drivers/media/video/uvc/uvc_queue.c

   1 /*
   2  *      uvc_queue.c  --  USB Video Class driver - Buffers management
   3  *
   4  *      Copyright (C) 2005-2008
   5  *          Laurent Pinchart (laurent.pinchart@skynet.be)
   6  *
   7  *      This program is free software; you can redistribute it and/or modify
   8  *      it under the terms of the GNU General Public License as published by
   9  *      the Free Software Foundation; either version 2 of the License, or
  10  *      (at your option) any later version.
  11  *
  12  */
  13
  14 #include <linux/kernel.h>
  15 #include <linux/version.h>
  16 #include <linux/list.h>
  17 #include <linux/module.h>
  18 #include <linux/usb.h>
  19 #include <linux/videodev2.h>
  20 #include <linux/vmalloc.h>
  21 #include <linux/wait.h>
  22 #include <asm/atomic.h>
  23
  24 #include "uvcvideo.h"
  25
  26 /* ------------------------------------------------------------------------
  27  * Video buffers queue management.
  28  *
  29  * Video queues is initialized by uvc_queue_init(). The function performs
  30  * basic initialization of the uvc_video_queue struct and never fails.
  31  *
  32  * Video buffer allocation and freeing are performed by uvc_alloc_buffers and
  33  * uvc_free_buffers respectively. The former acquires the video queue lock,
  34  * while the later must be called with the lock held (so that allocation can
  35  * free previously allocated buffers). Trying to free buffers that are mapped
  36  * to user space will return -EBUSY.
  37  *
  38  * Video buffers are managed using two queues. However, unlike most USB video
  39  * drivers which use an in queue and an out queue, we use a main queue which
  40  * holds all queued buffers (both 'empty' and 'done' buffers), and an irq
  41  * queue which holds empty buffers. This design (copied from video-buf)
  42  * minimizes locking in interrupt, as only one queue is shared between
  43  * interrupt and user contexts.
  44  *
  45  * Use cases
  46  * ---------
  47  *
  48  * Unless stated otherwise, all operations which modify the irq buffers queue
  49  * are protected by the irq spinlock.
  50  *
  51  * 1. The user queues the buffers, starts streaming and dequeues a buffer.
  52  *
  53  *    The buffers are added to the main and irq queues. Both operations are
  54  *    protected by the queue lock, and the latert is protected by the irq
  55  *    spinlock as well.
  56  *
  57  *    The completion handler fetches a buffer from the irq queue and fills it
  58  *    with video data. If no buffer is available (irq queue empty), the handler
  59  *    returns immediately.
  60  *
  61  *    When the buffer is full, the completion handler removes it from the irq
  62  *    queue, marks it as ready (UVC_BUF_STATE_DONE) and wake its wait queue.
  63  *    At that point, any process waiting on the buffer will be woken up. If a
  64  *    process tries to dequeue a buffer after it has been marked ready, the
  65  *    dequeing will succeed immediately.
  66  *
  67  * 2. Buffers are queued, user is waiting on a buffer and the device gets
  68  *    disconnected.
  69  *
  70  *    When the device is disconnected, the kernel calls the completion handler
  71  *    with an appropriate status code. The handler marks all buffers in the
  72  *    irq queue as being erroneous (UVC_BUF_STATE_ERROR) and wakes them up so
  73  *    that any process waiting on a buffer gets woken up.
  74  *
  75  *    Waking up up the first buffer on the irq list is not enough, as the
  76  *    process waiting on the buffer might restart the dequeue operation
  77  *    immediately.
  78  *
  79  */
  80
  81 void uvc_queue_init(struct uvc_video_queue *queue)
  82 {
  83         mutex_init(&queue->mutex);
  84         spin_lock_init(&queue->irqlock);
  85         INIT_LIST_HEAD(&queue->mainqueue);
  86         INIT_LIST_HEAD(&queue->irqqueue);
  87 }
  88
  89 /*
  90  * Allocate the video buffers.
