Adding upstream version 4.19.249.upstream/4.19.249

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

1 files changed, 1196 insertions, 0 deletions

diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
new file mode 100644
index 000000000..b60a4200f
--- /dev/null
+++ b/drivers/usb/class/cdc-wdm.c
@@ -0,0 +1,1196 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * cdc-wdm.c
+ *
+ * This driver supports USB CDC WCM Device Management.
+ *
+ * Copyright (c) 2007-2009 Oliver Neukum
+ *
+ * Some code taken from cdc-acm.c
+ *
+ * Released under the GPLv2.
+ *
+ * Many thanks to Carl Nordbeck
+ */
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/ioctl.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/uaccess.h>
+#include <linux/bitops.h>
+#include <linux/poll.h>
+#include <linux/usb.h>
+#include <linux/usb/cdc.h>
+#include <asm/byteorder.h>
+#include <asm/unaligned.h>
+#include <linux/usb/cdc-wdm.h>
+
+#define DRIVER_AUTHOR "Oliver Neukum"
+#define DRIVER_DESC "USB Abstract Control Model driver for USB WCM Device Management"
+
+static const struct usb_device_id wdm_ids[] = {
+	{
+		.match_flags = USB_DEVICE_ID_MATCH_INT_CLASS |
+				 USB_DEVICE_ID_MATCH_INT_SUBCLASS,
+		.bInterfaceClass = USB_CLASS_COMM,
+		.bInterfaceSubClass = USB_CDC_SUBCLASS_DMM
+	},
+	{ }
+};
+
+MODULE_DEVICE_TABLE (usb, wdm_ids);
+
+#define WDM_MINOR_BASE	176
+
+
+#define WDM_IN_USE		1
+#define WDM_DISCONNECTING	2
+#define WDM_RESULT		3
+#define WDM_READ		4
+#define WDM_INT_STALL		5
+#define WDM_POLL_RUNNING	6
+#define WDM_RESPONDING		7
+#define WDM_SUSPENDING		8
+#define WDM_RESETTING		9
+#define WDM_OVERFLOW		10
+
+#define WDM_MAX			16
+
+/* we cannot wait forever at flush() */
+#define WDM_FLUSH_TIMEOUT	(30 * HZ)
+
+/* CDC-WMC r1.1 requires wMaxCommand to be "at least 256 decimal (0x100)" */
+#define WDM_DEFAULT_BUFSIZE	256
+
+static DEFINE_MUTEX(wdm_mutex);
+static DEFINE_SPINLOCK(wdm_device_list_lock);
+static LIST_HEAD(wdm_device_list);
+
+/* --- method tables --- */
+
+struct wdm_device {
+	u8			*inbuf; /* buffer for response */
+	u8			*outbuf; /* buffer for command */
+	u8			*sbuf; /* buffer for status */
+	u8			*ubuf; /* buffer for copy to user space */
+
+	struct urb		*command;
+	struct urb		*response;
+	struct urb		*validity;
+	struct usb_interface	*intf;
+	struct usb_ctrlrequest	*orq;
+	struct usb_ctrlrequest	*irq;
+	spinlock_t		iuspin;
+
+	unsigned long		flags;
+	u16			bufsize;
+	u16			wMaxCommand;
+	u16			wMaxPacketSize;
+	__le16			inum;
+	int			reslength;
+	int			length;
+	int			read;
+	int			count;
+	dma_addr_t		shandle;
+	dma_addr_t		ihandle;
+	struct mutex		wlock;
+	struct mutex		rlock;
+	wait_queue_head_t	wait;
+	struct work_struct	rxwork;
+	struct work_struct	service_outs_intr;
+	int			werr;
+	int			rerr;
+	int                     resp_count;
+
+	struct list_head	device_list;
+	int			(*manage_power)(struct usb_interface *, int);
+};
+
+static struct usb_driver wdm_driver;
+
+/* return intfdata if we own the interface, else look up intf in the list */
+static struct wdm_device *wdm_find_device(struct usb_interface *intf)
+{
+	struct wdm_device *desc;
+
+	spin_lock(&wdm_device_list_lock);
+	list_for_each_entry(desc, &wdm_device_list, device_list)
+		if (desc->intf == intf)
+			goto found;
+	desc = NULL;
+found:
+	spin_unlock(&wdm_device_list_lock);
+
+	return desc;
+}
+
+static struct wdm_device *wdm_find_device_by_minor(int minor)
+{
+	struct wdm_device *desc;
+
+	spin_lock(&wdm_device_list_lock);
+	list_for_each_entry(desc, &wdm_device_list, device_list)
+		if (desc->intf->minor == minor)
+			goto found;
+	desc = NULL;
+found:
+	spin_unlock(&wdm_device_list_lock);
+
+	return desc;
+}
+
+/* --- callbacks --- */
+static void wdm_out_callback(struct urb *urb)
+{
+	struct wdm_device *desc;
+	unsigned long flags;
+
+	desc = urb->context;
+	spin_lock_irqsave(&desc->iuspin, flags);
+	desc->werr = urb->status;
+	spin_unlock_irqrestore(&desc->iuspin, flags);
+	kfree(desc->outbuf);
+	desc->outbuf = NULL;
+	clear_bit(WDM_IN_USE, &desc->flags);
+	wake_up_all(&desc->wait);
+}
+
+static void wdm_in_callback(struct urb *urb)
+{
+	unsigned long flags;
+	struct wdm_device *desc = urb->context;
+	int status = urb->status;
+	int length = urb->actual_length;
+
+	spin_lock_irqsave(&desc->iuspin, flags);
+	clear_bit(WDM_RESPONDING, &desc->flags);
+
+	if (status) {
+		switch (status) {
+		case -ENOENT:
+			dev_dbg(&desc->intf->dev,
+				"nonzero urb status received: -ENOENT\n");
+			goto skip_error;
+		case -ECONNRESET:
+			dev_dbg(&desc->intf->dev,
+				"nonzero urb status received: -ECONNRESET\n");
+			goto skip_error;
+		case -ESHUTDOWN:
+			dev_dbg(&desc->intf->dev,
+				"nonzero urb status received: -ESHUTDOWN\n");
+			goto skip_error;
+		case -EPIPE:
+			dev_err(&desc->intf->dev,
+				"nonzero urb status received: -EPIPE\n");
+			break;
+		default:
+			dev_err(&desc->intf->dev,
+				"Unexpected error %d\n", status);
+			break;
+		}
+	}
+
+	/*
+	 * only set a new error if there is no previous error.
