2 * uvc_queue.c -- USB Video Class driver - Buffers management
4 * Copyright (C) 2005-2010
5 * Laurent Pinchart (laurent.pinchart@ideasonboard.com)
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.field = V4L2_FIELD_NONE;
139 queue->buffer[i].buf.memory = V4L2_MEMORY_MMAP;
140 queue->buffer[i].buf.flags = 0;
141 init_waitqueue_head(&queue->buffer[i].wait);
145 queue->count = nbuffers;
146 queue->buf_size = bufsize;
150 mutex_unlock(&queue->mutex);
155 * Free the video buffers.
157 * This function must be called with the queue lock held.
159 int uvc_free_buffers(struct uvc_video_queue *queue)
163 for (i = 0; i < queue->count; ++i) {
164 if (queue->buffer[i].vma_use_count != 0)
177 * Check if buffers have been allocated.
179 int uvc_queue_allocated(struct uvc_video_queue *queue)
183 mutex_lock(&queue->mutex);
184 allocated = queue->count != 0;
185 mutex_unlock(&queue->mutex);
190 static void __uvc_query_buffer(struct uvc_buffer *buf,
191 struct v4l2_buffer *v4l2_buf)
193 memcpy(v4l2_buf, &buf->buf, sizeof *v4l2_buf);
195 if (buf->vma_use_count)
196 v4l2_buf->flags |= V4L2_BUF_FLAG_MAPPED;
198 switch (buf->state) {
199 case UVC_BUF_STATE_ERROR:
200 case UVC_BUF_STATE_DONE:
201 v4l2_buf->flags |= V4L2_BUF_FLAG_DONE;
203 case UVC_BUF_STATE_QUEUED:
204 case UVC_BUF_STATE_ACTIVE:
205 case UVC_BUF_STATE_READY:
206 v4l2_buf->flags |= V4L2_BUF_FLAG_QUEUED;
208 case UVC_BUF_STATE_IDLE:
214 int uvc_query_buffer(struct uvc_video_queue *queue,
215 struct v4l2_buffer *v4l2_buf)
219 mutex_lock(&queue->mutex);
220 if (v4l2_buf->index >= queue->count) {
225 __uvc_query_buffer(&queue->buffer[v4l2_buf->index], v4l2_buf);
228 mutex_unlock(&queue->mutex);
233 * Queue a video buffer. Attempting to queue a buffer that has already been
234 * queued will return -EINVAL.
236 int uvc_queue_buffer(struct uvc_video_queue *queue,
237 struct v4l2_buffer *v4l2_buf)
239 struct uvc_buffer *buf;
243 uvc_trace(UVC_TRACE_CAPTURE, "Queuing buffer %u.\n", v4l2_buf->index);
245 if (v4l2_buf->type != queue->type ||
246 v4l2_buf->memory != V4L2_MEMORY_MMAP) {
247 uvc_trace(UVC_TRACE_CAPTURE, "[E] Invalid buffer type (%u) "
248 "and/or memory (%u).\n", v4l2_buf->type,
253 mutex_lock(&queue->mutex);
254 if (v4l2_buf->index >= queue->count) {
255 uvc_trace(UVC_TRACE_CAPTURE, "[E] Out of range index.\n");
260 buf = &queue->buffer[v4l2_buf->index];
261 if (buf->state != UVC_BUF_STATE_IDLE) {
262 uvc_trace(UVC_TRACE_CAPTURE, "[E] Invalid buffer state "
263 "(%u).\n", buf->state);
268 if (v4l2_buf->type == V4L2_BUF_TYPE_VIDEO_OUTPUT &&
269 v4l2_buf->bytesused > buf->buf.length) {
270 uvc_trace(UVC_TRACE_CAPTURE, "[E] Bytes used out of bounds.\n");
275 spin_lock_irqsave(&queue->irqlock, flags);
276 if (queue->flags & UVC_QUEUE_DISCONNECTED) {
277 spin_unlock_irqrestore(&queue->irqlock, flags);
281 buf->state = UVC_BUF_STATE_QUEUED;
282 if (v4l2_buf->type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
283 buf->buf.bytesused = 0;
285 buf->buf.bytesused = v4l2_buf->bytesused;
287 list_add_tail(&buf->stream, &queue->mainqueue);
288 list_add_tail(&buf->queue, &queue->irqqueue);
289 spin_unlock_irqrestore(&queue->irqlock, flags);
292 mutex_unlock(&queue->mutex);
296 static int uvc_queue_waiton(struct uvc_buffer *buf, int nonblocking)
299 return (buf->state != UVC_BUF_STATE_QUEUED &&
300 buf->state != UVC_BUF_STATE_ACTIVE &&
301 buf->state != UVC_BUF_STATE_READY)
305 return wait_event_interruptible(buf->wait,
306 buf->state != UVC_BUF_STATE_QUEUED &&
307 buf->state != UVC_BUF_STATE_ACTIVE &&
308 buf->state != UVC_BUF_STATE_READY);
312 * Dequeue a video buffer. If nonblocking is false, block until a buffer is
315 int uvc_dequeue_buffer(struct uvc_video_queue *queue,
316 struct v4l2_buffer *v4l2_buf, int nonblocking)
318 struct uvc_buffer *buf;
321 if (v4l2_buf->type != queue->type ||
322 v4l2_buf->memory != V4L2_MEMORY_MMAP) {
323 uvc_trace(UVC_TRACE_CAPTURE, "[E] Invalid buffer type (%u) "
324 "and/or memory (%u).\n", v4l2_buf->type,
329 mutex_lock(&queue->mutex);
330 if (list_empty(&queue->mainqueue)) {
331 uvc_trace(UVC_TRACE_CAPTURE, "[E] Empty buffer queue.\n");
336 buf = list_first_entry(&queue->mainqueue, struct uvc_buffer, stream);
337 if ((ret = uvc_queue_waiton(buf, nonblocking)) < 0)
340 uvc_trace(UVC_TRACE_CAPTURE, "Dequeuing buffer %u (%u, %u bytes).\n",
341 buf->buf.index, buf->state, buf->buf.bytesused);
343 switch (buf->state) {
344 case UVC_BUF_STATE_ERROR:
345 uvc_trace(UVC_TRACE_CAPTURE, "[W] Corrupted data "
346 "(transmission error).\n");
348 case UVC_BUF_STATE_DONE:
349 buf->state = UVC_BUF_STATE_IDLE;
352 case UVC_BUF_STATE_IDLE:
353 case UVC_BUF_STATE_QUEUED:
354 case UVC_BUF_STATE_ACTIVE:
355 case UVC_BUF_STATE_READY:
357 uvc_trace(UVC_TRACE_CAPTURE, "[E] Invalid buffer state %u "
358 "(driver bug?).\n", buf->state);
363 list_del(&buf->stream);
364 __uvc_query_buffer(buf, v4l2_buf);
367 mutex_unlock(&queue->mutex);
372 * Poll the video queue.
