2 * uvc_queue.c -- USB Video Class driver - Buffers management
4 * Copyright (C) 2005-2009
5 * Laurent Pinchart (laurent.pinchart@skynet.be)
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.
14 #include <linux/kernel.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>
26 /* ------------------------------------------------------------------------
27 * Video buffers queue management.
29 * Video queues is initialized by uvc_queue_init(). The function performs
30 * basic initialization of the uvc_video_queue struct and never fails.
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.
38 * Video buffers are managed using two queues. However, unlike most USB video
39 * drivers that use an in queue and an out queue, we use a main queue to hold
40 * all queued buffers (both 'empty' and 'done' buffers), and an irq queue to
41 * hold empty buffers. This design (copied from video-buf) minimizes locking
42 * in interrupt, as only one queue is shared between interrupt and user
48 * Unless stated otherwise, all operations that modify the irq buffers queue
49 * are protected by the irq spinlock.
51 * 1. The user queues the buffers, starts streaming and dequeues a buffer.
53 * The buffers are added to the main and irq queues. Both operations are
54 * protected by the queue lock, and the later is protected by the irq
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.
61 * When the buffer is full, the completion handler removes it from the irq
62 * queue, marks it as done (UVC_BUF_STATE_DONE) and wakes 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 done, the
65 * dequeing will succeed immediately.
67 * 2. Buffers are queued, user is waiting on a buffer and the device gets
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.
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
81 void uvc_queue_init(struct uvc_video_queue *queue, enum v4l2_buf_type type,
84 mutex_init(&queue->mutex);
85 spin_lock_init(&queue->irqlock);
86 INIT_LIST_HEAD(&queue->mainqueue);
87 INIT_LIST_HEAD(&queue->irqqueue);
88 queue->flags = drop_corrupted ? UVC_QUEUE_DROP_CORRUPTED : 0;
93 * Allocate the video buffers.
95 * Pages are reserved to make sure they will not be swapped, as they will be
96 * filled in the URB completion handler.
98 * Buffers will be individually mapped, so they must all be page aligned.
100 int uvc_alloc_buffers(struct uvc_video_queue *queue, unsigned int nbuffers,
101 unsigned int buflength)
103 unsigned int bufsize = PAGE_ALIGN(buflength);
108 if (nbuffers > UVC_MAX_VIDEO_BUFFERS)
109 nbuffers = UVC_MAX_VIDEO_BUFFERS;
111 mutex_lock(&queue->mutex);
113 if ((ret = uvc_free_buffers(queue)) < 0)
116 /* Bail out if no buffers should be allocated. */
120 /* Decrement the number of buffers until allocation succeeds. */
121 for (; nbuffers > 0; --nbuffers) {
122 mem = vmalloc_32(nbuffers * bufsize);
132 for (i = 0; i < nbuffers; ++i) {
133 memset(&queue->buffer[i], 0, sizeof queue->buffer[i]);
134 queue->buffer[i].buf.index = i;
135 queue->buffer[i].buf.m.offset = i * bufsize;
136 queue->buffer[i].buf.length = buflength;
137 queue->buffer[i].buf.type = queue->type;
138 queue->buffer[i].buf.sequence = 0;
139 queue->buffer[i].buf.field = V4L2_FIELD_NONE;
140 queue->buffer[i].buf.memory = V4L2_MEMORY_MMAP;
141 queue->buffer[i].buf.flags = 0;
142 init_waitqueue_head(&queue->buffer[i].wait);
146 queue->count = nbuffers;
147 queue->buf_size = bufsize;
151 mutex_unlock(&queue->mutex);
156 * Free the video buffers.
158 * This function must be called with the queue lock held.
160 int uvc_free_buffers(struct uvc_video_queue *queue)
164 for (i = 0; i < queue->count; ++i) {
165 if (queue->buffer[i].vma_use_count != 0)
178 * Check if buffers have been allocated.
180 int uvc_queue_allocated(struct uvc_video_queue *queue)
184 mutex_lock(&queue->mutex);
185 allocated = queue->count != 0;
186 mutex_unlock(&queue->mutex);
191 static void __uvc_query_buffer(struct uvc_buffer *buf,
192 struct v4l2_buffer *v4l2_buf)
194 memcpy(v4l2_buf, &buf->buf, sizeof *v4l2_buf);
196 if (buf->vma_use_count)
197 v4l2_buf->flags |= V4L2_BUF_FLAG_MAPPED;
199 switch (buf->state) {
200 case UVC_BUF_STATE_ERROR:
201 case UVC_BUF_STATE_DONE:
202 v4l2_buf->flags |= V4L2_BUF_FLAG_DONE;
204 case UVC_BUF_STATE_QUEUED:
205 case UVC_BUF_STATE_ACTIVE:
206 case UVC_BUF_STATE_READY:
207 v4l2_buf->flags |= V4L2_BUF_FLAG_QUEUED;
209 case UVC_BUF_STATE_IDLE:
215 int uvc_query_buffer(struct uvc_video_queue *queue,
216 struct v4l2_buffer *v4l2_buf)
220 mutex_lock(&queue->mutex);
221 if (v4l2_buf->index >= queue->count) {
226 __uvc_query_buffer(&queue->buffer[v4l2_buf->index], v4l2_buf);
229 mutex_unlock(&queue->mutex);
234 * Queue a video buffer. Attempting to queue a buffer that has already been
235 * queued will return -EINVAL.