+	 * Errors are only cleared during read/open
+	 * Avoid propagating -EPIPE (stall) to userspace since it is
+	 * better handled as an empty read
+	 */
+	if (desc->rerr == 0 && status != -EPIPE)
+		desc->rerr = status;
+
+	if (length + desc->length > desc->wMaxCommand) {
+		/* The buffer would overflow */
+		set_bit(WDM_OVERFLOW, &desc->flags);
+	} else {
+		/* we may already be in overflow */
+		if (!test_bit(WDM_OVERFLOW, &desc->flags)) {
+			memmove(desc->ubuf + desc->length, desc->inbuf, length);
+			desc->length += length;
+			desc->reslength = length;
+		}
+	}
+skip_error:
+
+	if (desc->rerr) {
+		/*
+		 * Since there was an error, userspace may decide to not read
+		 * any data after poll'ing.
+		 * We should respond to further attempts from the device to send
+		 * data, so that we can get unstuck.
+		 */
+		schedule_work(&desc->service_outs_intr);
+	} else {
+		set_bit(WDM_READ, &desc->flags);
+		wake_up(&desc->wait);
+	}
+	spin_unlock_irqrestore(&desc->iuspin, flags);
+}
+
+static void wdm_int_callback(struct urb *urb)
+{
+	unsigned long flags;
+	int rv = 0;
+	int responding;
+	int status = urb->status;
+	struct wdm_device *desc;
+	struct usb_cdc_notification *dr;
+
+	desc = urb->context;
+	dr = (struct usb_cdc_notification *)desc->sbuf;
+
+	if (status) {
+		switch (status) {
+		case -ESHUTDOWN:
+		case -ENOENT:
+		case -ECONNRESET:
+			return; /* unplug */
+		case -EPIPE:
+			set_bit(WDM_INT_STALL, &desc->flags);
+			dev_err(&desc->intf->dev, "Stall on int endpoint\n");
+			goto sw; /* halt is cleared in work */
+		default:
+			dev_err(&desc->intf->dev,
+				"nonzero urb status received: %d\n", status);
+			break;
+		}
+	}
+
+	if (urb->actual_length < sizeof(struct usb_cdc_notification)) {
+		dev_err(&desc->intf->dev, "wdm_int_callback - %d bytes\n",
+			urb->actual_length);
+		goto exit;
+	}
+
+	switch (dr->bNotificationType) {
+	case USB_CDC_NOTIFY_RESPONSE_AVAILABLE:
+		dev_dbg(&desc->intf->dev,
+			"NOTIFY_RESPONSE_AVAILABLE received: index %d len %d\n",
+			le16_to_cpu(dr->wIndex), le16_to_cpu(dr->wLength));
+		break;
+
+	case USB_CDC_NOTIFY_NETWORK_CONNECTION:
+
+		dev_dbg(&desc->intf->dev,
+			"NOTIFY_NETWORK_CONNECTION %s network\n",
+			dr->wValue ? "connected to" : "disconnected from");
+		goto exit;
+	case USB_CDC_NOTIFY_SPEED_CHANGE:
+		dev_dbg(&desc->intf->dev, "SPEED_CHANGE received (len %u)\n",
+			urb->actual_length);
+		goto exit;
+	default:
+		clear_bit(WDM_POLL_RUNNING, &desc->flags);
+		dev_err(&desc->intf->dev,
+			"unknown notification %d received: index %d len %d\n",
+			dr->bNotificationType,
+			le16_to_cpu(dr->wIndex),
+			le16_to_cpu(dr->wLength));
+		goto exit;
+	}
+
+	spin_lock_irqsave(&desc->iuspin, flags);
+	responding = test_and_set_bit(WDM_RESPONDING, &desc->flags);
+	if (!desc->resp_count++ && !responding
+		&& !test_bit(WDM_DISCONNECTING, &desc->flags)
+		&& !test_bit(WDM_SUSPENDING, &desc->flags)) {
+		rv = usb_submit_urb(desc->response, GFP_ATOMIC);
+		dev_dbg(&desc->intf->dev, "submit response URB %d\n", rv);
+	}
+	spin_unlock_irqrestore(&desc->iuspin, flags);
+	if (rv < 0) {
+		clear_bit(WDM_RESPONDING, &desc->flags);
+		if (rv == -EPERM)
+			return;
+		if (rv == -ENOMEM) {
+sw:
+			rv = schedule_work(&desc->rxwork);
+			if (rv)
+				dev_err(&desc->intf->dev,
+					"Cannot schedule work\n");
+		}
+	}
+exit:
+	rv = usb_submit_urb(urb, GFP_ATOMIC);
+	if (rv)
+		dev_err(&desc->intf->dev,
+			"%s - usb_submit_urb failed with result %d\n",
