text: // SPDX-License-Identifier: GPL-2.0+
  /*
   * inode.c -- user mode filesystem api for usb gadget controllers
   *
   * Copyright (C) 2003-2004 David Brownell
   * Copyright (C) 2003 Agilent Technologies
   */
  
  
  /* #define VERBOSE_DEBUG */
  
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/fs.h>
  #include <linux/fs_context.h>
  #include <linux/pagemap.h>
  #include <linux/uts.h>
  #include <linux/wait.h>
  #include <linux/compiler.h>
  #include <linux/uaccess.h>
  #include <linux/sched.h>
  #include <linux/slab.h>
  #include <linux/poll.h>
  #include <linux/kthread.h>
  #include <linux/aio.h>
  #include <linux/uio.h>
  #include <linux/refcount.h>
  #include <linux/delay.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");
  
  static int ep_open(struct inode *, struct file *);
  
  
  /*----------------------------------------------------------------------*/
  
  #define GADGETFS_MAGIC		0xaee71ee7
  
  /* /dev/gadget/$CHIP represents ep0 and the whole device */
  enum ep0_state {
  	/* DISABLED 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;
  	refcount_t			count;
  	int				udc_usage;
  	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,
  					gadget_registered : 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)
  {
  	refcount_inc (&data->count);
  }
  
  static void put_dev (struct dev_data *data)
  {
  	if (likely (!refcount_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;
  	refcount_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;
  	refcount_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;
  };
  
  static inline void get_ep (struct ep_data *data)
  {
  	refcount_inc (&data->count);
  }
  
  static void put_ep (struct ep_data *data)
  {
  	if (likely (!refcount_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, bool is_write)
  {
  	int	val;
  
  	if (f_flags & O_NONBLOCK) {
  		if (!mutex_trylock(&epdata->lock))
  			goto nonblock;
  		if (epdata->state != STATE_EP_ENABLED &&
  		    (!is_write || epdata->state != STATE_EP_READY)) {
  			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:
  		return 0;
  	case STATE_EP_READY:			/* not configured yet */
  		if (is_write)
  			return 0;
  		fallthrough;
  	case STATE_EP_UNBOUND:			/* clean disconnect */
  		break;
  	// case STATE_EP_DISABLED:		/* "can't happen" */
  	default:				/* error! */
  		pr_debug ("%s: ep %p not available, state %d\n",
  				shortname, epdata, epdata->state);
  	}
  	mutex_unlock(&epdata->lock);
  	return -ENODEV;
  }
  
  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_for_completion_interruptible(&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_for_completion(&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;
  }
  
  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, false)) < 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;
  	struct iov_iter		to;
  	const void		*to_free;
  	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 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;
  
  	kthread_use_mm(mm);
  	ret = copy_to_iter(priv->buf, priv->actual, &priv->to);
  	kthread_unuse_mm(mm);
  	if (!ret)
  		ret = -EFAULT;
  
  	/* completing the iocb can drop the ctx and mm, don't touch mm after */
  	iocb->ki_complete(iocb, ret, ret);
  
  	kfree(priv->buf);
  	kfree(priv->to_free);
  	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->to_free == NULL || unlikely(req->actual == 0)) {
  		kfree(req->buf);
  		kfree(priv->to_free);
  		kfree(priv);
  		iocb->private = NULL;
  		/* aio_complete() reports bytes-transferred _and_ faults */
  
  		iocb->ki_complete(iocb,
  				req->actual ? req->actual : (long)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;
  		INIT_WORK(&priv->work, ep_user_copy_worker);
  		schedule_work(&priv->work);
  	}
  
  	usb_ep_free_request(ep, req);
  	spin_unlock(&epdata->dev->lock);
  	put_ep(epdata);
  }
  
  static ssize_t ep_aio(struct kiocb *iocb,
  		      struct kiocb_priv *priv,
  		      struct ep_data *epdata,
  		      char *buf,
  		      size_t len)
  {
  	struct usb_request *req;
  	ssize_t value;
  
  	iocb->private = priv;
  	priv->iocb = iocb;
  
