linux-kernel - Re: [PATCH] leds: pca9532: Extend pca9532 device tree support

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Date:   Wed, 8 Feb 2017 17:12:09 +0100
From:   Felix Brack <fb@...c.ch>
To:     Jacek Anaszewski <jacek.anaszewski@...il.com>, riku.voipio@....fi,
        rpurdie@...ys.net, pavel@....cz, linux-leds@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     f.brack@...s.ch
Subject: Re: [PATCH] leds: pca9532: Extend pca9532 device tree support

Hello Jacek,

On 07.02.2017 21:45, Jacek Anaszewski wrote:
> Hi Felix,
> 
> Thanks for the patch.
> 
> On 02/07/2017 07:11 PM, Felix Brack wrote:
>> This patch extends the device tree support for the pca9532 allowing LEDs to blink, dim or even being unchanged, i.e. not being turned off during driver initialization.
> 
> Isn't it possible to apply desired settings with existing LED subsystem
> brightness file, and delay_on/off files exposed by timer trigger?
> 
> Best regards,
> Jacek Anaszewski
> 

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'.

regards, Felix