
+ */
+static int __ffs_data_do_os_desc(enum ffs_os_desc_type type,
+				 struct usb_os_desc_header *h, void *data,
+				 unsigned len, void *priv)
+{
+	struct ffs_data *ffs = priv;
+	u8 length;
+
+	ENTER();
+
+	switch (type) {
+	case FFS_OS_DESC_EXT_COMPAT: {
+		struct usb_ext_compat_desc *d = data;
+		int i;
+
+		if (len < sizeof(*d) ||
+		    d->bFirstInterfaceNumber >= ffs->interfaces_count)
+			return -EINVAL;
+		if (d->Reserved1 != 1) {
+			/*
+			 * According to the spec, Reserved1 must be set to 1
+			 * but older kernels incorrectly rejected non-zero
+			 * values.  We fix it here to avoid returning EINVAL
+			 * in response to values we used to accept.
+			 */
+			pr_debug("usb_ext_compat_desc::Reserved1 forced to 1\n");
+			d->Reserved1 = 1;
+		}
+		for (i = 0; i < ARRAY_SIZE(d->Reserved2); ++i)
+			if (d->Reserved2[i])
+				return -EINVAL;
+
+		length = sizeof(struct usb_ext_compat_desc);
+	}
+		break;
+	case FFS_OS_DESC_EXT_PROP: {
+		struct usb_ext_prop_desc *d = data;
+		u32 type, pdl;
+		u16 pnl;
+
+		if (len < sizeof(*d) || h->interface >= ffs->interfaces_count)
+			return -EINVAL;
+		length = le32_to_cpu(d->dwSize);
+		if (len < length)
+			return -EINVAL;
+		type = le32_to_cpu(d->dwPropertyDataType);
+		if (type < USB_EXT_PROP_UNICODE ||
+		    type > USB_EXT_PROP_UNICODE_MULTI) {
+			pr_vdebug("unsupported os descriptor property type: %d",
+				  type);
+			return -EINVAL;
+		}
+		pnl = le16_to_cpu(d->wPropertyNameLength);
+		if (length < 14 + pnl) {
+			pr_vdebug("invalid os descriptor length: %d pnl:%d (descriptor %d)\n",
+				  length, pnl, type);
+			return -EINVAL;
+		}
+		pdl = le32_to_cpu(*(__le32 *)((u8 *)data + 10 + pnl));
+		if (length != 14 + pnl + pdl) {
+			pr_vdebug("invalid os descriptor length: %d pnl:%d pdl:%d (descriptor %d)\n",
+				  length, pnl, pdl, type);
+			return -EINVAL;
+		}
+		++ffs->ms_os_descs_ext_prop_count;
+		/* property name reported to the host as "WCHAR"s */
+		ffs->ms_os_descs_ext_prop_name_len += pnl * 2;
+		ffs->ms_os_descs_ext_prop_data_len += pdl;
+	}
+		break;
+	default:
+		pr_vdebug("unknown descriptor: %d\n", type);
+		return -EINVAL;
+	}
+	return length;
+}
+
+static int __ffs_data_got_descs(struct ffs_data *ffs,
+				char *const _data, size_t len)
+{
+	char *data = _data, *raw_descs;
+	unsigned os_descs_count = 0, counts[3], flags;
+	int ret = -EINVAL, i;
+	struct ffs_desc_helper helper;
+
+	ENTER();
+
+	if (get_unaligned_le32(data + 4) != len)
+		goto error;
+
+	switch (get_unaligned_le32(data)) {
+	case FUNCTIONFS_DESCRIPTORS_MAGIC:
+		flags = FUNCTIONFS_HAS_FS_DESC | FUNCTIONFS_HAS_HS_DESC;
+		data += 8;
+		len  -= 8;
+		break;
+	case FUNCTIONFS_DESCRIPTORS_MAGIC_V2:
+		flags = get_unaligned_le32(data + 8);
+		ffs->user_flags = flags;
+		if (flags & ~(FUNCTIONFS_HAS_FS_DESC |
+			      FUNCTIONFS_HAS_HS_DESC |
+			      FUNCTIONFS_HAS_SS_DESC |
+			      FUNCTIONFS_HAS_MS_OS_DESC |
+			      FUNCTIONFS_VIRTUAL_ADDR |
+			      FUNCTIONFS_EVENTFD |
+			      FUNCTIONFS_ALL_CTRL_RECIP |
+			      FUNCTIONFS_CONFIG0_SETUP)) {
+			ret = -ENOSYS;
+			goto error;
+		}
+		data += 12;
+		len  -= 12;
+		break;
+	default:
+		goto error;
+	}
+
+	if (flags & FUNCTIONFS_EVENTFD) {
+		if (len < 4)
+			goto error;
+		ffs->ffs_eventfd =
+			eventfd_ctx_fdget((int)get_unaligned_le32(data));
+		if (IS_ERR(ffs->ffs_eventfd)) {
+			ret = PTR_ERR(ffs->ffs_eventfd);
+			ffs->ffs_eventfd = NULL;
+			goto error;
+		}
+		data += 4;
+		len  -= 4;
+	}
+
+	/* Read fs_count, hs_count and ss_count (if present) */
+	for (i = 0; i < 3; ++i) {
+		if (!(flags & (1 << i))) {
+			counts[i] = 0;
+		} else if (len < 4) {
+			goto error;
+		} else {
+			counts[i] = get_unaligned_le32(data);
+			data += 4;
+			len  -= 4;
+		}
+	}
+	if (flags & (1 << i)) {
+		if (len < 4) {
+			goto error;
+		}
+		os_descs_count = get_unaligned_le32(data);
+		data += 4;
+		len -= 4;
+	}
+
+	/* Read descriptors */
+	raw_descs = data;
+	helper.ffs = ffs;
+	for (i = 0; i < 3; ++i) {
+		if (!counts[i])
+			continue;
+		helper.interfaces_count = 0;
+		helper.eps_count = 0;
+		ret = ffs_do_descs(counts[i], data, len,
+				   __ffs_data_do_entity, &helper);
+		if (ret < 0)
+			goto error;
+		if (!ffs->eps_count && !ffs->interfaces_count) {
+			ffs->eps_count = helper.eps_count;
+			ffs->interfaces_count = helper.interfaces_count;
+		} else {
