usb: gadget: Gadget directory cleanup - group legacy gadgets

The drivers/usb/gadget directory contains many files.
Files which are related can be distributed into separate directories.
This patch moves the legacy gadgets (i.e. those not using configfs)
into a separate directory.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

1 files changed, 2142 insertions, 0 deletions

diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c
new file mode 100644
index 000000000000..ee6c16416c30
--- /dev/null
+++ b/drivers/usb/gadget/legacy/inode.c
@@ -0,0 +1,2142 @@
+/*
+ * inode.c -- user mode filesystem api for usb gadget controllers
+ *
+ * Copyright (C) 2003-2004 David Brownell
+ * Copyright (C) 2003 Agilent Technologies
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+
+/* #define VERBOSE_DEBUG */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/pagemap.h>
+#include <linux/uts.h>
+#include <linux/wait.h>
+#include <linux/compiler.h>
+#include <asm/uaccess.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/poll.h>
+#include <linux/mmu_context.h>
+#include <linux/aio.h>
+
+#include <linux/device.h>
+#include <linux/moduleparam.h>
+
+#include <linux/usb/gadgetfs.h>
+#include <linux/usb/gadget.h>
+
+
+/*
+ * The gadgetfs API maps each endpoint to a file descriptor so that you
+ * can use standard synchronous read/write calls for I/O.  There's some
+ * O_NONBLOCK and O_ASYNC/FASYNC style i/o support.  Example usermode
+ * drivers show how this works in practice.  You can also use AIO to
+ * eliminate I/O gaps between requests, to help when streaming data.
+ *
+ * Key parts that must be USB-specific are protocols defining how the
+ * read/write operations relate to the hardware state machines.  There
+ * are two types of files.  One type is for the device, implementing ep0.
+ * The other type is for each IN or OUT endpoint.  In both cases, the
+ * user mode driver must configure the hardware before using it.
+ *
+ * - First, dev_config() is called when /dev/gadget/$CHIP is configured
+ *   (by writing configuration and device descriptors).  Afterwards it
+ *   may serve as a source of device events, used to handle all control
+ *   requests other than basic enumeration.
+ *
+ * - Then, after a SET_CONFIGURATION control request, ep_config() is
+ *   called when each /dev/gadget/ep* file is configured (by writing
+ *   endpoint descriptors).  Afterwards these files are used to write()
+ *   IN data or to read() OUT data.  To halt the endpoint, a "wrong
+ *   direction" request is issued (like reading an IN endpoint).
+ *
+ * Unlike "usbfs" the only ioctl()s are for things that are rare, and maybe
+ * not possible on all hardware.  For example, precise fault handling with
+ * respect to data left in endpoint fifos after aborted operations; or
+ * selective clearing of endpoint halts, to implement SET_INTERFACE.
+ */
+
+#define	DRIVER_DESC	"USB Gadget filesystem"
+#define	DRIVER_VERSION	"24 Aug 2004"
+
+static const char driver_desc [] = DRIVER_DESC;
+static const char shortname [] = "gadgetfs";
+
+MODULE_DESCRIPTION (DRIVER_DESC);
+MODULE_AUTHOR ("David Brownell");
+MODULE_LICENSE ("GPL");
+
+
+/*----------------------------------------------------------------------*/
+
+#define GADGETFS_MAGIC		0xaee71ee7
+
+/* /dev/gadget/$CHIP represents ep0 and the whole device */
+enum ep0_state {
+	/* DISBLED is the initial state.
+	 */
+	STATE_DEV_DISABLED = 0,
+
+	/* Only one open() of /dev/gadget/$CHIP; only one file tracks
+	 * ep0/device i/o modes and binding to the controller.  Driver
+	 * must always write descriptors to initialize the device, then
+	 * the device becomes UNCONNECTED until enumeration.
+	 */
+	STATE_DEV_OPENED,
+
+	/* From then on, ep0 fd is in either of two basic modes:
+	 * - (UN)CONNECTED: read usb_gadgetfs_event(s) from it
+	 * - SETUP: read/write will transfer control data and succeed;
+	 *   or if "wrong direction", performs protocol stall
+	 */
+	STATE_DEV_UNCONNECTED,
+	STATE_DEV_CONNECTED,
+	STATE_DEV_SETUP,
+
+	/* UNBOUND means the driver closed ep0, so the device won't be
+	 * accessible again (DEV_DISABLED) until all fds are closed.
+	 */
+	STATE_DEV_UNBOUND,
+};
+
+/* enough for the whole queue: most events invalidate others */
+#define	N_EVENT			5
+
+struct dev_data {
+	spinlock_t			lock;
+	atomic_t			count;
+	enum ep0_state			state;		/* P: lock */
+	struct usb_gadgetfs_event	event [N_EVENT];
+	unsigned			ev_next;
+	struct fasync_struct		*fasync;
+	u8				current_config;
+
+	/* drivers reading ep0 MUST handle control requests (SETUP)
+	 * reported that way; else the host will time out.
+	 */
+	unsigned			usermode_setup : 1,
+					setup_in : 1,
+					setup_can_stall : 1,
+					setup_out_ready : 1,
+					setup_out_error : 1,
+					setup_abort : 1;
+	unsigned			setup_wLength;
+
+	/* the rest is basically write-once */
+	struct usb_config_descriptor	*config, *hs_config;
+	struct usb_device_descriptor	*dev;
+	struct usb_request		*req;
+	struct usb_gadget		*gadget;
+	struct list_head		epfiles;
+	void				*buf;
+	wait_queue_head_t		wait;
+	struct super_block		*sb;
+	struct dentry			*dentry;
+
+	/* except this scratch i/o buffer for ep0 */
+	u8				rbuf [256];
+};
+
+static inline void get_dev (struct dev_data *data)
+{
+	atomic_inc (&data->count);
+}
+
+static void put_dev (struct dev_data *data)
+{
+	if (likely (!atomic_dec_and_test (&data->count)))
+		return;
+	/* needs no more cleanup */
+	BUG_ON (waitqueue_active (&data->wait));
+	kfree (data);
+}
+
+static struct dev_data *dev_new (void)
+{
+	struct dev_data		*dev;
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return NULL;
+	dev->state = STATE_DEV_DISABLED;
+	atomic_set (&dev->count, 1);
+	spin_lock_init (&dev->lock);
+	INIT_LIST_HEAD (&dev->epfiles);
+	init_waitqueue_head (&dev->wait);
+	return dev;
+}
+
+/*----------------------------------------------------------------------*/
+
+/* other /dev/gadget/$ENDPOINT files represent endpoints */
+enum ep_state {
+	STATE_EP_DISABLED = 0,
+	STATE_EP_READY,
+	STATE_EP_ENABLED,
+	STATE_EP_UNBOUND,
+};
+
+struct ep_data {
+	struct mutex			lock;
+	enum ep_state			state;
+	atomic_t			count;
+	struct dev_data			*dev;
+	/* must hold dev->lock before accessing ep or req */
+	struct usb_ep			*ep;
+	struct usb_request		*req;
+	ssize_t				status;
+	char				name [16];
+	struct usb_endpoint_descriptor	desc, hs_desc;
+	struct list_head		epfiles;
+	wait_queue_head_t		wait;
+	struct dentry			*dentry;
+	struct inode			*inode;
+};
+
+static inline void get_ep (struct ep_data *data)
+{
+	atomic_inc (&data->count);
+}
+
+static void put_ep (struct ep_data *data)
+{
+	if (likely (!atomic_dec_and_test (&data->count)))
+		return;
+	put_dev (data->dev);
+	/* needs no more cleanup */
+	BUG_ON (!list_empty (&data->epfiles));
+	BUG_ON (waitqueue_active (&data->wait));
+	kfree (data);
+}
+
+/*----------------------------------------------------------------------*/
+
+/* most "how to use the hardware" policy choices are in userspace:
+ * mapping endpoint roles (which the driver needs) to the capabilities
+ * which the usb controller has.  most of those capabilities are exposed
+ * implicitly, starting with the driver name and then endpoint names.
+ */
+
+static const char *CHIP;
+
+/*----------------------------------------------------------------------*/
+
+/* NOTE:  don't use dev_printk calls before binding to the gadget
+ * at the end of ep0 configuration, or after unbind.
+ */
+
+/* too wordy: dev_printk(level , &(d)->gadget->dev , fmt , ## args) */
+#define xprintk(d,level,fmt,args...) \
+	printk(level "%s: " fmt , shortname , ## args)
+
+#ifdef DEBUG
+#define DBG(dev,fmt,args...) \
+	xprintk(dev , KERN_DEBUG , fmt , ## args)
+#else
+#define DBG(dev,fmt,args...) \
+	do { } while (0)
+#endif /* DEBUG */
+
+#ifdef VERBOSE_DEBUG
+#define VDEBUG	DBG
+#else
+#define VDEBUG(dev,fmt,args...) \
+	do { } while (0)
+#endif /* DEBUG */
+
+#define ERROR(dev,fmt,args...) \
+	xprintk(dev , KERN_ERR , fmt , ## args)
+#define INFO(dev,fmt,args...) \
+	xprintk(dev , KERN_INFO , fmt , ## args)
+
+
+/*----------------------------------------------------------------------*/
+
+/* SYNCHRONOUS ENDPOINT OPERATIONS (bulk/intr/iso)
+ *
+ * After opening, configure non-control endpoints.  Then use normal
+ * stream read() and write() requests; and maybe ioctl() to get more
+ * precise FIFO status when recovering from cancellation.
