linux-kernel - Re: [PATCH v7 14/17] media: rkvdec: Add H264 support for the VDPU381 variant

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Message-ID: <bf4a8049f49b8d6d8a39faecee025dce51d59db3.camel@collabora.com>
Date: Mon, 22 Dec 2025 08:19:16 -0500
From: Nicolas Dufresne <nicolas.dufresne@...labora.com>
To: Jianfeng Liu <liujianfeng1994@...il.com>, detlev.casanova@...labora.com
Cc: corbet@....net, daniel.almeida@...labora.com, didi.debian@...ow.org, 
	ezequiel@...guardiasur.com.ar, hansg@...nel.org, heiko@...ech.de, 
	hverkuil@...nel.org, james.cowgill@...ize.com, jonas@...boo.se, 
	kernel@...labora.com, laurent.pinchart@...asonboard.com, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-media@...r.kernel.org, linux-rockchip@...ts.infradead.org, 
	mchehab@...nel.org, opensource206@...il.com, ribalda@...omium.org, 
	sakari.ailus@...ux.intel.com, yunkec@...gle.com
Subject: Re: [PATCH v7 14/17] media: rkvdec: Add H264 support for the
 VDPU381 variant

Hi,

Le dimanche 21 décembre 2025 à 00:46 +0800, Jianfeng Liu a écrit :
> Hi,
> 
> On Thu, 18 Dec 2025 18:28:24 -0500, Detlev Casanova wrote:
> > +static int rkvdec_h264_start(struct rkvdec_ctx *ctx)
> > +{
> > +	struct rkvdec_dev *rkvdec = ctx->dev;
> > +	struct rkvdec_h264_priv_tbl *priv_tbl;
> > +	struct rkvdec_h264_ctx *h264_ctx;
> > +	struct v4l2_ctrl *ctrl;
> > +	int ret;
> > +
> > +	ctrl = v4l2_ctrl_find(&ctx->ctrl_hdl,
> > +			      V4L2_CID_STATELESS_H264_SPS);
> > +	if (!ctrl)
> > +		return -EINVAL;
> > +
> > +	h264_ctx = kzalloc(sizeof(*h264_ctx), GFP_KERNEL);
> > +	if (!h264_ctx)
> > +		return -ENOMEM;
> 
> I can see the sps validation is removed:
> 
> 	ret = rkvdec_h264_validate_sps(ctx, ctrl->p_new.p_h264_sps);
> 	if (ret)
> 		return ret;
> 
> This should fix decoding issue with chromium when minimum size of h264
> decoder is lower than 32. While I find this issue is caused by chromium
> not following v4l2 stateless spec, and I think checking sps at start
> should be still necessary.

One of the missing part of rkvdec is that once you set the OUTPUT format we only
reset the capture format, but we should also reset the SPS control to a matching
default, matching the resolution and resetting the depth. In fact, I don't even
see code that verify the bit depth against already allocated memory, and the is
not capable of converting.

I tend to agree with Jianfeng, that we should leave that un-modified until we
have time to fully address and test this situation.

Nicolas

> 
> I have sent a fix to chromium[1] and it should get merged later.
> 
> [1] https://chromium-review.googlesource.com/c/chromium/src/+/7274555
> 
> Best regards,
> Jianfeng

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