linux-kernel - Re: [PATCH] drm/loongson: Fix two warnings because of passing wrong type

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Date:   Mon, 10 Jul 2023 13:26:49 +0300
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     Sui Jingfeng <suijingfeng@...ngson.cn>,
        Sui Jingfeng <suijingfeng@...ngson.cn>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Li Yi <liyi@...ngson.cn>
Cc:     loongson-kernel@...ts.loongnix.cn, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] drm/loongson: Fix two warnings because of passing wrong
 type

On Mon, 10 Jul 2023, Sui Jingfeng <suijingfeng@...ngson.cn> wrote:
> When accessing I/O memory, we should pass '__iomem *' type instead of
> 'void *' simply, otherwise sparse tests will complain. After applied
> this patch, the following two sparse warnings got fixed.

Usually the commit message should explain why it's okay to cast away the
warning.

Because realistically this doesn't "fix" the warning, this merely hides
it.

BR,
Jani.

>
> 1) drivers/gpu/drm/loongson/lsdc_benchmark.c:27:35:
>    sparse:     expected void volatile [noderef] __iomem *
>    sparse:     got void *kptr
>
> 2) drivers/gpu/drm/loongson/lsdc_benchmark.c:42:51:
>    sparse:     expected void const volatile [noderef] __iomem *
>    sparse:     got void *kptr
>
> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202307100243.v3hv6aes-lkp@intel.com/
> Signed-off-by: Sui Jingfeng <suijingfeng@...ngson.cn>
> ---
>  drivers/gpu/drm/loongson/lsdc_benchmark.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/loongson/lsdc_benchmark.c b/drivers/gpu/drm/loongson/lsdc_benchmark.c
> index b088646a2ff9..36e352820bdb 100644
> --- a/drivers/gpu/drm/loongson/lsdc_benchmark.c
> +++ b/drivers/gpu/drm/loongson/lsdc_benchmark.c
> @@ -24,7 +24,7 @@ static void lsdc_copy_gtt_to_vram_cpu(struct lsdc_bo *src_bo,
>  	lsdc_bo_kmap(dst_bo);
>  
>  	while (n--)
> -		memcpy_toio(dst_bo->kptr, src_bo->kptr, size);
> +		memcpy_toio((void __iomem *)dst_bo->kptr, src_bo->kptr, size);
>  
>  	lsdc_bo_kunmap(src_bo);
>  	lsdc_bo_kunmap(dst_bo);
> @@ -39,7 +39,7 @@ static void lsdc_copy_vram_to_gtt_cpu(struct lsdc_bo *src_bo,
>  	lsdc_bo_kmap(dst_bo);
>  
>  	while (n--)
> -		memcpy_fromio(dst_bo->kptr, src_bo->kptr, size);
> +		memcpy_fromio(dst_bo->kptr, (void __iomem *)src_bo->kptr, size);
>  
>  	lsdc_bo_kunmap(src_bo);
>  	lsdc_bo_kunmap(dst_bo);

-- 
Jani Nikula, Intel Open Source Graphics Center