linux-kernel - Re: [PATCH] media: iris: Fix fps calculation

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Message-ID: <fcb402a8-f0d1-d268-5bcb-0806433e5356@oss.qualcomm.com>
Date: Tue, 14 Oct 2025 12:15:04 +0530
From: Dikshita Agarwal <dikshita.agarwal@....qualcomm.com>
To: Ricardo Ribalda <ribalda@...omium.org>,
        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+cisco@...nel.org>
Cc: linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: iris: Fix fps calculation



On 10/13/2025 7:43 PM, Ricardo Ribalda wrote:
> iris_venc_s_param() uses do_div to divide two 64 bits operators, this is
> wrong. Luckily for us, both of the operators fit in 32 bits, so we can use
> a normal division.
> 
> Now that we are at it, mark the fps smaller than 1 as invalid, the code
> does not seem to handle them properly.
> 
> The following cocci warning is fixed with this patch:
> ./platform/qcom/iris/iris_venc.c:378:1-7: WARNING: do_div() does a 64-by-32 division, please consider using div64_u64 instead
> 
> Fixes: 4ff586ff28e3 ("media: iris: Add support for G/S_PARM for encoder video device")
> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> ---
>  drivers/media/platform/qcom/iris/iris_venc.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/platform/qcom/iris/iris_venc.c b/drivers/media/platform/qcom/iris/iris_venc.c
> index 099bd5ed4ae0294725860305254c4cad1ec88d7e..1234c61d9e44c632b065a5c44d3290f6e1491892 100644
> --- a/drivers/media/platform/qcom/iris/iris_venc.c
> +++ b/drivers/media/platform/qcom/iris/iris_venc.c
> @@ -371,11 +371,10 @@ int iris_venc_s_param(struct iris_inst *inst, struct v4l2_streamparm *s_parm)
>  	us_per_frame = timeperframe->numerator * (u64)USEC_PER_SEC;
>  	do_div(us_per_frame, timeperframe->denominator);
>  
> -	if (!us_per_frame)
> +	if (!us_per_frame || us_per_frame > USEC_PER_SEC)
>  		return -EINVAL;
>  
> -	fps = (u64)USEC_PER_SEC;
> -	do_div(fps, us_per_frame);
> +	fps = USEC_PER_SEC / (u32)us_per_frame;
>  	if (fps > max_rate) {
>  		ret = -ENOMEM;
>  		goto reset_rate;
> 
> ---
> base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787
> change-id: 20251013-iris-9addbd27ef76
> 
> Best regards,

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

Thanks,
Dikshita