linux-kernel - Re: [PATCH v5 06/23] staging: media: tegra-video: vi: adjust get

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Message-ID: <bd6262c6-a31c-43a6-8ec5-2735fb2fe0d2@kernel.org>
Date: Mon, 27 Oct 2025 16:44:30 +0100
From: Hans Verkuil <hverkuil+cisco@...nel.org>
To: Svyatoslav Ryhel <clamor95@...il.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Thierry Reding
 <thierry.reding@...il.com>, Jonathan Hunter <jonathanh@...dia.com>,
 Sowjanya Komatineni <skomatineni@...dia.com>,
 Luca Ceresoli <luca.ceresoli@...tlin.com>,
 Prashant Gaikwad <pgaikwad@...dia.com>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd
 <sboyd@...nel.org>, Mikko Perttunen <mperttunen@...dia.com>,
 Mauro Carvalho Chehab <mchehab@...nel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Jonas Schwöbel <jonasschwoebel@...oo.de>,
 Dmitry Osipenko <digetx@...il.com>,
 Charan Pedumuru <charan.pedumuru@...il.com>,
 Diogo Ivo <diogo.ivo@...nico.ulisboa.pt>, Aaron Kling
 <webgeek1234@...il.com>, Arnd Bergmann <arnd@...db.de>
Cc: dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
 linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-media@...r.kernel.org, linux-clk@...r.kernel.org,
 linux-staging@...ts.linux.dev
Subject: Re: [PATCH v5 06/23] staging: media: tegra-video: vi: adjust
 get_selection op check

Hi Svyatoslav,

On 22/10/2025 16:20, Svyatoslav Ryhel wrote:
> Get_selection operation may be implemented only for sink pad and may
> return error code. Set try_crop to 0 instead of returning error.

Can you mention why try_crop is set to 0 instead of returning an error?

That would be good to have in the commit log. And in fact, it's not
clear to me either why you want this.

> 
> Signed-off-by: Svyatoslav Ryhel <clamor95@...il.com>
> ---
>  drivers/staging/media/tegra-video/vi.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/staging/media/tegra-video/vi.c b/drivers/staging/media/tegra-video/vi.c
> index 7c44a3448588..856b7c18b551 100644
> --- a/drivers/staging/media/tegra-video/vi.c
> +++ b/drivers/staging/media/tegra-video/vi.c
> @@ -476,15 +476,11 @@ static int __tegra_channel_try_format(struct tegra_vi_channel *chan,
>  	fse.code = fmtinfo->code;
>  	ret = v4l2_subdev_call(subdev, pad, enum_frame_size, sd_state, &fse);
>  	if (ret) {
> -		if (!v4l2_subdev_has_op(subdev, pad, get_selection)) {
> +		if (!v4l2_subdev_has_op(subdev, pad, get_selection) ||
> +		    v4l2_subdev_call(subdev, pad, get_selection, NULL, &sdsel)) {
>  			try_crop->width = 0;
>  			try_crop->height = 0;

This looks all a bit magical. Which subdev is queried here? I.e. what is the corresponding
subdev driver that implements get_selection?

>  		} else {
> -			ret = v4l2_subdev_call(subdev, pad, get_selection,
> -					       NULL, &sdsel);
> -			if (ret)
> -				return -EINVAL;
> -
>  			try_crop->width = sdsel.r.width;
>  			try_crop->height = sdsel.r.height;
>  		}

It looks odd (esp. setting try_crop to 0), and I wonder if this code path has been tested.

Regards,

	Hans