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Date:   Fri, 24 Jun 2022 20:00:05 +0100
From:   Paul Cercueil <paul@crapouillou.net>
Subject: Re: [PATCH] drm/ingenic: Use resource_size function on resource
 object
To:     Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Cc:     airlied@linux.ie, daniel@ffwll.ch, linux-mips@vger.kernel.org,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        Sam Ravnborg <sam@ravnborg.org>
Message-Id: <5SWZDR.5KODQDXQB5142@crapouillou.net>
In-Reply-To: <20220624013159.88646-1-jiapeng.chong@linux.alibaba.com>
References: <20220624013159.88646-1-jiapeng.chong@linux.alibaba.com>
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Hi,

Le ven., juin 24 2022 at 09:31:59 +0800, Jiapeng Chong=20
<jiapeng.chong@linux.alibaba.com> a =E9crit :
> This was found by coccicheck:
>=20
> ./drivers/gpu/drm/ingenic/ingenic-drm-drv.c:1149:35-38: WARNING:=20
> Suspicious code. resource_size is maybe missing with res.
>=20
> Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
> ---
>  drivers/gpu/drm/ingenic/ingenic-drm-drv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>=20
> diff --git a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c=20
> b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> index 2c559885347a..5514b163999f 100644
> --- a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> +++ b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> @@ -1146,7 +1146,7 @@ static int ingenic_drm_bind(struct device *dev,=20
> bool has_components)
>  	}
>=20
>  	regmap_config =3D ingenic_drm_regmap_config;
> -	regmap_config.max_register =3D res->end - res->start;
> +	regmap_config.max_register =3D resource_size(res);

These two are not equivalent. resource_size() is (res->end - res->start=20
+ 1).

If the memory resource has a size of 0x10 bytes, then using=20
resource_size() will set .max_register =3D=3D 0x10, which is invalid, as it=
=20
is already outside the memory resource.

Cheers,
-Paul


>  	priv->map =3D devm_regmap_init_mmio(dev, base,
>  					  &regmap_config);
>  	if (IS_ERR(priv->map)) {
> --
> 2.20.1.7.g153144c
>=20