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

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Date:   Fri, 4 Jun 2021 07:14:28 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Sebastian Reichel <sebastian.reichel@...labora.com>,
        Wei Ming Chen <jj251510319013@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] power: supply: oplc_battery: Use fallthrough
 pseudo-keyword



On 6/4/21 06:54, Sebastian Reichel wrote:
> [+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

Exactly; it's not documented because it doesn't need to be marked
with fallthrough; :)

Not sure what was the motivation for this patch.

--
Gustavo

> 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
>>