linux-kernel - Re: [PATCH] drm/amd/display: Correctly initialize some memory in get_available_dsc

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Message-ID: <20b45faa-bc4f-3e90-f61a-f6d7407df6c0@amd.com>
Date:   Wed, 26 Apr 2023 13:28:53 -0400
From:   Hamza Mahfooz <hamza.mahfooz@....com>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     dri-devel@...ts.freedesktop.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org
Subject: Re: [PATCH] drm/amd/display: Correctly initialize some memory in
 get_available_dsc_slices()

On 4/25/23 03:53, Christophe JAILLET wrote:
> The intent here is to clear the 'available_slices' buffer before setting
> some values in it.
> 
> This is an array of int, so in order to fully initialize it, we must clear
> MIN_AVAILABLE_SLICES_SIZE * sizeof(int) bytes.
> 
> Compute the right length of the buffer when calling memset().
> 
> Fixes: 97bda0322b8a ("drm/amd/display: Add DSC support for Navi (v2)")
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
> NOT even compile-tested.
> 
> make -j7  drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.o
> 
> on my setup, it fails with:
>    CC      drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.o
> drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c:27:10: fatal error: dc_hw_types.h: Aucun fichier ou dossier de ce type
>     27 | #include "dc_hw_types.h"
>        |          ^~~~~~~~~~~~~~~
> 
> I've not investigated why.
> ---
>   drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c b/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c
> index b9a05bb025db..1d7384b2be28 100644
> --- a/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c
> +++ b/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c
> @@ -645,7 +645,7 @@ static int get_available_dsc_slices(union dsc_enc_slice_caps slice_caps, int *av
>   {
>   	int idx = 0;
>   
> -	memset(available_slices, -1, MIN_AVAILABLE_SLICES_SIZE);
> +	memset(available_slices, -1, MIN_AVAILABLE_SLICES_SIZE * sizeof(*available_slices));

Actually, I believe we can drop this memset(). Since,
get_available_dsc_slices() returns the number of indices set, and all of
the users of get_available_dsc_slices() don't cross that bound.

>   
>   	if (slice_caps.bits.NUM_SLICES_1)
>   		available_slices[idx++] = 1;
-- 
Hamza