  91  *
  92  * Pages are reserved to make sure they will not be swaped, as they will be
  93  * filled in URB completion handler.
  94  *
  95  * Buffers will be individually mapped, so they must all be page aligned.
  96  */
  97 int uvc_alloc_buffers(struct uvc_video_queue *queue, unsigned int nbuffers,
  98                 unsigned int buflength)
  99 {
 100         unsigned int bufsize = PAGE_ALIGN(buflength);
 101         unsigned int i;
 102         void *mem = NULL;
 103         int ret;
 104
 105         if (nbuffers > UVC_MAX_VIDEO_BUFFERS)
 106                 nbuffers = UVC_MAX_VIDEO_BUFFERS;
 107
 108         mutex_lock(&queue->mutex);
 109
 110         if ((ret = uvc_free_buffers(queue)) < 0)
 111                 goto done;
 112
 113         /* Bail out if no buffers should be allocated. */
 114         if (nbuffers == 0)
 115                 goto done;
 116
 117         /* Decrement the number of buffers until allocation succeeds. */
 118         for (; nbuffers > 0; --nbuffers) {
 119                 mem = vmalloc_32(nbuffers * bufsize);
 120                 if (mem != NULL)
 121                         break;
 122         }
 123
 124         if (mem == NULL) {
 125                 ret = -ENOMEM;
 126                 goto done;
 127         }
 128
 129         for (i = 0; i < nbuffers; ++i) {
 130                 memset(&queue->buffer[i], 0, sizeof queue->buffer[i]);
 131                 queue->buffer[i].buf.index = i;
 132                 queue->buffer[i].buf.m.offset = i * bufsize;
 133                 queue->buffer[i].buf.length = buflength;
 134                 queue->buffer[i].buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
 135                 queue->buffer[i].buf.sequence = 0;
 136                 queue->buffer[i].buf.field = V4L2_FIELD_NONE;
 137                 queue->buffer[i].buf.memory = V4L2_MEMORY_MMAP;
 138                 queue->buffer[i].buf.flags = 0;
 139                 init_waitqueue_head(&queue->buffer[i].wait);
 140         }
 141
 142         queue->mem = mem;
 143         queue->count = nbuffers;
 144         queue->buf_size = bufsize;
 145         ret = nbuffers;
 146
 147 done:
 148         mutex_unlock(&queue->mutex);
 149         return ret;
 150 }
 151
 152 /*
 153  * Free the video buffers.
 154  *
 155  * This function must be called with the queue lock held.
 156  */
 157 int uvc_free_buffers(struct uvc_video_queue *queue)
 158 {
 159         unsigned int i;
 160
 161         for (i = 0; i < queue->count; ++i) {
 162                 if (queue->buffer[i].vma_use_count != 0)
 163                         return -EBUSY;
 164         }
 165
 166         if (queue->count) {
 167                 vfree(queue->mem);
 168                 queue->count = 0;
 169         }
 170
 171         return 0;
 172 }
 173
 174 static void __uvc_query_buffer(struct uvc_buffer *buf,
 175                 struct v4l2_buffer *v4l2_buf)
 176 {
 177         memcpy(v4l2_buf, &buf->buf, sizeof *v4l2_buf);
 178
 179         if (buf->vma_use_count)
 180                 v4l2_buf->flags |= V4L2_BUF_FLAG_MAPPED;
 181
 182         switch (buf->state) {
 183         case UVC_BUF_STATE_ERROR:
 184         case UVC_BUF_STATE_DONE:
 185                 v4l2_buf->flags |= V4L2_BUF_FLAG_DONE;
 186                 break;
 187         case UVC_BUF_STATE_QUEUED:
 188         case UVC_BUF_STATE_ACTIVE:
 189                 v4l2_buf->flags |= V4L2_BUF_FLAG_QUEUED;
 190                 break;
 191         case UVC_BUF_STATE_IDLE:
 192         default:
 193                 break;
 194         }
 195 }
 196
 197 int uvc_query_buffer(struct uvc_video_queue *queue,
 198                 struct v4l2_buffer *v4l2_buf)
 199 {
 200         int ret = 0;
 201
 202         mutex_lock(&queue->mutex);
 203         if (v4l2_buf->index >= queue->count) {
 204                 ret = -EINVAL;
 205                 goto done;
 206         }
 207
 208         __uvc_query_buffer(&queue->buffer[v4l2_buf->index], v4l2_buf);
 209
 210 done:
 211        mutex_unlock(&queue->mutex);
 212        return ret;
 213 }
 214
 215 /*
 216  * Queue a video buffer. Attempting to queue a buffer that has already been
 217  * queued will return -EINVAL.
