drivers/usb/core/urb.c

   1 #include <linux/module.h>
   2 #include <linux/string.h>
   3 #include <linux/bitops.h>
   4 #include <linux/slab.h>
   5 #include <linux/init.h>
   6 #include <linux/log2.h>
   7 #include <linux/usb.h>
   8 #include <linux/wait.h>
   9 #include <linux/usb/hcd.h>
  10 #include <linux/scatterlist.h>
  11
  12 #define to_urb(d) container_of(d, struct urb, kref)
  13
  14
  15 static void urb_destroy(struct kref *kref)
  16 {
  17         struct urb *urb = to_urb(kref);
  18
  19         if (urb->transfer_flags & URB_FREE_BUFFER)
  20                 kfree(urb->transfer_buffer);
  21
  22         kfree(urb);
  23 }
  24
  25 /**
  26  * usb_init_urb - initializes a urb so that it can be used by a USB driver
  27  * @urb: pointer to the urb to initialize
  28  *
  29  * Initializes a urb so that the USB subsystem can use it properly.
  30  *
  31  * If a urb is created with a call to usb_alloc_urb() it is not
  32  * necessary to call this function.  Only use this if you allocate the
  33  * space for a struct urb on your own.  If you call this function, be
  34  * careful when freeing the memory for your urb that it is no longer in
  35  * use by the USB core.
  36  *
  37  * Only use this function if you _really_ understand what you are doing.
  38  */
  39 void usb_init_urb(struct urb *urb)
  40 {
  41         if (urb) {
  42                 memset(urb, 0, sizeof(*urb));
  43                 kref_init(&urb->kref);
  44                 INIT_LIST_HEAD(&urb->anchor_list);
  45         }
  46 }
  47 EXPORT_SYMBOL_GPL(usb_init_urb);
  48
  49 /**
  50  * usb_alloc_urb - creates a new urb for a USB driver to use
  51  * @iso_packets: number of iso packets for this urb
  52  * @mem_flags: the type of memory to allocate, see kmalloc() for a list of
  53  *      valid options for this.
  54  *
  55  * Creates an urb for the USB driver to use, initializes a few internal
  56  * structures, incrementes the usage counter, and returns a pointer to it.
  57  *
  58  * If the driver want to use this urb for interrupt, control, or bulk
  59  * endpoints, pass '0' as the number of iso packets.
  60  *
  61  * The driver must call usb_free_urb() when it is finished with the urb.
  62  *
  63  * Return: A pointer to the new urb, or %NULL if no memory is available.
  64  */
  65 struct urb *usb_alloc_urb(int iso_packets, gfp_t mem_flags)
  66 {
  67         struct urb *urb;
  68
  69         urb = kmalloc(sizeof(struct urb) +
  70                 iso_packets * sizeof(struct usb_iso_packet_descriptor),
  71                 mem_flags);
  72         if (!urb) {
  73                 printk(KERN_ERR "alloc_urb: kmalloc failed\n");
  74                 return NULL;
  75         }
  76         usb_init_urb(urb);
  77         return urb;
  78 }
  79 EXPORT_SYMBOL_GPL(usb_alloc_urb);
  80
  81 /**
  82  * usb_free_urb - frees the memory used by a urb when all users of it are finished
  83  * @urb: pointer to the urb to free, may be NULL
  84  *
  85  * Must be called when a user of a urb is finished with it.  When the last user
  86  * of the urb calls this function, the memory of the urb is freed.
  87  *
  88  * Note: The transfer buffer associated with the urb is not freed unless the
  89  * URB_FREE_BUFFER transfer flag is set.
  90  */
  91 void usb_free_urb(struct urb *urb)
  92 {
  93         if (urb)
  94                 kref_put(&urb->kref, urb_destroy);
  95 }
  96 EXPORT_SYMBOL_GPL(usb_free_urb);
  97
  98 /**
  99  * usb_get_urb - increments the reference count of the urb
 100  * @urb: pointer to the urb to modify, may be NULL
 101  *
 102  * This must be  called whenever a urb is transferred from a device driver to a
 103  * host controller driver.  This allows proper reference counting to happen
 104  * for urbs.
 105  *
 106  * Return: A pointer to the urb with the incremented reference counter.
