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From:   Kees Cook <keescook@chromium.org>
Date:   Mon, 22 Oct 2018 07:10:02 -0700
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Subject: Re: [PATCH 2/2] Compiler Attributes: auxdisplay: panel: use __fallthrough
To:     Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
        "Gustavo A. R. Silva" <gustavo@embeddedor.com>
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On Sun, Oct 21, 2018 at 10:14 AM, Miguel Ojeda
<miguel.ojeda.sandonis@gmail.com> wrote:
> Let gcc know these cases are meant to fall through to the next label
> by annotating them with the new __fallthrough statement attribute;
> and remove the comment since it conveys the same information
> (which was also parsed by gcc to suppress the warning).
>
> Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
> ---
>  drivers/auxdisplay/panel.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/auxdisplay/panel.c b/drivers/auxdisplay/panel.c
> index 21b9b2f2470a..0755034e49ba 100644
> --- a/drivers/auxdisplay/panel.c
> +++ b/drivers/auxdisplay/panel.c
> @@ -1367,7 +1367,7 @@ static void panel_process_inputs(void)
>                                 break;
>                         input->rise_timer = 0;
>                         input->state = INPUT_ST_RISING;
> -                       /* fall through */
> +                       __fallthrough;
>                 case INPUT_ST_RISING:
>                         if ((phys_curr & input->mask) != input->value) {
>                                 input->state = INPUT_ST_LOW;
> @@ -1380,11 +1380,11 @@ static void panel_process_inputs(void)
>                         }
>                         input->high_timer = 0;
>                         input->state = INPUT_ST_HIGH;
> -                       /* fall through */
> +                       __fallthrough;
>                 case INPUT_ST_HIGH:
>                         if (input_state_high(input))
>                                 break;
> -                       /* fall through */
> +                       __fallthrough;
>                 case INPUT_ST_FALLING:
>                         input_state_falling(input);
>                 }
> --
> 2.17.1
>

I would prefer we continue to use the comment style until we've got
confirmed support for (at least) Clang, Coverity, CPPcheck, smatch,
and eclipse.

-Kees

-- 
Kees Cook
Pixel Security