media: media videobuf2: Be more flexible on the number of queue stored buffers

Add 'max_num_buffers' field in vb2_queue struct to let drivers decide
how many buffers could be stored in a queue.
This require 'bufs' array to be allocated at queue init time and freed
when releasing the queue.
By default VB2_MAX_FRAME remains the limit.

Signed-off-by: Benjamin Gaignard <[e-mail]>
Signed-off-by: Hans Verkuil <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/common/videobuf2/videobuf2-core.c

···
  */
 static void vb2_queue_add_buffer(struct vb2_queue *q, struct vb2_buffer *vb, unsigned int index)
 {
-	WARN_ON(index >= VB2_MAX_FRAME || q->bufs[index] || vb->vb2_queue);
+	WARN_ON(index >= q->max_num_buffers || q->bufs[index] || vb->vb2_queue);
 
 	q->bufs[index] = vb;
 	vb->index = index;
···
 	struct vb2_buffer *vb;
 	int ret;
 
-	/* Ensure that q->num_buffers+num_buffers is below VB2_MAX_FRAME */
+	/*
+	 * Ensure that the number of already queue + the number of buffers already
+	 * in the queue is below q->max_num_buffers
+	 */
 	num_buffers = min_t(unsigned int, num_buffers,
-			    VB2_MAX_FRAME - q_num_buffers);
+			    q->max_num_buffers - q_num_buffers);
 
 	for (buffer = 0; buffer < num_buffers; ++buffer) {
 		/* Allocate vb2 buffer structures */
···
 	unsigned plane_sizes[VB2_MAX_PLANES] = { };
 	bool non_coherent_mem = flags & V4L2_MEMORY_FLAG_NON_COHERENT;
 	unsigned int i;
-	int ret;
+	int ret = 0;
 
 	if (q->streaming) {
 		dprintk(q, 1, "streaming active\n");
···
 	/*
 	 * Make sure the requested values and current defaults are sane.
 	 */
-	WARN_ON(q->min_buffers_needed > VB2_MAX_FRAME);
 	num_buffers = max_t(unsigned int, *count, q->min_buffers_needed);
-	num_buffers = min_t(unsigned int, num_buffers, VB2_MAX_FRAME);
+	num_buffers = min_t(unsigned int, num_buffers, q->max_num_buffers);
 	memset(q->alloc_devs, 0, sizeof(q->alloc_devs));
 	/*
 	 * Set this now to ensure that drivers see the correct q->memory value
 	 * in the queue_setup op.
 	 */
 	mutex_lock(&q->mmap_lock);
+	if (!q->bufs)
+		q->bufs = kcalloc(q->max_num_buffers, sizeof(*q->bufs), GFP_KERNEL);
+	if (!q->bufs)
+		ret = -ENOMEM;
 	q->memory = memory;
 	mutex_unlock(&q->mmap_lock);
+	if (ret)
+		return ret;
 	set_queue_coherency(q, non_coherent_mem);
 
 	/*
···
 	bool no_previous_buffers = !q_num_bufs;
 	int ret = 0;
 
-	if (q_num_bufs == VB2_MAX_FRAME) {
+	if (q->num_buffers == q->max_num_buffers) {
 		dprintk(q, 1, "maximum number of buffers already allocated\n");
 		return -ENOBUFS;
 	}
···
 		 */
 		mutex_lock(&q->mmap_lock);
 		q->memory = memory;
+		if (!q->bufs)
+			q->bufs = kcalloc(q->max_num_buffers, sizeof(*q->bufs), GFP_KERNEL);
+		if (!q->bufs)
+			ret = -ENOMEM;
 		mutex_unlock(&q->mmap_lock);
+		if (ret)
+			return ret;
 		q->waiting_for_buffers = !q->is_output;
 		set_queue_coherency(q, non_coherent_mem);
 	} else {
···
 			return -EINVAL;
 	}
 
