[PATCHv2 1/3] media: rkvdec: Fix .buf_prepare

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

From: Ezequiel Garcia <ezequiel@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 rkvdec-h264.c.

Fixes: cd33c830448ba ("media: rkvdec: Add the rkvdec driver")
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
[Changed the comment and used V4L2_TYPE_IS_CAPTURE macro]
Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
---
 drivers/staging/media/rkvdec/rkvdec.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/media/rkvdec/rkvdec.c b/drivers/staging/media/rkvdec/rkvdec.c
index d821661d30f3..cd65ad2af8d4 100644
--- a/drivers/staging/media/rkvdec/rkvdec.c
+++ b/drivers/staging/media/rkvdec/rkvdec.c
@@ -481,7 +481,15 @@ static int rkvdec_buf_prepare(struct vb2_buffer *vb)
 		if (vb2_plane_size(vb, i) < sizeimage)
 			return -EINVAL;
 	}
-	vb2_set_plane_payload(vb, 0, f->fmt.pix_mp.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, f->fmt.pix_mp.plane_fmt[0].sizeimage);
+
 	return 0;
 }
 
-- 
2.17.1


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