linux-kernel - Re: [PATCH][next] drm/amd/display: Fix fall-through warning for Clang

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Date:   Thu, 17 Jun 2021 15:20:17 -0400
From:   Harry Wentland <harry.wentland@....com>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Leo Li <sunpeng.li@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] drm/amd/display: Fix fall-through warning for Clang



On 2021-06-16 4:52 p.m., Gustavo A. R. Silva wrote:
> In preparation to enable -Wimplicit-fallthrough for Clang, fix
> the following warning by replacing a /* fall through */ comment
> with the new pseudo-keyword macro fallthrough:
> 
> rivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_aux.c:672:4: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>                         case AUX_TRANSACTION_REPLY_I2C_OVER_AUX_DEFER:
>                         ^
> 
> Notice that Clang doesn't recognize /* fall through */ comments as
> implicit fall-through markings, so in order to globally enable
> -Wimplicit-fallthrough for Clang, these comments need to be
> replaced with fallthrough; in the whole codebase.
> 
> Link: https://github.com/KSPP/linux/issues/115
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Reviewed-by: Harry Wentland <harry.wentland@....com>

Harry

> ---
> JFYI: We had thousands of these sorts of warnings and now we are down
>       to just 15 in linux-next. This is one of those last remaining
>       warnings.
> 
>  drivers/gpu/drm/amd/display/dc/dce/dce_aux.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c b/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
> index 28631714f697..2fb88e54a4bf 100644
> --- a/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
> +++ b/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
> @@ -668,7 +668,7 @@ bool dce_aux_transfer_with_retries(struct ddc_service *ddc,
>  				/* polling_timeout_period is in us */
>  				defer_time_in_ms += aux110->polling_timeout_period / 1000;
>  				++aux_defer_retries;
> -				/* fall through */
> +				fallthrough;
>  			case AUX_TRANSACTION_REPLY_I2C_OVER_AUX_DEFER:
>  				retry_on_defer = true;
>  				fallthrough;
>