+			__func__, rv);
+
+}
+
+static void poison_urbs(struct wdm_device *desc)
+{
+	/* the order here is essential */
+	usb_poison_urb(desc->command);
+	usb_poison_urb(desc->validity);
+	usb_poison_urb(desc->response);
+}
+
+static void unpoison_urbs(struct wdm_device *desc)
+{
+	/*
+	 *  the order here is not essential
+	 *  it is symmetrical just to be nice
+	 */
+	usb_unpoison_urb(desc->response);
+	usb_unpoison_urb(desc->validity);
+	usb_unpoison_urb(desc->command);
+}
+
+static void free_urbs(struct wdm_device *desc)
+{
+	usb_free_urb(desc->validity);
+	usb_free_urb(desc->response);
+	usb_free_urb(desc->command);
+}
+
+static void cleanup(struct wdm_device *desc)
+{
+	kfree(desc->sbuf);
+	kfree(desc->inbuf);
+	kfree(desc->orq);
+	kfree(desc->irq);
+	kfree(desc->ubuf);
+	free_urbs(desc);
+	kfree(desc);
+}
+
+static ssize_t wdm_write
+(struct file *file, const char __user *buffer, size_t count, loff_t *ppos)
+{
+	u8 *buf;
+	int rv = -EMSGSIZE, r, we;
+	struct wdm_device *desc = file->private_data;
+	struct usb_ctrlrequest *req;
+
+	if (count > desc->wMaxCommand)
+		count = desc->wMaxCommand;
+
+	spin_lock_irq(&desc->iuspin);
+	we = desc->werr;
+	desc->werr = 0;
+	spin_unlock_irq(&desc->iuspin);
+	if (we < 0)
+		return usb_translate_errors(we);
+
+	buf = memdup_user(buffer, count);
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
+
+	/* concurrent writes and disconnect */
+	r = mutex_lock_interruptible(&desc->wlock);
+	rv = -ERESTARTSYS;
+	if (r)
+		goto out_free_mem;
+
+	if (test_bit(WDM_DISCONNECTING, &desc->flags)) {
+		rv = -ENODEV;
+		goto out_free_mem_lock;
+	}
+
+	r = usb_autopm_get_interface(desc->intf);
+	if (r < 0) {
+		rv = usb_translate_errors(r);
+		goto out_free_mem_lock;
+	}
+
+	if (!(file->f_flags & O_NONBLOCK))
+		r = wait_event_interruptible(desc->wait, !test_bit(WDM_IN_USE,
+								&desc->flags));
+	else
+		if (test_bit(WDM_IN_USE, &desc->flags))
+			r = -EAGAIN;
+
+	if (test_bit(WDM_RESETTING, &desc->flags))
+		r = -EIO;
+
+	if (test_bit(WDM_DISCONNECTING, &desc->flags))
+		r = -ENODEV;
+
+	if (r < 0) {
+		rv = r;
+		goto out_free_mem_pm;
+	}
+
+	req = desc->orq;
+	usb_fill_control_urb(
+		desc->command,
+		interface_to_usbdev(desc->intf),
+		/* using common endpoint 0 */
+		usb_sndctrlpipe(interface_to_usbdev(desc->intf), 0),
+		(unsigned char *)req,
+		buf,
+		count,
+		wdm_out_callback,
+		desc
+	);
+
+	req->bRequestType = (USB_DIR_OUT | USB_TYPE_CLASS |
+			     USB_RECIP_INTERFACE);
+	req->bRequest = USB_CDC_SEND_ENCAPSULATED_COMMAND;
+	req->wValue = 0;
+	req->wIndex = desc->inum; /* already converted */
+	req->wLength = cpu_to_le16(count);
+	set_bit(WDM_IN_USE, &desc->flags);
+	desc->outbuf = buf;
+
+	rv = usb_submit_urb(desc->command, GFP_KERNEL);
+	if (rv < 0) {
+		desc->outbuf = NULL;
+		clear_bit(WDM_IN_USE, &desc->flags);
+		wake_up_all(&desc->wait); /* for wdm_wait_for_response() */
+		dev_err(&desc->intf->dev, "Tx URB error: %d\n", rv);
+		rv = usb_translate_errors(rv);
+		goto out_free_mem_pm;
+	} else {
+		dev_dbg(&desc->intf->dev, "Tx URB has been submitted index=%d\n",
+			le16_to_cpu(req->wIndex));
+	}
+
+	usb_autopm_put_interface(desc->intf);
+	mutex_unlock(&desc->wlock);
+	return count;
+
+out_free_mem_pm:
+	usb_autopm_put_interface(desc->intf);
+out_free_mem_lock:
+	mutex_unlock(&desc->wlock);
+out_free_mem:
+	kfree(buf);
+	return rv;
+}
+
+/*
+ * Submit the read urb if resp_count is non-zero.