 218  */
 219 int uvc_queue_buffer(struct uvc_video_queue *queue,
 220         struct v4l2_buffer *v4l2_buf)
 221 {
 222         struct uvc_buffer *buf;
 223         unsigned long flags;
 224         int ret = 0;
 225
 226         uvc_trace(UVC_TRACE_CAPTURE, "Queuing buffer %u.\n", v4l2_buf->index);
 227
 228         if (v4l2_buf->type != V4L2_BUF_TYPE_VIDEO_CAPTURE ||
 229             v4l2_buf->memory != V4L2_MEMORY_MMAP) {
 230                 uvc_trace(UVC_TRACE_CAPTURE, "[E] Invalid buffer type (%u) "
 231                         "and/or memory (%u).\n", v4l2_buf->type,
 232                         v4l2_buf->memory);
 233                 return -EINVAL;
 234         }
 235
 236         mutex_lock(&queue->mutex);
 237         if (v4l2_buf->index >= queue->count)  {
 238                 uvc_trace(UVC_TRACE_CAPTURE, "[E] Out of range index.\n");
 239                 ret = -EINVAL;
 240                 goto done;
 241         }
 242
 243         buf = &queue->buffer[v4l2_buf->index];
 244         if (buf->state != UVC_BUF_STATE_IDLE) {
 245                 uvc_trace(UVC_TRACE_CAPTURE, "[E] Invalid buffer state "
 246                         "(%u).\n", buf->state);
 247                 ret = -EINVAL;
 248                 goto done;
 249         }
 250
 251         spin_lock_irqsave(&queue->irqlock, flags);
 252         if (queue->flags & UVC_QUEUE_DISCONNECTED) {
 253                 spin_unlock_irqrestore(&queue->irqlock, flags);
 254                 ret = -ENODEV;
 255                 goto done;
 256         }
 257         buf->state = UVC_BUF_STATE_QUEUED;
 258         buf->buf.bytesused = 0;
 259         list_add_tail(&buf->stream, &queue->mainqueue);
 260         list_add_tail(&buf->queue, &queue->irqqueue);
 261         spin_unlock_irqrestore(&queue->irqlock, flags);
 262
 263 done:
 264         mutex_unlock(&queue->mutex);
 265         return ret;
 266 }
 267
 268 static int uvc_queue_waiton(struct uvc_buffer *buf, int nonblocking)
 269 {
 270         if (nonblocking) {
 271                 return (buf->state != UVC_BUF_STATE_QUEUED &&
 272                         buf->state != UVC_BUF_STATE_ACTIVE)
 273                         ? 0 : -EAGAIN;
 274         }
 275
 276         return wait_event_interruptible(buf->wait,
 277                 buf->state != UVC_BUF_STATE_QUEUED &&
 278                 buf->state != UVC_BUF_STATE_ACTIVE);
 279 }
 280
 281 /*
 282  * Dequeue a video buffer. If nonblocking is false, block until a buffer is
 283  * available.