+ */
+
+static void epio_complete (struct usb_ep *ep, struct usb_request *req)
+{
+	struct ep_data	*epdata = ep->driver_data;
+
+	if (!req->context)
+		return;
+	if (req->status)
+		epdata->status = req->status;
+	else
+		epdata->status = req->actual;
+	complete ((struct completion *)req->context);
+}
+
+/* tasklock endpoint, returning when it's connected.
+ * still need dev->lock to use epdata->ep.
+ */
+static int
+get_ready_ep (unsigned f_flags, struct ep_data *epdata)
+{
+	int	val;
+
+	if (f_flags & O_NONBLOCK) {
+		if (!mutex_trylock(&epdata->lock))
+			goto nonblock;
+		if (epdata->state != STATE_EP_ENABLED) {
+			mutex_unlock(&epdata->lock);
+nonblock:
+			val = -EAGAIN;
+		} else
+			val = 0;
+		return val;
+	}
+
+	val = mutex_lock_interruptible(&epdata->lock);
+	if (val < 0)
+		return val;
+
+	switch (epdata->state) {
+	case STATE_EP_ENABLED:
+		break;
+	// case STATE_EP_DISABLED:		/* "can't happen" */
+	// case STATE_EP_READY:			/* "can't happen" */
+	default:				/* error! */
+		pr_debug ("%s: ep %p not available, state %d\n",
+				shortname, epdata, epdata->state);
+		// FALLTHROUGH
+	case STATE_EP_UNBOUND:			/* clean disconnect */
+		val = -ENODEV;
+		mutex_unlock(&epdata->lock);
+	}
+	return val;
+}
+
+static ssize_t
+ep_io (struct ep_data *epdata, void *buf, unsigned len)
+{
+	DECLARE_COMPLETION_ONSTACK (done);
+	int value;
+
+	spin_lock_irq (&epdata->dev->lock);
+	if (likely (epdata->ep != NULL)) {
+		struct usb_request	*req = epdata->req;
+
+		req->context = &done;
+		req->complete = epio_complete;
+		req->buf = buf;
+		req->length = len;
+		value = usb_ep_queue (epdata->ep, req, GFP_ATOMIC);
+	} else
+		value = -ENODEV;
+	spin_unlock_irq (&epdata->dev->lock);
+
+	if (likely (value == 0)) {
+		value = wait_event_interruptible (done.wait, done.done);
+		if (value != 0) {
+			spin_lock_irq (&epdata->dev->lock);
+			if (likely (epdata->ep != NULL)) {
+				DBG (epdata->dev, "%s i/o interrupted\n",
+						epdata->name);
+				usb_ep_dequeue (epdata->ep, epdata->req);
+				spin_unlock_irq (&epdata->dev->lock);
+
+				wait_event (done.wait, done.done);
+				if (epdata->status == -ECONNRESET)
+					epdata->status = -EINTR;
+			} else {
+				spin_unlock_irq (&epdata->dev->lock);
+
+				DBG (epdata->dev, "endpoint gone\n");
+				epdata->status = -ENODEV;
+			}
+		}
+		return epdata->status;
+	}
+	return value;
+}
+
+
+/* handle a synchronous OUT bulk/intr/iso transfer */
+static ssize_t
+ep_read (struct file *fd, char __user *buf, size_t len, loff_t *ptr)
+{
+	struct ep_data		*data = fd->private_data;
+	void			*kbuf;
+	ssize_t			value;
+
+	if ((value = get_ready_ep (fd->f_flags, data)) < 0)
+		return value;
+
+	/* halt any endpoint by doing a "wrong direction" i/o call */
+	if (usb_endpoint_dir_in(&data->desc)) {
+		if (usb_endpoint_xfer_isoc(&data->desc)) {
+			mutex_unlock(&data->lock);
+			return -EINVAL;
+		}
+		DBG (data->dev, "%s halt\n", data->name);
+		spin_lock_irq (&data->dev->lock);
+		if (likely (data->ep != NULL))
+			usb_ep_set_halt (data->ep);
+		spin_unlock_irq (&data->dev->lock);
+		mutex_unlock(&data->lock);
+		return -EBADMSG;
+	}
+
+	/* FIXME readahead for O_NONBLOCK and poll(); careful with ZLPs */
+
+	value = -ENOMEM;
+	kbuf = kmalloc (len, GFP_KERNEL);
+	if (unlikely (!kbuf))
+		goto free1;
+
+	value = ep_io (data, kbuf, len);
+	VDEBUG (data->dev, "%s read %zu OUT, status %d\n",
+		data->name, len, (int) value);
+	if (value >= 0 && copy_to_user (buf, kbuf, value))
+		value = -EFAULT;
+
+free1:
+	mutex_unlock(&data->lock);
+	kfree (kbuf);
+	return value;
+}
+
+/* handle a synchronous IN bulk/intr/iso transfer */
+static ssize_t
+ep_write (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
+{
+	struct ep_data		*data = fd->private_data;
+	void			*kbuf;
+	ssize_t			value;
+
+	if ((value = get_ready_ep (fd->f_flags, data)) < 0)
+		return value;
+
+	/* halt any endpoint by doing a "wrong direction" i/o call */
+	if (!usb_endpoint_dir_in(&data->desc)) {
+		if (usb_endpoint_xfer_isoc(&data->desc)) {
+			mutex_unlock(&data->lock);
+			return -EINVAL;
+		}
+		DBG (data->dev, "%s halt\n", data->name);
+		spin_lock_irq (&data->dev->lock);
+		if (likely (data->ep != NULL))
+			usb_ep_set_halt (data->ep);
+		spin_unlock_irq (&data->dev->lock);
+		mutex_unlock(&data->lock);
+		return -EBADMSG;
+	}
+
+	/* FIXME writebehind for O_NONBLOCK and poll(), qlen = 1 */
+
+	value = -ENOMEM;
+	kbuf = memdup_user(buf, len);
+	if (!kbuf) {
+		value = PTR_ERR(kbuf);
+		goto free1;
+	}
+
+	value = ep_io (data, kbuf, len);
+	VDEBUG (data->dev, "%s write %zu IN, status %d\n",
+		data->name, len, (int) value);
+free1:
+	mutex_unlock(&data->lock);
+	return value;
+}
+
+static int
+ep_release (struct inode *inode, struct file *fd)
+{
+	struct ep_data		*data = fd->private_data;
+	int value;
+
+	value = mutex_lock_interruptible(&data->lock);
+	if (value < 0)
+		return value;
+
+	/* clean up if this can be reopened */
+	if (data->state != STATE_EP_UNBOUND) {
+		data->state = STATE_EP_DISABLED;
+		data->desc.bDescriptorType = 0;
+		data->hs_desc.bDescriptorType = 0;
+		usb_ep_disable(data->ep);
+	}
+	mutex_unlock(&data->lock);
+	put_ep (data);
+	return 0;
+}
+
+static long ep_ioctl(struct file *fd, unsigned code, unsigned long value)
+{
+	struct ep_data		*data = fd->private_data;
+	int			status;
+
+	if ((status = get_ready_ep (fd->f_flags, data)) < 0)
+		return status;
+
+	spin_lock_irq (&data->dev->lock);
+	if (likely (data->ep != NULL)) {
+		switch (code) {
+		case GADGETFS_FIFO_STATUS:
+			status = usb_ep_fifo_status (data->ep);
+			break;
+		case GADGETFS_FIFO_FLUSH:
+			usb_ep_fifo_flush (data->ep);
+			break;
+		case GADGETFS_CLEAR_HALT:
+			status = usb_ep_clear_halt (data->ep);
+			break;
+		default:
+			status = -ENOTTY;
+		}
+	} else
+		status = -ENODEV;
+	spin_unlock_irq (&data->dev->lock);
+	mutex_unlock(&data->lock);
+	return status;
+}
+
+/*----------------------------------------------------------------------*/
+
+/* ASYNCHRONOUS ENDPOINT I/O OPERATIONS (bulk/intr/iso) */
+
+struct kiocb_priv {
+	struct usb_request	*req;
+	struct ep_data		*epdata;
+	struct kiocb		*iocb;
+	struct mm_struct	*mm;
+	struct work_struct	work;
+	void			*buf;
+	const struct iovec	*iv;
+	unsigned long		nr_segs;
+	unsigned		actual;
+};
+
+static int ep_aio_cancel(struct kiocb *iocb)
+{
+	struct kiocb_priv	*priv = iocb->private;
+	struct ep_data		*epdata;
+	int			value;
+
+	local_irq_disable();
+	epdata = priv->epdata;
+	// spin_lock(&epdata->dev->lock);
+	if (likely(epdata && epdata->ep && priv->req))
+		value = usb_ep_dequeue (epdata->ep, priv->req);
+	else
+		value = -EINVAL;
+	// spin_unlock(&epdata->dev->lock);
+	local_irq_enable();
+
+	return value;
+}
+
+static ssize_t ep_copy_to_user(struct kiocb_priv *priv)
+{
+	ssize_t			len, total;
+	void			*to_copy;
+	int			i;
+
+	/* copy stuff into user buffers */
+	total = priv->actual;
+	len = 0;
+	to_copy = priv->buf;
+	for (i=0; i < priv->nr_segs; i++) {
+		ssize_t this = min((ssize_t)(priv->iv[i].iov_len), total);
+
+		if (copy_to_user(priv->iv[i].iov_base, to_copy, this)) {
+			if (len == 0)
+				len = -EFAULT;
+			break;
+		}
+
+		total -= this;
+		len += this;
+		to_copy += this;
+		if (total == 0)
+			break;
+	}
+
+	return len;
+}
+
+static void ep_user_copy_worker(struct work_struct *work)
+{
+	struct kiocb_priv *priv = container_of(work, struct kiocb_priv, work);
+	struct mm_struct *mm = priv->mm;
+	struct kiocb *iocb = priv->iocb;
+	size_t ret;
+
+	use_mm(mm);
+	ret = ep_copy_to_user(priv);
+	unuse_mm(mm);
+
+	/* completing the iocb can drop the ctx and mm, don't touch mm after */
+	aio_complete(iocb, ret, ret);
+
+	kfree(priv->buf);
+	kfree(priv);
+}
+
+static void ep_aio_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	struct kiocb		*iocb = req->context;
+	struct kiocb_priv	*priv = iocb->private;
+	struct ep_data		*epdata = priv->epdata;
+
+	/* lock against disconnect (and ideally, cancel) */
+	spin_lock(&epdata->dev->lock);
+	priv->req = NULL;
+	priv->epdata = NULL;
+
+	/* if this was a write or a read returning no data then we
+	 * don't need to copy anything to userspace, so we can
+	 * complete the aio request immediately.