+ *
+ * Called with desc->iuspin locked
+ */
+static int service_outstanding_interrupt(struct wdm_device *desc)
+{
+	int rv = 0;
+
+	/* submit read urb only if the device is waiting for it */
+	if (!desc->resp_count || !--desc->resp_count)
+		goto out;
+
+	if (test_bit(WDM_DISCONNECTING, &desc->flags)) {
+		rv = -ENODEV;
+		goto out;
+	}
+	if (test_bit(WDM_RESETTING, &desc->flags)) {
+		rv = -EIO;
+		goto out;
+	}
+
+	set_bit(WDM_RESPONDING, &desc->flags);
+	spin_unlock_irq(&desc->iuspin);
+	rv = usb_submit_urb(desc->response, GFP_KERNEL);
+	spin_lock_irq(&desc->iuspin);
+	if (rv) {
+		if (!test_bit(WDM_DISCONNECTING, &desc->flags))
+			dev_err(&desc->intf->dev,
+				"usb_submit_urb failed with result %d\n", rv);
+
+		/* make sure the next notification trigger a submit */
+		clear_bit(WDM_RESPONDING, &desc->flags);
+		desc->resp_count = 0;
+	}
+out:
+	return rv;
+}
+
+static ssize_t wdm_read
+(struct file *file, char __user *buffer, size_t count, loff_t *ppos)
+{
+	int rv, cntr;
+	int i = 0;
+	struct wdm_device *desc = file->private_data;
+
+
+	rv = mutex_lock_interruptible(&desc->rlock); /*concurrent reads */
+	if (rv < 0)
+		return -ERESTARTSYS;
+
+	cntr = READ_ONCE(desc->length);
+	if (cntr == 0) {
+		desc->read = 0;
+retry:
+		if (test_bit(WDM_DISCONNECTING, &desc->flags)) {
+			rv = -ENODEV;
+			goto err;
+		}
+		if (test_bit(WDM_OVERFLOW, &desc->flags)) {
+			clear_bit(WDM_OVERFLOW, &desc->flags);
+			rv = -ENOBUFS;
+			goto err;
+		}
+		i++;
+		if (file->f_flags & O_NONBLOCK) {
+			if (!test_bit(WDM_READ, &desc->flags)) {
+				rv = -EAGAIN;
+				goto err;
+			}
+			rv = 0;
+		} else {
+			rv = wait_event_interruptible(desc->wait,
+				test_bit(WDM_READ, &desc->flags));
+		}
+
+		/* may have happened while we slept */
+		if (test_bit(WDM_DISCONNECTING, &desc->flags)) {
+			rv = -ENODEV;
+			goto err;
+		}
+		if (test_bit(WDM_RESETTING, &desc->flags)) {
+			rv = -EIO;
+			goto err;
+		}
+		usb_mark_last_busy(interface_to_usbdev(desc->intf));
+		if (rv < 0) {
+			rv = -ERESTARTSYS;
+			goto err;
+		}
+
+		spin_lock_irq(&desc->iuspin);
+
+		if (desc->rerr) { /* read completed, error happened */
+			rv = usb_translate_errors(desc->rerr);
+			desc->rerr = 0;
+			spin_unlock_irq(&desc->iuspin);
+			goto err;
+		}
+		/*
+		 * recheck whether we've lost the race
+		 * against the completion handler
+		 */
+		if (!test_bit(WDM_READ, &desc->flags)) { /* lost race */
+			spin_unlock_irq(&desc->iuspin);
+			goto retry;
+		}
+
+		if (!desc->reslength) { /* zero length read */
+			dev_dbg(&desc->intf->dev, "zero length - clearing WDM_READ\n");
+			clear_bit(WDM_READ, &desc->flags);
+			rv = service_outstanding_interrupt(desc);
+			spin_unlock_irq(&desc->iuspin);
+			if (rv < 0)
+				goto err;
+			goto retry;
+		}
+		cntr = desc->length;
+		spin_unlock_irq(&desc->iuspin);
+	}
+
+	if (cntr > count)
+		cntr = count;
+	rv = copy_to_user(buffer, desc->ubuf, cntr);
+	if (rv > 0) {
+		rv = -EFAULT;
+		goto err;
+	}
+
+	spin_lock_irq(&desc->iuspin);
+
+	for (i = 0; i < desc->length - cntr; i++)
+		desc->ubuf[i] = desc->ubuf[i + cntr];
+
+	desc->length -= cntr;
+	/* in case we had outstanding data */
+	if (!desc->length) {
+		clear_bit(WDM_READ, &desc->flags);
+		service_outstanding_interrupt(desc);
+	}
+	spin_unlock_irq(&desc->iuspin);
+	rv = cntr;
+
+err:
+	mutex_unlock(&desc->rlock);
+	return rv;
+}
+
+static int wdm_wait_for_response(struct file *file, long timeout)
+{
+	struct wdm_device *desc = file->private_data;
+	long rv; /* Use long here because (int) MAX_SCHEDULE_TIMEOUT < 0. */
+
+	/*
+	 * Needs both flags. We cannot do with one because resetting it would
+	 * cause a race with write() yet we need to signal a disconnect.