 284  */
 285 int uvc_dequeue_buffer(struct uvc_video_queue *queue,
 286                 struct v4l2_buffer *v4l2_buf, int nonblocking)
 287 {
 288         struct uvc_buffer *buf;
 289         int ret = 0;
 290
 291         if (v4l2_buf->type != V4L2_BUF_TYPE_VIDEO_CAPTURE ||
 292             v4l2_buf->memory != V4L2_MEMORY_MMAP) {
 293                 uvc_trace(UVC_TRACE_CAPTURE, "[E] Invalid buffer type (%u) "
 294                         "and/or memory (%u).\n", v4l2_buf->type,
 295                         v4l2_buf->memory);
 296                 return -EINVAL;
 297         }
 298
 299         mutex_lock(&queue->mutex);
 300         if (list_empty(&queue->mainqueue)) {
 301                 uvc_trace(UVC_TRACE_CAPTURE, "[E] Empty buffer queue.\n");
 302                 ret = -EINVAL;
 303                 goto done;
 304         }
 305
 306         buf = list_first_entry(&queue->mainqueue, struct uvc_buffer, stream);
 307         if ((ret = uvc_queue_waiton(buf, nonblocking)) < 0)
 308                 goto done;
 309
 310         uvc_trace(UVC_TRACE_CAPTURE, "Dequeuing buffer %u (%u, %u bytes).\n",
 311                 buf->buf.index, buf->state, buf->buf.bytesused);
 312
 313         switch (buf->state) {
 314         case UVC_BUF_STATE_ERROR:
 315                 uvc_trace(UVC_TRACE_CAPTURE, "[W] Corrupted data "
 316                         "(transmission error).\n");
 317                 ret = -EIO;
 318         case UVC_BUF_STATE_DONE:
 319                 buf->state = UVC_BUF_STATE_IDLE;
 320                 break;
 321
 322         case UVC_BUF_STATE_IDLE:
 323         case UVC_BUF_STATE_QUEUED:
 324         case UVC_BUF_STATE_ACTIVE:
 325         default:
 326                 uvc_trace(UVC_TRACE_CAPTURE, "[E] Invalid buffer state %u "
 327                         "(driver bug?).\n", buf->state);
 328                 ret = -EINVAL;
 329                 goto done;
 330         }
 331
 332         list_del(&buf->stream);
 333         __uvc_query_buffer(buf, v4l2_buf);
 334
 335 done:
 336         mutex_unlock(&queue->mutex);
 337         return ret;
 338 }
 339
 340 /*
 341  * Poll the video queue.
 342  *
 343  * This function implements video queue polling and is intended to be used by
 344  * the device poll handler.
 345  */
 346 unsigned int uvc_queue_poll(struct uvc_video_queue *queue, struct file *file,
 347                 poll_table *wait)
 348 {
 349         struct uvc_buffer *buf;
 350         unsigned int mask = 0;
 351
 352         mutex_lock(&queue->mutex);
 353         if (list_empty(&queue->mainqueue)) {
 354                 mask |= POLLERR;
 355                 goto done;
 356         }
 357         buf = list_first_entry(&queue->mainqueue, struct uvc_buffer, stream);
 358
 359         poll_wait(file, &buf->wait, wait);
 360         if (buf->state == UVC_BUF_STATE_DONE ||
 361             buf->state == UVC_BUF_STATE_ERROR)
 362                 mask |= POLLIN | POLLRDNORM;
 363
 364 done:
 365         mutex_unlock(&queue->mutex);
 366         return mask;
 367 }
 368
 369 /*
 370  * Enable or disable the video buffers queue.
 371  *
 372  * The queue must be enabled before starting video acquisition and must be
 373  * disabled after stopping it. This ensures that the video buffers queue
 374  * state can be properly initialized before buffers are accessed from the
 375  * interrupt handler.
 376  *
 377  * Enabling the video queue initializes parameters (such as sequence number,
 378  * sync pattern, ...). If the queue is already enabled, return -EBUSY.
