linux-kernel - Re: [PATCH v7 09/12] media: rkvdec: Add get_image

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Message-ID: <af5275a0017bc802379ee63df23fcafd44c8c285.camel@collabora.com>
Date: Tue, 08 Apr 2025 13:13:03 -0400
From: Nicolas Dufresne <nicolas.dufresne@...labora.com>
To: Hans Verkuil <hverkuil@...all.nl>, Sebastian Fricke	
 <sebastian.fricke@...labora.com>, Mauro Carvalho Chehab
 <mchehab@...nel.org>,  Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Boris Brezillon	
 <boris.brezillon@...labora.com>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-rockchip@...ts.infradead.org, linux-staging@...ts.linux.dev, Mauro
 Carvalho Chehab <mchehab+huawei@...nel.org>, Alex Bee
 <knaerzche@...il.com>, Benjamin Gaignard	
 <benjamin.gaignard@...labora.com>, Detlev Casanova	
 <detlev.casanova@...labora.com>, Dan Carpenter <dan.carpenter@...aro.org>, 
 Jonas Karlman <jonas@...boo.se>, Christopher Obbard
 <christopher.obbard@...aro.org>
Subject: Re: [PATCH v7 09/12] media: rkvdec: Add get_image_fmt ops

(just trimmed a bit)

Le mardi 08 avril 2025 à 16:32 +0200, Hans Verkuil a écrit :
> So can we agree on the following (I think):
> 
> 1) rkvdec_try_ctrl no longer checks the image_fmt. Effectively this means that there
>    is no longer any need to change rkvdec_try_ctrl in this patch.

Correct.

> 
> 2) in rkvdec_s_ctrl we do the image_fmt check: if it changes, but vb2_is_busy is true,
>    then return -EBUSY, otherwise call rkvdec_reset_decoded_fmt(). This code is specific
>    for V4L2_CID_STATELESS_H264_SPS, so just make sure it is under an if/switch for that
>    control ID.

Correct. In practice, the IOCTL implementation function will be renamed
to what Jonas proposed (translated to s_ctrl instead of try), with some
name like s_sps_ctrl() (can't remember exactly). This is because
upcoming HEVC will endup sharing this code. Its going to be 1 control
per codec that supports 10bit.

> 
> 3) I'll see if I can make a patch to clarify in the control documentation that setting
>    it can change the format.

Thanks.

> 
> 4) I'll make a patch for the cedrus driver as well to align with the approach in rkvdec.

Thank you ! Glad we got to the bottom of it. As for rkvdec TODO, I will
prepare an upstaging patch series, and fix anything needed.

Nicolas