+	 */
+	if (priv->iv == NULL || unlikely(req->actual == 0)) {
+		kfree(req->buf);
+		kfree(priv);
+		iocb->private = NULL;
+		/* aio_complete() reports bytes-transferred _and_ faults */
+		aio_complete(iocb, req->actual ? req->actual : req->status,
+				req->status);
+	} else {
+		/* ep_copy_to_user() won't report both; we hide some faults */
+		if (unlikely(0 != req->status))
+			DBG(epdata->dev, "%s fault %d len %d\n",
+				ep->name, req->status, req->actual);
+
+		priv->buf = req->buf;
+		priv->actual = req->actual;
+		schedule_work(&priv->work);
+	}
+	spin_unlock(&epdata->dev->lock);
+
+	usb_ep_free_request(ep, req);
+	put_ep(epdata);
+}
+
+static ssize_t
+ep_aio_rwtail(
+	struct kiocb	*iocb,
+	char		*buf,
+	size_t		len,
+	struct ep_data	*epdata,
+	const struct iovec *iv,
+	unsigned long	nr_segs
+)
+{
+	struct kiocb_priv	*priv;
+	struct usb_request	*req;
+	ssize_t			value;
+
+	priv = kmalloc(sizeof *priv, GFP_KERNEL);
+	if (!priv) {
+		value = -ENOMEM;
+fail:
+		kfree(buf);
+		return value;
+	}
+	iocb->private = priv;
+	priv->iocb = iocb;
+	priv->iv = iv;
+	priv->nr_segs = nr_segs;
+	INIT_WORK(&priv->work, ep_user_copy_worker);
+
+	value = get_ready_ep(iocb->ki_filp->f_flags, epdata);
+	if (unlikely(value < 0)) {
+		kfree(priv);
+		goto fail;
+	}
+
+	kiocb_set_cancel_fn(iocb, ep_aio_cancel);
+	get_ep(epdata);
+	priv->epdata = epdata;
+	priv->actual = 0;
+	priv->mm = current->mm; /* mm teardown waits for iocbs in exit_aio() */
+
+	/* each kiocb is coupled to one usb_request, but we can't
+	 * allocate or submit those if the host disconnected.
+	 */
+	spin_lock_irq(&epdata->dev->lock);
+	if (likely(epdata->ep)) {
+		req = usb_ep_alloc_request(epdata->ep, GFP_ATOMIC);
+		if (likely(req)) {
+			priv->req = req;
+			req->buf = buf;
+			req->length = len;
+			req->complete = ep_aio_complete;
+			req->context = iocb;
+			value = usb_ep_queue(epdata->ep, req, GFP_ATOMIC);
+			if (unlikely(0 != value))
+				usb_ep_free_request(epdata->ep, req);
+		} else
+			value = -EAGAIN;
+	} else
+		value = -ENODEV;
+	spin_unlock_irq(&epdata->dev->lock);
+
+	mutex_unlock(&epdata->lock);
+
+	if (unlikely(value)) {
+		kfree(priv);
+		put_ep(epdata);
+	} else
+		value = -EIOCBQUEUED;
+	return value;
+}
+
+static ssize_t
+ep_aio_read(struct kiocb *iocb, const struct iovec *iov,
+		unsigned long nr_segs, loff_t o)
+{
+	struct ep_data		*epdata = iocb->ki_filp->private_data;
+	char			*buf;
+
+	if (unlikely(usb_endpoint_dir_in(&epdata->desc)))
+		return -EINVAL;
+
+	buf = kmalloc(iocb->ki_nbytes, GFP_KERNEL);
+	if (unlikely(!buf))
+		return -ENOMEM;
+
+	return ep_aio_rwtail(iocb, buf, iocb->ki_nbytes, epdata, iov, nr_segs);
+}
+
+static ssize_t
+ep_aio_write(struct kiocb *iocb, const struct iovec *iov,
+		unsigned long nr_segs, loff_t o)
+{
+	struct ep_data		*epdata = iocb->ki_filp->private_data;
+	char			*buf;
+	size_t			len = 0;
+	int			i = 0;
+
+	if (unlikely(!usb_endpoint_dir_in(&epdata->desc)))
+		return -EINVAL;
+
+	buf = kmalloc(iocb->ki_nbytes, GFP_KERNEL);
+	if (unlikely(!buf))
+		return -ENOMEM;
+
+	for (i=0; i < nr_segs; i++) {
+		if (unlikely(copy_from_user(&buf[len], iov[i].iov_base,
+				iov[i].iov_len) != 0)) {
+			kfree(buf);
+			return -EFAULT;
+		}
+		len += iov[i].iov_len;
+	}
+	return ep_aio_rwtail(iocb, buf, len, epdata, NULL, 0);
+}
+
+/*----------------------------------------------------------------------*/
+
+/* used after endpoint configuration */
+static const struct file_operations ep_io_operations = {
+	.owner =	THIS_MODULE,
+	.llseek =	no_llseek,
+
+	.read =		ep_read,
+	.write =	ep_write,
+	.unlocked_ioctl = ep_ioctl,
+	.release =	ep_release,
+
+	.aio_read =	ep_aio_read,
+	.aio_write =	ep_aio_write,
+};
+
+/* ENDPOINT INITIALIZATION
+ *
+ *     fd = open ("/dev/gadget/$ENDPOINT", O_RDWR)
+ *     status = write (fd, descriptors, sizeof descriptors)
+ *
+ * That write establishes the endpoint configuration, configuring
+ * the controller to process bulk, interrupt, or isochronous transfers
+ * at the right maxpacket size, and so on.
+ *
+ * The descriptors are message type 1, identified by a host order u32
+ * at the beginning of what's written.  Descriptor order is: full/low
+ * speed descriptor, then optional high speed descriptor.
+ */
+static ssize_t
+ep_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
+{
+	struct ep_data		*data = fd->private_data;
+	struct usb_ep		*ep;
+	u32			tag;
+	int			value, length = len;
+
+	value = mutex_lock_interruptible(&data->lock);
+	if (value < 0)
+		return value;
+
+	if (data->state != STATE_EP_READY) {
+		value = -EL2HLT;
+		goto fail;
+	}
+
+	value = len;
+	if (len < USB_DT_ENDPOINT_SIZE + 4)
+		goto fail0;
+
+	/* we might need to change message format someday */
+	if (copy_from_user (&tag, buf, 4)) {
+		goto fail1;
+	}
+	if (tag != 1) {
+		DBG(data->dev, "config %s, bad tag %d\n", data->name, tag);
+		goto fail0;
+	}
+	buf += 4;
+	len -= 4;
+
+	/* NOTE:  audio endpoint extensions not accepted here;
+	 * just don't include the extra bytes.