+			if (ffs->eps_count != helper.eps_count) {
+				ret = -EINVAL;
+				goto error;
+			}
+			if (ffs->interfaces_count != helper.interfaces_count) {
+				ret = -EINVAL;
+				goto error;
+			}
+		}
+		data += ret;
+		len  -= ret;
+	}
+	if (os_descs_count) {
+		ret = ffs_do_os_descs(os_descs_count, data, len,
+				      __ffs_data_do_os_desc, ffs);
+		if (ret < 0)
+			goto error;
+		data += ret;
+		len -= ret;
+	}
+
+	if (raw_descs == data || len) {
+		ret = -EINVAL;
+		goto error;
+	}
+
+	ffs->raw_descs_data	= _data;
+	ffs->raw_descs		= raw_descs;
+	ffs->raw_descs_length	= data - raw_descs;
+	ffs->fs_descs_count	= counts[0];
+	ffs->hs_descs_count	= counts[1];
+	ffs->ss_descs_count	= counts[2];
+	ffs->ms_os_descs_count	= os_descs_count;
+
+	return 0;
+
+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;
+	const char *data = _data;
+	struct usb_string *s;
+
+	ENTER();
+
+	if (len < 16 ||
+	    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 (!str_count != !lang_count)
+		goto error;
+
+	/* Do we have at least as many strings as descriptors need? */
+	needed_count = ffs->strings_count;
+	if (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 everything in one chunk so there's less maintenance. */
+	{
+		unsigned i = 0;
+		vla_group(d);
+		vla_item(d, struct usb_gadget_strings *, stringtabs,
+			size_add(lang_count, 1));
+		vla_item(d, struct usb_gadget_strings, stringtab, lang_count);
+		vla_item(d, struct usb_string, strings,
+			size_mul(lang_count, (needed_count + 1)));
+
+		char *vlabuf = kmalloc(vla_group_size(d), GFP_KERNEL);
+
+		if (!vlabuf) {
+			kfree(_data);
+			return -ENOMEM;
+		}
+
+		/* Initialize the VLA pointers */
+		stringtabs = vla_ptr(vlabuf, d, stringtabs);
+		t = vla_ptr(vlabuf, d, stringtab);
+		i = lang_count;
+		do {
+			*stringtabs++ = t++;
+		} while (--i);
+		*stringtabs = NULL;
+
+		/* stringtabs = vlabuf = d_stringtabs for later kfree */
+		stringtabs = vla_ptr(vlabuf, d, stringtabs);
+		t = vla_ptr(vlabuf, d, stringtab);
+		s = vla_ptr(vlabuf, d, strings);
+	}
+
+	/* For each language */
+	data += 16;
+	len -= 16;
+
+	do { /* lang_count > 0 so we can use do-while */
+		unsigned needed = needed_count;
+		u32 str_per_lang = str_count;
+
+		if (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 (length == len)
+				goto error_free;
+
+			/*
+			 * User may provide more strings then we need,
+			 * if that's the case we simply ignore the
+			 * rest
+			 */
+			if (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_per_lang);
+
+		s->id = 0;   /* terminator */
+		s->s = NULL;
+		++s;
+
+	} while (--lang_count);
+
+	/* Some garbage left? */
+	if (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_CANCELLED;
+
+	/*
+	 * Logic of this function guarantees that there are at most four pending
+	 * evens on ffs->ev.types queue.  This is important because the queue
+	 * has space for four elements only and __ffs_ep0_read_events function
+	 * depends on that limit as well.  If more event types are added, those
+	 * limits have to be revisited or guaranteed to still hold.
+	 */
+	switch (type) {
+	case FUNCTIONFS_RESUME:
+		rem_type2 = FUNCTIONFS_SUSPEND;
+		fallthrough;
+	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:
+		WARN(1, "%d: unknown event, this should not happen\n", type);
+		return;
+	}
+
+	{
+		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
+				pr_vdebug("purging event %d\n", *ev);
+		ffs->ev.count = out - ffs->ev.types;
+	}
+
+	pr_vdebug("adding event %d\n", type);
+	ffs->ev.types[ffs->ev.count++] = type;
+	wake_up_locked(&ffs->ev.waitq);
+	if (ffs->ffs_eventfd)
+		eventfd_signal(ffs->ffs_eventfd, 1);
+}
+
+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_ep_addr2idx(struct ffs_data *ffs, u8 endpoint_address)
+{
+	int i;
+
+	for (i = 1; i < ARRAY_SIZE(ffs->eps_addrmap); ++i)
+		if (ffs->eps_addrmap[i] == endpoint_address)
+			return i;
+	return -ENOENT;
+}
+
+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;
+	unsigned ep_desc_id;
+	int idx;
+	static const char *speed_names[] = { "full", "high", "super" };
+
+	if (type != FFS_DESCRIPTOR)
+		return 0;
+
+	/*
+	 * If ss_descriptors is not NULL, we are reading super speed
+	 * descriptors; if hs_descriptors is not NULL, we are reading high
+	 * speed descriptors; otherwise, we are reading full speed
+	 * descriptors.
