linux-kernel - Re: [PATCH] drm/amd/display: fix compilation error due to shifting negative value

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Date:   Fri, 2 Jun 2023 10:28:38 -0400
From:   Hamza Mahfooz <hamza.mahfooz@....com>
To:     "GONG, Ruiqi" <gongruiqi@...weicloud.com>,
        Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Pan Xinhui <Xinhui.Pan@....com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     Xiu Jianfeng <xiujianfeng@...wei.com>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Wang Weiyang <wangweiyang2@...wei.com>,
        amd-gfx@...ts.freedesktop.org, gongruiqi1@...wei.com
Subject: Re: [PATCH] drm/amd/display: fix compilation error due to shifting
 negative value

On 6/2/23 06:12, GONG, Ruiqi wrote:
> Currently compiling linux-next with allmodconfig triggers the following
> error:
> 
> ./drivers/gpu/drm/amd/amdgpu/../display/include/fixed31_32.h: In function ‘dc_fixpt_truncate’:
> ./drivers/gpu/drm/amd/amdgpu/../display/include/fixed31_32.h:528:22: error: left shift of negative value [-Werror=shift-negative-value]
>    528 |  arg.value &= (~0LL) << (FIXED31_32_BITS_PER_FRACTIONAL_PART - frac_bits);
>        |                      ^~
> 
> Use `unsigned long long` instead.
> 
> Signed-off-by: GONG, Ruiqi <gongruiqi@...weicloud.com>

Applied, thanks!

> ---
>   drivers/gpu/drm/amd/display/include/fixed31_32.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/include/fixed31_32.h b/drivers/gpu/drm/amd/display/include/fixed31_32.h
> index ece97ae0e826..d4cf7ead1d87 100644
> --- a/drivers/gpu/drm/amd/display/include/fixed31_32.h
> +++ b/drivers/gpu/drm/amd/display/include/fixed31_32.h
> @@ -525,7 +525,7 @@ static inline struct fixed31_32 dc_fixpt_truncate(struct fixed31_32 arg, unsigne
>   
>   	if (negative)
>   		arg.value = -arg.value;
> -	arg.value &= (~0LL) << (FIXED31_32_BITS_PER_FRACTIONAL_PART - frac_bits);
> +	arg.value &= (~0ULL) << (FIXED31_32_BITS_PER_FRACTIONAL_PART - frac_bits);
>   	if (negative)
>   		arg.value = -arg.value;
>   	return arg;
-- 
Hamza