media: v4l2: Add REMOVE_BUFS ioctl

VIDIOC_REMOVE_BUFS ioctl allows to remove buffers from a queue.
The number of buffers to remove in given by count field of
struct v4l2_remove_buffers and the range start at the index
specified in the same structure.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Reviewed-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
[hverkuil: vidioc-remove-bufs.rst: mention no bufs are freed on error]

1 files changed, 38 insertions, 0 deletions

diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index 009cea95d662..0b2b48e1b2df 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -1691,6 +1691,44 @@ int vb2_core_prepare_buf(struct vb2_queue *q, struct vb2_buffer *vb, void *pb)
 }
 EXPORT_SYMBOL_GPL(vb2_core_prepare_buf);
 
+int vb2_core_remove_bufs(struct vb2_queue *q, unsigned int start, unsigned int count)
+{
+	unsigned int i, ret = 0;
+	unsigned int q_num_bufs = vb2_get_num_buffers(q);
+
+	if (count == 0)
+		return 0;
+
+	if (count > q_num_bufs)
+		return -EINVAL;
+
+	if (start > q->max_num_buffers - count)
+		return -EINVAL;
+
+	mutex_lock(&q->mmap_lock);
+
+	/* Check that all buffers in the range exist */
+	for (i = start; i < start + count; i++) {
+		struct vb2_buffer *vb = vb2_get_buffer(q, i);
+
+		if (!vb) {
+			ret = -EINVAL;
+			goto unlock;
+		}
+		if (vb->state != VB2_BUF_STATE_DEQUEUED) {
+			ret = -EBUSY;
+			goto unlock;
+		}
+	}
+	__vb2_queue_free(q, start, count);
+	dprintk(q, 2, "%u buffers removed\n", count);
+
+unlock:
+	mutex_unlock(&q->mmap_lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(vb2_core_remove_bufs);
+
 /*
  * vb2_start_streaming() - Attempt to start streaming.
  * @q:		videobuf2 queue