linux-kernel - Re: [PATCH] power: supply: oplc_battery: Use fallthrough pseudo-keyword

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Date:   Fri, 4 Jun 2021 13:54:24 +0200
From:   Sebastian Reichel <sebastian.reichel@...labora.com>
To:     Wei Ming Chen <jj251510319013@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Kees Cook <keescook@...omium.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: Re: [PATCH] power: supply: oplc_battery: Use fallthrough
 pseudo-keyword

[+cc Kees and Gustavo]

Hi,

On Fri, May 07, 2021 at 08:47:24PM +0800, Wei Ming Chen wrote:
> Add pseudo-keyword macro fallthrough[1]
> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through
> 
> Signed-off-by: Wei Ming Chen <jj251510319013@...il.com>
> ---

I suppose completely empty case branch is also ok and just not
documented? I mean it does not hurt much in this case, but quite
a few power-supply drivers have something like this and it would
IMHO reduce readability to add fallthrough; to all of them.

property_is_writable(dev, prop) {
    switch (prop) {
        case A:
        case C:
        case E:
            return true;
        default:
            return false;
    }
}

Thanks,

-- Sebastian

>  drivers/power/supply/olpc_battery.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/power/supply/olpc_battery.c b/drivers/power/supply/olpc_battery.c
> index e0476ec06601..743b7f1cf9ea 100644
> --- a/drivers/power/supply/olpc_battery.c
> +++ b/drivers/power/supply/olpc_battery.c
> @@ -238,6 +238,7 @@ static int olpc_bat_get_charge_full_design(union power_supply_propval *val)
>  	case POWER_SUPPLY_TECHNOLOGY_LiFe:
>  		switch (mfr) {
>  		case 1: /* Gold Peak, fall through */
> +			fallthrough;
>  		case 2: /* BYD */
>  			val->intval = 2800000;
>  			break;
> -- 
> 2.25.1
> 

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