+	 */
+	rv = wait_event_interruptible_timeout(desc->wait,
+			      !test_bit(WDM_IN_USE, &desc->flags) ||
+			      test_bit(WDM_DISCONNECTING, &desc->flags),
+			      timeout);
+
+	/*
+	 * To report the correct error. This is best effort.
+	 * We are inevitably racing with the hardware.
+	 */
+	if (test_bit(WDM_DISCONNECTING, &desc->flags))
+		return -ENODEV;
+	if (!rv)
+		return -EIO;
+	if (rv < 0)
+		return -EINTR;
+
+	spin_lock_irq(&desc->iuspin);
+	rv = desc->werr;
+	desc->werr = 0;
+	spin_unlock_irq(&desc->iuspin);
+
+	return usb_translate_errors(rv);
+
+}
+
+/*
+ * You need to send a signal when you react to malicious or defective hardware.
+ * Also, don't abort when fsync() returned -EINVAL, for older kernels which do
+ * not implement wdm_flush() will return -EINVAL.
+ */
+static int wdm_fsync(struct file *file, loff_t start, loff_t end, int datasync)
+{
+	return wdm_wait_for_response(file, MAX_SCHEDULE_TIMEOUT);
+}
+
+/*
+ * Same with wdm_fsync(), except it uses finite timeout in order to react to
+ * malicious or defective hardware which ceased communication after close() was
+ * implicitly called due to process termination.
+ */
+static int wdm_flush(struct file *file, fl_owner_t id)
+{
+	return wdm_wait_for_response(file, WDM_FLUSH_TIMEOUT);
+}
+
+static __poll_t wdm_poll(struct file *file, struct poll_table_struct *wait)
+{
+	struct wdm_device *desc = file->private_data;
+	unsigned long flags;
+	__poll_t mask = 0;
+
+	spin_lock_irqsave(&desc->iuspin, flags);
+	if (test_bit(WDM_DISCONNECTING, &desc->flags)) {
+		mask = EPOLLHUP | EPOLLERR;
+		spin_unlock_irqrestore(&desc->iuspin, flags);
+		goto desc_out;
+	}
+	if (test_bit(WDM_READ, &desc->flags))
+		mask = EPOLLIN | EPOLLRDNORM;
+	if (desc->rerr || desc->werr)
+		mask |= EPOLLERR;
+	if (!test_bit(WDM_IN_USE, &desc->flags))
+		mask |= EPOLLOUT | EPOLLWRNORM;
+	spin_unlock_irqrestore(&desc->iuspin, flags);
+
+	poll_wait(file, &desc->wait, wait);
+
+desc_out:
+	return mask;
+}
+
+static int wdm_open(struct inode *inode, struct file *file)
+{
+	int minor = iminor(inode);
+	int rv = -ENODEV;
+	struct usb_interface *intf;
+	struct wdm_device *desc;
+
+	mutex_lock(&wdm_mutex);
+	desc = wdm_find_device_by_minor(minor);
+	if (!desc)
+		goto out;
+
+	intf = desc->intf;
+	if (test_bit(WDM_DISCONNECTING, &desc->flags))
+		goto out;
+	file->private_data = desc;
+
+	rv = usb_autopm_get_interface(desc->intf);
+	if (rv < 0) {
+		dev_err(&desc->intf->dev, "Error autopm - %d\n", rv);
+		goto out;
+	}
+
+	/* using write lock to protect desc->count */
+	mutex_lock(&desc->wlock);
+	if (!desc->count++) {
+		desc->werr = 0;
+		desc->rerr = 0;
+		rv = usb_submit_urb(desc->validity, GFP_KERNEL);
+		if (rv < 0) {
+			desc->count--;
+			dev_err(&desc->intf->dev,
+				"Error submitting int urb - %d\n", rv);
+			rv = usb_translate_errors(rv);
+		}
+	} else {
+		rv = 0;
+	}
+	mutex_unlock(&desc->wlock);
+	if (desc->count == 1)
+		desc->manage_power(intf, 1);
+	usb_autopm_put_interface(desc->intf);
+out:
+	mutex_unlock(&wdm_mutex);
+	return rv;
+}
+
+static int wdm_release(struct inode *inode, struct file *file)
+{
+	struct wdm_device *desc = file->private_data;
+
+	mutex_lock(&wdm_mutex);
+
+	/* using write lock to protect desc->count */
+	mutex_lock(&desc->wlock);
+	desc->count--;
+	mutex_unlock(&desc->wlock);
+
+	if (!desc->count) {
+		if (!test_bit(WDM_DISCONNECTING, &desc->flags)) {
+			dev_dbg(&desc->intf->dev, "wdm_release: cleanup\n");
+			poison_urbs(desc);
+			spin_lock_irq(&desc->iuspin);
+			desc->resp_count = 0;
