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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Released under the GPLv2 only.
  */
 
 #include <linux/module.h>
 #include <linux/string.h>
 #include <linux/bitops.h>
 #include <linux/slab.h>
 #include <linux/log2.h>
 #include <linux/usb.h>
 #include <linux/wait.h>
 #include <linux/usb/hcd.h>
 #include <linux/scatterlist.h>
 
 #define to_urb(d) container_of(d, struct urb, kref)
 
 
 static void urb_destroy(struct kref *kref)
 {
     struct urb *urb = to_urb(kref);
 
     if (urb->transfer_flags & URB_FREE_BUFFER)
         kfree(urb->transfer_buffer);
 
     kfree(urb);
 }
 
 /**
  * usb_init_urb - initializes a urb so that it can be used by a USB driver
  * @urb: pointer to the urb to initialize
  *
  * Initializes a urb so that the USB subsystem can use it properly.
  *
  * If a urb is created with a call to usb_alloc_urb() it is not
  * necessary to call this function.  Only use this if you allocate the
  * space for a struct urb on your own.  If you call this function, be
  * careful when freeing the memory for your urb that it is no longer in
  * use by the USB core.
  *
  * Only use this function if you _really_ understand what you are doing.
  */
 void usb_init_urb(struct urb *urb)
 {
     if (urb) {
         memset(urb, 0, sizeof(*urb));
         kref_init(&urb->kref);
         INIT_LIST_HEAD(&urb->urb_list);
         INIT_LIST_HEAD(&urb->anchor_list);
     }
 }
 EXPORT_SYMBOL_GPL(usb_init_urb);
 
 /**
  * usb_alloc_urb - creates a new urb for a USB driver to use
  * @iso_packets: number of iso packets for this urb
  * @mem_flags: the type of memory to allocate, see kmalloc() for a list of
  *  valid options for this.
  *
  * Creates an urb for the USB driver to use, initializes a few internal
  * structures, increments the usage counter, and returns a pointer to it.
  *
  * If the driver want to use this urb for interrupt, control, or bulk
  * endpoints, pass '0' as the number of iso packets.
  *
  * The driver must call usb_free_urb() when it is finished with the urb.
  *
  * Return: A pointer to the new urb, or %NULL if no memory is available.
  */
 struct urb *usb_alloc_urb(int iso_packets, gfp_t mem_flags)
 {
     struct urb *urb;
 
     urb = kmalloc(struct_size(urb, iso_frame_desc, iso_packets),
               mem_flags);
     if (!urb)
         return NULL;
     usb_init_urb(urb);
     return urb;
 }
 EXPORT_SYMBOL_GPL(usb_alloc_urb);
 
 /**
  * usb_free_urb - frees the memory used by a urb when all users of it are finished
  * @urb: pointer to the urb to free, may be NULL
  *
  * Must be called when a user of a urb is finished with it.  When the last user
  * of the urb calls this function, the memory of the urb is freed.
  *
  * Note: The transfer buffer associated with the urb is not freed unless the
  * URB_FREE_BUFFER transfer flag is set.
  */
 void usb_free_urb(struct urb *urb)
 {
     if (urb)
         kref_put(&urb->kref, urb_destroy);
 }
 EXPORT_SYMBOL_GPL(usb_free_urb);
 
 /**
  * usb_get_urb - increments the reference count of the urb
  * @urb: pointer to the urb to modify, may be NULL
  *
  * This must be  called whenever a urb is transferred from a device driver to a
  * host controller driver.  This allows proper reference counting to happen
  * for urbs.
  *
  * Return: A pointer to the urb with the incremented reference counter.
  */
 struct urb *usb_get_urb(struct urb *urb)
 {
     if (urb)
         kref_get(&urb->kref);
     return urb;
 }
 EXPORT_SYMBOL_GPL(usb_get_urb);
 
 /**
  * usb_anchor_urb - anchors an URB while it is processed
  * @urb: pointer to the urb to anchor
  * @anchor: pointer to the anchor
  *
  * This can be called to have access to URBs which are to be executed
  * without bothering to track them
  */
 void usb_anchor_urb(struct urb *urb, struct usb_anchor *anchor)
 {
     unsigned long flags;
 
     spin_lock_irqsave(&anchor->lock, flags);
     usb_get_urb(urb);
     list_add_tail(&urb->anchor_list, &anchor->urb_list);
     urb->anchor = anchor;
 
     if (unlikely(anchor->poisoned))
         atomic_inc(&urb->reject);
 
     spin_unlock_irqrestore(&anchor->lock, flags);
 }
 EXPORT_SYMBOL_GPL(usb_anchor_urb);
 
 static int usb_anchor_check_wakeup(struct usb_anchor *anchor)
 {
     return atomic_read(&anchor->suspend_wakeups) == 0 &&
         list_empty(&anchor->urb_list);
 }
 