+	 */
+	if (func->function.ss_descriptors) {
+		ep_desc_id = 2;
+		func->function.ss_descriptors[(long)valuep] = desc;
+	} else if (func->function.hs_descriptors) {
+		ep_desc_id = 1;
+		func->function.hs_descriptors[(long)valuep] = desc;
+	} else {
+		ep_desc_id = 0;
+		func->function.fs_descriptors[(long)valuep]    = desc;
+	}
+
+	if (!desc || desc->bDescriptorType != USB_DT_ENDPOINT)
+		return 0;
+
+	idx = ffs_ep_addr2idx(func->ffs, ds->bEndpointAddress) - 1;
+	if (idx < 0)
+		return idx;
+
+	ffs_ep = func->eps + idx;
+
+	if (ffs_ep->descs[ep_desc_id]) {
+		pr_err("two %sspeed descriptors for EP %d\n",
+			  speed_names[ep_desc_id],
+			  ds->bEndpointAddress & USB_ENDPOINT_NUMBER_MASK);
+		return -EINVAL;
+	}
+	ffs_ep->descs[ep_desc_id] = 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;
+		u8 bEndpointAddress;
+		u16 wMaxPacketSize;
+
+		/*
+		 * We back up bEndpointAddress because autoconfig overwrites
+		 * it with physical endpoint address.
+		 */
+		bEndpointAddress = ds->bEndpointAddress;
+		/*
+		 * We back up wMaxPacketSize because autoconfig treats
+		 * endpoint descriptors as if they were full speed.
+		 */
+		wMaxPacketSize = ds->wMaxPacketSize;
+		pr_vdebug("autoconfig\n");
+		ep = usb_ep_autoconfig(func->gadget, ds);
+		if (!ep)
+			return -ENOTSUPP;
+		ep->driver_data = func->eps + idx;
+
+		req = usb_ep_alloc_request(ep, GFP_KERNEL);
+		if (!req)
+			return -ENOMEM;
+
+		ffs_ep->ep  = ep;
+		ffs_ep->req = req;
+		func->eps_revmap[ds->bEndpointAddress &
+				 USB_ENDPOINT_NUMBER_MASK] = idx + 1;
+		/*
+		 * If we use virtual address mapping, we restore
+		 * original bEndpointAddress value.
+		 */
+		if (func->ffs->user_flags & FUNCTIONFS_VIRTUAL_ADDR)
+			ds->bEndpointAddress = bEndpointAddress;
+		/*
+		 * Restore wMaxPacketSize which was potentially
+		 * overwritten by autoconfig.
+		 */
+		ds->wMaxPacketSize = wMaxPacketSize;
+	}
+	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 (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 (!func->eps[idx].ep)
+			return -EINVAL;
+
+		{
+			struct usb_endpoint_descriptor **descs;
+			descs = func->eps[idx].descs;
+			newValue = descs[descs[0] ? 0 : 1]->bEndpointAddress;
+		}
+		break;
+	}
+
+	pr_vdebug("%02x -> %02x\n", *valuep, newValue);
+	*valuep = newValue;
+	return 0;
+}
+
+static int __ffs_func_bind_do_os_desc(enum ffs_os_desc_type type,
+				      struct usb_os_desc_header *h, void *data,
+				      unsigned len, void *priv)
+{
+	struct ffs_function *func = priv;
+	u8 length = 0;
+
+	switch (type) {
+	case FFS_OS_DESC_EXT_COMPAT: {
+		struct usb_ext_compat_desc *desc = data;
+		struct usb_os_desc_table *t;
+
+		t = &func->function.os_desc_table[desc->bFirstInterfaceNumber];
+		t->if_id = func->interfaces_nums[desc->bFirstInterfaceNumber];
+		memcpy(t->os_desc->ext_compat_id, &desc->CompatibleID,
+		       ARRAY_SIZE(desc->CompatibleID) +
+		       ARRAY_SIZE(desc->SubCompatibleID));
+		length = sizeof(*desc);
+	}
+		break;
+	case FFS_OS_DESC_EXT_PROP: {
+		struct usb_ext_prop_desc *desc = data;
+		struct usb_os_desc_table *t;
+		struct usb_os_desc_ext_prop *ext_prop;
+		char *ext_prop_name;
+		char *ext_prop_data;
+
+		t = &func->function.os_desc_table[h->interface];
+		t->if_id = func->interfaces_nums[h->interface];
+
+		ext_prop = func->ffs->ms_os_descs_ext_prop_avail;