237 int uvc_queue_buffer(struct uvc_video_queue *queue,
238 struct v4l2_buffer *v4l2_buf)
240 struct uvc_buffer *buf;
244 uvc_trace(UVC_TRACE_CAPTURE, "Queuing buffer %u.\n", v4l2_buf->index);
246 if (v4l2_buf->type != queue->type ||
247 v4l2_buf->memory != V4L2_MEMORY_MMAP) {
248 uvc_trace(UVC_TRACE_CAPTURE, "[E] Invalid buffer type (%u) "
249 "and/or memory (%u).\n", v4l2_buf->type,
254 mutex_lock(&queue->mutex);
255 if (v4l2_buf->index >= queue->count) {
256 uvc_trace(UVC_TRACE_CAPTURE, "[E] Out of range index.\n");
261 buf = &queue->buffer[v4l2_buf->index];
262 if (buf->state != UVC_BUF_STATE_IDLE) {
263 uvc_trace(UVC_TRACE_CAPTURE, "[E] Invalid buffer state "
264 "(%u).\n", buf->state);
269 if (v4l2_buf->type == V4L2_BUF_TYPE_VIDEO_OUTPUT &&
270 v4l2_buf->bytesused > buf->buf.length) {
271 uvc_trace(UVC_TRACE_CAPTURE, "[E] Bytes used out of bounds.\n");
276 spin_lock_irqsave(&queue->irqlock, flags);
277 if (queue->flags & UVC_QUEUE_DISCONNECTED) {
278 spin_unlock_irqrestore(&queue->irqlock, flags);
282 buf->state = UVC_BUF_STATE_QUEUED;
283 if (v4l2_buf->type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
284 buf->buf.bytesused = 0;
286 buf->buf.bytesused = v4l2_buf->bytesused;
288 list_add_tail(&buf->stream, &queue->mainqueue);
289 list_add_tail(&buf->queue, &queue->irqqueue);
290 spin_unlock_irqrestore(&queue->irqlock, flags);
293 mutex_unlock(&queue->mutex);
297 static int uvc_queue_waiton(struct uvc_buffer *buf, int nonblocking)
300 return (buf->state != UVC_BUF_STATE_QUEUED &&
301 buf->state != UVC_BUF_STATE_ACTIVE &&
302 buf->state != UVC_BUF_STATE_READY)
306 return wait_event_interruptible(buf->wait,
307 buf->state != UVC_BUF_STATE_QUEUED &&
308 buf->state != UVC_BUF_STATE_ACTIVE &&
309 buf->state != UVC_BUF_STATE_READY);
313 * Dequeue a video buffer. If nonblocking is false, block until a buffer is
316 int uvc_dequeue_buffer(struct uvc_video_queue *queue,
317 struct v4l2_buffer *v4l2_buf, int nonblocking)
319 struct uvc_buffer *buf;
322 if (v4l2_buf->type != queue->type ||
323 v4l2_buf->memory != V4L2_MEMORY_MMAP) {
324 uvc_trace(UVC_TRACE_CAPTURE, "[E] Invalid buffer type (%u) "
325 "and/or memory (%u).\n", v4l2_buf->type,
330 mutex_lock(&queue->mutex);
331 if (list_empty(&queue->mainqueue)) {
332 uvc_trace(UVC_TRACE_CAPTURE, "[E] Empty buffer queue.\n");
337 buf = list_first_entry(&queue->mainqueue, struct uvc_buffer, stream);
338 if ((ret = uvc_queue_waiton(buf, nonblocking)) < 0)
341 uvc_trace(UVC_TRACE_CAPTURE, "Dequeuing buffer %u (%u, %u bytes).\n",
342 buf->buf.index, buf->state, buf->buf.bytesused);
344 switch (buf->state) {
345 case UVC_BUF_STATE_ERROR:
346 uvc_trace(UVC_TRACE_CAPTURE, "[W] Corrupted data "
347 "(transmission error).\n");
349 case UVC_BUF_STATE_DONE:
350 buf->state = UVC_BUF_STATE_IDLE;
353 case UVC_BUF_STATE_IDLE:
354 case UVC_BUF_STATE_QUEUED:
355 case UVC_BUF_STATE_ACTIVE:
356 case UVC_BUF_STATE_READY:
358 uvc_trace(UVC_TRACE_CAPTURE, "[E] Invalid buffer state %u "
359 "(driver bug?).\n", buf->state);
364 list_del(&buf->stream);
365 __uvc_query_buffer(buf, v4l2_buf);
368 mutex_unlock(&queue->mutex);
373 * Poll the video queue.