 107  */
 108 struct urb *usb_get_urb(struct urb *urb)
 109 {
 110         if (urb)
 111                 kref_get(&urb->kref);
 112         return urb;
 113 }
 114 EXPORT_SYMBOL_GPL(usb_get_urb);
 115
 116 /**
 117  * usb_anchor_urb - anchors an URB while it is processed
 118  * @urb: pointer to the urb to anchor
 119  * @anchor: pointer to the anchor
 120  *
 121  * This can be called to have access to URBs which are to be executed
 122  * without bothering to track them
 123  */
 124 void usb_anchor_urb(struct urb *urb, struct usb_anchor *anchor)
 125 {
 126         unsigned long flags;
 127
 128         spin_lock_irqsave(&anchor->lock, flags);
 129         usb_get_urb(urb);
 130         list_add_tail(&urb->anchor_list, &anchor->urb_list);
 131         urb->anchor = anchor;
 132
 133         if (unlikely(anchor->poisoned)) {
 134                 atomic_inc(&urb->reject);
 135         }
 136
 137         spin_unlock_irqrestore(&anchor->lock, flags);
 138 }
 139 EXPORT_SYMBOL_GPL(usb_anchor_urb);
 140
 141 /* Callers must hold anchor->lock */
 142 static void __usb_unanchor_urb(struct urb *urb, struct usb_anchor *anchor)
 143 {
 144         urb->anchor = NULL;
 145         list_del(&urb->anchor_list);
 146         usb_put_urb(urb);
 147         if (list_empty(&anchor->urb_list))
 148                 wake_up(&anchor->wait);
 149 }
 150
 151 /**
 152  * usb_unanchor_urb - unanchors an URB
 153  * @urb: pointer to the urb to anchor
 154  *
 155  * Call this to stop the system keeping track of this URB
 156  */
 157 void usb_unanchor_urb(struct urb *urb)
 158 {
 159         unsigned long flags;
 160         struct usb_anchor *anchor;
 161
 162         if (!urb)
 163                 return;
 164
 165         anchor = urb->anchor;
 166         if (!anchor)
 167                 return;
 168
 169         spin_lock_irqsave(&anchor->lock, flags);
 170         /*
 171          * At this point, we could be competing with another thread which
 172          * has the same intention. To protect the urb from being unanchored
 173          * twice, only the winner of the race gets the job.
 174          */
 175         if (likely(anchor == urb->anchor))
 176                 __usb_unanchor_urb(urb, anchor);
 177         spin_unlock_irqrestore(&anchor->lock, flags);
 178 }
 179 EXPORT_SYMBOL_GPL(usb_unanchor_urb);
 180
 181 /*-------------------------------------------------------------------*/
 182
 183 /**
 184  * usb_submit_urb - issue an asynchronous transfer request for an endpoint
 185  * @urb: pointer to the urb describing the request
 186  * @mem_flags: the type of memory to allocate, see kmalloc() for a list
 187  *      of valid options for this.
 188  *
 189  * This submits a transfer request, and transfers control of the URB
 190  * describing that request to the USB subsystem.  Request completion will
 191  * be indicated later, asynchronously, by calling the completion handler.
 192  * The three types of completion are success, error, and unlink
 193  * (a software-induced fault, also called "request cancellation").
 194  *
 195  * URBs may be submitted in interrupt context.
 196  *
 197  * The caller must have correctly initialized the URB before submitting
 198  * it.  Functions such as usb_fill_bulk_urb() and usb_fill_control_urb() are
 199  * available to ensure that most fields are correctly initialized, for
 200  * the particular kind of transfer, although they will not initialize
 201  * any transfer flags.
 202  *
 203  * If the submission is successful, the complete() callback from the URB
 204  * will be called exactly once, when the USB core and Host Controller Driver
 205  * (HCD) are finished with the URB.  When the completion function is called,
 206  * control of the URB is returned to the device driver which issued the
 207  * request.  The completion handler may then immediately free or reuse that
 208  * URB.
 209  *
 210  * With few exceptions, USB device drivers should never access URB fields
 211  * provided by usbcore or the HCD until its complete() is called.
 212  * The exceptions relate to periodic transfer scheduling.  For both
 213  * interrupt and isochronous urbs, as part of successful URB submission
 214  * urb->interval is modified to reflect the actual transfer period used
 215  * (normally some power of two units).  And for isochronous urbs,
 216  * urb->start_frame is modified to reflect when the URB's transfers were
 217  * scheduled to start.
 218  *
 219  * Not all isochronous transfer scheduling policies will work, but most
 220  * host controller drivers should easily handle ISO queues going from now
 221  * until 10-200 msec into the future.  Drivers should try to keep at
 222  * least one or two msec of data in the queue; many controllers require
 223  * that new transfers start at least 1 msec in the future when they are
 224  * added.  If the driver is unable to keep up and the queue empties out,
 225  * the behavior for new submissions is governed by the URB_ISO_ASAP flag.
 226  * If the flag is set, or if the queue is idle, then the URB is always
 227  * assigned to the first available (and not yet expired) slot in the
 228  * endpoint's schedule.  If the flag is not set and the queue is active
 229  * then the URB is always assigned to the next slot in the schedule
 230  * following the end of the endpoint's previous URB, even if that slot is
 231  * in the past.  When a packet is assigned in this way to a slot that has
 232  * already expired, the packet is not transmitted and the corresponding
 233  * usb_iso_packet_descriptor's status field will return -EXDEV.  If this
 234  * would happen to all the packets in the URB, submission fails with a
 235  * -EXDEV error code.
 236  *
 237  * For control endpoints, the synchronous usb_control_msg() call is
 238  * often used (in non-interrupt context) instead of this call.
 239  * That is often used through convenience wrappers, for the requests
 240  * that are standardized in the USB 2.0 specification.  For bulk
 241  * endpoints, a synchronous usb_bulk_msg() call is available.
