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

["Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>]

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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).

From reading the code comments led_set_brightness_sync() sounds like the
right function to call, so maybe we only need to fix gpio-led (and maybe
some others)?

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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