 /* Callers must hold anchor->lock */
 static void __usb_unanchor_urb(struct urb *urb, struct usb_anchor *anchor)
 {
     urb->anchor = NULL;
     list_del(&urb->anchor_list);
     usb_put_urb(urb);
     if (usb_anchor_check_wakeup(anchor))
         wake_up(&anchor->wait);
 }
 
 /**
  * usb_unanchor_urb - unanchors an URB
  * @urb: pointer to the urb to anchor
  *
  * Call this to stop the system keeping track of this URB
  */
 void usb_unanchor_urb(struct urb *urb)
 {
     unsigned long flags;
     struct usb_anchor *anchor;
 
     if (!urb)
         return;
 
     anchor = urb->anchor;
     if (!anchor)
         return;
 
     spin_lock_irqsave(&anchor->lock, flags);
     /*
      * At this point, we could be competing with another thread which
      * has the same intention. To protect the urb from being unanchored
      * twice, only the winner of the race gets the job.
      */
     if (likely(anchor == urb->anchor))
         __usb_unanchor_urb(urb, anchor);
     spin_unlock_irqrestore(&anchor->lock, flags);
 }
 EXPORT_SYMBOL_GPL(usb_unanchor_urb);
 
 /*-------------------------------------------------------------------*/
 
 static const int pipetypes[4] = {
     PIPE_CONTROL, PIPE_ISOCHRONOUS, PIPE_BULK, PIPE_INTERRUPT
 };
 
 /**
  * usb_pipe_type_check - sanity check of a specific pipe for a usb device
  * @dev: struct usb_device to be checked
  * @pipe: pipe to check
  *
  * This performs a light-weight sanity check for the endpoint in the
  * given usb device.  It returns 0 if the pipe is valid for the specific usb
  * device, otherwise a negative error code.
  */
 int usb_pipe_type_check(struct usb_device *dev, unsigned int pipe)
 {
     const struct usb_host_endpoint *ep;
 
     ep = usb_pipe_endpoint(dev, pipe);
     if (!ep)
         return -EINVAL;
     if (usb_pipetype(pipe) != pipetypes[usb_endpoint_type(&ep->desc)])
         return -EINVAL;
     return 0;
 }
 EXPORT_SYMBOL_GPL(usb_pipe_type_check);
 
 /**
  * usb_urb_ep_type_check - sanity check of endpoint in the given urb
  * @urb: urb to be checked
  *
  * This performs a light-weight sanity check for the endpoint in the
  * given urb.  It returns 0 if the urb contains a valid endpoint, otherwise
  * a negative error code.
  */
 int usb_urb_ep_type_check(const struct urb *urb)
 {
     return usb_pipe_type_check(urb->dev, urb->pipe);
 }
 EXPORT_SYMBOL_GPL(usb_urb_ep_type_check);
 