  	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);
  	value = -ENODEV;
  	if (unlikely(epdata->ep == NULL))
  		goto fail;
  
  	req = usb_ep_alloc_request(epdata->ep, GFP_ATOMIC);
  	value = -ENOMEM;
  	if (unlikely(!req))
  		goto fail;
  
  	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);
  		goto fail;
  	}
  	spin_unlock_irq(&epdata->dev->lock);
  	return -EIOCBQUEUED;
  
  fail:
  	spin_unlock_irq(&epdata->dev->lock);
  	kfree(priv->to_free);
  	kfree(priv);
  	put_ep(epdata);
  	return value;
  }
  
  static ssize_t
  ep_read_iter(struct kiocb *iocb, struct iov_iter *to)
  {
  	struct file *file = iocb->ki_filp;
  	struct ep_data *epdata = file->private_data;
  	size_t len = iov_iter_count(to);
  	ssize_t value;
  	char *buf;
  
  	if ((value = get_ready_ep(file->f_flags, epdata, false)) < 0)
  		return value;
  
  	/* halt any endpoint by doing a "wrong direction" i/o call */
  	if (usb_endpoint_dir_in(&epdata->desc)) {
  		if (usb_endpoint_xfer_isoc(&epdata->desc) ||
  		    !is_sync_kiocb(iocb)) {
  			mutex_unlock(&epdata->lock);
  			return -EINVAL;
  		}
  		DBG (epdata->dev, "%s halt\n", epdata->name);
  		spin_lock_irq(&epdata->dev->lock);
  		if (likely(epdata->ep != NULL))
  			usb_ep_set_halt(epdata->ep);
  		spin_unlock_irq(&epdata->dev->lock);
  		mutex_unlock(&epdata->lock);
  		return -EBADMSG;
  	}
  
  	buf = kmalloc(len, GFP_KERNEL);
  	if (unlikely(!buf)) {
  		mutex_unlock(&epdata->lock);
  		return -ENOMEM;
  	}
  	if (is_sync_kiocb(iocb)) {
  		value = ep_io(epdata, buf, len);
  		if (value >= 0 && (copy_to_iter(buf, value, to) != value))
  			value = -EFAULT;
  	} else {
  		struct kiocb_priv *priv = kzalloc(sizeof *priv, GFP_KERNEL);
  		value = -ENOMEM;
  		if (!priv)
  			goto fail;
  		priv->to_free = dup_iter(&priv->to, to, GFP_KERNEL);
  		if (!priv->to_free) {
  			kfree(priv);
  			goto fail;
  		}
  		value = ep_aio(iocb, priv, epdata, buf, len);
  		if (value == -EIOCBQUEUED)
  			buf = NULL;
  	}
  fail:
  	kfree(buf);
  	mutex_unlock(&epdata->lock);
  	return value;
  }
  
  static ssize_t ep_config(struct ep_data *, const char *, size_t);
  
  static ssize_t
  ep_write_iter(struct kiocb *iocb, struct iov_iter *from)
  {
  	struct file *file = iocb->ki_filp;
  	struct ep_data *epdata = file->private_data;
  	size_t len = iov_iter_count(from);
  	bool configured;
  	ssize_t value;
  	char *buf;
  
  	if ((value = get_ready_ep(file->f_flags, epdata, true)) < 0)
  		return value;
  
  	configured = epdata->state == STATE_EP_ENABLED;
  
  	/* halt any endpoint by doing a "wrong direction" i/o call */
  	if (configured && !usb_endpoint_dir_in(&epdata->desc)) {
  		if (usb_endpoint_xfer_isoc(&epdata->desc) ||
  		    !is_sync_kiocb(iocb)) {
  			mutex_unlock(&epdata->lock);
  			return -EINVAL;
  		}
  		DBG (epdata->dev, "%s halt\n", epdata->name);
  		spin_lock_irq(&epdata->dev->lock);
  		if (likely(epdata->ep != NULL))
  			usb_ep_set_halt(epdata->ep);
  		spin_unlock_irq(&epdata->dev->lock);
  		mutex_unlock(&epdata->lock);
  		return -EBADMSG;
  	}
  
