[PATCHv2 3/3] media: cedrus: Fix .buf_prepare

[Andrzej Pietrasiewicz <andrzej.p@collabora.com>]

The driver should only set the payload on .buf_prepare if the
buffer is CAPTURE type. If an OUTPUT buffer has a zero bytesused
set by userspace then v4l2-core will set it to buffer length.

If we overwrite bytesused for OUTPUT buffers, too, then
vb2_get_plane_payload() will return incorrect value which might be then
written to hw registers by the driver in cedrus_h264.c or cedrus_vp8.c.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
---
 drivers/staging/media/sunxi/cedrus/cedrus_video.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_video.c b/drivers/staging/media/sunxi/cedrus/cedrus_video.c
index b62eb8e84057..bf731caf2ed5 100644
--- a/drivers/staging/media/sunxi/cedrus/cedrus_video.c
+++ b/drivers/staging/media/sunxi/cedrus/cedrus_video.c
@@ -457,7 +457,13 @@ static int cedrus_buf_prepare(struct vb2_buffer *vb)
 	if (vb2_plane_size(vb, 0) < pix_fmt->sizeimage)
 		return -EINVAL;
 
-	vb2_set_plane_payload(vb, 0, pix_fmt->sizeimage);
+	/*
+	 * Buffer's bytesused must be written by driver for CAPTURE buffers.
+	 * (for OUTPUT buffers, if userspace passes 0 bytesused, v4l2-core sets
+	 * it to buffer length).
+	 */
+	if (V4L2_TYPE_IS_CAPTURE(vq->type))
+		vb2_set_plane_payload(vb, 0, pix_fmt->sizeimage);
 
 	return 0;
 }
-- 
2.17.1