 /**
  * usb_submit_urb - issue an asynchronous transfer request for an endpoint
  * @urb: pointer to the urb describing the request
  * @mem_flags: the type of memory to allocate, see kmalloc() for a list
  *  of valid options for this.
  *
  * This submits a transfer request, and transfers control of the URB
  * describing that request to the USB subsystem.  Request completion will
  * be indicated later, asynchronously, by calling the completion handler.
  * The three types of completion are success, error, and unlink
  * (a software-induced fault, also called "request cancellation").
  *
  * URBs may be submitted in interrupt context.
  *
  * The caller must have correctly initialized the URB before submitting
  * it.  Functions such as usb_fill_bulk_urb() and usb_fill_control_urb() are
  * available to ensure that most fields are correctly initialized, for
  * the particular kind of transfer, although they will not initialize
  * any transfer flags.
  *
  * If the submission is successful, the complete() callback from the URB
  * will be called exactly once, when the USB core and Host Controller Driver
  * (HCD) are finished with the URB.  When the completion function is called,
  * control of the URB is returned to the device driver which issued the
  * request.  The completion handler may then immediately free or reuse that
  * URB.
  *
  * With few exceptions, USB device drivers should never access URB fields
  * provided by usbcore or the HCD until its complete() is called.
  * The exceptions relate to periodic transfer scheduling.  For both
  * interrupt and isochronous urbs, as part of successful URB submission
  * urb->interval is modified to reflect the actual transfer period used
  * (normally some power of two units).  And for isochronous urbs,
  * urb->start_frame is modified to reflect when the URB's transfers were
  * scheduled to start.
  *
  * Not all isochronous transfer scheduling policies will work, but most
  * host controller drivers should easily handle ISO queues going from now
  * until 10-200 msec into the future.  Drivers should try to keep at
  * least one or two msec of data in the queue; many controllers require
  * that new transfers start at least 1 msec in the future when they are
  * added.  If the driver is unable to keep up and the queue empties out,
  * the behavior for new submissions is governed by the URB_ISO_ASAP flag.
  * If the flag is set, or if the queue is idle, then the URB is always
  * assigned to the first available (and not yet expired) slot in the
  * endpoint's schedule.  If the flag is not set and the queue is active
  * then the URB is always assigned to the next slot in the schedule
  * following the end of the endpoint's previous URB, even if that slot is
  * in the past.  When a packet is assigned in this way to a slot that has
  * already expired, the packet is not transmitted and the corresponding
  * usb_iso_packet_descriptor's status field will return -EXDEV.  If this
  * would happen to all the packets in the URB, submission fails with a
  * -EXDEV error code.
  *
  * For control endpoints, the synchronous usb_control_msg() call is
  * often used (in non-interrupt context) instead of this call.
  * That is often used through convenience wrappers, for the requests
  * that are standardized in the USB 2.0 specification.  For bulk
  * endpoints, a synchronous usb_bulk_msg() call is available.
  *
  * Return:
  * 0 on successful submissions. A negative error number otherwise.
  *
  * Request Queuing:
  *
  * URBs may be submitted to endpoints before previous ones complete, to
  * minimize the impact of interrupt latencies and system overhead on data
  * throughput.  With that queuing policy, an endpoint's queue would never
  * be empty.  This is required for continuous isochronous data streams,
  * and may also be required for some kinds of interrupt transfers. Such
  * queuing also maximizes bandwidth utilization by letting USB controllers
  * start work on later requests before driver software has finished the
  * completion processing for earlier (successful) requests.
  *
  * As of Linux 2.6, all USB endpoint transfer queues support depths greater
  * than one.  This was previously a HCD-specific behavior, except for ISO
  * transfers.  Non-isochronous endpoint queues are inactive during cleanup
  * after faults (transfer errors or cancellation).
  *
  * Reserved Bandwidth Transfers:
  *
  * Periodic transfers (interrupt or isochronous) are performed repeatedly,
  * using the interval specified in the urb.  Submitting the first urb to
  * the endpoint reserves the bandwidth necessary to make those transfers.
  * If the USB subsystem can't allocate sufficient bandwidth to perform
  * the periodic request, submitting such a periodic request should fail.
  *
  * For devices under xHCI, the bandwidth is reserved at configuration time, or
  * when the alt setting is selected.  If there is not enough bus bandwidth, the
  * configuration/alt setting request will fail.  Therefore, submissions to
  * periodic endpoints on devices under xHCI should never fail due to bandwidth
  * constraints.
  *
  * Device drivers must explicitly request that repetition, by ensuring that
  * some URB is always on the endpoint's queue (except possibly for short
  * periods during completion callbacks).  When there is no longer an urb
  * queued, the endpoint's bandwidth reservation is canceled.  This means
  * drivers can use their completion handlers to ensure they keep bandwidth
  * they need, by reinitializing and resubmitting the just-completed urb
  * until the driver longer needs that periodic bandwidth.
  *
  * Memory Flags:
  *
  * The general rules for how to decide which mem_flags to use
  * are the same as for kmalloc.  There are four
  * different possible values; GFP_KERNEL, GFP_NOFS, GFP_NOIO and
  * GFP_ATOMIC.
  *
  * GFP_NOFS is not ever used, as it has not been implemented yet.
  *
  * GFP_ATOMIC is used when
  *   (a) you are inside a completion handler, an interrupt, bottom half,
  *       tasklet or timer, or
  *   (b) you are holding a spinlock or rwlock (does not apply to
  *       semaphores), or
  *   (c) current->state != TASK_RUNNING, this is the case only after
  *       you've changed it.
  *
  * GFP_NOIO is used in the block io path and error handling of storage
  * devices.
  *
  * All other situations use GFP_KERNEL.
  *
  * Some more specific rules for mem_flags can be inferred, such as
  *  (1) start_xmit, timeout, and receive methods of network drivers must
  *      use GFP_ATOMIC (they are called with a spinlock held);
  *  (2) queuecommand methods of scsi drivers must use GFP_ATOMIC (also
  *      called with a spinlock held);
  *  (3) If you use a kernel thread with a network driver you must use
  *      GFP_NOIO, unless (b) or (c) apply;
  *  (4) after you have done a down() you can use GFP_KERNEL, unless (b) or (c)
  *      apply or your are in a storage driver's block io path;
  *  (5) USB probe and disconnect can use GFP_KERNEL unless (b) or (c) apply; and
  *  (6) changing firmware on a running storage or net device uses
  *      GFP_NOIO, unless b) or c) apply
  *
  */
 int usb_submit_urb(struct urb *urb, gfp_t mem_flags)
 {
     int             xfertype, max;
     struct usb_device       *dev;
     struct usb_host_endpoint    *ep;
     int             is_out;
     unsigned int            allowed;
 
     if (!urb || !urb->complete)
         return -EINVAL;
     if (urb->hcpriv) {
         WARN_ONCE(1, "URB %pK submitted while active\n", urb);
         return -EBUSY;
     }
 
     dev = urb->dev;
     if ((!dev) || (dev->state < USB_STATE_UNAUTHENTICATED))
         return -ENODEV;
 
     /* For now, get the endpoint from the pipe.  Eventually drivers
      * will be required to set urb->ep directly and we will eliminate
      * urb->pipe.
      */
     ep = usb_pipe_endpoint(dev, urb->pipe);
     if (!ep)
         return -ENOENT;
 
     urb->ep = ep;
     urb->status = -EINPROGRESS;
     urb->actual_length = 0;
 
