[PATCHv2 2/3] media: hantro: Fix .buf_prepare

[Andrzej Pietrasiewicz]

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 hantro_g1_h264_dec.c.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p at collabora.com>
---
 drivers/staging/media/hantro/hantro_v4l2.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/media/hantro/hantro_v4l2.c b/drivers/staging/media/hantro/hantro_v4l2.c
index 1bc118e375a1..7ccc6405036a 100644
--- a/drivers/staging/media/hantro/hantro_v4l2.c
+++ b/drivers/staging/media/hantro/hantro_v4l2.c
@@ -639,7 +639,14 @@ static int hantro_buf_prepare(struct vb2_buffer *vb)
 	ret = hantro_buf_plane_check(vb, pix_fmt);
 	if (ret)
 		return ret;
-	vb2_set_plane_payload(vb, 0, pix_fmt->plane_fmt[0].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->plane_fmt[0].sizeimage);
+
 	return 0;
 }
 
-- 
2.17.1