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

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Message-ID: <725c338e-af4c-1332-6c27-462c2dc1b97f@gmail.com>
Date:   Wed, 8 Feb 2017 20:42:20 +0100
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Felix Brack <fb@...c.ch>, 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

Hi Felix,

On 02/08/2017 05:12 PM, Felix Brack wrote:
> 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'.

It looks like all you need is default-state property.
I'd rather avoid exposing prescaler and pwm registers in DT.

-- 
Best regards,
Jacek Anaszewski