 242  *
 243  * Return:
 244  * 0 on successful submissions. A negative error number otherwise.
 245  *
 246  * Request Queuing:
 247  *
 248  * URBs may be submitted to endpoints before previous ones complete, to
 249  * minimize the impact of interrupt latencies and system overhead on data
 250  * throughput.  With that queuing policy, an endpoint's queue would never
 251  * be empty.  This is required for continuous isochronous data streams,
 252  * and may also be required for some kinds of interrupt transfers. Such
 253  * queuing also maximizes bandwidth utilization by letting USB controllers
 254  * start work on later requests before driver software has finished the
 255  * completion processing for earlier (successful) requests.
 256  *
 257  * As of Linux 2.6, all USB endpoint transfer queues support depths greater
 258  * than one.  This was previously a HCD-specific behavior, except for ISO
 259  * transfers.  Non-isochronous endpoint queues are inactive during cleanup
 260  * after faults (transfer errors or cancellation).
 261  *
 262  * Reserved Bandwidth Transfers:
 263  *
 264  * Periodic transfers (interrupt or isochronous) are performed repeatedly,
 265  * using the interval specified in the urb.  Submitting the first urb to
 266  * the endpoint reserves the bandwidth necessary to make those transfers.
 267  * If the USB subsystem can't allocate sufficient bandwidth to perform
 268  * the periodic request, submitting such a periodic request should fail.
 269  *
 270  * For devices under xHCI, the bandwidth is reserved at configuration time, or
 271  * when the alt setting is selected.  If there is not enough bus bandwidth, the
 272  * configuration/alt setting request will fail.  Therefore, submissions to
 273  * periodic endpoints on devices under xHCI should never fail due to bandwidth
 274  * constraints.
 275  *
 276  * Device drivers must explicitly request that repetition, by ensuring that
 277  * some URB is always on the endpoint's queue (except possibly for short
 278  * periods during completion callacks).  When there is no longer an urb
 279  * queued, the endpoint's bandwidth reservation is canceled.  This means
 280  * drivers can use their completion handlers to ensure they keep bandwidth
 281  * they need, by reinitializing and resubmitting the just-completed urb
 282  * until the driver longer needs that periodic bandwidth.
 283  *
 284  * Memory Flags:
 285  *
 286  * The general rules for how to decide which mem_flags to use
 287  * are the same as for kmalloc.  There are four
 288  * different possible values; GFP_KERNEL, GFP_NOFS, GFP_NOIO and
 289  * GFP_ATOMIC.
 290  *
 291  * GFP_NOFS is not ever used, as it has not been implemented yet.
 292  *
 293  * GFP_ATOMIC is used when
 294  *   (a) you are inside a completion handler, an interrupt, bottom half,
 295  *       tasklet or timer, or
 296  *   (b) you are holding a spinlock or rwlock (does not apply to
 297  *       semaphores), or
 298  *   (c) current->state != TASK_RUNNING, this is the case only after
 299  *       you've changed it.
 300  *
 301  * GFP_NOIO is used in the block io path and error handling of storage
 302  * devices.
 303  *
 304  * All other situations use GFP_KERNEL.
 305  *
 306  * Some more specific rules for mem_flags can be inferred, such as
 307  *  (1) start_xmit, timeout, and receive methods of network drivers must
 308  *      use GFP_ATOMIC (they are called with a spinlock held);
 309  *  (2) queuecommand methods of scsi drivers must use GFP_ATOMIC (also
 310  *      called with a spinlock held);
 311  *  (3) If you use a kernel thread with a network driver you must use
 312  *      GFP_NOIO, unless (b) or (c) apply;
 313  *  (4) after you have done a down() you can use GFP_KERNEL, unless (b) or (c)
 314  *      apply or your are in a storage driver's block io path;
 315  *  (5) USB probe and disconnect can use GFP_KERNEL unless (b) or (c) apply; and
 316  *  (6) changing firmware on a running storage or net device uses
 317  *      GFP_NOIO, unless b) or c) apply
 318  *
 319  */
 320 int usb_submit_urb(struct urb *urb, gfp_t mem_flags)
 321 {
 322         int                             xfertype, max;
 323         struct usb_device               *dev;
 324         struct usb_host_endpoint        *ep;
 325         int                             is_out;
 326
 327         if (!urb || !urb->complete)
 328                 return -EINVAL;
 329         if (urb->hcpriv) {
 330                 WARN_ONCE(1, "URB %p submitted while active\n", urb);
 331                 return -EBUSY;
 332         }
 333
 334         dev = urb->dev;
 335         if ((!dev) || (dev->state < USB_STATE_UNAUTHENTICATED))
 336                 return -ENODEV;
 337
 338         /* For now, get the endpoint from the pipe.  Eventually drivers
 339          * will be required to set urb->ep directly and we will eliminate
 340          * urb->pipe.
