linux-kernel - Re: [PATCH] drm/ingenic: Use resource

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

Hi,

Le ven., juin 24 2022 at 09:31:59 +0800, Jiapeng Chong 
<jiapeng.chong@...ux.alibaba.com> a écrit :
> This was found by coccicheck:
> 
> ./drivers/gpu/drm/ingenic/ingenic-drm-drv.c:1149:35-38: WARNING: 
> Suspicious code. resource_size is maybe missing with res.
> 
> Signed-off-by: Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
> ---
>  drivers/gpu/drm/ingenic/ingenic-drm-drv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c 
> 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, 
> bool has_components)
>  	}
> 
>  	regmap_config = ingenic_drm_regmap_config;
> -	regmap_config.max_register = res->end - res->start;
> +	regmap_config.max_register = resource_size(res);

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

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

Cheers,
-Paul


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