linux-kernel - Re: [PATCH RFC] input/elants

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Date:   Thu, 11 Feb 2021 03:19:44 +0100
From:   Michał Mirosław <mirq-linux@...e.qmqm.pl>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        linux-input@...r.kernel.org, Randy Dunlap <rdunlap@...radead.org>
Subject: Re: [PATCH RFC] input/elants_i2c: Detect enum overflow

On Wed, Feb 10, 2021 at 10:25:28AM -0600, Josh Poimboeuf wrote:
> If an enum value were to get added without updating this switch
> statement, the unreachable() annotation would trigger undefined
> behavior, causing execution to fall through the end of the function,
> into the next one.
> 
> Make the error handling more robust for an unexpected enum value, by
> doing BUG() instead of unreachable().
> 
> Fixes the following objtool warning:
> 
>   drivers/input/touchscreen/elants_i2c.o: warning: objtool: elants_i2c_initialize() falls through to next function elants_i2c_resume()
> 
> Reported-by: Randy Dunlap <rdunlap@...radead.org>
> Acked-by: Randy Dunlap <rdunlap@...radead.org>
> Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>

Reviewed-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>

> ---
>  drivers/input/touchscreen/elants_i2c.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/input/touchscreen/elants_i2c.c b/drivers/input/touchscreen/elants_i2c.c
> index 6f57ec579f00..4c2b579f6c8b 100644
> --- a/drivers/input/touchscreen/elants_i2c.c
> +++ b/drivers/input/touchscreen/elants_i2c.c
> @@ -656,8 +656,7 @@ static int elants_i2c_initialize(struct elants_data *ts)
>  			error = elants_i2c_query_ts_info_ektf(ts);
>  		break;
>  	default:
> -		unreachable();
> -		break;
> +		BUG();
>  	}
>  
>  	if (error)
> -- 
> 2.29.2
>