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

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Date:   Tue, 30 Jul 2019 09:58:22 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Sebastian Reichel <sre@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] HSI: ssi_protocol: Mark expected switch fall-throughs

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 <gustavo@...eddedor.com>

Reviewed-by: Kees Cook <keescook@...omium.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