     /* Lots of sanity checks, so HCDs can rely on clean data
      * and don't need to duplicate tests
      */
     xfertype = usb_endpoint_type(&ep->desc);
     if (xfertype == USB_ENDPOINT_XFER_CONTROL) {
         struct usb_ctrlrequest *setup =
                 (struct usb_ctrlrequest *) urb->setup_packet;
 
         if (!setup)
             return -ENOEXEC;
         is_out = !(setup->bRequestType & USB_DIR_IN) ||
                 !setup->wLength;
         dev_WARN_ONCE(&dev->dev, (usb_pipeout(urb->pipe) != is_out),
                 "BOGUS control dir, pipe %x doesn't match bRequestType %x\n",
                 urb->pipe, setup->bRequestType);
         if (le16_to_cpu(setup->wLength) != urb->transfer_buffer_length) {
             dev_dbg(&dev->dev, "BOGUS control len %d doesn't match transfer length %d\n",
                     le16_to_cpu(setup->wLength),
                     urb->transfer_buffer_length);
             return -EBADR;
         }
     } else {
         is_out = usb_endpoint_dir_out(&ep->desc);
     }
 
     /* Clear the internal flags and cache the direction for later use */
     urb->transfer_flags &= ~(URB_DIR_MASK | URB_DMA_MAP_SINGLE |
             URB_DMA_MAP_PAGE | URB_DMA_MAP_SG | URB_MAP_LOCAL |
             URB_SETUP_MAP_SINGLE | URB_SETUP_MAP_LOCAL |
             URB_DMA_SG_COMBINED);
     urb->transfer_flags |= (is_out ? URB_DIR_OUT : URB_DIR_IN);
 
     if (xfertype != USB_ENDPOINT_XFER_CONTROL &&
             dev->state < USB_STATE_CONFIGURED)
         return -ENODEV;
 
     max = usb_endpoint_maxp(&ep->desc);
     if (max <= 0) {
         dev_dbg(&dev->dev,
             "bogus endpoint ep%d%s in %s (bad maxpacket %d)\n",
             usb_endpoint_num(&ep->desc), is_out ? "out" : "in",
             __func__, max);
         return -EMSGSIZE;
     }
 
     /* periodic transfers limit size per frame/uframe,
      * but drivers only control those sizes for ISO.
      * while we're checking, initialize return status.
      */
     if (xfertype == USB_ENDPOINT_XFER_ISOC) {
         int n, len;
 
         /* SuperSpeed isoc endpoints have up to 16 bursts of up to
          * 3 packets each
          */
         if (dev->speed >= USB_SPEED_SUPER) {
             int     burst = 1 + ep->ss_ep_comp.bMaxBurst;
             int     mult = USB_SS_MULT(ep->ss_ep_comp.bmAttributes);
             max *= burst;
             max *= mult;
         }
 
         if (dev->speed == USB_SPEED_SUPER_PLUS &&
             USB_SS_SSP_ISOC_COMP(ep->ss_ep_comp.bmAttributes)) {
             struct usb_ssp_isoc_ep_comp_descriptor *isoc_ep_comp;
 
             isoc_ep_comp = &ep->ssp_isoc_ep_comp;
             max = le32_to_cpu(isoc_ep_comp->dwBytesPerInterval);
         }
 
         /* "high bandwidth" mode, 1-3 packets/uframe? */
         if (dev->speed == USB_SPEED_HIGH)
             max *= usb_endpoint_maxp_mult(&ep->desc);
 
         if (urb->number_of_packets <= 0)
             return -EINVAL;
         for (n = 0; n < urb->number_of_packets; n++) {
             len = urb->iso_frame_desc[n].length;
             if (len < 0 || len > max)
                 return -EMSGSIZE;
             urb->iso_frame_desc[n].status = -EXDEV;
             urb->iso_frame_desc[n].actual_length = 0;
         }
     } else if (urb->num_sgs && !urb->dev->bus->no_sg_constraint &&
             dev->speed != USB_SPEED_WIRELESS) {
         struct scatterlist *sg;
         int i;
 
         for_each_sg(urb->sg, sg, urb->num_sgs - 1, i)
             if (sg->length % max)
                 return -EINVAL;
     }
 
     /* the I/O buffer must be mapped/unmapped, except when length=0 */
     if (urb->transfer_buffer_length > INT_MAX)
         return -EMSGSIZE;
 
     /*
      * stuff that drivers shouldn't do, but which shouldn't
      * cause problems in HCDs if they get it wrong.
      */
 
     /* Check that the pipe's type matches the endpoint's type */
     if (usb_pipe_type_check(urb->dev, urb->pipe))
         dev_WARN(&dev->dev, "BOGUS urb xfer, pipe %x != type %x\n",
             usb_pipetype(urb->pipe), pipetypes[xfertype]);
 