 341          */
 342         ep = usb_pipe_endpoint(dev, urb->pipe);
 343         if (!ep)
 344                 return -ENOENT;
 345
 346         urb->ep = ep;
 347         urb->status = -EINPROGRESS;
 348         urb->actual_length = 0;
 349
 350         /* Lots of sanity checks, so HCDs can rely on clean data
 351          * and don't need to duplicate tests
 352          */
 353         xfertype = usb_endpoint_type(&ep->desc);
 354         if (xfertype == USB_ENDPOINT_XFER_CONTROL) {
 355                 struct usb_ctrlrequest *setup =
 356                                 (struct usb_ctrlrequest *) urb->setup_packet;
 357
 358                 if (!setup)
 359                         return -ENOEXEC;
 360                 is_out = !(setup->bRequestType & USB_DIR_IN) ||
 361                                 !setup->wLength;
 362         } else {
 363                 is_out = usb_endpoint_dir_out(&ep->desc);
 364         }
 365
 366         /* Clear the internal flags and cache the direction for later use */
 367         urb->transfer_flags &= ~(URB_DIR_MASK | URB_DMA_MAP_SINGLE |
 368                         URB_DMA_MAP_PAGE | URB_DMA_MAP_SG | URB_MAP_LOCAL |
 369                         URB_SETUP_MAP_SINGLE | URB_SETUP_MAP_LOCAL |
 370                         URB_DMA_SG_COMBINED);
 371         urb->transfer_flags |= (is_out ? URB_DIR_OUT : URB_DIR_IN);
 372
 373         if (xfertype != USB_ENDPOINT_XFER_CONTROL &&
 374                         dev->state < USB_STATE_CONFIGURED)
 375                 return -ENODEV;
 376
 377         max = usb_endpoint_maxp(&ep->desc);
 378         if (max <= 0) {
 379                 dev_dbg(&dev->dev,
 380                         "bogus endpoint ep%d%s in %s (bad maxpacket %d)\n",
 381                         usb_endpoint_num(&ep->desc), is_out ? "out" : "in",
 382                         __func__, max);
 383                 return -EMSGSIZE;
 384         }
 385
 386         /* periodic transfers limit size per frame/uframe,
 387          * but drivers only control those sizes for ISO.
 388          * while we're checking, initialize return status.
 389          */
 390         if (xfertype == USB_ENDPOINT_XFER_ISOC) {
 391                 int     n, len;
 392
 393                 /* SuperSpeed isoc endpoints have up to 16 bursts of up to
 394                  * 3 packets each
 395                  */
 396                 if (dev->speed >= USB_SPEED_SUPER) {
 397                         int     burst = 1 + ep->ss_ep_comp.bMaxBurst;
 398                         int     mult = USB_SS_MULT(ep->ss_ep_comp.bmAttributes);
 399                         max *= burst;
 400                         max *= mult;
 401                 }
 402
 403                 /* "high bandwidth" mode, 1-3 packets/uframe? */
 404                 if (dev->speed == USB_SPEED_HIGH) {
 405                         int     mult = 1 + ((max >> 11) & 0x03);
 406                         max &= 0x07ff;
 407                         max *= mult;
 408                 }
 409
 410                 if (urb->number_of_packets <= 0)
 411                         return -EINVAL;
 412                 for (n = 0; n < urb->number_of_packets; n++) {
 413                         len = urb->iso_frame_desc[n].length;
 414                         if (len < 0 || len > max)
 415                                 return -EMSGSIZE;
 416                         urb->iso_frame_desc[n].status = -EXDEV;
 417                         urb->iso_frame_desc[n].actual_length = 0;
 418                 }
 419         } else if (urb->num_sgs && !urb->dev->bus->no_sg_constraint &&
 420                         dev->speed != USB_SPEED_WIRELESS) {
 421                 struct scatterlist *sg;
 422                 int i;
 423
 424                 for_each_sg(urb->sg, sg, urb->num_sgs - 1, i)
 425                         if (sg->length % max)
 426                                 return -EINVAL;
 427         }
 428
 429         /* the I/O buffer must be mapped/unmapped, except when length=0 */
 430         if (urb->transfer_buffer_length > INT_MAX)
 431                 return -EMSGSIZE;
 432
 433 #ifdef DEBUG
 434         /* stuff that drivers shouldn't do, but which shouldn't
 435          * cause problems in HCDs if they get it wrong.
