media: vb2: add vb2_find_timestamp()

Use v4l2_timeval_to_ns instead of timeval_to_ns to ensure that
both kernelspace and userspace will use the same conversion
function.

Next add a new vb2_find_timestamp() function to find buffers
with a specific timestamp.

This function will only look at DEQUEUED and DONE buffers, i.e.
buffers that are already processed.
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

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

@@ -143,7 +143,7 @@ static void __copy_timestamp(struct vb2_buffer *vb, const void *pb)
 		 * and the timecode field and flag if needed.
 		 */
 		if (q->copy_timestamp)
-			vb->timestamp = timeval_to_ns(&b->timestamp);
+			vb->timestamp = v4l2_timeval_to_ns(&b->timestamp);
 		vbuf->flags |= b->flags & V4L2_BUF_FLAG_TIMECODE;
 		if (b->flags & V4L2_BUF_FLAG_TIMECODE)
 			vbuf->timecode = b->timecode;
@@ -589,6 +589,23 @@ static const struct vb2_buf_ops v4l2_buf_ops = {
 	.copy_timestamp		= __copy_timestamp,
 };
 
+int vb2_find_timestamp(const struct vb2_queue *q, u64 timestamp,
+		       unsigned int start_idx)
+{
+	unsigned int i;
+
+	for (i = start_idx; i < q->num_buffers; i++) {
+		struct vb2_buffer *vb = q->bufs[i];
+
+		if ((vb->state == VB2_BUF_STATE_DEQUEUED ||
+		     vb->state == VB2_BUF_STATE_DONE) &&
+		    vb->timestamp == timestamp)
+			return i;
+	}
+	return -1;
+}
+EXPORT_SYMBOL_GPL(vb2_find_timestamp);
+
 /*
  * vb2_querybuf() - query video buffer information
  * @q:		videobuf queue

include/media/videobuf2-v4l2.h

@@ -55,6 +55,23 @@ struct vb2_v4l2_buffer {
 #define to_vb2_v4l2_buffer(vb) \
 	container_of(vb, struct vb2_v4l2_buffer, vb2_buf)
 
+/**
+ * vb2_find_timestamp() - Find buffer with given timestamp in the queue
+ *
+ * @q:		pointer to &struct vb2_queue with videobuf2 queue.
+ * @timestamp:	the timestamp to find. Only buffers in state DEQUEUED or DONE
+ *		are considered.
+ * @start_idx:	the start index (usually 0) in the buffer array to start
+ *		searching from. Note that there may be multiple buffers
+ *		with the same timestamp value, so you can restart the search
+ *		by setting @start_idx to the previously found index + 1.
+ *
+ * Returns the buffer index of the buffer with the given @timestamp, or
+ * -1 if no buffer with @timestamp was found.
+ */
+int vb2_find_timestamp(const struct vb2_queue *q, u64 timestamp,
+		       unsigned int start_idx);
+
 int vb2_querybuf(struct vb2_queue *q, struct v4l2_buffer *b);
 
 /**