Re: [PATCH] leds: pca9532: Extend pca9532 device tree support

From: Jacek Anaszewski
Date: Thu Feb 09 2017 - 16:14:23 EST


On 02/09/2017 03:24 PM, Pavel Machek wrote:
> Hi!
>
>>>> This might be a misunderstanding. My patch is not meant to replace
>>>> anything for driving the LEDs once the kernel is fully loaded. The LED
>>>> subsystem offers quite a lot of possibilities to do this.
>>>>
>>>> My patch mainly deals with the 'default' state of the LEDs immediately
>>>> when the driver gets loaded.
>>>> Here is an example: I have a system with a LED named 'RUN' which is
>>>> turned on steady by U-Boot (indicating "system booting"). When the
>>>> PCA9532 driver loads this LED gets turned off due to initialization.
>>>> However I would like it remain lit until later a script will make that
>>>> 'RUN' LED blink (indicating "system running"). This script will of
>>>> course use the existing LED subsystem to do so. To keep the 'RUN' LED
>>>> lit I need the DT property 'default-state' being set to 'PCA9532_KEEP'.
>>>
>>> It looks like all you need is default-state property.
>>
>> For the example with keeping the 'RUN' led turned on, yes. However I
>> would have to configure PSC and PWM registers to make the 'RUN' LED
>> blink, for example.
>
> Is that really useful? Keeping the state from u-boot until userland can take
> control... ok, why not.
>
> If it is useful, right, you can do it. But it will have to be generic for all
> the LEDs, not like this.
>
> You'll want something like
>
> default_trigger = blinking;

Actually it can be achieved currently by setting "timer" here.

> default_trigger_parameters = < 2 sec on, 1 sec off >;
>
> or something. You may want to coordinate with the USB LED people, which want
> default triggers with parametrs.

--
Best regards,
Jacek Anaszewski