 379  *
 380  * Disabling the video queue cancels the queue and removes all buffers from
 381  * the main queue.
 382  *
 383  * This function can't be called from interrupt context. Use
 384  * uvc_queue_cancel() instead.
 385  */
 386 int uvc_queue_enable(struct uvc_video_queue *queue, int enable)
 387 {
 388         unsigned int i;
 389         int ret = 0;
 390
 391         mutex_lock(&queue->mutex);
 392         if (enable) {
 393                 if (uvc_queue_streaming(queue)) {
 394                         ret = -EBUSY;
 395                         goto done;
 396                 }
 397                 queue->sequence = 0;
 398                 queue->flags |= UVC_QUEUE_STREAMING;
 399         } else {
 400                 uvc_queue_cancel(queue, 0);
 401                 INIT_LIST_HEAD(&queue->mainqueue);
 402
 403                 for (i = 0; i < queue->count; ++i)
 404                         queue->buffer[i].state = UVC_BUF_STATE_IDLE;
 405
 406                 queue->flags &= ~UVC_QUEUE_STREAMING;
 407         }
 408
 409 done:
 410         mutex_unlock(&queue->mutex);
 411         return ret;
 412 }
 413
 414 /*
 415  * Cancel the video buffers queue.
 416  *
 417  * Cancelling the queue marks all buffers on the irq queue as erroneous,
 418  * wakes them up and remove them from the queue.
 419  *
 420  * If the disconnect parameter is set, further calls to uvc_queue_buffer will
 421  * fail with -ENODEV.
 422  *
 423  * This function acquires the irq spinlock and can be called from interrupt
 424  * context.
 425  */
 426 void uvc_queue_cancel(struct uvc_video_queue *queue, int disconnect)
 427 {
 428         struct uvc_buffer *buf;
 429         unsigned long flags;
 430
 431         spin_lock_irqsave(&queue->irqlock, flags);
 432         while (!list_empty(&queue->irqqueue)) {
 433                 buf = list_first_entry(&queue->irqqueue, struct uvc_buffer,
 434                                        queue);
 435                 list_del(&buf->queue);
 436                 buf->state = UVC_BUF_STATE_ERROR;
 437                 wake_up(&buf->wait);
 438         }
 439         /* This must be protected by the irqlock spinlock to avoid race
 440          * conditions between uvc_queue_buffer and the disconnection event that
 441          * could result in an interruptible wait in uvc_dequeue_buffer. Do not
 442          * blindly replace this logic by checking for the UVC_DEV_DISCONNECTED
 443          * state outside the queue code.
 444          */
 445         if (disconnect)
 446                 queue->flags |= UVC_QUEUE_DISCONNECTED;
 447         spin_unlock_irqrestore(&queue->irqlock, flags);
 448 }
 449
 450 struct uvc_buffer *uvc_queue_next_buffer(struct uvc_video_queue *queue,
 451                 struct uvc_buffer *buf)
 452 {
 453         struct uvc_buffer *nextbuf;
 454         unsigned long flags;
 455
 456         if ((queue->flags & UVC_QUEUE_DROP_INCOMPLETE) &&
 457             buf->buf.length != buf->buf.bytesused) {
 458                 buf->state = UVC_BUF_STATE_QUEUED;
 459                 buf->buf.bytesused = 0;
 460                 return buf;
 461         }
 462
 463         spin_lock_irqsave(&queue->irqlock, flags);
 464         list_del(&buf->queue);
 465         if (!list_empty(&queue->irqqueue))
 466                 nextbuf = list_first_entry(&queue->irqqueue, struct uvc_buffer,
 467                                            queue);
 468         else
 469                 nextbuf = NULL;
 470         spin_unlock_irqrestore(&queue->irqlock, flags);
 471
 472         buf->buf.sequence = queue->sequence++;
 473         do_gettimeofday(&buf->buf.timestamp);
 474
 475         wake_up(&buf->wait);
 476         return nextbuf;
 477 }