     /* Check against a simple/standard policy */
     allowed = (URB_NO_TRANSFER_DMA_MAP | URB_NO_INTERRUPT | URB_DIR_MASK |
             URB_FREE_BUFFER);
     switch (xfertype) {
     case USB_ENDPOINT_XFER_BULK:
     case USB_ENDPOINT_XFER_INT:
         if (is_out)
             allowed |= URB_ZERO_PACKET;
         fallthrough;
     default:            /* all non-iso endpoints */
         if (!is_out)
             allowed |= URB_SHORT_NOT_OK;
         break;
     case USB_ENDPOINT_XFER_ISOC:
         allowed |= URB_ISO_ASAP;
         break;
     }
     allowed &= urb->transfer_flags;
 
     /* warn if submitter gave bogus flags */
     if (allowed != urb->transfer_flags)
         dev_WARN(&dev->dev, "BOGUS urb flags, %x --> %x\n",
             urb->transfer_flags, allowed);
 
     /*
      * Force periodic transfer intervals to be legal values that are
      * a power of two (so HCDs don't need to).
      *
      * FIXME want bus->{intr,iso}_sched_horizon values here.  Each HC
      * supports different values... this uses EHCI/UHCI defaults (and
      * EHCI can use smaller non-default values).
      */
     switch (xfertype) {
     case USB_ENDPOINT_XFER_ISOC:
     case USB_ENDPOINT_XFER_INT:
         /* too small? */
         switch (dev->speed) {
         case USB_SPEED_WIRELESS:
             if ((urb->interval < 6)
                 && (xfertype == USB_ENDPOINT_XFER_INT))
                 return -EINVAL;
             fallthrough;
         default:
             if (urb->interval <= 0)
                 return -EINVAL;
             break;
         }
         /* too big? */
         switch (dev->speed) {
         case USB_SPEED_SUPER_PLUS:
         case USB_SPEED_SUPER:   /* units are 125us */
             /* Handle up to 2^(16-1) microframes */
             if (urb->interval > (1 << 15))
                 return -EINVAL;
             max = 1 << 15;
             break;
         case USB_SPEED_WIRELESS:
             if (urb->interval > 16)
                 return -EINVAL;
             break;
         case USB_SPEED_HIGH:    /* units are microframes */
             /* NOTE usb handles 2^15 */
             if (urb->interval > (1024 * 8))
                 urb->interval = 1024 * 8;
             max = 1024 * 8;
             break;
         case USB_SPEED_FULL:    /* units are frames/msec */
         case USB_SPEED_LOW:
             if (xfertype == USB_ENDPOINT_XFER_INT) {
                 if (urb->interval > 255)
                     return -EINVAL;
                 /* NOTE ohci only handles up to 32 */
                 max = 128;
             } else {
                 if (urb->interval > 1024)
                     urb->interval = 1024;
                 /* NOTE usb and ohci handle up to 2^15 */
                 max = 1024;
             }
             break;
         default:
             return -EINVAL;
         }
         if (dev->speed != USB_SPEED_WIRELESS) {
             /* Round down to a power of 2, no more than max */
             urb->interval = min(max, 1 << ilog2(urb->interval));
         }
     }
 
     return usb_hcd_submit_urb(urb, mem_flags);
 }
 EXPORT_SYMBOL_GPL(usb_submit_urb);
 
