Re: [PATCH] vt: keyboard: Use led_set_brightness() in LED trigger activate() callback

[Hans de Goede <hdegoede@redhat.com>]

Hi Jiri,

On 5/13/24 7:09 AM, Jiri Slaby wrote:
> On 11. 05. 24, 17:20, Hans de Goede wrote:
>> A LED trigger's activate() callback gets called when the LED trigger
>> gets activated for a specific LED, so that the trigger code can ensure
>> the LED state matches the current state of the trigger condition.
>>
>> led_trigger_event() is intended for trigger condition state changes and
>> iterates over _all_ LEDs which are controlled by this trigger changing
>> the brightness of each of them.
>>
>> In the activate() case only the brightness of the LED which is being
>> activated needs to change and that LED is passed as an argument to
>> activate(), switch to led_set_brightness() to only change the brightness
>> of the LED being activated.
> 
> LGTM, but could you elaborate on what behavior this fixes? Should it be backported to stable?

It does not really fix any user visible behavior. This is just something which
I noticed while looking at all LED trigger activate callbacks because of some
LED core patches I was writing.

The code before this patch gets the job done, it syncs the VT capslock/numlock/etc
status to the LEDs of a newly registered input device.

But it also ends up calling led_set_brightness() on all already registered
capslock/numlock/etc LEDs which is not necessary.

So this is just a small optimization, not a bug fix.

Regards,

Hans


> 
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>>   drivers/tty/vt/keyboard.c | 4 +---
>>   1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c
>> index a2116e135a82..804355da46f5 100644
>> --- a/drivers/tty/vt/keyboard.c
>> +++ b/drivers/tty/vt/keyboard.c
>> @@ -1033,9 +1033,7 @@ static int kbd_led_trigger_activate(struct led_classdev *cdev)
>>         tasklet_disable(&keyboard_tasklet);
>>       if (ledstate != -1U)
>> -        led_trigger_event(&trigger->trigger,
>> -                  ledstate & trigger->mask ?
>> -                    LED_FULL : LED_OFF);
>> +        led_set_brightness(cdev, ledstate & trigger->mask ? LED_FULL : LED_OFF);
>>       tasklet_enable(&keyboard_tasklet);
>>         return 0;
> 
> thanks,