+	 */
+
+	/* full/low speed descriptor, then high speed */
+	if (copy_from_user (&data->desc, buf, USB_DT_ENDPOINT_SIZE)) {
+		goto fail1;
+	}
+	if (data->desc.bLength != USB_DT_ENDPOINT_SIZE
+			|| data->desc.bDescriptorType != USB_DT_ENDPOINT)
+		goto fail0;
+	if (len != USB_DT_ENDPOINT_SIZE) {
+		if (len != 2 * USB_DT_ENDPOINT_SIZE)
+			goto fail0;
+		if (copy_from_user (&data->hs_desc, buf + USB_DT_ENDPOINT_SIZE,
+					USB_DT_ENDPOINT_SIZE)) {
+			goto fail1;
+		}
+		if (data->hs_desc.bLength != USB_DT_ENDPOINT_SIZE
+				|| data->hs_desc.bDescriptorType
+					!= USB_DT_ENDPOINT) {
+			DBG(data->dev, "config %s, bad hs length or type\n",
+					data->name);
+			goto fail0;
+		}
+	}
+
+	spin_lock_irq (&data->dev->lock);
+	if (data->dev->state == STATE_DEV_UNBOUND) {
+		value = -ENOENT;
+		goto gone;
+	} else if ((ep = data->ep) == NULL) {
+		value = -ENODEV;
+		goto gone;
+	}
+	switch (data->dev->gadget->speed) {
+	case USB_SPEED_LOW:
+	case USB_SPEED_FULL:
+		ep->desc = &data->desc;
+		value = usb_ep_enable(ep);
+		if (value == 0)
+			data->state = STATE_EP_ENABLED;
+		break;
+	case USB_SPEED_HIGH:
+		/* fails if caller didn't provide that descriptor... */
+		ep->desc = &data->hs_desc;
+		value = usb_ep_enable(ep);
+		if (value == 0)
+			data->state = STATE_EP_ENABLED;
+		break;
+	default:
+		DBG(data->dev, "unconnected, %s init abandoned\n",
+				data->name);
+		value = -EINVAL;
+	}
+	if (value == 0) {
+		fd->f_op = &ep_io_operations;
+		value = length;
+	}
+gone:
+	spin_unlock_irq (&data->dev->lock);
+	if (value < 0) {
+fail:
+		data->desc.bDescriptorType = 0;
+		data->hs_desc.bDescriptorType = 0;
+	}
+	mutex_unlock(&data->lock);
+	return value;
+fail0:
+	value = -EINVAL;
+	goto fail;
+fail1:
+	value = -EFAULT;
+	goto fail;
+}
+
+static int
+ep_open (struct inode *inode, struct file *fd)
+{
+	struct ep_data		*data = inode->i_private;
+	int			value = -EBUSY;
+
+	if (mutex_lock_interruptible(&data->lock) != 0)
+		return -EINTR;
+	spin_lock_irq (&data->dev->lock);
+	if (data->dev->state == STATE_DEV_UNBOUND)
+		value = -ENOENT;
+	else if (data->state == STATE_EP_DISABLED) {
+		value = 0;
+		data->state = STATE_EP_READY;
+		get_ep (data);
+		fd->private_data = data;
+		VDEBUG (data->dev, "%s ready\n", data->name);
+	} else
+		DBG (data->dev, "%s state %d\n",
+			data->name, data->state);
+	spin_unlock_irq (&data->dev->lock);
+	mutex_unlock(&data->lock);
+	return value;
+}
+
+/* used before endpoint configuration */
+static const struct file_operations ep_config_operations = {
+	.llseek =	no_llseek,
+
+	.open =		ep_open,
+	.write =	ep_config,
+	.release =	ep_release,
+};
+
+/*----------------------------------------------------------------------*/
+
+/* EP0 IMPLEMENTATION can be partly in userspace.
+ *
+ * Drivers that use this facility receive various events, including
+ * control requests the kernel doesn't handle.  Drivers that don't
+ * use this facility may be too simple-minded for real applications.
+ */
+
+static inline void ep0_readable (struct dev_data *dev)
+{
+	wake_up (&dev->wait);
+	kill_fasync (&dev->fasync, SIGIO, POLL_IN);
+}
+
+static void clean_req (struct usb_ep *ep, struct usb_request *req)
+{
+	struct dev_data		*dev = ep->driver_data;
+
+	if (req->buf != dev->rbuf) {
+		kfree(req->buf);
+		req->buf = dev->rbuf;
+	}
+	req->complete = epio_complete;
+	dev->setup_out_ready = 0;
+}
+
+static void ep0_complete (struct usb_ep *ep, struct usb_request *req)
+{
+	struct dev_data		*dev = ep->driver_data;
+	unsigned long		flags;
+	int			free = 1;
+
+	/* for control OUT, data must still get to userspace */
+	spin_lock_irqsave(&dev->lock, flags);
+	if (!dev->setup_in) {
+		dev->setup_out_error = (req->status != 0);
+		if (!dev->setup_out_error)
+			free = 0;
+		dev->setup_out_ready = 1;
+		ep0_readable (dev);
+	}
+
+	/* clean up as appropriate */
+	if (free && req->buf != &dev->rbuf)
+		clean_req (ep, req);
+	req->complete = epio_complete;
+	spin_unlock_irqrestore(&dev->lock, flags);
+}
+
+static int setup_req (struct usb_ep *ep, struct usb_request *req, u16 len)
+{
+	struct dev_data	*dev = ep->driver_data;
+
+	if (dev->setup_out_ready) {
+		DBG (dev, "ep0 request busy!\n");
+		return -EBUSY;
+	}
+	if (len > sizeof (dev->rbuf))
+		req->buf = kmalloc(len, GFP_ATOMIC);
+	if (req->buf == NULL) {
+		req->buf = dev->rbuf;
+		return -ENOMEM;
+	}
+	req->complete = ep0_complete;
+	req->length = len;
+	req->zero = 0;
+	return 0;
+}
+
+static ssize_t
+ep0_read (struct file *fd, char __user *buf, size_t len, loff_t *ptr)
+{
+	struct dev_data			*dev = fd->private_data;
+	ssize_t				retval;
+	enum ep0_state			state;
+
+	spin_lock_irq (&dev->lock);
+
+	/* report fd mode change before acting on it */
+	if (dev->setup_abort) {
+		dev->setup_abort = 0;
+		retval = -EIDRM;
+		goto done;
+	}
+
+	/* control DATA stage */
+	if ((state = dev->state) == STATE_DEV_SETUP) {
+
+		if (dev->setup_in) {		/* stall IN */
+			VDEBUG(dev, "ep0in stall\n");
+			(void) usb_ep_set_halt (dev->gadget->ep0);
+			retval = -EL2HLT;
+			dev->state = STATE_DEV_CONNECTED;
+
+		} else if (len == 0) {		/* ack SET_CONFIGURATION etc */
+			struct usb_ep		*ep = dev->gadget->ep0;
+			struct usb_request	*req = dev->req;
+
+			if ((retval = setup_req (ep, req, 0)) == 0)
+				retval = usb_ep_queue (ep, req, GFP_ATOMIC);
+			dev->state = STATE_DEV_CONNECTED;
+
+			/* assume that was SET_CONFIGURATION */
+			if (dev->current_config) {
+				unsigned power;
+
+				if (gadget_is_dualspeed(dev->gadget)
+						&& (dev->gadget->speed
+							== USB_SPEED_HIGH))
+					power = dev->hs_config->bMaxPower;
+				else
+					power = dev->config->bMaxPower;
+				usb_gadget_vbus_draw(dev->gadget, 2 * power);
+			}
+
+		} else {			/* collect OUT data */
+			if ((fd->f_flags & O_NONBLOCK) != 0
+					&& !dev->setup_out_ready) {
+				retval = -EAGAIN;
+				goto done;
+			}
+			spin_unlock_irq (&dev->lock);
+			retval = wait_event_interruptible (dev->wait,
+					dev->setup_out_ready != 0);
+
+			/* FIXME state could change from under us */
+			spin_lock_irq (&dev->lock);
+			if (retval)
+				goto done;
+
+			if (dev->state != STATE_DEV_SETUP) {
+				retval = -ECANCELED;
+				goto done;
+			}
+			dev->state = STATE_DEV_CONNECTED;
+
+			if (dev->setup_out_error)
+				retval = -EIO;
+			else {
+				len = min (len, (size_t)dev->req->actual);
+// FIXME don't call this with the spinlock held ...
