linux-kernel - Re: [PATCH] media: iris: set default size when S

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Message-ID: <34097d61-ce31-0ea9-bb89-7b91162a0c71@oss.qualcomm.com>
Date: Tue, 28 Oct 2025 17:27:22 +0530
From: Dikshita Agarwal <dikshita.agarwal@....qualcomm.com>
To: Val Packett <val@...kett.cool>,
        Vikash Garodia <vikash.garodia@....qualcomm.com>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Bryan O'Donoghue <bod@...nel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hverkuil@...nel.org>,
        Stefan Schmidt <stefan.schmidt@...aro.org>,
        Vedang Nagar <quic_vnagar@...cinc.com>
Cc: linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: iris: set default size when S_FMT is called with
 zero size



On 10/13/2025 5:20 AM, Val Packett wrote:
> According to 4.5.1.5 of the M2M stateful decoder UAPI documentation,
> providing the width and the height is "required only if it cannot be
> parsed from the stream", otherwise zero can be passed.
> 
> The iris driver would only set the state fields to DEFAULT_WIDTH/HEIGHT
> once upon init, but they would get overwritten with zeroes from one S_FMT
> call and the next S_FMT call would already see zeroes in place of the
> defaults. For clients that used that sequence and did not pass a size,
> such as rpi-ffmpeg, this would then result in REQBUFS failing due to
> the zero size remembered in the state.
> 
> Fix by explicitly falling back to the defaults in S_FMT.
> 
> Fixes: b530b95de22c ("media: iris: implement s_fmt, g_fmt and try_fmt ioctls")
> Link: https://github.com/jc-kynesim/rpi-ffmpeg/issues/103
> Signed-off-by: Val Packett <val@...kett.cool>
> ---
> Somehow Venus didn't have this issue and didn't explicitly handle this..

In venus driver, try_fmt is clamping the resolution between min and max
supported which might be handling this case.

> 
> I'm not familiar with this code so if there's a better way to comply
> with the UAPI requirements by just not even getting to overwrite the
> state with the provided 0 size, I could not figure it out.
> 
> Still, let's get this fixed one way or another.
> 
> Thanks,
> ~val
> ---
>  drivers/media/platform/qcom/iris/iris_vdec.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/media/platform/qcom/iris/iris_vdec.c b/drivers/media/platform/qcom/iris/iris_vdec.c
> index ae13c3e1b426..6be09d82e24d 100644
> --- a/drivers/media/platform/qcom/iris/iris_vdec.c
> +++ b/drivers/media/platform/qcom/iris/iris_vdec.c
> @@ -196,6 +196,11 @@ int iris_vdec_s_fmt(struct iris_inst *inst, struct v4l2_format *f)
>  	if (vb2_is_busy(q))
>  		return -EBUSY;
>  

Can you pls add a small comment here.

with that,

Reviewed-by: Dikshita Agarwal <dikshita.agarwal@....qualcomm.com>

> +	if (f->fmt.pix_mp.width == 0 && f->fmt.pix_mp.height == 0) {
> +		f->fmt.pix_mp.width = DEFAULT_WIDTH;
> +		f->fmt.pix_mp.height = DEFAULT_HEIGHT;
> +	}
> +
>  	iris_vdec_try_fmt(inst, f);
>  
>  	switch (f->type) {