+			clear_bit(WDM_RESPONDING, &desc->flags);
+			spin_unlock_irq(&desc->iuspin);
+			desc->manage_power(desc->intf, 0);
+			unpoison_urbs(desc);
+		} else {
+			/* must avoid dev_printk here as desc->intf is invalid */
+			pr_debug(KBUILD_MODNAME " %s: device gone - cleaning up\n", __func__);
+			cleanup(desc);
+		}
+	}
+	mutex_unlock(&wdm_mutex);
+	return 0;
+}
+
+static long wdm_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct wdm_device *desc = file->private_data;
+	int rv = 0;
+
+	switch (cmd) {
+	case IOCTL_WDM_MAX_COMMAND:
+		if (copy_to_user((void __user *)arg, &desc->wMaxCommand, sizeof(desc->wMaxCommand)))
+			rv = -EFAULT;
+		break;
+	default:
+		rv = -ENOTTY;
+	}
+	return rv;
+}
+
+static const struct file_operations wdm_fops = {
+	.owner =	THIS_MODULE,
+	.read =		wdm_read,
+	.write =	wdm_write,
+	.fsync =	wdm_fsync,
+	.open =		wdm_open,
+	.flush =	wdm_flush,
+	.release =	wdm_release,
+	.poll =		wdm_poll,
+	.unlocked_ioctl = wdm_ioctl,
+	.compat_ioctl = wdm_ioctl,
+	.llseek =	noop_llseek,
+};
+
+static struct usb_class_driver wdm_class = {
+	.name =		"cdc-wdm%d",
+	.fops =		&wdm_fops,
+	.minor_base =	WDM_MINOR_BASE,
+};
+
+/* --- error handling --- */
+static void wdm_rxwork(struct work_struct *work)
+{
+	struct wdm_device *desc = container_of(work, struct wdm_device, rxwork);
+	unsigned long flags;
+	int rv = 0;
+	int responding;
+
+	spin_lock_irqsave(&desc->iuspin, flags);
+	if (test_bit(WDM_DISCONNECTING, &desc->flags)) {
+		spin_unlock_irqrestore(&desc->iuspin, flags);
+	} else {
+		responding = test_and_set_bit(WDM_RESPONDING, &desc->flags);
+		spin_unlock_irqrestore(&desc->iuspin, flags);
+		if (!responding)
+			rv = usb_submit_urb(desc->response, GFP_KERNEL);
+		if (rv < 0 && rv != -EPERM) {
+			spin_lock_irqsave(&desc->iuspin, flags);
+			clear_bit(WDM_RESPONDING, &desc->flags);
+			if (!test_bit(WDM_DISCONNECTING, &desc->flags))
+				schedule_work(&desc->rxwork);
+			spin_unlock_irqrestore(&desc->iuspin, flags);
+		}
+	}
+}
+
+static void service_interrupt_work(struct work_struct *work)
+{
+	struct wdm_device *desc;
+
+	desc = container_of(work, struct wdm_device, service_outs_intr);
+
+	spin_lock_irq(&desc->iuspin);
+	service_outstanding_interrupt(desc);
+	if (!desc->resp_count) {
+		set_bit(WDM_READ, &desc->flags);
+		wake_up(&desc->wait);
+	}
+	spin_unlock_irq(&desc->iuspin);
+}
+
+/* --- hotplug --- */
+
+static int wdm_create(struct usb_interface *intf, struct usb_endpoint_descriptor *ep,
+		u16 bufsize, int (*manage_power)(struct usb_interface *, int))
+{
+	int rv = -ENOMEM;
+	struct wdm_device *desc;
+
+	desc = kzalloc(sizeof(struct wdm_device), GFP_KERNEL);
+	if (!desc)
+		goto out;
+	INIT_LIST_HEAD(&desc->device_list);
+	mutex_init(&desc->rlock);
+	mutex_init(&desc->wlock);
+	spin_lock_init(&desc->iuspin);
+	init_waitqueue_head(&desc->wait);
+	desc->wMaxCommand = bufsize;
+	/* this will be expanded and needed in hardware endianness */
+	desc->inum = cpu_to_le16((u16)intf->cur_altsetting->desc.bInterfaceNumber);
+	desc->intf = intf;
+	INIT_WORK(&desc->rxwork, wdm_rxwork);
+	INIT_WORK(&desc->service_outs_intr, service_interrupt_work);
+
+	rv = -EINVAL;
+	if (!usb_endpoint_is_int_in(ep))
+		goto err;
+
+	desc->wMaxPacketSize = usb_endpoint_maxp(ep);
+
+	desc->orq = kmalloc(sizeof(struct usb_ctrlrequest), GFP_KERNEL);
+	if (!desc->orq)
+		goto err;
+	desc->irq = kmalloc(sizeof(struct usb_ctrlrequest), GFP_KERNEL);
+	if (!desc->irq)
+		goto err;
+
+	desc->validity = usb_alloc_urb(0, GFP_KERNEL);
+	if (!desc->validity)
+		goto err;
+
+	desc->response = usb_alloc_urb(0, GFP_KERNEL);