+				if (copy_to_user (buf, dev->req->buf, len))
+					retval = -EFAULT;
+				else
+					retval = len;
+				clean_req (dev->gadget->ep0, dev->req);
+				/* NOTE userspace can't yet choose to stall */
+			}
+		}
+		goto done;
+	}
+
+	/* else normal: return event data */
+	if (len < sizeof dev->event [0]) {
+		retval = -EINVAL;
+		goto done;
+	}
+	len -= len % sizeof (struct usb_gadgetfs_event);
+	dev->usermode_setup = 1;
+
+scan:
+	/* return queued events right away */
+	if (dev->ev_next != 0) {
+		unsigned		i, n;
+
+		n = len / sizeof (struct usb_gadgetfs_event);
+		if (dev->ev_next < n)
+			n = dev->ev_next;
+
+		/* ep0 i/o has special semantics during STATE_DEV_SETUP */
+		for (i = 0; i < n; i++) {
+			if (dev->event [i].type == GADGETFS_SETUP) {
+				dev->state = STATE_DEV_SETUP;
+				n = i + 1;
+				break;
+			}
+		}
+		spin_unlock_irq (&dev->lock);
+		len = n * sizeof (struct usb_gadgetfs_event);
+		if (copy_to_user (buf, &dev->event, len))
+			retval = -EFAULT;
+		else
+			retval = len;
+		if (len > 0) {
+			/* NOTE this doesn't guard against broken drivers;
+			 * concurrent ep0 readers may lose events.
+			 */
+			spin_lock_irq (&dev->lock);
+			if (dev->ev_next > n) {
+				memmove(&dev->event[0], &dev->event[n],
+					sizeof (struct usb_gadgetfs_event)
+						* (dev->ev_next - n));
+			}
+			dev->ev_next -= n;
+			spin_unlock_irq (&dev->lock);
+		}
+		return retval;
+	}
+	if (fd->f_flags & O_NONBLOCK) {
+		retval = -EAGAIN;
+		goto done;
+	}
+
+	switch (state) {
+	default:
+		DBG (dev, "fail %s, state %d\n", __func__, state);
+		retval = -ESRCH;
+		break;
+	case STATE_DEV_UNCONNECTED:
+	case STATE_DEV_CONNECTED:
+		spin_unlock_irq (&dev->lock);
+		DBG (dev, "%s wait\n", __func__);
+
+		/* wait for events */
+		retval = wait_event_interruptible (dev->wait,
+				dev->ev_next != 0);
+		if (retval < 0)
+			return retval;
+		spin_lock_irq (&dev->lock);
+		goto scan;
+	}
+
+done:
+	spin_unlock_irq (&dev->lock);
+	return retval;
+}
+
+static struct usb_gadgetfs_event *
+next_event (struct dev_data *dev, enum usb_gadgetfs_event_type type)
+{
+	struct usb_gadgetfs_event	*event;
+	unsigned			i;
+
+	switch (type) {
+	/* these events purge the queue */
+	case GADGETFS_DISCONNECT:
+		if (dev->state == STATE_DEV_SETUP)
+			dev->setup_abort = 1;
+		// FALL THROUGH
+	case GADGETFS_CONNECT:
+		dev->ev_next = 0;
+		break;
+	case GADGETFS_SETUP:		/* previous request timed out */
+	case GADGETFS_SUSPEND:		/* same effect */
+		/* these events can't be repeated */
+		for (i = 0; i != dev->ev_next; i++) {
+			if (dev->event [i].type != type)
+				continue;
+			DBG(dev, "discard old event[%d] %d\n", i, type);
+			dev->ev_next--;
+			if (i == dev->ev_next)
+				break;
+			/* indices start at zero, for simplicity */
+			memmove (&dev->event [i], &dev->event [i + 1],
+				sizeof (struct usb_gadgetfs_event)
+					* (dev->ev_next - i));
+		}
+		break;
+	default:
+		BUG ();
+	}
+	VDEBUG(dev, "event[%d] = %d\n", dev->ev_next, type);
+	event = &dev->event [dev->ev_next++];
+	BUG_ON (dev->ev_next > N_EVENT);
+	memset (event, 0, sizeof *event);
+	event->type = type;
+	return event;
+}
+
+static ssize_t
+ep0_write (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
+{
+	struct dev_data		*dev = fd->private_data;
+	ssize_t			retval = -ESRCH;
+
+	spin_lock_irq (&dev->lock);
+
+	/* report fd mode change before acting on it */
+	if (dev->setup_abort) {
+		dev->setup_abort = 0;
+		retval = -EIDRM;
+
+	/* data and/or status stage for control request */
+	} else if (dev->state == STATE_DEV_SETUP) {
+
+		/* IN DATA+STATUS caller makes len <= wLength */
+		if (dev->setup_in) {
+			retval = setup_req (dev->gadget->ep0, dev->req, len);
+			if (retval == 0) {
+				dev->state = STATE_DEV_CONNECTED;
+				spin_unlock_irq (&dev->lock);
+				if (copy_from_user (dev->req->buf, buf, len))
+					retval = -EFAULT;
+				else {
+					if (len < dev->setup_wLength)
+						dev->req->zero = 1;
+					retval = usb_ep_queue (
+						dev->gadget->ep0, dev->req,
+						GFP_KERNEL);
+				}
+				if (retval < 0) {
+					spin_lock_irq (&dev->lock);
+					clean_req (dev->gadget->ep0, dev->req);
+					spin_unlock_irq (&dev->lock);
+				} else
+					retval = len;
+
+				return retval;
+			}
+
+		/* can stall some OUT transfers */
+		} else if (dev->setup_can_stall) {
+			VDEBUG(dev, "ep0out stall\n");
+			(void) usb_ep_set_halt (dev->gadget->ep0);
+			retval = -EL2HLT;
+			dev->state = STATE_DEV_CONNECTED;
+		} else {
+			DBG(dev, "bogus ep0out stall!\n");
+		}
+	} else
+		DBG (dev, "fail %s, state %d\n", __func__, dev->state);
+
+	spin_unlock_irq (&dev->lock);
+	return retval;
+}
+
+static int
+ep0_fasync (int f, struct file *fd, int on)
+{
+	struct dev_data		*dev = fd->private_data;
+	// caller must F_SETOWN before signal delivery happens
+	VDEBUG (dev, "%s %s\n", __func__, on ? "on" : "off");
+	return fasync_helper (f, fd, on, &dev->fasync);
+}
+
+static struct usb_gadget_driver gadgetfs_driver;
+
+static int
+dev_release (struct inode *inode, struct file *fd)
+{
+	struct dev_data		*dev = fd->private_data;
+
+	/* closing ep0 === shutdown all */
+
+	usb_gadget_unregister_driver (&gadgetfs_driver);
+
+	/* at this point "good" hardware has disconnected the
+	 * device from USB; the host won't see it any more.
+	 * alternatively, all host requests will time out.
+	 */
+
+	kfree (dev->buf);
+	dev->buf = NULL;
+	put_dev (dev);
+
+	return 0;
+}
+
+static unsigned int
+ep0_poll (struct file *fd, poll_table *wait)
+{
+       struct dev_data         *dev = fd->private_data;
+       int                     mask = 0;
+
+       poll_wait(fd, &dev->wait, wait);
+
+       spin_lock_irq (&dev->lock);
+
+       /* report fd mode change before acting on it */
+       if (dev->setup_abort) {
+               dev->setup_abort = 0;
+               mask = POLLHUP;
+               goto out;
+       }
+
+       if (dev->state == STATE_DEV_SETUP) {
+               if (dev->setup_in || dev->setup_can_stall)
+                       mask = POLLOUT;
+       } else {
+               if (dev->ev_next != 0)
+                       mask = POLLIN;
+       }
+out:
+       spin_unlock_irq(&dev->lock);
+       return mask;
+}
+
+static long dev_ioctl (struct file *fd, unsigned code, unsigned long value)
+{
+	struct dev_data		*dev = fd->private_data;
+	struct usb_gadget	*gadget = dev->gadget;
+	long ret = -ENOTTY;
+
+	if (gadget->ops->ioctl)
+		ret = gadget->ops->ioctl (gadget, code, value);
+
+	return ret;
+}
+
+/* used after device configuration */
+static const struct file_operations ep0_io_operations = {
+	.owner =	THIS_MODULE,
+	.llseek =	no_llseek,
+
+	.read =		ep0_read,
+	.write =	ep0_write,
+	.fasync =	ep0_fasync,
+	.poll =		ep0_poll,
+	.unlocked_ioctl =	dev_ioctl,
+	.release =	dev_release,
+};
+
+/*----------------------------------------------------------------------*/
+
+/* The in-kernel gadget driver handles most ep0 issues, in particular
+ * enumerating the single configuration (as provided from user space).
+ *
+ * Unrecognized ep0 requests may be handled in user space.
