linux-kernel - Re: [PATCH 4/5] devicetree: leds: Introduce "panic-blink" optional property

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Date:	Wed, 6 Apr 2016 13:13:21 -0300
From:	Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
To:	Rob Herring <robh@...nel.org>
Cc:	Linux LED Subsystem <linux-leds@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Richard Purdie <rpurdie@...ys.net>,
	Jacek Anaszewski <j.anaszewski@...sung.com>
Subject: Re: [PATCH 4/5] devicetree: leds: Introduce "panic-blink" optional property

On 6 April 2016 at 12:12, Rob Herring <robh@...nel.org> wrote:
> On Mon, Apr 4, 2016 at 3:22 PM, Ezequiel Garcia
> <ezequiel@...guardiasur.com.ar> wrote:
>> It's desirable to specify which LEDs are to be blinked on a kernel
>> panic. Therefore, introduce a devicetree boolean property to mark
>> which LEDs should be treated this way.
>>
>> Signed-off-by: Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
>> ---
>>  Documentation/devicetree/bindings/leds/common.txt | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/leds/common.txt b/Documentation/devicetree/bindings/leds/common.txt
>> index 68419843e32f..dd409df9203a 100644
>> --- a/Documentation/devicetree/bindings/leds/common.txt
>> +++ b/Documentation/devicetree/bindings/leds/common.txt
>> @@ -37,6 +37,8 @@ Optional properties for child nodes:
>>                       property is mandatory for the LEDs in the non-flash modes
>>                       (e.g. torch or indicator).
>>
>> +- panic-blink : Mark this LED to be used by the panic LED trigger.
>> +
>
> We already have a way to specify LED triggers. Why can't that be used?
>

Because this is not about specifying a LED trigger.

The use case is the following: a LED is assigned to some LED trigger.
When the kernel panics, we want to switch that LED to the panic trigger,
so it blinks signalling the panic.

IOW, this allows a LED to be used for "normal operation stuff trigger",
but blink if the kernel panics.
-- 
Ezequiel García, VanguardiaSur
www.vanguardiasur.com.ar