 /*-------------------------------------------------------------------*/
 
 /**
  * usb_unlink_urb - abort/cancel a transfer request for an endpoint
  * @urb: pointer to urb describing a previously submitted request,
  *  may be NULL
  *
  * This routine cancels an in-progress request.  URBs complete only once
  * per submission, and may be canceled only once per submission.
  * Successful cancellation means termination of @urb will be expedited
  * and the completion handler will be called with a status code
  * indicating that the request has been canceled (rather than any other
  * code).
  *
  * Drivers should not call this routine or related routines, such as
  * usb_kill_urb() or usb_unlink_anchored_urbs(), after their disconnect
  * method has returned.  The disconnect function should synchronize with
  * a driver's I/O routines to insure that all URB-related activity has
  * completed before it returns.
  *
  * This request is asynchronous, however the HCD might call the ->complete()
  * callback during unlink. Therefore when drivers call usb_unlink_urb(), they
  * must not hold any locks that may be taken by the completion function.
  * Success is indicated by returning -EINPROGRESS, at which time the URB will
  * probably not yet have been given back to the device driver. When it is
  * eventually called, the completion function will see @urb->status ==
  * -ECONNRESET.
  * Failure is indicated by usb_unlink_urb() returning any other value.
  * Unlinking will fail when @urb is not currently "linked" (i.e., it was
  * never submitted, or it was unlinked before, or the hardware is already
  * finished with it), even if the completion handler has not yet run.
  *
  * The URB must not be deallocated while this routine is running.  In
  * particular, when a driver calls this routine, it must insure that the
  * completion handler cannot deallocate the URB.
  *
  * Return: -EINPROGRESS on success. See description for other values on
  * failure.
  *
  * Unlinking and Endpoint Queues:
  *
  * [The behaviors and guarantees described below do not apply to virtual
  * root hubs but only to endpoint queues for physical USB devices.]
  *
  * Host Controller Drivers (HCDs) place all the URBs for a particular
  * endpoint in a queue.  Normally the queue advances as the controller
  * hardware processes each request.  But when an URB terminates with an
  * error its queue generally stops (see below), at least until that URB's
  * completion routine returns.  It is guaranteed that a stopped queue
  * will not restart until all its unlinked URBs have been fully retired,
  * with their completion routines run, even if that's not until some time
  * after the original completion handler returns.  The same behavior and
  * guarantee apply when an URB terminates because it was unlinked.
  *
  * Bulk and interrupt endpoint queues are guaranteed to stop whenever an
  * URB terminates with any sort of error, including -ECONNRESET, -ENOENT,
  * and -EREMOTEIO.  Control endpoint queues behave the same way except
  * that they are not guaranteed to stop for -EREMOTEIO errors.  Queues
  * for isochronous endpoints are treated differently, because they must
  * advance at fixed rates.  Such queues do not stop when an URB
  * encounters an error or is unlinked.  An unlinked isochronous URB may
  * leave a gap in the stream of packets; it is undefined whether such
  * gaps can be filled in.
  *
  * Note that early termination of an URB because a short packet was
  * received will generate a -EREMOTEIO error if and only if the
  * URB_SHORT_NOT_OK flag is set.  By setting this flag, USB device
  * drivers can build deep queues for large or complex bulk transfers
  * and clean them up reliably after any sort of aborted transfer by
  * unlinking all pending URBs at the first fault.
  *
  * When a control URB terminates with an error other than -EREMOTEIO, it
  * is quite likely that the status stage of the transfer will not take
  * place.
  */
 int usb_unlink_urb(struct urb *urb)
 {
     if (!urb)
         return -EINVAL;
     if (!urb->dev)
         return -ENODEV;
     if (!urb->ep)
         return -EIDRM;
     return usb_hcd_unlink_urb(urb, -ECONNRESET);
 }
 EXPORT_SYMBOL_GPL(usb_unlink_urb);
 
 /**
  * usb_kill_urb - cancel a transfer request and wait for it to finish
  * @urb: pointer to URB describing a previously submitted request,
  *  may be NULL
  *
  * This routine cancels an in-progress request.  It is guaranteed that
  * upon return all completion handlers will have finished and the URB
  * will be totally idle and available for reuse.  These features make
  * this an ideal way to stop I/O in a disconnect() callback or close()
  * function.  If the request has not already finished or been unlinked
  * the completion handler will see urb->status == -ENOENT.
  *
  * While the routine is running, attempts to resubmit the URB will fail
  * with error -EPERM.  Thus even if the URB's completion handler always
  * tries to resubmit, it will not succeed and the URB will become idle.
  *
  * The URB must not be deallocated while this routine is running.  In
  * particular, when a driver calls this routine, it must insure that the
  * completion handler cannot deallocate the URB.
  *
  * This routine may not be used in an interrupt context (such as a bottom
  * half or a completion handler), or when holding a spinlock, or in other
  * situations where the caller can't schedule().
  *
  * This routine should not be called by a driver after its disconnect
  * method has returned.
  */
 void usb_kill_urb(struct urb *urb)
 {
     might_sleep();
     if (!(urb && urb->dev && urb->ep))
         return;
     atomic_inc(&urb->reject);
     /*
      * Order the write of urb->reject above before the read
      * of urb->use_count below.  Pairs with the barriers in
      * __usb_hcd_giveback_urb() and usb_hcd_submit_urb().
      */
     smp_mb__after_atomic();
 
     usb_hcd_unlink_urb(urb, -ENOENT);
     wait_event(usb_kill_urb_queue, atomic_read(&urb->use_count) == 0);
 
     atomic_dec(&urb->reject);
 }
 EXPORT_SYMBOL_GPL(usb_kill_urb);
 
 /**
  * usb_poison_urb - reliably kill a transfer and prevent further use of an URB
  * @urb: pointer to URB describing a previously submitted request,
  *  may be NULL
  *
  * This routine cancels an in-progress request.  It is guaranteed that
  * upon return all completion handlers will have finished and the URB
  * will be totally idle and cannot be reused.  These features make
  * this an ideal way to stop I/O in a disconnect() callback.
  * If the request has not already finished or been unlinked
  * the completion handler will see urb->status == -ENOENT.
  *
  * After and while the routine runs, attempts to resubmit the URB will fail
  * with error -EPERM.  Thus even if the URB's completion handler always
  * tries to resubmit, it will not succeed and the URB will become idle.
  *
  * The URB must not be deallocated while this routine is running.  In
  * particular, when a driver calls this routine, it must insure that the
  * completion handler cannot deallocate the URB.
  *
  * This routine may not be used in an interrupt context (such as a bottom
  * half or a completion handler), or when holding a spinlock, or in other
  * situations where the caller can't schedule().
  *
  * This routine should not be called by a driver after its disconnect
  * method has returned.
  */
 void usb_poison_urb(struct urb *urb)
 {
     might_sleep();
     if (!urb)
         return;
     atomic_inc(&urb->reject);
     /*
      * Order the write of urb->reject above before the read
      * of urb->use_count below.  Pairs with the barriers in
      * __usb_hcd_giveback_urb() and usb_hcd_submit_urb().
      */
     smp_mb__after_atomic();
 