+ */
+
+static void make_qualifier (struct dev_data *dev)
+{
+	struct usb_qualifier_descriptor		qual;
+	struct usb_device_descriptor		*desc;
+
+	qual.bLength = sizeof qual;
+	qual.bDescriptorType = USB_DT_DEVICE_QUALIFIER;
+	qual.bcdUSB = cpu_to_le16 (0x0200);
+
+	desc = dev->dev;
+	qual.bDeviceClass = desc->bDeviceClass;
+	qual.bDeviceSubClass = desc->bDeviceSubClass;
+	qual.bDeviceProtocol = desc->bDeviceProtocol;
+
+	/* assumes ep0 uses the same value for both speeds ... */
+	qual.bMaxPacketSize0 = dev->gadget->ep0->maxpacket;
+
+	qual.bNumConfigurations = 1;
+	qual.bRESERVED = 0;
+
+	memcpy (dev->rbuf, &qual, sizeof qual);
+}
+
+static int
+config_buf (struct dev_data *dev, u8 type, unsigned index)
+{
+	int		len;
+	int		hs = 0;
+
+	/* only one configuration */
+	if (index > 0)
+		return -EINVAL;
+
+	if (gadget_is_dualspeed(dev->gadget)) {
+		hs = (dev->gadget->speed == USB_SPEED_HIGH);
+		if (type == USB_DT_OTHER_SPEED_CONFIG)
+			hs = !hs;
+	}
+	if (hs) {
+		dev->req->buf = dev->hs_config;
+		len = le16_to_cpu(dev->hs_config->wTotalLength);
+	} else {
+		dev->req->buf = dev->config;
+		len = le16_to_cpu(dev->config->wTotalLength);
+	}
+	((u8 *)dev->req->buf) [1] = type;
+	return len;
+}
+
+static int
+gadgetfs_setup (struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
+{
+	struct dev_data			*dev = get_gadget_data (gadget);
+	struct usb_request		*req = dev->req;
+	int				value = -EOPNOTSUPP;
+	struct usb_gadgetfs_event	*event;
+	u16				w_value = le16_to_cpu(ctrl->wValue);
+	u16				w_length = le16_to_cpu(ctrl->wLength);
+
+	spin_lock (&dev->lock);
+	dev->setup_abort = 0;
+	if (dev->state == STATE_DEV_UNCONNECTED) {
+		if (gadget_is_dualspeed(gadget)
+				&& gadget->speed == USB_SPEED_HIGH
+				&& dev->hs_config == NULL) {
+			spin_unlock(&dev->lock);
+			ERROR (dev, "no high speed config??\n");
+			return -EINVAL;
+		}
+
+		dev->state = STATE_DEV_CONNECTED;
+
+		INFO (dev, "connected\n");
+		event = next_event (dev, GADGETFS_CONNECT);
+		event->u.speed = gadget->speed;
+		ep0_readable (dev);
+
+	/* host may have given up waiting for response.  we can miss control
+	 * requests handled lower down (device/endpoint status and features);
+	 * then ep0_{read,write} will report the wrong status. controller
+	 * driver will have aborted pending i/o.
+	 */
+	} else if (dev->state == STATE_DEV_SETUP)
+		dev->setup_abort = 1;
+
+	req->buf = dev->rbuf;
+	req->context = NULL;
+	value = -EOPNOTSUPP;
+	switch (ctrl->bRequest) {
+
+	case USB_REQ_GET_DESCRIPTOR:
+		if (ctrl->bRequestType != USB_DIR_IN)
+			goto unrecognized;
+		switch (w_value >> 8) {
+
+		case USB_DT_DEVICE:
+			value = min (w_length, (u16) sizeof *dev->dev);
+			dev->dev->bMaxPacketSize0 = dev->gadget->ep0->maxpacket;
+			req->buf = dev->dev;
+			break;
+		case USB_DT_DEVICE_QUALIFIER:
+			if (!dev->hs_config)
+				break;
+			value = min (w_length, (u16)
+				sizeof (struct usb_qualifier_descriptor));
+			make_qualifier (dev);
+			break;
+		case USB_DT_OTHER_SPEED_CONFIG:
+			// FALLTHROUGH
+		case USB_DT_CONFIG:
+			value = config_buf (dev,
+					w_value >> 8,
+					w_value & 0xff);
+			if (value >= 0)
+				value = min (w_length, (u16) value);
+			break;
+		case USB_DT_STRING:
+			goto unrecognized;
+
+		default:		// all others are errors
+			break;
+		}
+		break;
+
+	/* currently one config, two speeds */
+	case USB_REQ_SET_CONFIGURATION:
+		if (ctrl->bRequestType != 0)
+			goto unrecognized;
+		if (0 == (u8) w_value) {
+			value = 0;
+			dev->current_config = 0;
+			usb_gadget_vbus_draw(gadget, 8 /* mA */ );
+			// user mode expected to disable endpoints
+		} else {
+			u8	config, power;
+
+			if (gadget_is_dualspeed(gadget)
+					&& gadget->speed == USB_SPEED_HIGH) {
+				config = dev->hs_config->bConfigurationValue;
+				power = dev->hs_config->bMaxPower;
+			} else {
+				config = dev->config->bConfigurationValue;
+				power = dev->config->bMaxPower;
+			}
+
+			if (config == (u8) w_value) {
+				value = 0;
+				dev->current_config = config;
+				usb_gadget_vbus_draw(gadget, 2 * power);
+			}
+		}
+
+		/* report SET_CONFIGURATION like any other control request,
+		 * except that usermode may not stall this.  the next
+		 * request mustn't be allowed start until this finishes:
+		 * endpoints and threads set up, etc.
+		 *
+		 * NOTE:  older PXA hardware (before PXA 255: without UDCCFR)
+		 * has bad/racey automagic that prevents synchronizing here.
+		 * even kernel mode drivers often miss them.
+		 */
+		if (value == 0) {
+			INFO (dev, "configuration #%d\n", dev->current_config);
+			usb_gadget_set_state(gadget, USB_STATE_CONFIGURED);
+			if (dev->usermode_setup) {
+				dev->setup_can_stall = 0;
+				goto delegate;
+			}
+		}
+		break;
+
+#ifndef	CONFIG_USB_PXA25X
+	/* PXA automagically handles this request too */
+	case USB_REQ_GET_CONFIGURATION:
+		if (ctrl->bRequestType != 0x80)
+			goto unrecognized;
+		*(u8 *)req->buf = dev->current_config;
+		value = min (w_length, (u16) 1);
+		break;
+#endif
+
+	default:
+unrecognized:
+		VDEBUG (dev, "%s req%02x.%02x v%04x i%04x l%d\n",
+			dev->usermode_setup ? "delegate" : "fail",
+			ctrl->bRequestType, ctrl->bRequest,
+			w_value, le16_to_cpu(ctrl->wIndex), w_length);
+
+		/* if there's an ep0 reader, don't stall */
+		if (dev->usermode_setup) {
+			dev->setup_can_stall = 1;
+delegate:
+			dev->setup_in = (ctrl->bRequestType & USB_DIR_IN)
+						? 1 : 0;
+			dev->setup_wLength = w_length;
+			dev->setup_out_ready = 0;
+			dev->setup_out_error = 0;
+			value = 0;
+
+			/* read DATA stage for OUT right away */
+			if (unlikely (!dev->setup_in && w_length)) {
+				value = setup_req (gadget->ep0, dev->req,
+							w_length);
+				if (value < 0)
+					break;
+				value = usb_ep_queue (gadget->ep0, dev->req,
+							GFP_ATOMIC);
+				if (value < 0) {
+					clean_req (gadget->ep0, dev->req);
+					break;
+				}
+
+				/* we can't currently stall these */
+				dev->setup_can_stall = 0;
+			}
+
+			/* state changes when reader collects event */
+			event = next_event (dev, GADGETFS_SETUP);
+			event->u.setup = *ctrl;
+			ep0_readable (dev);
+			spin_unlock (&dev->lock);
+			return 0;
+		}
+	}
+
+	/* proceed with data transfer and status phases? */
+	if (value >= 0 && dev->state != STATE_DEV_SETUP) {
+		req->length = value;
+		req->zero = value < w_length;
+		value = usb_ep_queue (gadget->ep0, req, GFP_ATOMIC);
+		if (value < 0) {
+			DBG (dev, "ep_queue --> %d\n", value);
+			req->status = 0;
+		}
+	}
+
+	/* device stalls when value < 0 */
+	spin_unlock (&dev->lock);
+	return value;