 436          */
 437         {
 438         unsigned int    allowed;
 439         static int pipetypes[4] = {
 440                 PIPE_CONTROL, PIPE_ISOCHRONOUS, PIPE_BULK, PIPE_INTERRUPT
 441         };
 442
 443         /* Check that the pipe's type matches the endpoint's type */
 444         if (usb_pipetype(urb->pipe) != pipetypes[xfertype])
 445                 dev_WARN(&dev->dev, "BOGUS urb xfer, pipe %x != type %x\n",
 446                         usb_pipetype(urb->pipe), pipetypes[xfertype]);
 447
 448         /* Check against a simple/standard policy */
 449         allowed = (URB_NO_TRANSFER_DMA_MAP | URB_NO_INTERRUPT | URB_DIR_MASK |
 450                         URB_FREE_BUFFER);
 451         switch (xfertype) {
 452         case USB_ENDPOINT_XFER_BULK:
 453                 if (is_out)
 454                         allowed |= URB_ZERO_PACKET;
 455                 /* FALLTHROUGH */
 456         case USB_ENDPOINT_XFER_CONTROL:
 457                 allowed |= URB_NO_FSBR; /* only affects UHCI */
 458                 /* FALLTHROUGH */
 459         default:                        /* all non-iso endpoints */
 460                 if (!is_out)
 461                         allowed |= URB_SHORT_NOT_OK;
 462                 break;
 463         case USB_ENDPOINT_XFER_ISOC:
 464                 allowed |= URB_ISO_ASAP;
 465                 break;
 466         }
 467         allowed &= urb->transfer_flags;
 468
 469         /* warn if submitter gave bogus flags */
 470         if (allowed != urb->transfer_flags)
 471                 dev_WARN(&dev->dev, "BOGUS urb flags, %x --> %x\n",
 472                         urb->transfer_flags, allowed);
 473         }
 474 #endif
 475         /*
 476          * Force periodic transfer intervals to be legal values that are
 477          * a power of two (so HCDs don't need to).
 478          *
 479          * FIXME want bus->{intr,iso}_sched_horizon values here.  Each HC
 480          * supports different values... this uses EHCI/UHCI defaults (and
 481          * EHCI can use smaller non-default values).
 482          */
 483         switch (xfertype) {
 484         case USB_ENDPOINT_XFER_ISOC:
 485         case USB_ENDPOINT_XFER_INT:
 486                 /* too small? */
 487                 switch (dev->speed) {
 488                 case USB_SPEED_WIRELESS:
 489                         if (urb->interval < 6)
 490                                 return -EINVAL;
 491                         break;
 492                 default:
 493                         if (urb->interval <= 0)
 494                                 return -EINVAL;
 495                         break;
 496                 }
 497                 /* too big? */
 498                 switch (dev->speed) {
 499                 case USB_SPEED_SUPER_PLUS:
 500                 case USB_SPEED_SUPER:   /* units are 125us */
 501                         /* Handle up to 2^(16-1) microframes */
 502                         if (urb->interval > (1 << 15))
 503                                 return -EINVAL;
 504                         max = 1 << 15;
 505                         break;
 506                 case USB_SPEED_WIRELESS:
 507                         if (urb->interval > 16)
 508                                 return -EINVAL;
 509                         break;
 510                 case USB_SPEED_HIGH:    /* units are microframes */
 511                         /* NOTE usb handles 2^15 */
 512                         if (urb->interval > (1024 * 8))
 513                                 urb->interval = 1024 * 8;
 514                         max = 1024 * 8;
 515                         break;
 516                 case USB_SPEED_FULL:    /* units are frames/msec */
 517                 case USB_SPEED_LOW:
 518                         if (xfertype == USB_ENDPOINT_XFER_INT) {
 519                                 if (urb->interval > 255)
 520                                         return -EINVAL;
 521                                 /* NOTE ohci only handles up to 32 */
 522                                 max = 128;
 523                         } else {
 524                                 if (urb->interval > 1024)
 525                                         urb->interval = 1024;
 526                                 /* NOTE usb and ohci handle up to 2^15 */
 527                                 max = 1024;
 528                         }
 529                         break;
 530                 default:
 531                         return -EINVAL;
 532                 }
 533                 if (dev->speed != USB_SPEED_WIRELESS) {
 534                         /* Round down to a power of 2, no more than max */
 535                         urb->interval = min(max, 1 << ilog2(urb->interval));
 536                 }
 537         }
 538
 539         return usb_hcd_submit_urb(urb, mem_flags);
 540 }
 541 EXPORT_SYMBOL_GPL(usb_submit_urb);
 542
 543 /*-------------------------------------------------------------------*/
 544
 545 /**
 546  * usb_unlink_urb - abort/cancel a transfer request for an endpoint
 547  * @urb: pointer to urb describing a previously submitted request,
 548  *      may be NULL
 549  *
 550  * This routine cancels an in-progress request.  URBs complete only once
 551  * per submission, and may be canceled only once per submission.
 552  * Successful cancellation means termination of @urb will be expedited
 553  * and the completion handler will be called with a status code
 554  * indicating that the request has been canceled (rather than any other
 555  * code).
 556  *
 557  * Drivers should not call this routine or related routines, such as
 558  * usb_kill_urb() or usb_unlink_anchored_urbs(), after their disconnect
 559  * method has returned.  The disconnect function should synchronize with
 560  * a driver's I/O routines to insure that all URB-related activity has
 561  * completed before it returns.
 562  *
 563  * This request is asynchronous, however the HCD might call the ->complete()
 564  * callback during unlink. Therefore when drivers call usb_unlink_urb(), they
 565  * must not hold any locks that may be taken by the completion function.
 566  * Success is indicated by returning -EINPROGRESS, at which time the URB will
 567  * probably not yet have been given back to the device driver. When it is
 568  * eventually called, the completion function will see @urb->status ==
 569  * -ECONNRESET.
 570  * Failure is indicated by usb_unlink_urb() returning any other value.