374 * This function implements video queue polling and is intended to be used by
375 * the device poll handler.
377 unsigned int uvc_queue_poll(struct uvc_video_queue *queue, struct file *file,
380 struct uvc_buffer *buf;
381 unsigned int mask = 0;
383 mutex_lock(&queue->mutex);
384 if (list_empty(&queue->mainqueue)) {
388 buf = list_first_entry(&queue->mainqueue, struct uvc_buffer, stream);
390 poll_wait(file, &buf->wait, wait);
391 if (buf->state == UVC_BUF_STATE_DONE ||
392 buf->state == UVC_BUF_STATE_ERROR) {
393 if (queue->type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
394 mask |= POLLIN | POLLRDNORM;
396 mask |= POLLOUT | POLLWRNORM;
400 mutex_unlock(&queue->mutex);
405 * Enable or disable the video buffers queue.
407 * The queue must be enabled before starting video acquisition and must be
408 * disabled after stopping it. This ensures that the video buffers queue
409 * state can be properly initialized before buffers are accessed from the
412 * Enabling the video queue returns -EBUSY if the queue is already enabled.
414 * Disabling the video queue cancels the queue and removes all buffers from
417 * This function can't be called from interrupt context. Use
418 * uvc_queue_cancel() instead.
420 int uvc_queue_enable(struct uvc_video_queue *queue, int enable)
425 mutex_lock(&queue->mutex);
427 if (uvc_queue_streaming(queue)) {
431 queue->flags |= UVC_QUEUE_STREAMING;
434 uvc_queue_cancel(queue, 0);
435 INIT_LIST_HEAD(&queue->mainqueue);
437 for (i = 0; i < queue->count; ++i) {
438 queue->buffer[i].error = 0;
439 queue->buffer[i].state = UVC_BUF_STATE_IDLE;
442 queue->flags &= ~UVC_QUEUE_STREAMING;
446 mutex_unlock(&queue->mutex);
451 * Cancel the video buffers queue.
453 * Cancelling the queue marks all buffers on the irq queue as erroneous,
454 * wakes them up and removes them from the queue.
456 * If the disconnect parameter is set, further calls to uvc_queue_buffer will
459 * This function acquires the irq spinlock and can be called from interrupt
462 void uvc_queue_cancel(struct uvc_video_queue *queue, int disconnect)
464 struct uvc_buffer *buf;
467 spin_lock_irqsave(&queue->irqlock, flags);
468 while (!list_empty(&queue->irqqueue)) {
469 buf = list_first_entry(&queue->irqqueue, struct uvc_buffer,
471 list_del(&buf->queue);
472 buf->state = UVC_BUF_STATE_ERROR;
475 /* This must be protected by the irqlock spinlock to avoid race
476 * conditions between uvc_queue_buffer and the disconnection event that
477 * could result in an interruptible wait in uvc_dequeue_buffer. Do not
478 * blindly replace this logic by checking for the UVC_DEV_DISCONNECTED
479 * state outside the queue code.
482 queue->flags |= UVC_QUEUE_DISCONNECTED;
483 spin_unlock_irqrestore(&queue->irqlock, flags);
486 struct uvc_buffer *uvc_queue_next_buffer(struct uvc_video_queue *queue,
487 struct uvc_buffer *buf)
489 struct uvc_buffer *nextbuf;
492 if ((queue->flags & UVC_QUEUE_DROP_CORRUPTED) && buf->error) {
494 buf->state = UVC_BUF_STATE_QUEUED;
495 buf->buf.bytesused = 0;
499 spin_lock_irqsave(&queue->irqlock, flags);
500 list_del(&buf->queue);
502 buf->state = UVC_BUF_STATE_DONE;
503 if (!list_empty(&queue->irqqueue))
504 nextbuf = list_first_entry(&queue->irqqueue, struct uvc_buffer,
508 spin_unlock_irqrestore(&queue->irqlock, flags);