     if (!urb->dev || !urb->ep)
         return;
 
     usb_hcd_unlink_urb(urb, -ENOENT);
     wait_event(usb_kill_urb_queue, atomic_read(&urb->use_count) == 0);
 }
 EXPORT_SYMBOL_GPL(usb_poison_urb);
 
 void usb_unpoison_urb(struct urb *urb)
 {
     if (!urb)
         return;
 
     atomic_dec(&urb->reject);
 }
 EXPORT_SYMBOL_GPL(usb_unpoison_urb);
 
 /**
  * usb_block_urb - reliably prevent further use of an URB
  * @urb: pointer to URB to be blocked, may be NULL
  *
  * After the routine has run, attempts to resubmit the URB will fail
  * with error -EPERM.  Thus even if the URB's completion handler always
  * tries to resubmit, it will not succeed and the URB will become idle.
  *
  * The URB must not be deallocated while this routine is running.  In
  * particular, when a driver calls this routine, it must insure that the
  * completion handler cannot deallocate the URB.
  */
 void usb_block_urb(struct urb *urb)
 {
     if (!urb)
         return;
 
     atomic_inc(&urb->reject);
 }
 EXPORT_SYMBOL_GPL(usb_block_urb);
 
 /**
  * usb_kill_anchored_urbs - kill all URBs associated with an anchor
  * @anchor: anchor the requests are bound to
  *
  * This kills all outstanding URBs starting from the back of the queue,
  * with guarantee that no completer callbacks will take place from the
  * anchor after this function returns.
  *
  * This routine should not be called by a driver after its disconnect
  * method has returned.
  */
 void usb_kill_anchored_urbs(struct usb_anchor *anchor)
 {
     struct urb *victim;
     int surely_empty;
 
     do {
         spin_lock_irq(&anchor->lock);
         while (!list_empty(&anchor->urb_list)) {
             victim = list_entry(anchor->urb_list.prev,
                         struct urb, anchor_list);
             /* make sure the URB isn't freed before we kill it */
             usb_get_urb(victim);
             spin_unlock_irq(&anchor->lock);
             /* this will unanchor the URB */
             usb_kill_urb(victim);
             usb_put_urb(victim);
             spin_lock_irq(&anchor->lock);
         }
         surely_empty = usb_anchor_check_wakeup(anchor);
 
         spin_unlock_irq(&anchor->lock);
         cpu_relax();
     } while (!surely_empty);
 }
 EXPORT_SYMBOL_GPL(usb_kill_anchored_urbs);
 
 
 /**
  * usb_poison_anchored_urbs - cease all traffic from an anchor
  * @anchor: anchor the requests are bound to
  *
  * this allows all outstanding URBs to be poisoned starting
  * from the back of the queue. Newly added URBs will also be
  * poisoned
  *
  * This routine should not be called by a driver after its disconnect
  * method has returned.
  */
 void usb_poison_anchored_urbs(struct usb_anchor *anchor)
 {
     struct urb *victim;
     int surely_empty;
 
     do {
         spin_lock_irq(&anchor->lock);
         anchor->poisoned = 1;
         while (!list_empty(&anchor->urb_list)) {
             victim = list_entry(anchor->urb_list.prev,
                         struct urb, anchor_list);
             /* make sure the URB isn't freed before we kill it */
             usb_get_urb(victim);
             spin_unlock_irq(&anchor->lock);
             /* this will unanchor the URB */
             usb_poison_urb(victim);
             usb_put_urb(victim);
             spin_lock_irq(&anchor->lock);
         }
         surely_empty = usb_anchor_check_wakeup(anchor);
 
         spin_unlock_irq(&anchor->lock);
         cpu_relax();
     } while (!surely_empty);
 }
 EXPORT_SYMBOL_GPL(usb_poison_anchored_urbs);
 
 /**
  * usb_unpoison_anchored_urbs - let an anchor be used successfully again
  * @anchor: anchor the requests are bound to
  *
  * Reverses the effect of usb_poison_anchored_urbs
  * the anchor can be used normally after it returns
  */
 void usb_unpoison_anchored_urbs(struct usb_anchor *anchor)
 {
     unsigned long flags;
     struct urb *lazarus;
 