 571  * Unlinking will fail when @urb is not currently "linked" (i.e., it was
 572  * never submitted, or it was unlinked before, or the hardware is already
 573  * finished with it), even if the completion handler has not yet run.
 574  *
 575  * The URB must not be deallocated while this routine is running.  In
 576  * particular, when a driver calls this routine, it must insure that the
 577  * completion handler cannot deallocate the URB.
 578  *
 579  * Return: -EINPROGRESS on success. See description for other values on
 580  * failure.
 581  *
 582  * Unlinking and Endpoint Queues:
 583  *
 584  * [The behaviors and guarantees described below do not apply to virtual
 585  * root hubs but only to endpoint queues for physical USB devices.]
 586  *
 587  * Host Controller Drivers (HCDs) place all the URBs for a particular
 588  * endpoint in a queue.  Normally the queue advances as the controller
 589  * hardware processes each request.  But when an URB terminates with an
 590  * error its queue generally stops (see below), at least until that URB's
 591  * completion routine returns.  It is guaranteed that a stopped queue
 592  * will not restart until all its unlinked URBs have been fully retired,
 593  * with their completion routines run, even if that's not until some time
 594  * after the original completion handler returns.  The same behavior and
 595  * guarantee apply when an URB terminates because it was unlinked.
 596  *
 597  * Bulk and interrupt endpoint queues are guaranteed to stop whenever an
 598  * URB terminates with any sort of error, including -ECONNRESET, -ENOENT,
 599  * and -EREMOTEIO.  Control endpoint queues behave the same way except
 600  * that they are not guaranteed to stop for -EREMOTEIO errors.  Queues
 601  * for isochronous endpoints are treated differently, because they must
 602  * advance at fixed rates.  Such queues do not stop when an URB
 603  * encounters an error or is unlinked.  An unlinked isochronous URB may
 604  * leave a gap in the stream of packets; it is undefined whether such
 605  * gaps can be filled in.
 606  *
 607  * Note that early termination of an URB because a short packet was
 608  * received will generate a -EREMOTEIO error if and only if the
 609  * URB_SHORT_NOT_OK flag is set.  By setting this flag, USB device
 610  * drivers can build deep queues for large or complex bulk transfers
 611  * and clean them up reliably after any sort of aborted transfer by
 612  * unlinking all pending URBs at the first fault.
 613  *
 614  * When a control URB terminates with an error other than -EREMOTEIO, it
 615  * is quite likely that the status stage of the transfer will not take
 616  * place.
 617  */
 618 int usb_unlink_urb(struct urb *urb)
 619 {
 620         if (!urb)
 621                 return -EINVAL;
 622         if (!urb->dev)
 623                 return -ENODEV;
 624         if (!urb->ep)
 625                 return -EIDRM;
 626         return usb_hcd_unlink_urb(urb, -ECONNRESET);
 627 }
 628 EXPORT_SYMBOL_GPL(usb_unlink_urb);
 629
 630 /**
 631  * usb_kill_urb - cancel a transfer request and wait for it to finish
 632  * @urb: pointer to URB describing a previously submitted request,
 633  *      may be NULL
 634  *
 635  * This routine cancels an in-progress request.  It is guaranteed that
 636  * upon return all completion handlers will have finished and the URB
 637  * will be totally idle and available for reuse.  These features make
 638  * this an ideal way to stop I/O in a disconnect() callback or close()
 639  * function.  If the request has not already finished or been unlinked
 640  * the completion handler will see urb->status == -ENOENT.
 641  *
 642  * While the routine is running, attempts to resubmit the URB will fail
 643  * with error -EPERM.  Thus even if the URB's completion handler always
 644  * tries to resubmit, it will not succeed and the URB will become idle.
 645  *
 646  * The URB must not be deallocated while this routine is running.  In
 647  * particular, when a driver calls this routine, it must insure that the
 648  * completion handler cannot deallocate the URB.
 649  *
 650  * This routine may not be used in an interrupt context (such as a bottom
 651  * half or a completion handler), or when holding a spinlock, or in other
 652  * situations where the caller can't schedule().
 653  *
 654  * This routine should not be called by a driver after its disconnect
 655  * method has returned.
 656  */
 657 void usb_kill_urb(struct urb *urb)
 658 {
 659         might_sleep();
 660         if (!(urb && urb->dev && urb->ep))
 661                 return;
 662         atomic_inc(&urb->reject);
 663
 664         usb_hcd_unlink_urb(urb, -ENOENT);
 665         wait_event(usb_kill_urb_queue, atomic_read(&urb->use_count) == 0);
 666
 667         atomic_dec(&urb->reject);
 668 }
 669 EXPORT_SYMBOL_GPL(usb_kill_urb);
 670
 671 /**
 672  * usb_poison_urb - reliably kill a transfer and prevent further use of an URB
 673  * @urb: pointer to URB describing a previously submitted request,
 674  *      may be NULL
 675  *
 676  * This routine cancels an in-progress request.  It is guaranteed that
 677  * upon return all completion handlers will have finished and the URB
 678  * will be totally idle and cannot be reused.  These features make
 679  * this an ideal way to stop I/O in a disconnect() callback.