+		func->ffs->ms_os_descs_ext_prop_avail += sizeof(*ext_prop);
+
+		ext_prop->type = le32_to_cpu(desc->dwPropertyDataType);
+		ext_prop->name_len = le16_to_cpu(desc->wPropertyNameLength);
+		ext_prop->data_len = le32_to_cpu(*(__le32 *)
+			usb_ext_prop_data_len_ptr(data, ext_prop->name_len));
+		length = ext_prop->name_len + ext_prop->data_len + 14;
+
+		ext_prop_name = func->ffs->ms_os_descs_ext_prop_name_avail;
+		func->ffs->ms_os_descs_ext_prop_name_avail +=
+			ext_prop->name_len;
+
+		ext_prop_data = func->ffs->ms_os_descs_ext_prop_data_avail;
+		func->ffs->ms_os_descs_ext_prop_data_avail +=
+			ext_prop->data_len;
+		memcpy(ext_prop_data,
+		       usb_ext_prop_data_ptr(data, ext_prop->name_len),
+		       ext_prop->data_len);
+		/* unicode data reported to the host as "WCHAR"s */
+		switch (ext_prop->type) {
+		case USB_EXT_PROP_UNICODE:
+		case USB_EXT_PROP_UNICODE_ENV:
+		case USB_EXT_PROP_UNICODE_LINK:
+		case USB_EXT_PROP_UNICODE_MULTI:
+			ext_prop->data_len *= 2;
+			break;
+		}
+		ext_prop->data = ext_prop_data;
+
+		memcpy(ext_prop_name, usb_ext_prop_name_ptr(data),
+		       ext_prop->name_len);
+		/* property name reported to the host as "WCHAR"s */
+		ext_prop->name_len *= 2;
+		ext_prop->name = ext_prop_name;
+
+		t->os_desc->ext_prop_len +=
+			ext_prop->name_len + ext_prop->data_len + 14;
+		++t->os_desc->ext_prop_count;
+		list_add_tail(&ext_prop->entry, &t->os_desc->ext_prop);
+	}
+		break;
+	default:
+		pr_vdebug("unknown descriptor: %d\n", type);
+	}
+
+	return length;
+}
+
+static inline struct f_fs_opts *ffs_do_functionfs_bind(struct usb_function *f,
+						struct usb_configuration *c)
+{
+	struct ffs_function *func = ffs_func_from_usb(f);
+	struct f_fs_opts *ffs_opts =
+		container_of(f->fi, struct f_fs_opts, func_inst);
+	struct ffs_data *ffs_data;
+	int ret;
+
+	ENTER();
+
+	/*
+	 * Legacy gadget triggers binding in functionfs_ready_callback,
+	 * which already uses locking; taking the same lock here would
+	 * cause a deadlock.
+	 *
+	 * Configfs-enabled gadgets however do need ffs_dev_lock.
+	 */
+	if (!ffs_opts->no_configfs)
+		ffs_dev_lock();
+	ret = ffs_opts->dev->desc_ready ? 0 : -ENODEV;
+	ffs_data = ffs_opts->dev->ffs_data;
+	if (!ffs_opts->no_configfs)
+		ffs_dev_unlock();
+	if (ret)
+		return ERR_PTR(ret);
+
+	func->ffs = ffs_data;
+	func->conf = c;
+	func->gadget = c->cdev->gadget;
+
+	/*
+	 * in drivers/usb/gadget/configfs.c:configfs_composite_bind()
+	 * configurations are bound in sequence with list_for_each_entry,
+	 * in each configuration its functions are bound in sequence
+	 * with list_for_each_entry, so we assume no race condition
+	 * with regard to ffs_opts->bound access
+	 */
+	if (!ffs_opts->refcnt) {
+		ret = functionfs_bind(func->ffs, c->cdev);
+		if (ret)
+			return ERR_PTR(ret);
+	}
+	ffs_opts->refcnt++;
+	func->function.strings = func->ffs->stringtabs;
+
+	return ffs_opts;
+}
+
+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 = !!func->ffs->hs_descs_count;
+	const int super = !!func->ffs->ss_descs_count;
+
+	int fs_len, hs_len, ss_len, ret, i;
+	struct ffs_ep *eps_ptr;
+
+	/* Make it a single chunk, less management later on */
+	vla_group(d);
+	vla_item_with_sz(d, struct ffs_ep, eps, ffs->eps_count);
+	vla_item_with_sz(d, struct usb_descriptor_header *, fs_descs,
+		full ? ffs->fs_descs_count + 1 : 0);