  	buf = kmalloc(len, GFP_KERNEL);
  	if (unlikely(!buf)) {
  		mutex_unlock(&epdata->lock);
  		return -ENOMEM;
  	}
  
  	if (unlikely(!copy_from_iter_full(buf, len, from))) {
  		value = -EFAULT;
  		goto out;
  	}
  
  	if (unlikely(!configured)) {
  		value = ep_config(epdata, buf, len);
  	} else if (is_sync_kiocb(iocb)) {
  		value = ep_io(epdata, buf, len);
  	} else {
  		struct kiocb_priv *priv = kzalloc(sizeof *priv, GFP_KERNEL);
  		value = -ENOMEM;
  		if (priv) {
  			value = ep_aio(iocb, priv, epdata, buf, len);
  			if (value == -EIOCBQUEUED)
  				buf = NULL;
  		}
  	}
  out:
  	kfree(buf);
  	mutex_unlock(&epdata->lock);
  	return value;
  }
  
  /*----------------------------------------------------------------------*/
  
  /* used after endpoint configuration */
  static const struct file_operations ep_io_operations = {
  	.owner =	THIS_MODULE,
  
  	.open =		ep_open,
  	.release =	ep_release,
  	.llseek =	no_llseek,
  	.unlocked_ioctl = ep_ioctl,
  	.read_iter =	ep_read_iter,
  	.write_iter =	ep_write_iter,
  };
  
  /* 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 ep_data *data, const char *buf, size_t len)
  {
  	struct usb_ep		*ep;
  	u32			tag;
  	int			value, length = len;
  
  	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 */
  	memcpy(&tag, buf, 4);
  	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 */
  	memcpy(&data->desc, buf, USB_DT_ENDPOINT_SIZE);
  	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;
  		memcpy(&data->hs_desc, buf + USB_DT_ENDPOINT_SIZE,
  			USB_DT_ENDPOINT_SIZE);
  		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 {
  		ep = data->ep;
  		if (ep == NULL) {
  			value = -ENODEV;
  			goto gone;
  		}
  	}
  	switch (data->dev->gadget->speed) {
  	case USB_SPEED_LOW:
  	case USB_SPEED_FULL:
  		ep->desc = &data->desc;
  		break;
  	case USB_SPEED_HIGH:
  		/* fails if caller didn't provide that descriptor... */
  		ep->desc = &data->hs_desc;
  		break;
  	default:
  		DBG(data->dev, "unconnected, %s init abandoned\n",
  				data->name);
  		value = -EINVAL;
  		goto gone;
  	}
  	value = usb_ep_enable(ep);
  	if (value == 0) {
  		data->state = STATE_EP_ENABLED;
  		value = length;
  	}
  gone:
  	spin_unlock_irq (&data->dev->lock);
  	if (value < 0) {
  fail:
  		data->desc.bDescriptorType = 0;
  		data->hs_desc.bDescriptorType = 0;
  	}
  	return value;
  fail0:
  	value = -EINVAL;
  	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;
  }
  
  /*----------------------------------------------------------------------*/
  
  /* 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);
  	if (dev->state <= STATE_DEV_OPENED) {
  		retval = -EINVAL;
  		goto done;
  	}
  
  	/* 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) {
  				++dev->udc_usage;
  				spin_unlock_irq (&dev->lock);
  				retval = usb_ep_queue (ep, req, GFP_KERNEL);
  				spin_lock_irq (&dev->lock);
  				--dev->udc_usage;
  			}
  			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);
  				++dev->udc_usage;
  				spin_unlock_irq(&dev->lock);
  				if (copy_to_user (buf, dev->req->buf, len))
  					retval = -EFAULT;
  				else
  					retval = len;
  				spin_lock_irq(&dev->lock);
  				--dev->udc_usage;
  				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;
  		fallthrough;
  	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;
  