 680  * If the request has not already finished or been unlinked
 681  * the completion handler will see urb->status == -ENOENT.
 682  *
 683  * After and while the routine runs, attempts to resubmit the URB will fail
 684  * with error -EPERM.  Thus even if the URB's completion handler always
 685  * tries to resubmit, it will not succeed and the URB will become idle.
 686  *
 687  * The URB must not be deallocated while this routine is running.  In
 688  * particular, when a driver calls this routine, it must insure that the
 689  * completion handler cannot deallocate the URB.
 690  *
 691  * This routine may not be used in an interrupt context (such as a bottom
 692  * half or a completion handler), or when holding a spinlock, or in other
 693  * situations where the caller can't schedule().
 694  *
 695  * This routine should not be called by a driver after its disconnect
 696  * method has returned.
 697  */
 698 void usb_poison_urb(struct urb *urb)
 699 {
 700         might_sleep();
 701         if (!urb)
 702                 return;
 703         atomic_inc(&urb->reject);
 704
 705         if (!urb->dev || !urb->ep)
 706                 return;
 707
 708         usb_hcd_unlink_urb(urb, -ENOENT);
 709         wait_event(usb_kill_urb_queue, atomic_read(&urb->use_count) == 0);
 710 }
 711 EXPORT_SYMBOL_GPL(usb_poison_urb);
 712
 713 void usb_unpoison_urb(struct urb *urb)
 714 {
 715         if (!urb)
 716                 return;
 717
 718         atomic_dec(&urb->reject);
 719 }
 720 EXPORT_SYMBOL_GPL(usb_unpoison_urb);
 721
 722 /**
 723  * usb_block_urb - reliably prevent further use of an URB
 724  * @urb: pointer to URB to be blocked, may be NULL
 725  *
 726  * After the routine has run, attempts to resubmit the URB will fail
 727  * with error -EPERM.  Thus even if the URB's completion handler always
 728  * tries to resubmit, it will not succeed and the URB will become idle.
 729  *
 730  * The URB must not be deallocated while this routine is running.  In
 731  * particular, when a driver calls this routine, it must insure that the
 732  * completion handler cannot deallocate the URB.
 733  */
 734 void usb_block_urb(struct urb *urb)
 735 {
 736         if (!urb)
 737                 return;
 738
 739         atomic_inc(&urb->reject);
 740 }
 741 EXPORT_SYMBOL_GPL(usb_block_urb);
 742
 743 /**
 744  * usb_kill_anchored_urbs - cancel transfer requests en masse
 745  * @anchor: anchor the requests are bound to
 746  *
 747  * this allows all outstanding URBs to be killed starting
 748  * from the back of the queue
 749  *
 750  * This routine should not be called by a driver after its disconnect
 751  * method has returned.
 752  */
 753 void usb_kill_anchored_urbs(struct usb_anchor *anchor)
 754 {
 755         struct urb *victim;
 756
 757         spin_lock_irq(&anchor->lock);
 758         while (!list_empty(&anchor->urb_list)) {
 759                 victim = list_entry(anchor->urb_list.prev, struct urb,
 760                                     anchor_list);
 761                 /* we must make sure the URB isn't freed before we kill it*/
 762                 usb_get_urb(victim);
 763                 spin_unlock_irq(&anchor->lock);
 764                 /* this will unanchor the URB */
 765                 usb_kill_urb(victim);
 766                 usb_put_urb(victim);
 767                 spin_lock_irq(&anchor->lock);
 768         }
 769         spin_unlock_irq(&anchor->lock);
 770 }
 771 EXPORT_SYMBOL_GPL(usb_kill_anchored_urbs);
 772
 773
 774 /**
 775  * usb_poison_anchored_urbs - cease all traffic from an anchor
 776  * @anchor: anchor the requests are bound to
 777  *
 778  * this allows all outstanding URBs to be poisoned starting
 779  * from the back of the queue. Newly added URBs will also be
 780  * poisoned
 781  *
 782  * This routine should not be called by a driver after its disconnect
 783  * method has returned.