+	vla_item_with_sz(d, struct usb_descriptor_header *, hs_descs,
+		high ? ffs->hs_descs_count + 1 : 0);
+	vla_item_with_sz(d, struct usb_descriptor_header *, ss_descs,
+		super ? ffs->ss_descs_count + 1 : 0);
+	vla_item_with_sz(d, short, inums, ffs->interfaces_count);
+	vla_item_with_sz(d, struct usb_os_desc_table, os_desc_table,
+			 c->cdev->use_os_string ? ffs->interfaces_count : 0);
+	vla_item_with_sz(d, char[16], ext_compat,
+			 c->cdev->use_os_string ? ffs->interfaces_count : 0);
+	vla_item_with_sz(d, struct usb_os_desc, os_desc,
+			 c->cdev->use_os_string ? ffs->interfaces_count : 0);
+	vla_item_with_sz(d, struct usb_os_desc_ext_prop, ext_prop,
+			 ffs->ms_os_descs_ext_prop_count);
+	vla_item_with_sz(d, char, ext_prop_name,
+			 ffs->ms_os_descs_ext_prop_name_len);
+	vla_item_with_sz(d, char, ext_prop_data,
+			 ffs->ms_os_descs_ext_prop_data_len);
+	vla_item_with_sz(d, char, raw_descs, ffs->raw_descs_length);
+	char *vlabuf;
+
+	ENTER();
+
+	/* Has descriptors only for speeds gadget does not support */
+	if (!(full | high | super))
+		return -ENOTSUPP;
+
+	/* Allocate a single chunk, less management later on */
+	vlabuf = kzalloc(vla_group_size(d), GFP_KERNEL);
+	if (!vlabuf)
+		return -ENOMEM;
+
+	ffs->ms_os_descs_ext_prop_avail = vla_ptr(vlabuf, d, ext_prop);
+	ffs->ms_os_descs_ext_prop_name_avail =
+		vla_ptr(vlabuf, d, ext_prop_name);
+	ffs->ms_os_descs_ext_prop_data_avail =
+		vla_ptr(vlabuf, d, ext_prop_data);
+
+	/* Copy descriptors  */
+	memcpy(vla_ptr(vlabuf, d, raw_descs), ffs->raw_descs,
+	       ffs->raw_descs_length);
+
+	memset(vla_ptr(vlabuf, d, inums), 0xff, d_inums__sz);
+	eps_ptr = vla_ptr(vlabuf, d, eps);
+	for (i = 0; i < ffs->eps_count; i++)
+		eps_ptr[i].num = -1;
+
+	/* Save pointers
+	 * d_eps == vlabuf, func->eps used to kfree vlabuf later
+	*/
+	func->eps             = vla_ptr(vlabuf, d, eps);
+	func->interfaces_nums = vla_ptr(vlabuf, d, inums);
+
+	/*
+	 * Go through all the endpoint descriptors and allocate
+	 * endpoints first, so that later we can rewrite the endpoint
+	 * numbers without worrying that it may be described later on.
+	 */
+	if (full) {
+		func->function.fs_descriptors = vla_ptr(vlabuf, d, fs_descs);
+		fs_len = ffs_do_descs(ffs->fs_descs_count,
+				      vla_ptr(vlabuf, d, raw_descs),
+				      d_raw_descs__sz,
+				      __ffs_func_bind_do_descs, func);
+		if (fs_len < 0) {
+			ret = fs_len;
+			goto error;
+		}
+	} else {
+		fs_len = 0;
+	}
+
+	if (high) {
+		func->function.hs_descriptors = vla_ptr(vlabuf, d, hs_descs);
+		hs_len = ffs_do_descs(ffs->hs_descs_count,
+				      vla_ptr(vlabuf, d, raw_descs) + fs_len,
+				      d_raw_descs__sz - fs_len,
+				      __ffs_func_bind_do_descs, func);
+		if (hs_len < 0) {
+			ret = hs_len;
+			goto error;
+		}
+	} else {
+		hs_len = 0;
+	}
+
+	if (super) {
+		func->function.ss_descriptors = func->function.ssp_descriptors =
+			vla_ptr(vlabuf, d, ss_descs);
+		ss_len = ffs_do_descs(ffs->ss_descs_count,
+				vla_ptr(vlabuf, d, raw_descs) + fs_len + hs_len,
+				d_raw_descs__sz - fs_len - hs_len,
+				__ffs_func_bind_do_descs, func);
+		if (ss_len < 0) {
+			ret = ss_len;
+			goto error;
+		}
+	} else {
+		ss_len = 0;
+	}
+
+	/*
+	 * Now handle interface numbers allocation and interface and
+	 * endpoint numbers rewriting.  We can do that in one go
+	 * now.
