Re: [PATCH] leds: trigger/tty: Use led_set_brightness_nosleep() to set brightness

[Jacek Anaszewski <jacek.anaszewski@gmail.com>]

Hi Uwe,

On 4/17/23 14:44, Uwe Kleine-König wrote:
> Hello,
> 
> On Mon, Apr 17, 2023 at 02:28:52PM +0200, Pavel Machek wrote:
>>> After commit ba8a86e4dadb ("leds: trigger/tty: Use
>>> led_set_brightness_sync() from workqueue") this is the second try to
>>> pick the right function to set the LED brightness from a trigger.
>>>
>>> led_set_brightness_sync() has the problem that it doesn't work for LEDs
>>> without a .brightness_set_blocking() callback. This is (among others)
>>> the case for LEDs connected to non-sleeping GPIOs.
>>>
>>> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
>>
>> I don't think this is right.
>>
>> _nosleep calls _nopm, which assmues it can't sleep, and schedules
>> another workqueue to set the LED.
> 
> Then which is the right variant?
> led_set_brightness() and led_set_brightness_nosleep() set via a workqueue
> (which is bad) and led_set_brightness_sync() doesn't work for some LEDs
> (notably LEDs on non-sleeping GPIOs).

Can you remind me the context of this patch, why using workqueue is
bad here?

-- 
Best regards,
Jacek Anaszewski