 784  */
 785 void usb_poison_anchored_urbs(struct usb_anchor *anchor)
 786 {
 787         struct urb *victim;
 788
 789         spin_lock_irq(&anchor->lock);
 790         anchor->poisoned = 1;
 791         while (!list_empty(&anchor->urb_list)) {
 792                 victim = list_entry(anchor->urb_list.prev, struct urb,
 793                                     anchor_list);
 794                 /* we must make sure the URB isn't freed before we kill it*/
 795                 usb_get_urb(victim);
 796                 spin_unlock_irq(&anchor->lock);
 797                 /* this will unanchor the URB */
 798                 usb_poison_urb(victim);
 799                 usb_put_urb(victim);
 800                 spin_lock_irq(&anchor->lock);
 801         }
 802         spin_unlock_irq(&anchor->lock);
 803 }
 804 EXPORT_SYMBOL_GPL(usb_poison_anchored_urbs);
 805
 806 /**
 807  * usb_unpoison_anchored_urbs - let an anchor be used successfully again
 808  * @anchor: anchor the requests are bound to
 809  *
 810  * Reverses the effect of usb_poison_anchored_urbs
 811  * the anchor can be used normally after it returns
 812  */
 813 void usb_unpoison_anchored_urbs(struct usb_anchor *anchor)
 814 {
 815         unsigned long flags;
 816         struct urb *lazarus;
 817
 818         spin_lock_irqsave(&anchor->lock, flags);
 819         list_for_each_entry(lazarus, &anchor->urb_list, anchor_list) {
 820                 usb_unpoison_urb(lazarus);
 821         }
 822         anchor->poisoned = 0;
 823         spin_unlock_irqrestore(&anchor->lock, flags);
 824 }
 825 EXPORT_SYMBOL_GPL(usb_unpoison_anchored_urbs);
 826 /**
 827  * usb_unlink_anchored_urbs - asynchronously cancel transfer requests en masse
 828  * @anchor: anchor the requests are bound to
 829  *
 830  * this allows all outstanding URBs to be unlinked starting
 831  * from the back of the queue. This function is asynchronous.
 832  * The unlinking is just tiggered. It may happen after this
 833  * function has returned.
 834  *
 835  * This routine should not be called by a driver after its disconnect
 836  * method has returned.
 837  */
 838 void usb_unlink_anchored_urbs(struct usb_anchor *anchor)
 839 {
 840         struct urb *victim;
 841
 842         while ((victim = usb_get_from_anchor(anchor)) != NULL) {
 843                 usb_unlink_urb(victim);
 844                 usb_put_urb(victim);
 845         }
 846 }
 847 EXPORT_SYMBOL_GPL(usb_unlink_anchored_urbs);
 848
 849 /**
 850  * usb_wait_anchor_empty_timeout - wait for an anchor to be unused
 851  * @anchor: the anchor you want to become unused
 852  * @timeout: how long you are willing to wait in milliseconds
 853  *
 854  * Call this is you want to be sure all an anchor's
 855  * URBs have finished
 856  *
 857  * Return: Non-zero if the anchor became unused. Zero on timeout.
 858  */
 859 int usb_wait_anchor_empty_timeout(struct usb_anchor *anchor,
 860                                   unsigned int timeout)
 861 {
 862         return wait_event_timeout(anchor->wait, list_empty(&anchor->urb_list),
 863                                   msecs_to_jiffies(timeout));
 864 }
 865 EXPORT_SYMBOL_GPL(usb_wait_anchor_empty_timeout);
 866
 867 /**
 868  * usb_get_from_anchor - get an anchor's oldest urb
 869  * @anchor: the anchor whose urb you want
 870  *
 871  * This will take the oldest urb from an anchor,
 872  * unanchor and return it
 873  *
 874  * Return: The oldest urb from @anchor, or %NULL if @anchor has no
 875  * urbs associated with it.
 876  */
 877 struct urb *usb_get_from_anchor(struct usb_anchor *anchor)
 878 {
 879         struct urb *victim;
 880         unsigned long flags;
 881
 882         spin_lock_irqsave(&anchor->lock, flags);
 883         if (!list_empty(&anchor->urb_list)) {
 884                 victim = list_entry(anchor->urb_list.next, struct urb,
 885                                     anchor_list);
 886                 usb_get_urb(victim);
 887                 __usb_unanchor_urb(victim, anchor);
 888         } else {
 889                 victim = NULL;
 890         }
 891         spin_unlock_irqrestore(&anchor->lock, flags);
 892
 893         return victim;
 894 }
 895
 896 EXPORT_SYMBOL_GPL(usb_get_from_anchor);
 897
 898 /**
 899  * usb_scuttle_anchored_urbs - unanchor all an anchor's urbs
 900  * @anchor: the anchor whose urbs you want to unanchor
 901  *
 902  * use this to get rid of all an anchor's urbs
 903  */
 904 void usb_scuttle_anchored_urbs(struct usb_anchor *anchor)
 905 {
 906         struct urb *victim;
 907         unsigned long flags;
 908
 909         spin_lock_irqsave(&anchor->lock, flags);
 910         while (!list_empty(&anchor->urb_list)) {
 911                 victim = list_entry(anchor->urb_list.prev, struct urb,
 912                                     anchor_list);
 913                 __usb_unanchor_urb(victim, anchor);
 914         }
 915         spin_unlock_irqrestore(&anchor->lock, flags);
 916 }
 917
 918 EXPORT_SYMBOL_GPL(usb_scuttle_anchored_urbs);
 919
 920 /**
 921  * usb_anchor_empty - is an anchor empty
 922  * @anchor: the anchor you want to query
 923  *
 924  * Return: 1 if the anchor has no urbs associated with it.
 925  */
 926 int usb_anchor_empty(struct usb_anchor *anchor)
 927 {
 928         return list_empty(&anchor->urb_list);
 929 }
 930
 931 EXPORT_SYMBOL_GPL(usb_anchor_empty);
 932