linux-kernel - Re: [Intel-gfx] [PATCH v2] drm/i915/tv: avoid possible division by zero

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Date:   Wed, 26 Jul 2023 09:21:50 +0800
From:   Su Hui <suhui@...china.com>
To:     Dan Carpenter <dan.carpenter@...aro.org>
Cc:     Andi Shyti <andi.shyti@...ux.intel.com>,
        jani.nikula@...ux.intel.com, joonas.lahtinen@...ux.intel.com,
        rodrigo.vivi@...el.com, tvrtko.ursulin@...ux.intel.com,
        airlied@...il.com, daniel@...ll.ch, nathan@...nel.org,
        ndesaulniers@...gle.com, trix@...hat.com, andrzej.hajda@...el.com,
        intel-gfx@...ts.freedesktop.org, llvm@...ts.linux.dev,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, mripard@...nel.org
Subject: Re: [Intel-gfx] [PATCH v2] drm/i915/tv: avoid possible division by
 zero

On 2023/7/25 13:51, Dan Carpenter wrote:
> The reason why the first five attempts had bugs is because we are
> trying to write it in the most complicated way possible, shifting by
> logical not what?
Wonderful! Should I add your name as signed-of-by?
I will send a v3 patch later.
Really thanks for your help!

Su Hui

> regards,
> dan carpenter
>
> diff --git a/drivers/gpu/drm/i915/display/intel_tv.c b/drivers/gpu/drm/i915/display/intel_tv.c
> index 36b479b46b60..6997b6cb1df2 100644
> --- a/drivers/gpu/drm/i915/display/intel_tv.c
> +++ b/drivers/gpu/drm/i915/display/intel_tv.c
> @@ -988,7 +988,13 @@ intel_tv_mode_to_mode(struct drm_display_mode *mode,
>   		      const struct tv_mode *tv_mode,
>   		      int clock)
>   {
> -	mode->clock = clock / (tv_mode->oversample >> !tv_mode->progressive);
> +	int div = tv_mode->oversample;
> +
> +	if (!tv_mode->progressive)
> +		div >>= 1;
> +	if (div == 0)
> +		div = 1;
> +	mode->clock = clock / div;
>   
>   	/*
>   	 * tv_mode horizontal timings:
> @@ -1135,6 +1141,8 @@ intel_tv_get_config(struct intel_encoder *encoder,
>   		break;
>   	default:
>   		tv_mode.oversample = 1;
> +		WARN_ON_ONCE(!tv_mode.progressive);
> +		tv_mode.progressive = true;
>   		break;
>   	}
>   
>