+	 */
+	ret = ffs_do_descs(ffs->fs_descs_count +
+			   (high ? ffs->hs_descs_count : 0) +
+			   (super ? ffs->ss_descs_count : 0),
+			   vla_ptr(vlabuf, d, raw_descs), d_raw_descs__sz,
+			   __ffs_func_bind_do_nums, func);
+	if (ret < 0)
+		goto error;
+
+	func->function.os_desc_table = vla_ptr(vlabuf, d, os_desc_table);
+	if (c->cdev->use_os_string) {
+		for (i = 0; i < ffs->interfaces_count; ++i) {
+			struct usb_os_desc *desc;
+
+			desc = func->function.os_desc_table[i].os_desc =
+				vla_ptr(vlabuf, d, os_desc) +
+				i * sizeof(struct usb_os_desc);
+			desc->ext_compat_id =
+				vla_ptr(vlabuf, d, ext_compat) + i * 16;
+			INIT_LIST_HEAD(&desc->ext_prop);
+		}
+		ret = ffs_do_os_descs(ffs->ms_os_descs_count,
+				      vla_ptr(vlabuf, d, raw_descs) +
+				      fs_len + hs_len + ss_len,
+				      d_raw_descs__sz - fs_len - hs_len -
+				      ss_len,
+				      __ffs_func_bind_do_os_desc, func);
+		if (ret < 0)
+			goto error;
+	}
+	func->function.os_desc_n =
+		c->cdev->use_os_string ? ffs->interfaces_count : 0;
+
+	/* 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;
+}
+
+static int ffs_func_bind(struct usb_configuration *c,
+			 struct usb_function *f)
+{
+	struct f_fs_opts *ffs_opts = ffs_do_functionfs_bind(f, c);
+	struct ffs_function *func = ffs_func_from_usb(f);
+	int ret;
+
+	if (IS_ERR(ffs_opts))
+		return PTR_ERR(ffs_opts);
+
+	ret = _ffs_func_bind(c, f);
+	if (ret && !--ffs_opts->refcnt)
+		functionfs_unbind(func->ffs);
+
+	return ret;
+}
+
+
+/* Other USB function hooks *************************************************/
+
+static void ffs_reset_work(struct work_struct *work)
+{
+	struct ffs_data *ffs = container_of(work,
+		struct ffs_data, reset_work);
+	ffs_data_reset(ffs);
+}
+
+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 (intf < 0)
+			return intf;
+	}
+
+	if (ffs->func)
+		ffs_func_eps_disable(ffs->func);
+
+	if (ffs->state == FFS_DEACTIVATED) {
+		ffs->state = FFS_CLOSING;
+		INIT_WORK(&ffs->reset_work, ffs_reset_work);
+		schedule_work(&ffs->reset_work);
+		return -ENODEV;
+	}
+
+	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 (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();
+
+	pr_vdebug("creq->bRequestType = %02x\n", creq->bRequestType);
+	pr_vdebug("creq->bRequest     = %02x\n", creq->bRequest);
+	pr_vdebug("creq->wValue       = %04x\n", le16_to_cpu(creq->wValue));
+	pr_vdebug("creq->wIndex       = %04x\n", le16_to_cpu(creq->wIndex));
+	pr_vdebug("creq->wLength      = %04x\n", le16_to_cpu(creq->wLength));
+
+	/*
+	 * Most requests directed to interface go through 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).  Other request recipient
+	 * types are only handled when the user flag FUNCTIONFS_ALL_CTRL_RECIP
+	 * is being used.
+	 */
+	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 (ret < 0)
+			return ret;
+		break;
+
+	case USB_RECIP_ENDPOINT:
+		ret = ffs_func_revmap_ep(func, le16_to_cpu(creq->wIndex));
+		if (ret < 0)
+			return ret;
+		if (func->ffs->user_flags & FUNCTIONFS_VIRTUAL_ADDR)
+			ret = func->ffs->eps_addrmap[ret];
+		break;
+
+	default:
+		if (func->ffs->user_flags & FUNCTIONFS_ALL_CTRL_RECIP)
+			ret = le16_to_cpu(creq->wIndex);
+		else
+			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 creq->wLength == 0 ? USB_GADGET_DELAYED_STATUS : 0;
+}
+
+static bool ffs_func_req_match(struct usb_function *f,
+			       const struct usb_ctrlrequest *creq,
+			       bool config0)
+{
+	struct ffs_function *func = ffs_func_from_usb(f);
+
+	if (config0 && !(func->ffs->user_flags & FUNCTIONFS_CONFIG0_SETUP))
+		return false;
+
+	switch (creq->bRequestType & USB_RECIP_MASK) {
+	case USB_RECIP_INTERFACE:
+		return (ffs_func_revmap_intf(func,
+					     le16_to_cpu(creq->wIndex)) >= 0);
+	case USB_RECIP_ENDPOINT:
+		return (ffs_func_revmap_ep(func,
+					   le16_to_cpu(creq->wIndex)) >= 0);
+	default:
+		return (bool) (func->ffs->user_flags &
+			       FUNCTIONFS_ALL_CTRL_RECIP);
+	}
+}
+
+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);
+}
+
+
+/* Endpoint 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;
+}
+
+
+/* Devices management *******************************************************/
+
+static LIST_HEAD(ffs_devices);
+
+static struct ffs_dev *_ffs_do_find_dev(const char *name)
+{
+	struct ffs_dev *dev;
+
+	if (!name)