+	if (!desc->response)
+		goto err;
+
+	desc->command = usb_alloc_urb(0, GFP_KERNEL);
+	if (!desc->command)
+		goto err;
+
+	desc->ubuf = kmalloc(desc->wMaxCommand, GFP_KERNEL);
+	if (!desc->ubuf)
+		goto err;
+
+	desc->sbuf = kmalloc(desc->wMaxPacketSize, GFP_KERNEL);
+	if (!desc->sbuf)
+		goto err;
+
+	desc->inbuf = kmalloc(desc->wMaxCommand, GFP_KERNEL);
+	if (!desc->inbuf)
+		goto err;
+
+	usb_fill_int_urb(
+		desc->validity,
+		interface_to_usbdev(intf),
+		usb_rcvintpipe(interface_to_usbdev(intf), ep->bEndpointAddress),
+		desc->sbuf,
+		desc->wMaxPacketSize,
+		wdm_int_callback,
+		desc,
+		ep->bInterval
+	);
+
+	desc->irq->bRequestType = (USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE);
+	desc->irq->bRequest = USB_CDC_GET_ENCAPSULATED_RESPONSE;
+	desc->irq->wValue = 0;
+	desc->irq->wIndex = desc->inum; /* already converted */
+	desc->irq->wLength = cpu_to_le16(desc->wMaxCommand);
+
+	usb_fill_control_urb(
+		desc->response,
+		interface_to_usbdev(intf),
+		/* using common endpoint 0 */
+		usb_rcvctrlpipe(interface_to_usbdev(desc->intf), 0),
+		(unsigned char *)desc->irq,
+		desc->inbuf,
+		desc->wMaxCommand,
+		wdm_in_callback,
+		desc
+	);
+
+	desc->manage_power = manage_power;
+
+	spin_lock(&wdm_device_list_lock);
+	list_add(&desc->device_list, &wdm_device_list);
+	spin_unlock(&wdm_device_list_lock);
+
+	rv = usb_register_dev(intf, &wdm_class);
+	if (rv < 0)
+		goto err;
+	else
+		dev_info(&intf->dev, "%s: USB WDM device\n", dev_name(intf->usb_dev));
+out:
+	return rv;
+err:
+	spin_lock(&wdm_device_list_lock);
+	list_del(&desc->device_list);
+	spin_unlock(&wdm_device_list_lock);
+	cleanup(desc);
+	return rv;
+}
+
+static int wdm_manage_power(struct usb_interface *intf, int on)
+{
+	/* need autopm_get/put here to ensure the usbcore sees the new value */
+	int rv = usb_autopm_get_interface(intf);
+
+	intf->needs_remote_wakeup = on;
+	if (!rv)
+		usb_autopm_put_interface(intf);
+	return 0;
+}
+
+static int wdm_probe(struct usb_interface *intf, const struct usb_device_id *id)
+{
+	int rv = -EINVAL;
+	struct usb_host_interface *iface;
+	struct usb_endpoint_descriptor *ep;
+	struct usb_cdc_parsed_header hdr;
+	u8 *buffer = intf->altsetting->extra;
+	int buflen = intf->altsetting->extralen;
+	u16 maxcom = WDM_DEFAULT_BUFSIZE;
+
+	if (!buffer)
+		goto err;
+
+	cdc_parse_cdc_header(&hdr, intf, buffer, buflen);
+
+	if (hdr.usb_cdc_dmm_desc)
+		maxcom = le16_to_cpu(hdr.usb_cdc_dmm_desc->wMaxCommand);
+
+	iface = intf->cur_altsetting;
+	if (iface->desc.bNumEndpoints != 1)
+		goto err;
+	ep = &iface->endpoint[0].desc;
+
+	rv = wdm_create(intf, ep, maxcom, &wdm_manage_power);
+
+err:
+	return rv;
+}
+
+/**
+ * usb_cdc_wdm_register - register a WDM subdriver
+ * @intf: usb interface the subdriver will associate with
+ * @ep: interrupt endpoint to monitor for notifications
+ * @bufsize: maximum message size to support for read/write
+ *
+ * Create WDM usb class character device and associate it with intf
+ * without binding, allowing another driver to manage the interface.
+ *
+ * The subdriver will manage the given interrupt endpoint exclusively
+ * and will issue control requests referring to the given intf. It
+ * will otherwise avoid interferring, and in particular not do
+ * usb_set_intfdata/usb_get_intfdata on intf.
+ *
+ * The return value is a pointer to the subdriver's struct usb_driver.
+ * The registering driver is responsible for calling this subdriver's
+ * disconnect, suspend, resume, pre_reset and post_reset methods from
+ * its own.
