[PATCH RFC 5/6] media: cedrus: Make the slice_params array size limitation more explicit

From: Boris Brezillon <boris.brezillon@collabora.com>
To: Mauro Carvalho Chehab <mchehab@kernel.org>,
	Hans Verkuil <hans.verkuil@cisco.com>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Sakari Ailus <sakari.ailus@iki.fi>,
	linux-media@vger.kernel.org
Cc: Tomasz Figa <tfiga@chromium.org>,
	Nicolas Dufresne <nicolas@ndufresne.ca>,
	kernel@collabora.com,
	Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
	Ezequiel Garcia <ezequiel@collabora.com>,
	Jonas Karlman <jonas@kwiboo.se>,
	Jernej Skrabec <jernej.skrabec@siol.net>,
	Alexandre Courbot <acourbot@chromium.org>,
	Thierry Reding <thierry.reding@gmail.com>,
	Boris Brezillon <boris.brezillon@collabora.com>
Subject: [PATCH RFC 5/6] media: cedrus: Make the slice_params array size limitation more explicit
Date: Mon,  3 Jun 2019 13:09:45 +0200	[thread overview]
Message-ID: <20190603110946.4952-6-boris.brezillon@collabora.com> (raw)
In-Reply-To: <20190603110946.4952-1-boris.brezillon@collabora.com>

The driver only supports per-slice decoding, and in that mode
decode_params->num_slices must be set to 1 and the slice_params array
should contain only one element.

The current code already had this limitation but it made it look like
the slice_params control was a single struct while, according to the
spec, it's actually an array. Make it more explicit by setting dims[0]
and adding a comment explaining why we have this limitation.

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
---
 drivers/staging/media/sunxi/cedrus/cedrus.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/staging/media/sunxi/cedrus/cedrus.c b/drivers/staging/media/sunxi/cedrus/cedrus.c
index 378032fe71f9..3661c6a04864 100644
--- a/drivers/staging/media/sunxi/cedrus/cedrus.c
+++ b/drivers/staging/media/sunxi/cedrus/cedrus.c
@@ -49,6 +49,12 @@ static const struct cedrus_control cedrus_controls[] = {
 	{
 		.cfg.id		= V4L2_CID_MPEG_VIDEO_H264_SLICE_PARAMS,
 		.cfg.elem_size	= sizeof(struct v4l2_ctrl_h264_slice_params),
+		/*
+		 * This driver does not support per-frame decoding (yet?).
+		 * Allow only on per-slice decoding operation, which implies
+		 * that only 1 slice param is passed per decoding operation.
+		 */
+		.cfg.dims[0]	= 1,
 		.codec		= CEDRUS_CODEC_H264,
 		.required	= true,
 	},
-- 
2.20.1