+		return NULL;
+
+	list_for_each_entry(dev, &ffs_devices, entry) {
+		if (strcmp(dev->name, name) == 0)
+			return dev;
+	}
+
+	return NULL;
+}
+
+/*
+ * ffs_lock must be taken by the caller of this function
+ */
+static struct ffs_dev *_ffs_get_single_dev(void)
+{
+	struct ffs_dev *dev;
+
+	if (list_is_singular(&ffs_devices)) {
+		dev = list_first_entry(&ffs_devices, struct ffs_dev, entry);
+		if (dev->single)
+			return dev;
+	}
+
+	return NULL;
+}
+
+/*
+ * ffs_lock must be taken by the caller of this function
+ */
+static struct ffs_dev *_ffs_find_dev(const char *name)
+{
+	struct ffs_dev *dev;
+
+	dev = _ffs_get_single_dev();
+	if (dev)
+		return dev;
+
+	return _ffs_do_find_dev(name);
+}
+
+/* Configfs support *********************************************************/
+
+static inline struct f_fs_opts *to_ffs_opts(struct config_item *item)
+{
+	return container_of(to_config_group(item), struct f_fs_opts,
+			    func_inst.group);
+}
+
+static void ffs_attr_release(struct config_item *item)
+{
+	struct f_fs_opts *opts = to_ffs_opts(item);
+
+	usb_put_function_instance(&opts->func_inst);
+}
+
+static struct configfs_item_operations ffs_item_ops = {
+	.release	= ffs_attr_release,
+};
+
+static const struct config_item_type ffs_func_type = {
+	.ct_item_ops	= &ffs_item_ops,
+	.ct_owner	= THIS_MODULE,
+};
+
+
+/* Function registration interface ******************************************/
+
+static void ffs_free_inst(struct usb_function_instance *f)
+{
+	struct f_fs_opts *opts;
+
+	opts = to_f_fs_opts(f);
+	ffs_release_dev(opts->dev);
+	ffs_dev_lock();
+	_ffs_free_dev(opts->dev);
+	ffs_dev_unlock();
+	kfree(opts);
+}
+
+static int ffs_set_inst_name(struct usb_function_instance *fi, const char *name)
+{
+	if (strlen(name) >= sizeof_field(struct ffs_dev, name))
+		return -ENAMETOOLONG;
+	return ffs_name_dev(to_f_fs_opts(fi)->dev, name);
+}
+
+static struct usb_function_instance *ffs_alloc_inst(void)
+{
+	struct f_fs_opts *opts;
+	struct ffs_dev *dev;
+
+	opts = kzalloc(sizeof(*opts), GFP_KERNEL);
+	if (!opts)
+		return ERR_PTR(-ENOMEM);
+
+	opts->func_inst.set_inst_name = ffs_set_inst_name;
+	opts->func_inst.free_func_inst = ffs_free_inst;
+	ffs_dev_lock();
+	dev = _ffs_alloc_dev();
+	ffs_dev_unlock();
+	if (IS_ERR(dev)) {
+		kfree(opts);
+		return ERR_CAST(dev);
+	}
+	opts->dev = dev;
+	dev->opts = opts;
+
+	config_group_init_type_name(&opts->func_inst.group, "",
+				    &ffs_func_type);
+	return &opts->func_inst;
+}
+
+static void ffs_free(struct usb_function *f)
+{
+	kfree(ffs_func_from_usb(f));
+}
+
+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;
+	struct f_fs_opts *opts =
+		container_of(f->fi, struct f_fs_opts, func_inst);
+	struct ffs_ep *ep = func->eps;
+	unsigned count = ffs->eps_count;
+	unsigned long flags;
+
+	ENTER();
+	if (ffs->func == func) {
+		ffs_func_eps_disable(func);
+		ffs->func = NULL;
+	}
+
+	/* Drain any pending AIO completions */
+	drain_workqueue(ffs->io_completion_wq);
+
+	ffs_event_add(ffs, FUNCTIONFS_UNBIND);
+	if (!--opts->refcnt)
+		functionfs_unbind(ffs);
+
+	/* cleanup after autoconfig */
+	spin_lock_irqsave(&func->ffs->eps_lock, flags);
+	while (count--) {
+		if (ep->ep && ep->req)
+			usb_ep_free_request(ep->ep, ep->req);
+		ep->req = NULL;
+		++ep;
+	}
+	spin_unlock_irqrestore(&func->ffs->eps_lock, flags);
+	kfree(func->eps);
+	func->eps = NULL;
+	/*
+	 * eps, descriptors and interfaces_nums are allocated in the
+	 * same chunk so only one free is required.
+	 */
+	func->function.fs_descriptors = NULL;
+	func->function.hs_descriptors = NULL;
+	func->function.ss_descriptors = NULL;
+	func->function.ssp_descriptors = NULL;
+	func->interfaces_nums = NULL;
+
+}
+
+static struct usb_function *ffs_alloc(struct usb_function_instance *fi)
+{
+	struct ffs_function *func;
+
+	ENTER();
+
+	func = kzalloc(sizeof(*func), GFP_KERNEL);
+	if (!func)
+		return ERR_PTR(-ENOMEM);
+
+	func->function.name    = "Function FS Gadget";
+
+	func->function.bind    = ffs_func_bind;
+	func->function.unbind  = ffs_func_unbind;
+	func->function.set_alt = ffs_func_set_alt;
+	func->function.disable = ffs_func_disable;
+	func->function.setup   = ffs_func_setup;
+	func->function.req_match = ffs_func_req_match;
+	func->function.suspend = ffs_func_suspend;
+	func->function.resume  = ffs_func_resume;
+	func->function.free_func = ffs_free;
