Re: Thinkpad ACPI led -- it keeps blinking

[Pavel Machek <pavel-+ZI9xUNit7I@public.gmane.org>]

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On Sat 2019-04-27 22:35:35, Jacek Anaszewski wrote:
> On 4/27/19 9:34 PM, Pavel Machek wrote:
> >On Sat 2019-04-27 18:55:37, Jacek Anaszewski wrote:
> >>On 4/26/19 11:42 PM, Pavel Machek wrote:
> >>>Hi!
> >>>
> >>>>Kernel 5.1.0-rc1 + some unrelated bits.
> >>>
> >>>I tried adding
> >>>https://marc.info/?l=linux-kernel&m=151622365715313&q=raw as Jacek
> >>>suggested, and it is still broken.
> >>>
> >>>Test code is this: ledtest actually works as expected on first try,
> >>>but keeps blinking on second run. Strange.
> >>
> >>Did it work for previous releases? If yes, then bisect should help here.
> >
> >Absolutely no idea :-(. I assume "no". Capslock LED on the same system
> >works as expected.
> >
> >I still hope thinkpad people will speak up, notice it does not work
> >for them, and debug it :-).
> 
> I see this driver implements blink_set:
> 
> tpacpi_leds[led].led_classdev.blink_set = &led_sysfs_blink_set;
> 
> and also applies some internal logic related to the type
> of supported LEDs, and the way how the hardware is accessed.
> 
> To eliminate the problem on the LED core side you could
> disable initialization of blink_set op in the driver.

Yep, software blinking will very likely work ok.

[  226.949924] LED set 0 to 2
[  226.950766] LED set 0 to 2... 0
[  232.613577] LED set 0 to 2
[  232.613991] LED set 0 to 0
[  232.614467] LED set 0 to 2... 0
[  232.616442] LED set 0 to 0... 0

Thinkpad ACPI driver is being asked to turn led to blink [232.613577]
LED set 0 to 2 and turn it off [  232.613991] LED set 0 to 0
simultaneously. It has no internal locking and ACPI is slow. That
can't end well.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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