+}
+
+static void destroy_ep_files (struct dev_data *dev)
+{
+	DBG (dev, "%s %d\n", __func__, dev->state);
+
+	/* dev->state must prevent interference */
+	spin_lock_irq (&dev->lock);
+	while (!list_empty(&dev->epfiles)) {
+		struct ep_data	*ep;
+		struct inode	*parent;
+		struct dentry	*dentry;
+
+		/* break link to FS */
+		ep = list_first_entry (&dev->epfiles, struct ep_data, epfiles);
+		list_del_init (&ep->epfiles);
+		dentry = ep->dentry;
+		ep->dentry = NULL;
+		parent = dentry->d_parent->d_inode;
+
+		/* break link to controller */
+		if (ep->state == STATE_EP_ENABLED)
+			(void) usb_ep_disable (ep->ep);
+		ep->state = STATE_EP_UNBOUND;
+		usb_ep_free_request (ep->ep, ep->req);
+		ep->ep = NULL;
+		wake_up (&ep->wait);
+		put_ep (ep);
+
+		spin_unlock_irq (&dev->lock);
+
+		/* break link to dcache */
+		mutex_lock (&parent->i_mutex);
+		d_delete (dentry);
+		dput (dentry);
+		mutex_unlock (&parent->i_mutex);
+
+		spin_lock_irq (&dev->lock);
+	}
+	spin_unlock_irq (&dev->lock);
+}
+
+
+static struct inode *
+gadgetfs_create_file (struct super_block *sb, char const *name,
+		void *data, const struct file_operations *fops,
+		struct dentry **dentry_p);
+
+static int activate_ep_files (struct dev_data *dev)
+{
+	struct usb_ep	*ep;
+	struct ep_data	*data;
+
+	gadget_for_each_ep (ep, dev->gadget) {
+
+		data = kzalloc(sizeof(*data), GFP_KERNEL);
+		if (!data)
+			goto enomem0;
+		data->state = STATE_EP_DISABLED;
+		mutex_init(&data->lock);
+		init_waitqueue_head (&data->wait);
+
+		strncpy (data->name, ep->name, sizeof (data->name) - 1);
+		atomic_set (&data->count, 1);
+		data->dev = dev;
+		get_dev (dev);
+
+		data->ep = ep;
+		ep->driver_data = data;
+
+		data->req = usb_ep_alloc_request (ep, GFP_KERNEL);
+		if (!data->req)
+			goto enomem1;
+
+		data->inode = gadgetfs_create_file (dev->sb, data->name,
+				data, &ep_config_operations,
+				&data->dentry);
+		if (!data->inode)
+			goto enomem2;
+		list_add_tail (&data->epfiles, &dev->epfiles);
+	}
+	return 0;
+
+enomem2:
+	usb_ep_free_request (ep, data->req);
+enomem1:
+	put_dev (dev);
+	kfree (data);
+enomem0:
+	DBG (dev, "%s enomem\n", __func__);
+	destroy_ep_files (dev);
+	return -ENOMEM;
+}
+
+static void
+gadgetfs_unbind (struct usb_gadget *gadget)
+{
+	struct dev_data		*dev = get_gadget_data (gadget);
+
+	DBG (dev, "%s\n", __func__);
+
+	spin_lock_irq (&dev->lock);
+	dev->state = STATE_DEV_UNBOUND;
+	spin_unlock_irq (&dev->lock);
+
+	destroy_ep_files (dev);
+	gadget->ep0->driver_data = NULL;
+	set_gadget_data (gadget, NULL);
+
+	/* we've already been disconnected ... no i/o is active */
+	if (dev->req)
+		usb_ep_free_request (gadget->ep0, dev->req);
+	DBG (dev, "%s done\n", __func__);
+	put_dev (dev);
+}
+
+static struct dev_data		*the_device;
+
+static int gadgetfs_bind(struct usb_gadget *gadget,
+		struct usb_gadget_driver *driver)
+{
+	struct dev_data		*dev = the_device;
+
+	if (!dev)
+		return -ESRCH;
+	if (0 != strcmp (CHIP, gadget->name)) {
+		pr_err("%s expected %s controller not %s\n",
+			shortname, CHIP, gadget->name);
+		return -ENODEV;
+	}
+
+	set_gadget_data (gadget, dev);
+	dev->gadget = gadget;
+	gadget->ep0->driver_data = dev;
+
+	/* preallocate control response and buffer */
+	dev->req = usb_ep_alloc_request (gadget->ep0, GFP_KERNEL);
+	if (!dev->req)
+		goto enomem;
+	dev->req->context = NULL;
+	dev->req->complete = epio_complete;
+
+	if (activate_ep_files (dev) < 0)
+		goto enomem;
+
+	INFO (dev, "bound to %s driver\n", gadget->name);
+	spin_lock_irq(&dev->lock);
+	dev->state = STATE_DEV_UNCONNECTED;
+	spin_unlock_irq(&dev->lock);
+	get_dev (dev);
+	return 0;
+
+enomem:
+	gadgetfs_unbind (gadget);
+	return -ENOMEM;
+}
+
+static void
+gadgetfs_disconnect (struct usb_gadget *gadget)
+{
+	struct dev_data		*dev = get_gadget_data (gadget);
+	unsigned long		flags;
+
+	spin_lock_irqsave (&dev->lock, flags);
+	if (dev->state == STATE_DEV_UNCONNECTED)
+		goto exit;
+	dev->state = STATE_DEV_UNCONNECTED;
+
+	INFO (dev, "disconnected\n");
+	next_event (dev, GADGETFS_DISCONNECT);
+	ep0_readable (dev);
+exit:
+	spin_unlock_irqrestore (&dev->lock, flags);
+}
+
+static void
+gadgetfs_suspend (struct usb_gadget *gadget)
+{
+	struct dev_data		*dev = get_gadget_data (gadget);
+
+	INFO (dev, "suspended from state %d\n", dev->state);
+	spin_lock (&dev->lock);
+	switch (dev->state) {
+	case STATE_DEV_SETUP:		// VERY odd... host died??
+	case STATE_DEV_CONNECTED:
+	case STATE_DEV_UNCONNECTED:
+		next_event (dev, GADGETFS_SUSPEND);
+		ep0_readable (dev);
+		/* FALLTHROUGH */
+	default:
+		break;
+	}
+	spin_unlock (&dev->lock);
+}
+
+static struct usb_gadget_driver gadgetfs_driver = {
+	.function	= (char *) driver_desc,
+	.bind		= gadgetfs_bind,
+	.unbind		= gadgetfs_unbind,
+	.setup		= gadgetfs_setup,
+	.disconnect	= gadgetfs_disconnect,
+	.suspend	= gadgetfs_suspend,
+
+	.driver	= {
+		.name		= (char *) shortname,
+	},
+};
+
+/*----------------------------------------------------------------------*/
+
+static void gadgetfs_nop(struct usb_gadget *arg) { }
+
+static int gadgetfs_probe(struct usb_gadget *gadget,
+		struct usb_gadget_driver *driver)
+{
+	CHIP = gadget->name;
+	return -EISNAM;
+}
+
+static struct usb_gadget_driver probe_driver = {
+	.max_speed	= USB_SPEED_HIGH,
+	.bind		= gadgetfs_probe,
+	.unbind		= gadgetfs_nop,
+	.setup		= (void *)gadgetfs_nop,
+	.disconnect	= gadgetfs_nop,
+	.driver	= {
+		.name		= "nop",
+	},
+};
+
+
+/* DEVICE INITIALIZATION
+ *
+ *     fd = open ("/dev/gadget/$CHIP", O_RDWR)
+ *     status = write (fd, descriptors, sizeof descriptors)
+ *
+ * That write establishes the device configuration, so the kernel can
+ * bind to the controller ... guaranteeing it can handle enumeration
+ * at all necessary speeds.  Descriptor order is:
+ *
+ * . message tag (u32, host order) ... for now, must be zero; it
+ *	would change to support features like multi-config devices
+ * . full/low speed config ... all wTotalLength bytes (with interface,
+ *	class, altsetting, endpoint, and other descriptors)
+ * . high speed config ... all descriptors, for high speed operation;
+ *	this one's optional except for high-speed hardware
+ * . device descriptor
+ *
+ * Endpoints are not yet enabled. Drivers must wait until device
+ * configuration and interface altsetting changes create
+ * the need to configure (or unconfigure) them.
+ *
+ * After initialization, the device stays active for as long as that
+ * $CHIP file is open.  Events must then be read from that descriptor,
+ * such as configuration notifications.