+
+	return &func->function;
+}
+
+/*
+ * ffs_lock must be taken by the caller of this function
+ */
+static struct ffs_dev *_ffs_alloc_dev(void)
+{
+	struct ffs_dev *dev;
+	int ret;
+
+	if (_ffs_get_single_dev())
+			return ERR_PTR(-EBUSY);
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return ERR_PTR(-ENOMEM);
+
+	if (list_empty(&ffs_devices)) {
+		ret = functionfs_init();
+		if (ret) {
+			kfree(dev);
+			return ERR_PTR(ret);
+		}
+	}
+
+	list_add(&dev->entry, &ffs_devices);
+
+	return dev;
+}
+
+int ffs_name_dev(struct ffs_dev *dev, const char *name)
+{
+	struct ffs_dev *existing;
+	int ret = 0;
+
+	ffs_dev_lock();
+
+	existing = _ffs_do_find_dev(name);
+	if (!existing)
+		strscpy(dev->name, name, ARRAY_SIZE(dev->name));
+	else if (existing != dev)
+		ret = -EBUSY;
+
+	ffs_dev_unlock();
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(ffs_name_dev);
+
+int ffs_single_dev(struct ffs_dev *dev)
+{
+	int ret;
+
+	ret = 0;
+	ffs_dev_lock();
+
+	if (!list_is_singular(&ffs_devices))
+		ret = -EBUSY;
+	else
+		dev->single = true;
+
+	ffs_dev_unlock();
+	return ret;
+}
+EXPORT_SYMBOL_GPL(ffs_single_dev);
+
+/*
+ * ffs_lock must be taken by the caller of this function
+ */
+static void _ffs_free_dev(struct ffs_dev *dev)
+{
+	list_del(&dev->entry);
+
+	kfree(dev);
+	if (list_empty(&ffs_devices))
+		functionfs_cleanup();
+}
+
+static int ffs_acquire_dev(const char *dev_name, struct ffs_data *ffs_data)
+{
+	int ret = 0;
+	struct ffs_dev *ffs_dev;
+
+	ENTER();
+	ffs_dev_lock();
+
+	ffs_dev = _ffs_find_dev(dev_name);
+	if (!ffs_dev) {
+		ret = -ENOENT;
+	} else if (ffs_dev->mounted) {
+		ret = -EBUSY;
+	} else if (ffs_dev->ffs_acquire_dev_callback &&
+		   ffs_dev->ffs_acquire_dev_callback(ffs_dev)) {
+		ret = -ENOENT;
+	} else {
+		ffs_dev->mounted = true;
+		ffs_dev->ffs_data = ffs_data;
+		ffs_data->private_data = ffs_dev;
+	}
+
+	ffs_dev_unlock();
+	return ret;
+}
+
+static void ffs_release_dev(struct ffs_dev *ffs_dev)
+{
+	ENTER();
+	ffs_dev_lock();
+
+	if (ffs_dev && ffs_dev->mounted) {
+		ffs_dev->mounted = false;
+		if (ffs_dev->ffs_data) {
+			ffs_dev->ffs_data->private_data = NULL;
+			ffs_dev->ffs_data = NULL;
+		}
+
+		if (ffs_dev->ffs_release_dev_callback)
+			ffs_dev->ffs_release_dev_callback(ffs_dev);
+	}
+
+	ffs_dev_unlock();
+}
+
+static int ffs_ready(struct ffs_data *ffs)
+{
+	struct ffs_dev *ffs_obj;
+	int ret = 0;
+
+	ENTER();
+	ffs_dev_lock();
+
+	ffs_obj = ffs->private_data;
+	if (!ffs_obj) {
+		ret = -EINVAL;
+		goto done;
+	}
+	if (WARN_ON(ffs_obj->desc_ready)) {
+		ret = -EBUSY;
+		goto done;
+	}
+
+	ffs_obj->desc_ready = true;
+
+	if (ffs_obj->ffs_ready_callback) {
+		ret = ffs_obj->ffs_ready_callback(ffs);
+		if (ret)
+			goto done;
+	}
+
+	set_bit(FFS_FL_CALL_CLOSED_CALLBACK, &ffs->flags);
+done:
+	ffs_dev_unlock();
+	return ret;
+}
+
+static void ffs_closed(struct ffs_data *ffs)
+{
+	struct ffs_dev *ffs_obj;
+	struct f_fs_opts *opts;
+	struct config_item *ci;
+
+	ENTER();
+	ffs_dev_lock();
+
+	ffs_obj = ffs->private_data;
+	if (!ffs_obj)
+		goto done;
+
+	ffs_obj->desc_ready = false;
+
+	if (test_and_clear_bit(FFS_FL_CALL_CLOSED_CALLBACK, &ffs->flags) &&
+	    ffs_obj->ffs_closed_callback)
+		ffs_obj->ffs_closed_callback(ffs);
+
+	if (ffs_obj->opts)
+		opts = ffs_obj->opts;
+	else
+		goto done;
+
+	if (opts->no_configfs || !opts->func_inst.group.cg_item.ci_parent
+	    || !kref_read(&opts->func_inst.group.cg_item.ci_kref))
+		goto done;
+
+	ci = opts->func_inst.group.cg_item.ci_parent->ci_parent;
+	ffs_dev_unlock();
+
+	if (test_bit(FFS_FL_BOUND, &ffs->flags))
+		unregister_gadget_item(ci);
+	return;
+done:
+	ffs_dev_unlock();
+}
+
+/* Misc helper functions ****************************************************/
+
+static int ffs_mutex_lock(struct mutex *mutex, unsigned nonblock)
+{
+	return nonblock
+		? mutex_trylock(mutex) ? 0 : -EAGAIN
+		: mutex_lock_interruptible(mutex);
+}
+
+static char *ffs_prepare_buffer(const char __user *buf, size_t len)
+{
+	char *data;
+
+	if (!len)
+		return NULL;
+
+	data = memdup_user(buf, len);
+	if (IS_ERR(data))
+		return data;
+
+	pr_vdebug("Buffer from user space:\n");
+	ffs_dump_mem("", data, len);
+
+	return data;
+}
+
+DECLARE_USB_FUNCTION_INIT(ffs, ffs_alloc_inst, ffs_alloc);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Michal Nazarewicz");