     spin_lock_irqsave(&anchor->lock, flags);
     list_for_each_entry(lazarus, &anchor->urb_list, anchor_list) {
         usb_unpoison_urb(lazarus);
     }
     anchor->poisoned = 0;
     spin_unlock_irqrestore(&anchor->lock, flags);
 }
 EXPORT_SYMBOL_GPL(usb_unpoison_anchored_urbs);
 /**
  * usb_unlink_anchored_urbs - asynchronously cancel transfer requests en masse
  * @anchor: anchor the requests are bound to
  *
  * this allows all outstanding URBs to be unlinked starting
  * from the back of the queue. This function is asynchronous.
  * The unlinking is just triggered. It may happen after this
  * function has returned.
  *
  * This routine should not be called by a driver after its disconnect
  * method has returned.
  */
 void usb_unlink_anchored_urbs(struct usb_anchor *anchor)
 {
     struct urb *victim;
 
     while ((victim = usb_get_from_anchor(anchor)) != NULL) {
         usb_unlink_urb(victim);
         usb_put_urb(victim);
     }
 }
 EXPORT_SYMBOL_GPL(usb_unlink_anchored_urbs);
 
 /**
  * usb_anchor_suspend_wakeups
  * @anchor: the anchor you want to suspend wakeups on
  *
  * Call this to stop the last urb being unanchored from waking up any
  * usb_wait_anchor_empty_timeout waiters. This is used in the hcd urb give-
  * back path to delay waking up until after the completion handler has run.
  */
 void usb_anchor_suspend_wakeups(struct usb_anchor *anchor)
 {
     if (anchor)
         atomic_inc(&anchor->suspend_wakeups);
 }
 EXPORT_SYMBOL_GPL(usb_anchor_suspend_wakeups);
 
 /**
  * usb_anchor_resume_wakeups
  * @anchor: the anchor you want to resume wakeups on
  *
  * Allow usb_wait_anchor_empty_timeout waiters to be woken up again, and
  * wake up any current waiters if the anchor is empty.
  */
 void usb_anchor_resume_wakeups(struct usb_anchor *anchor)
 {
     if (!anchor)
         return;
 
     atomic_dec(&anchor->suspend_wakeups);
     if (usb_anchor_check_wakeup(anchor))
         wake_up(&anchor->wait);
 }
 EXPORT_SYMBOL_GPL(usb_anchor_resume_wakeups);
 
 /**
  * usb_wait_anchor_empty_timeout - wait for an anchor to be unused
  * @anchor: the anchor you want to become unused
  * @timeout: how long you are willing to wait in milliseconds
  *
  * Call this is you want to be sure all an anchor's
  * URBs have finished
  *
  * Return: Non-zero if the anchor became unused. Zero on timeout.
  */
 int usb_wait_anchor_empty_timeout(struct usb_anchor *anchor,
                   unsigned int timeout)
 {
     return wait_event_timeout(anchor->wait,
                   usb_anchor_check_wakeup(anchor),
                   msecs_to_jiffies(timeout));
 }
 EXPORT_SYMBOL_GPL(usb_wait_anchor_empty_timeout);
 
 /**
  * usb_get_from_anchor - get an anchor's oldest urb
  * @anchor: the anchor whose urb you want
  *
  * This will take the oldest urb from an anchor,
  * unanchor and return it
  *
  * Return: The oldest urb from @anchor, or %NULL if @anchor has no
  * urbs associated with it.
  */
 struct urb *usb_get_from_anchor(struct usb_anchor *anchor)
 {
     struct urb *victim;
     unsigned long flags;
 
     spin_lock_irqsave(&anchor->lock, flags);
     if (!list_empty(&anchor->urb_list)) {
         victim = list_entry(anchor->urb_list.next, struct urb,
                     anchor_list);
         usb_get_urb(victim);
         __usb_unanchor_urb(victim, anchor);
     } else {
         victim = NULL;
     }
     spin_unlock_irqrestore(&anchor->lock, flags);
 
     return victim;
 }
 
 EXPORT_SYMBOL_GPL(usb_get_from_anchor);
 
 /**
  * usb_scuttle_anchored_urbs - unanchor all an anchor's urbs
  * @anchor: the anchor whose urbs you want to unanchor
  *
  * use this to get rid of all an anchor's urbs
  */
 void usb_scuttle_anchored_urbs(struct usb_anchor *anchor)
 {
     struct urb *victim;
     unsigned long flags;
     int surely_empty;
 
     do {
         spin_lock_irqsave(&anchor->lock, flags);
         while (!list_empty(&anchor->urb_list)) {
             victim = list_entry(anchor->urb_list.prev,
                         struct urb, anchor_list);
             __usb_unanchor_urb(victim, anchor);
         }
         surely_empty = usb_anchor_check_wakeup(anchor);
 
         spin_unlock_irqrestore(&anchor->lock, flags);
         cpu_relax();
     } while (!surely_empty);
 }
 
 EXPORT_SYMBOL_GPL(usb_scuttle_anchored_urbs);
 
 /**
  * usb_anchor_empty - is an anchor empty
  * @anchor: the anchor you want to query
  *
  * Return: 1 if the anchor has no urbs associated with it.
  */
 int usb_anchor_empty(struct usb_anchor *anchor)
 {
     return list_empty(&anchor->urb_list);
 }
 
 EXPORT_SYMBOL_GPL(usb_anchor_empty);
 

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