-	num_buffers = min(*count, VB2_MAX_FRAME - q_num_bufs);
+	num_buffers = min(*count, q->max_num_buffers - q_num_bufs);
 
 	if (requested_planes && requested_sizes) {
 		num_planes = requested_planes;
···
 	/*
 	 * Sanity check
 	 */
+	/*
+	 * For drivers who don't support max_num_buffers ensure
+	 * a backward compatibility.
+	 */
+	if (!q->max_num_buffers)
+		q->max_num_buffers = VB2_MAX_FRAME;
+
+	/* The maximum is limited by offset cookie encoding pattern */
+	q->max_num_buffers = min_t(unsigned int, q->max_num_buffers, MAX_BUFFER_INDEX);
+
 	if (WARN_ON(!q)			  ||
 	    WARN_ON(!q->ops)		  ||
 	    WARN_ON(!q->mem_ops)	  ||
···
 	    WARN_ON(!q->io_modes)	  ||
 	    WARN_ON(!q->ops->queue_setup) ||
 	    WARN_ON(!q->ops->buf_queue))
+		return -EINVAL;
+
+	if (WARN_ON(q->max_num_buffers > MAX_BUFFER_INDEX) ||
+	    WARN_ON(q->min_buffers_needed > q->max_num_buffers))
 		return -EINVAL;
 
 	if (WARN_ON(q->requires_requests && !q->supports_requests))
···
 	__vb2_queue_cancel(q);
 	mutex_lock(&q->mmap_lock);
 	__vb2_queue_free(q, vb2_get_num_buffers(q));
+	kfree(q->bufs);
+	q->bufs = NULL;
 	mutex_unlock(&q->mmap_lock);
 }
 EXPORT_SYMBOL_GPL(vb2_core_queue_release);

drivers/media/common/videobuf2/videobuf2-v4l2.c

···
 	 * This loop doesn't scale if there is a really large number of buffers.
 	 * Maybe something more efficient will be needed in this case.
 	 */
-	for (i = 0; i < vb2_get_num_buffers(q); i++) {
+	for (i = 0; i < q->max_num_buffers; i++) {
 		vb2 = vb2_get_buffer(q, i);
 
 		if (!vb2)
···
 
 	if (lock)
 		mutex_lock(lock);
-	if (file->private_data == vdev->queue->owner) {
+	if (!vdev->queue->owner || file->private_data == vdev->queue->owner) {
 		vb2_queue_release(vdev->queue);
 		vdev->queue->owner = NULL;
 	}
···
 	 */
 	get_device(&vdev->dev);
 	video_unregister_device(vdev);
-	if (vdev->queue && vdev->queue->owner) {
+	if (vdev->queue) {
 		struct mutex *lock = vdev->queue->lock ?
 			vdev->queue->lock : vdev->lock;
 

include/media/videobuf2-core.h

···
  * @dma_dir:	DMA mapping direction.
  * @bufs:	videobuf2 buffer structures
  * @num_buffers: number of allocated/used buffers
+ * @max_num_buffers: upper limit of number of allocated/used buffers.
+ *		     If set to 0 v4l2 core will change it VB2_MAX_FRAME
+ *		     for backward compatibility.
  * @queued_list: list of buffers currently queued from userspace
  * @queued_count: number of buffers queued and ready for streaming.
  * @owned_by_drv_count: number of buffers owned by the driver
···
 	struct mutex			mmap_lock;
 	unsigned int			memory;
 	enum dma_data_direction		dma_dir;
-	struct vb2_buffer		*bufs[VB2_MAX_FRAME];
+	struct vb2_buffer		**bufs;
 	unsigned int			num_buffers;
+	unsigned int			max_num_buffers;
 
 	struct list_head		queued_list;
 	unsigned int			queued_count;
···
 static inline struct vb2_buffer *vb2_get_buffer(struct vb2_queue *q,
 						unsigned int index)
 {
+	if (!q->bufs)
+		return NULL;
+
+	if (index >= q->max_num_buffers)
+		return NULL;
+
 	if (index < q->num_buffers)
 		return q->bufs[index];
 	return NULL;