  	/* 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) {
  
  		len = min_t(size_t, len, dev->setup_wLength);
  		if (dev->setup_in) {
  			retval = setup_req (dev->gadget->ep0, dev->req, len);
  			if (retval == 0) {
  				dev->state = STATE_DEV_CONNECTED;
  				++dev->udc_usage;
  				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);
  				}
  				spin_lock_irq(&dev->lock);
  				--dev->udc_usage;
  				if (retval < 0) {
  					clean_req (dev->gadget->ep0, dev->req);
  				} 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);
  
  	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 */
  
  	if (dev->gadget_registered) {
  		usb_gadget_unregister_driver (&gadgetfs_driver);
  		dev->gadget_registered = false;
  	}
  
  	/* 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;
  
  	/* other endpoints were all decoupled from this device */
  	spin_lock_irq(&dev->lock);
  	dev->state = STATE_DEV_DISABLED;
  	spin_unlock_irq(&dev->lock);
  
  	put_dev (dev);
  	return 0;
  }
  
  static __poll_t
  ep0_poll (struct file *fd, poll_table *wait)
  {
         struct dev_data         *dev = fd->private_data;
         __poll_t                mask = 0;
  
  	if (dev->state <= STATE_DEV_OPENED)
  		return DEFAULT_POLLMASK;
  
  	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 = EPOLLHUP;
  		goto out;
  	}
  
  	if (dev->state == STATE_DEV_SETUP) {
  		if (dev->setup_in || dev->setup_can_stall)
  			mask = EPOLLOUT;
  	} else {
  		if (dev->ev_next != 0)
  			mask = EPOLLIN;
  	}
  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;
  
  	spin_lock_irq(&dev->lock);
  	if (dev->state == STATE_DEV_OPENED ||
  			dev->state == STATE_DEV_UNBOUND) {
  		/* Not bound to a UDC */
  	} else if (gadget->ops->ioctl) {
  		++dev->udc_usage;
  		spin_unlock_irq(&dev->lock);
  
  		ret = gadget->ops->ioctl (gadget, code, value);
  
  		spin_lock_irq(&dev->lock);
  		--dev->udc_usage;
  	}
  	spin_unlock_irq(&dev->lock);
  
  	return ret;
  }
  
  /*----------------------------------------------------------------------*/
  
  /* 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;
  	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:
  		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;
  
  			/* 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;
  
  				++dev->udc_usage;
  				spin_unlock (&dev->lock);
  				value = usb_ep_queue (gadget->ep0, dev->req,
  							GFP_KERNEL);
  				spin_lock (&dev->lock);
  				--dev->udc_usage;
  				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;
  
  		++dev->udc_usage;
  		spin_unlock (&dev->lock);
  		value = usb_ep_queue (gadget->ep0, req, GFP_KERNEL);
  		spin_lock(&dev->lock);
  		--dev->udc_usage;
  		spin_unlock(&dev->lock);
  		if (value < 0) {
  			DBG (dev, "ep_queue --> %d\n", value);
  			req->status = 0;
  		}
  		return value;
  	}
  
  	/* 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);
  		spin_unlock_irq (&dev->lock);
  
  		dentry = ep->dentry;
  		ep->dentry = NULL;
  		parent = d_inode(dentry->d_parent);
  
  		/* break link to controller */
  		mutex_lock(&ep->lock);
  		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;
  		mutex_unlock(&ep->lock);
  
  		wake_up (&ep->wait);
  		put_ep (ep);
  
  		/* break link to dcache */
  		inode_lock(parent);
  		d_delete (dentry);
  		dput (dentry);
  		inode_unlock(parent);
  
  		spin_lock_irq (&dev->lock);
  	}
  	spin_unlock_irq (&dev->lock);
  }
  
  
  static struct dentry *
  gadgetfs_create_file (struct super_block *sb, char const *name,
  		void *data, const struct file_operations *fops);
  
  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);
  		refcount_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->dentry = gadgetfs_create_file (dev->sb, data->name,
  				data, &ep_io_operations);
  		if (!data->dentry)
  			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;
  	while (dev->udc_usage > 0) {
  		spin_unlock_irq(&dev->lock);
  		usleep_range(1000, 2000);
  		spin_lock_irq(&dev->lock);
  	}
  	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);
  	unsigned long		flags;
  