+ */
+struct usb_driver *usb_cdc_wdm_register(struct usb_interface *intf,
+					struct usb_endpoint_descriptor *ep,
+					int bufsize,
+					int (*manage_power)(struct usb_interface *, int))
+{
+	int rv = -EINVAL;
+
+	rv = wdm_create(intf, ep, bufsize, manage_power);
+	if (rv < 0)
+		goto err;
+
+	return &wdm_driver;
+err:
+	return ERR_PTR(rv);
+}
+EXPORT_SYMBOL(usb_cdc_wdm_register);
+
+static void wdm_disconnect(struct usb_interface *intf)
+{
+	struct wdm_device *desc;
+	unsigned long flags;
+
+	usb_deregister_dev(intf, &wdm_class);
+	desc = wdm_find_device(intf);
+	mutex_lock(&wdm_mutex);
+
+	/* the spinlock makes sure no new urbs are generated in the callbacks */
+	spin_lock_irqsave(&desc->iuspin, flags);
+	set_bit(WDM_DISCONNECTING, &desc->flags);
+	set_bit(WDM_READ, &desc->flags);
+	spin_unlock_irqrestore(&desc->iuspin, flags);
+	wake_up_all(&desc->wait);
+	mutex_lock(&desc->rlock);
+	mutex_lock(&desc->wlock);
+	poison_urbs(desc);
+	cancel_work_sync(&desc->rxwork);
+	cancel_work_sync(&desc->service_outs_intr);
+	mutex_unlock(&desc->wlock);
+	mutex_unlock(&desc->rlock);
+
+	/* the desc->intf pointer used as list key is now invalid */
+	spin_lock(&wdm_device_list_lock);
+	list_del(&desc->device_list);
+	spin_unlock(&wdm_device_list_lock);
+
+	if (!desc->count)
+		cleanup(desc);
+	else
+		dev_dbg(&intf->dev, "%d open files - postponing cleanup\n", desc->count);
+	mutex_unlock(&wdm_mutex);
+}
+
+#ifdef CONFIG_PM
+static int wdm_suspend(struct usb_interface *intf, pm_message_t message)
+{
+	struct wdm_device *desc = wdm_find_device(intf);
+	int rv = 0;
+
+	dev_dbg(&desc->intf->dev, "wdm%d_suspend\n", intf->minor);
+
+	/* if this is an autosuspend the caller does the locking */
+	if (!PMSG_IS_AUTO(message)) {
+		mutex_lock(&desc->rlock);
+		mutex_lock(&desc->wlock);
+	}
+	spin_lock_irq(&desc->iuspin);
+
+	if (PMSG_IS_AUTO(message) &&
+			(test_bit(WDM_IN_USE, &desc->flags)
+			|| test_bit(WDM_RESPONDING, &desc->flags))) {
+		spin_unlock_irq(&desc->iuspin);
+		rv = -EBUSY;
+	} else {
+
+		set_bit(WDM_SUSPENDING, &desc->flags);
+		spin_unlock_irq(&desc->iuspin);
+		/* callback submits work - order is essential */
+		poison_urbs(desc);
+		cancel_work_sync(&desc->rxwork);
+		cancel_work_sync(&desc->service_outs_intr);
+		unpoison_urbs(desc);
+	}
+	if (!PMSG_IS_AUTO(message)) {
+		mutex_unlock(&desc->wlock);
+		mutex_unlock(&desc->rlock);
+	}
+
+	return rv;
+}
+#endif
+
+static int recover_from_urb_loss(struct wdm_device *desc)
+{
+	int rv = 0;
+
+	if (desc->count) {
+		rv = usb_submit_urb(desc->validity, GFP_NOIO);
+		if (rv < 0)
+			dev_err(&desc->intf->dev,
+				"Error resume submitting int urb - %d\n", rv);
+	}
+	return rv;
+}
+
+#ifdef CONFIG_PM
+static int wdm_resume(struct usb_interface *intf)
+{
+	struct wdm_device *desc = wdm_find_device(intf);
+	int rv;
+
+	dev_dbg(&desc->intf->dev, "wdm%d_resume\n", intf->minor);
+
+	clear_bit(WDM_SUSPENDING, &desc->flags);
+	rv = recover_from_urb_loss(desc);
+
+	return rv;
+}
+#endif
+
+static int wdm_pre_reset(struct usb_interface *intf)
+{
+	struct wdm_device *desc = wdm_find_device(intf);
+
+	/*
+	 * we notify everybody using poll of
+	 * an exceptional situation
+	 * must be done before recovery lest a spontaneous
+	 * message from the device is lost
+	 */
+	spin_lock_irq(&desc->iuspin);
+	set_bit(WDM_RESETTING, &desc->flags);	/* inform read/write */
+	set_bit(WDM_READ, &desc->flags);	/* unblock read */
+	clear_bit(WDM_IN_USE, &desc->flags);	/* unblock write */
+	desc->rerr = -EINTR;
+	spin_unlock_irq(&desc->iuspin);
+	wake_up_all(&desc->wait);
+	mutex_lock(&desc->rlock);
+	mutex_lock(&desc->wlock);
+	poison_urbs(desc);
+	cancel_work_sync(&desc->rxwork);
+	cancel_work_sync(&desc->service_outs_intr);
+	return 0;
+}
+
+static int wdm_post_reset(struct usb_interface *intf)
+{
+	struct wdm_device *desc = wdm_find_device(intf);
+	int rv;
+
+	unpoison_urbs(desc);
+	clear_bit(WDM_OVERFLOW, &desc->flags);
+	clear_bit(WDM_RESETTING, &desc->flags);
+	rv = recover_from_urb_loss(desc);
+	mutex_unlock(&desc->wlock);
+	mutex_unlock(&desc->rlock);
+	return rv;
+}
+
+static struct usb_driver wdm_driver = {
+	.name =		"cdc_wdm",
+	.probe =	wdm_probe,
+	.disconnect =	wdm_disconnect,
+#ifdef CONFIG_PM
+	.suspend =	wdm_suspend,
+	.resume =	wdm_resume,
+	.reset_resume =	wdm_resume,
+#endif
+	.pre_reset =	wdm_pre_reset,
+	.post_reset =	wdm_post_reset,
+	.id_table =	wdm_ids,
+	.supports_autosuspend = 1,
+	.disable_hub_initiated_lpm = 1,
+};
+
+module_usb_driver(wdm_driver);
+
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");