+ */
+
+static int is_valid_config (struct usb_config_descriptor *config)
+{
+	return config->bDescriptorType == USB_DT_CONFIG
+		&& config->bLength == USB_DT_CONFIG_SIZE
+		&& config->bConfigurationValue != 0
+		&& (config->bmAttributes & USB_CONFIG_ATT_ONE) != 0
+		&& (config->bmAttributes & USB_CONFIG_ATT_WAKEUP) == 0;
+	/* FIXME if gadget->is_otg, _must_ include an otg descriptor */
+	/* FIXME check lengths: walk to end */
+}
+
+static ssize_t
+dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
+{
+	struct dev_data		*dev = fd->private_data;
+	ssize_t			value = len, length = len;
+	unsigned		total;
+	u32			tag;
+	char			*kbuf;
+
+	if (len < (USB_DT_CONFIG_SIZE + USB_DT_DEVICE_SIZE + 4))
+		return -EINVAL;
+
+	/* we might need to change message format someday */
+	if (copy_from_user (&tag, buf, 4))
+		return -EFAULT;
+	if (tag != 0)
+		return -EINVAL;
+	buf += 4;
+	length -= 4;
+
+	kbuf = memdup_user(buf, length);
+	if (IS_ERR(kbuf))
+		return PTR_ERR(kbuf);
+
+	spin_lock_irq (&dev->lock);
+	value = -EINVAL;
+	if (dev->buf)
+		goto fail;
+	dev->buf = kbuf;
+
+	/* full or low speed config */
+	dev->config = (void *) kbuf;
+	total = le16_to_cpu(dev->config->wTotalLength);
+	if (!is_valid_config (dev->config) || total >= length)
+		goto fail;
+	kbuf += total;
+	length -= total;
+
+	/* optional high speed config */
+	if (kbuf [1] == USB_DT_CONFIG) {
+		dev->hs_config = (void *) kbuf;
+		total = le16_to_cpu(dev->hs_config->wTotalLength);
+		if (!is_valid_config (dev->hs_config) || total >= length)
+			goto fail;
+		kbuf += total;
+		length -= total;
+	}
+
+	/* could support multiple configs, using another encoding! */
+
+	/* device descriptor (tweaked for paranoia) */
+	if (length != USB_DT_DEVICE_SIZE)
+		goto fail;
+	dev->dev = (void *)kbuf;
+	if (dev->dev->bLength != USB_DT_DEVICE_SIZE
+			|| dev->dev->bDescriptorType != USB_DT_DEVICE
+			|| dev->dev->bNumConfigurations != 1)
+		goto fail;
+	dev->dev->bNumConfigurations = 1;
+	dev->dev->bcdUSB = cpu_to_le16 (0x0200);
+
+	/* triggers gadgetfs_bind(); then we can enumerate. */
+	spin_unlock_irq (&dev->lock);
+	if (dev->hs_config)
+		gadgetfs_driver.max_speed = USB_SPEED_HIGH;
+	else
+		gadgetfs_driver.max_speed = USB_SPEED_FULL;
+
+	value = usb_gadget_probe_driver(&gadgetfs_driver);
+	if (value != 0) {
+		kfree (dev->buf);
+		dev->buf = NULL;
+	} else {
+		/* at this point "good" hardware has for the first time
+		 * let the USB the host see us.  alternatively, if users
+		 * unplug/replug that will clear all the error state.
+		 *
+		 * note:  everything running before here was guaranteed
+		 * to choke driver model style diagnostics.  from here
+		 * on, they can work ... except in cleanup paths that
+		 * kick in after the ep0 descriptor is closed.
+		 */
+		fd->f_op = &ep0_io_operations;
+		value = len;
+	}
+	return value;
+
+fail:
+	spin_unlock_irq (&dev->lock);
+	pr_debug ("%s: %s fail %Zd, %p\n", shortname, __func__, value, dev);
+	kfree (dev->buf);
+	dev->buf = NULL;
+	return value;
+}
+
+static int
+dev_open (struct inode *inode, struct file *fd)
+{
+	struct dev_data		*dev = inode->i_private;
+	int			value = -EBUSY;
+
+	spin_lock_irq(&dev->lock);
+	if (dev->state == STATE_DEV_DISABLED) {
+		dev->ev_next = 0;
+		dev->state = STATE_DEV_OPENED;
+		fd->private_data = dev;
+		get_dev (dev);
+		value = 0;
+	}
+	spin_unlock_irq(&dev->lock);
+	return value;
+}
+
+static const struct file_operations dev_init_operations = {
+	.llseek =	no_llseek,
+
+	.open =		dev_open,
+	.write =	dev_config,
+	.fasync =	ep0_fasync,
+	.unlocked_ioctl = dev_ioctl,
+	.release =	dev_release,
+};
+
+/*----------------------------------------------------------------------*/
+
+/* FILESYSTEM AND SUPERBLOCK OPERATIONS
+ *
+ * Mounting the filesystem creates a controller file, used first for
+ * device configuration then later for event monitoring.
+ */
+
+
+/* FIXME PAM etc could set this security policy without mount options
+ * if epfiles inherited ownership and permissons from ep0 ...
+ */
+
+static unsigned default_uid;
+static unsigned default_gid;
+static unsigned default_perm = S_IRUSR | S_IWUSR;
+
+module_param (default_uid, uint, 0644);
+module_param (default_gid, uint, 0644);
+module_param (default_perm, uint, 0644);
+
+
+static struct inode *
+gadgetfs_make_inode (struct super_block *sb,
+		void *data, const struct file_operations *fops,
+		int mode)
+{
+	struct inode *inode = new_inode (sb);
+
+	if (inode) {
+		inode->i_ino = get_next_ino();
+		inode->i_mode = mode;
+		inode->i_uid = make_kuid(&init_user_ns, default_uid);
+		inode->i_gid = make_kgid(&init_user_ns, default_gid);
+		inode->i_atime = inode->i_mtime = inode->i_ctime
+				= CURRENT_TIME;
+		inode->i_private = data;
+		inode->i_fop = fops;
+	}
+	return inode;
+}
+
+/* creates in fs root directory, so non-renamable and non-linkable.
+ * so inode and dentry are paired, until device reconfig.
+ */
+static struct inode *
+gadgetfs_create_file (struct super_block *sb, char const *name,
+		void *data, const struct file_operations *fops,
+		struct dentry **dentry_p)
+{
+	struct dentry	*dentry;
+	struct inode	*inode;
+
+	dentry = d_alloc_name(sb->s_root, name);
+	if (!dentry)
+		return NULL;
+
+	inode = gadgetfs_make_inode (sb, data, fops,
+			S_IFREG | (default_perm & S_IRWXUGO));
+	if (!inode) {
+		dput(dentry);
+		return NULL;
+	}
+	d_add (dentry, inode);
+	*dentry_p = dentry;
+	return inode;
+}
+
+static const struct super_operations gadget_fs_operations = {
+	.statfs =	simple_statfs,
+	.drop_inode =	generic_delete_inode,
+};
+
+static int
+gadgetfs_fill_super (struct super_block *sb, void *opts, int silent)
+{
+	struct inode	*inode;
+	struct dev_data	*dev;
+
+	if (the_device)
+		return -ESRCH;
+
+	/* fake probe to determine $CHIP */
+	CHIP = NULL;
+	usb_gadget_probe_driver(&probe_driver);
+	if (!CHIP)
+		return -ENODEV;
+
+	/* superblock */
+	sb->s_blocksize = PAGE_CACHE_SIZE;
+	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
+	sb->s_magic = GADGETFS_MAGIC;
+	sb->s_op = &gadget_fs_operations;
+	sb->s_time_gran = 1;
+
+	/* root inode */
+	inode = gadgetfs_make_inode (sb,
+			NULL, &simple_dir_operations,
+			S_IFDIR | S_IRUGO | S_IXUGO);
+	if (!inode)
+		goto Enomem;
+	inode->i_op = &simple_dir_inode_operations;
+	if (!(sb->s_root = d_make_root (inode)))
+		goto Enomem;
+
+	/* the ep0 file is named after the controller we expect;
+	 * user mode code can use it for sanity checks, like we do.
+	 */
+	dev = dev_new ();
+	if (!dev)
+		goto Enomem;
+
+	dev->sb = sb;
+	if (!gadgetfs_create_file (sb, CHIP,
+				dev, &dev_init_operations,
+				&dev->dentry)) {
+		put_dev(dev);
+		goto Enomem;
+	}
+
+	/* other endpoint files are available after hardware setup,
+	 * from binding to a controller.
+	 */
+	the_device = dev;
+	return 0;
+
+Enomem:
+	return -ENOMEM;
+}
+
+/* "mount -t gadgetfs path /dev/gadget" ends up here */
+static struct dentry *
+gadgetfs_mount (struct file_system_type *t, int flags,
+		const char *path, void *opts)
+{
+	return mount_single (t, flags, opts, gadgetfs_fill_super);
+}
+
+static void
+gadgetfs_kill_sb (struct super_block *sb)
+{
+	kill_litter_super (sb);
+	if (the_device) {
+		put_dev (the_device);
+		the_device = NULL;
+	}
+}
+
+/*----------------------------------------------------------------------*/
+
+static struct file_system_type gadgetfs_type = {
+	.owner		= THIS_MODULE,
+	.name		= shortname,
+	.mount		= gadgetfs_mount,
+	.kill_sb	= gadgetfs_kill_sb,
+};
+MODULE_ALIAS_FS("gadgetfs");
+
+/*----------------------------------------------------------------------*/
+
+static int __init init (void)
+{
+	int status;
+
+	status = register_filesystem (&gadgetfs_type);
+	if (status == 0)
+		pr_info ("%s: %s, version " DRIVER_VERSION "\n",
+			shortname, driver_desc);
+	return status;
+}
+module_init (init);
+
+static void __exit cleanup (void)
+{
+	pr_debug ("unregister %s\n", shortname);
+	unregister_filesystem (&gadgetfs_type);
+}
+module_exit (cleanup);
+