375 * This function implements video queue polling and is intended to be used by
376 * the device poll handler.
378 unsigned int uvc_queue_poll(struct uvc_video_queue *queue, struct file *file,
381 struct uvc_buffer *buf;
382 unsigned int mask = 0;
384 mutex_lock(&queue->mutex);
385 if (list_empty(&queue->mainqueue)) {
389 buf = list_first_entry(&queue->mainqueue, struct uvc_buffer, stream);
391 poll_wait(file, &buf->wait, wait);
392 if (buf->state == UVC_BUF_STATE_DONE ||
393 buf->state == UVC_BUF_STATE_ERROR) {
394 if (queue->type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
395 mask |= POLLIN | POLLRDNORM;
397 mask |= POLLOUT | POLLWRNORM;
401 mutex_unlock(&queue->mutex);
406 * Enable or disable the video buffers queue.
408 * The queue must be enabled before starting video acquisition and must be
409 * disabled after stopping it. This ensures that the video buffers queue
410 * state can be properly initialized before buffers are accessed from the
413 * Enabling the video queue initializes parameters (such as sequence number,
414 * sync pattern, ...). If the queue is already enabled, return -EBUSY.
416 * Disabling the video queue cancels the queue and removes all buffers from
419 * This function can't be called from interrupt context. Use
420 * uvc_queue_cancel() instead.
422 int uvc_queue_enable(struct uvc_video_queue *queue, int enable)
427 mutex_lock(&queue->mutex);
429 if (uvc_queue_streaming(queue)) {
434 queue->flags |= UVC_QUEUE_STREAMING;
437 uvc_queue_cancel(queue, 0);
438 INIT_LIST_HEAD(&queue->mainqueue);
440 for (i = 0; i < queue->count; ++i) {
441 queue->buffer[i].error = 0;
442 queue->buffer[i].state = UVC_BUF_STATE_IDLE;
445 queue->flags &= ~UVC_QUEUE_STREAMING;
449 mutex_unlock(&queue->mutex);
454 * Cancel the video buffers queue.
456 * Cancelling the queue marks all buffers on the irq queue as erroneous,
457 * wakes them up and removes them from the queue.
459 * If the disconnect parameter is set, further calls to uvc_queue_buffer will
462 * This function acquires the irq spinlock and can be called from interrupt
465 void uvc_queue_cancel(struct uvc_video_queue *queue, int disconnect)
467 struct uvc_buffer *buf;
470 spin_lock_irqsave(&queue->irqlock, flags);
471 while (!list_empty(&queue->irqqueue)) {
472 buf = list_first_entry(&queue->irqqueue, struct uvc_buffer,
474 list_del(&buf->queue);
475 buf->state = UVC_BUF_STATE_ERROR;
478 /* This must be protected by the irqlock spinlock to avoid race
479 * conditions between uvc_queue_buffer and the disconnection event that
480 * could result in an interruptible wait in uvc_dequeue_buffer. Do not
481 * blindly replace this logic by checking for the UVC_DEV_DISCONNECTED
482 * state outside the queue code.
485 queue->flags |= UVC_QUEUE_DISCONNECTED;
486 spin_unlock_irqrestore(&queue->irqlock, flags);
489 struct uvc_buffer *uvc_queue_next_buffer(struct uvc_video_queue *queue,
490 struct uvc_buffer *buf)
492 struct uvc_buffer *nextbuf;
495 if ((queue->flags & UVC_QUEUE_DROP_CORRUPTED) && buf->error) {
497 buf->state = UVC_BUF_STATE_QUEUED;
498 buf->buf.bytesused = 0;
502 spin_lock_irqsave(&queue->irqlock, flags);
503 list_del(&buf->queue);
505 buf->state = UVC_BUF_STATE_DONE;
506 if (!list_empty(&queue->irqqueue))
507 nextbuf = list_first_entry(&queue->irqqueue, struct uvc_buffer,
511 spin_unlock_irqrestore(&queue->irqlock, flags);
513 buf->buf.sequence = queue->sequence++;