  	INFO (dev, "suspended from state %d\n", dev->state);
  	spin_lock_irqsave(&dev->lock, flags);
  	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_irqrestore(&dev->lock, flags);
  }
  
  static struct usb_gadget_driver gadgetfs_driver = {
  	.function	= (char *) driver_desc,
  	.bind		= gadgetfs_bind,
  	.unbind		= gadgetfs_unbind,
  	.setup		= gadgetfs_setup,
  	.reset		= gadgetfs_disconnect,
  	.disconnect	= gadgetfs_disconnect,
  	.suspend	= gadgetfs_suspend,
  
  	.driver	= {
  		.name		= shortname,
  	},
  };
  
  /*----------------------------------------------------------------------*/
  /* 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,
  		unsigned int total)
  {
  	return config->bDescriptorType == USB_DT_CONFIG
  		&& config->bLength == USB_DT_CONFIG_SIZE
  		&& total >= 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, length = len;
  	unsigned		total;
  	u32			tag;
  	char			*kbuf;
  
  	spin_lock_irq(&dev->lock);
  	if (dev->state > STATE_DEV_OPENED) {
  		value = ep0_write(fd, buf, len, ptr);
  		spin_unlock_irq(&dev->lock);
  		return value;
  	}
  	spin_unlock_irq(&dev->lock);
  
  	if ((len < (USB_DT_CONFIG_SIZE + USB_DT_DEVICE_SIZE + 4)) ||
  	    (len > PAGE_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) {
  		kfree(kbuf);
  		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) ||
  			total > length - USB_DT_DEVICE_SIZE)
  		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) ||
  				total > length - USB_DT_DEVICE_SIZE)
  			goto fail;
  		kbuf += total;
  		length -= total;
  	} else {
  		dev->hs_config = NULL;
  	}
  
  	/* 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->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.
  		 */
  		value = len;
  		dev->gadget_registered = true;
  	}
  	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 ep0_operations = {
  	.llseek =	no_llseek,
  
  	.open =		dev_open,
  	.read =		ep0_read,
  	.write =	dev_config,
  	.fasync =	ep0_fasync,
  	.poll =		ep0_poll,
  	.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);
  		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 dentry *
  gadgetfs_create_file (struct super_block *sb, char const *name,
  		void *data, const struct file_operations *fops)
  {
  	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);
  	return dentry;
  }
  
  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, struct fs_context *fc)
  {
  	struct inode	*inode;
  	struct dev_data	*dev;
  
  	if (the_device)
  		return -ESRCH;
  
  	CHIP = usb_get_gadget_udc_name();
  	if (!CHIP)
  		return -ENODEV;
  
  	/* superblock */
  	sb->s_blocksize = PAGE_SIZE;
  	sb->s_blocksize_bits = PAGE_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;
  	dev->dentry = gadgetfs_create_file(sb, CHIP, dev, &ep0_operations);
  	if (!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:
  	kfree(CHIP);
  	CHIP = NULL;
  
  	return -ENOMEM;
  }
  
  /* "mount -t gadgetfs path /dev/gadget" ends up here */
  static int gadgetfs_get_tree(struct fs_context *fc)
  {
  	return get_tree_single(fc, gadgetfs_fill_super);
  }
  
  static const struct fs_context_operations gadgetfs_context_ops = {
  	.get_tree	= gadgetfs_get_tree,
  };
  
  static int gadgetfs_init_fs_context(struct fs_context *fc)
  {
  	fc->ops = &gadgetfs_context_ops;
  	return 0;
  }
  
  static void
  gadgetfs_kill_sb (struct super_block *sb)
  {
  	kill_litter_super (sb);
  	if (the_device) {
  		put_dev (the_device);
  		the_device = NULL;
  	}
  	kfree(CHIP);
  	CHIP = NULL;
  }
  
  /*----------------------------------------------------------------------*/
  
  static struct file_system_type gadgetfs_type = {
  	.owner		= THIS_MODULE,
  	.name		= shortname,
  	.init_fs_context = gadgetfs_init_fs_context,
  	.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);
  
  