Re: [PATCH] HSI: ssi_protocol: Mark expected switch fall-throughs

[Kees Cook]

On Mon, Jul 29, 2019 at 05:45:19PM -0500, Gustavo A. R. Silva wrote:
> Mark switch cases where we are expecting to fall through.
> 
> This patch fixes the following warning (Building: arm):
> 
> drivers/hsi/clients/ssi_protocol.c: In function ‘ssip_set_rxstate’:
> drivers/hsi/clients/ssi_protocol.c:291:6: warning: this statement may fall 
> through [-Wimplicit-fallthrough=]
>    if (atomic_read(&ssi->tx_usecnt))
>       ^
> drivers/hsi/clients/ssi_protocol.c:294:2: note: here
>   case RECEIVING:
>   ^~~~
> 
> drivers/hsi/clients/ssi_protocol.c: In function ‘ssip_keep_alive’:
> drivers/hsi/clients/ssi_protocol.c:466:7: warning: this statement may fall 
> through [-Wimplicit-fallthrough=]
>     if (atomic_read(&ssi->tx_usecnt) == 0)
>        ^
> drivers/hsi/clients/ssi_protocol.c:472:3: note: here
>    case SEND_IDLE:
>    ^~~~
> 
> Notice that, in this particular case, the code comment is
> modified in accordance with what GCC is expecting to find.
> 
> Signed-off-by: Gustavo A. R. Silva <gust...@embeddedor.com>

Reviewed-by: Kees Cook <keesc...@chromium.org>

-Kees

> ---
>  drivers/hsi/clients/ssi_protocol.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/hsi/clients/ssi_protocol.c 
> b/drivers/hsi/clients/ssi_protocol.c
> index 9aeed98b87a1..504d00ec1ea7 100644
> --- a/drivers/hsi/clients/ssi_protocol.c
> +++ b/drivers/hsi/clients/ssi_protocol.c
> @@ -290,7 +290,7 @@ static void ssip_set_rxstate(struct ssi_protocol *ssi, 
> unsigned int state)
>               /* CMT speech workaround */
>               if (atomic_read(&ssi->tx_usecnt))
>                       break;
> -             /* Otherwise fall through */
> +             /* Else, fall through */
>       case RECEIVING:
>               mod_timer(&ssi->keep_alive, jiffies +
>                                               msecs_to_jiffies(SSIP_KATOUT));
> @@ -465,9 +465,10 @@ static void ssip_keep_alive(struct timer_list *t)
>               case SEND_READY:
>                       if (atomic_read(&ssi->tx_usecnt) == 0)
>                               break;
> +                     /* Fall through */
>                       /*
> -                      * Fall through. Workaround for cmt-speech
> -                      * in that case we relay on audio timers.
> +                      * Workaround for cmt-speech in that case
> +                      * we relay on audio timers.
>                        */
>               case SEND_IDLE:
>                       spin_unlock(&ssi->lock);
> -- 
> 2.22.0
> 

-- 
Kees Cook