linux-kernel - Re: [GIT PULL] LED updates

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Date:	Fri, 08 Feb 2008 08:03:33 +0100
From:	Németh Márton <nm127@...email.hu>
To:	Richard Purdie <rpurdie@...ys.net>,
	Henrique de Moraes Holschuh <hmh@....eng.br>
CC:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL] LED updates

Richard Purdie wrote:
> On Thu, 2008-02-07 at 19:38 -0200, Henrique de Moraes Holschuh wrote:
>> On Thu, 07 Feb 2008, Richard Purdie wrote:
>>> Márton Németh:
>>>       leds: Add support for hardware accelerated LED flashing
>>>       leds: hw acceleration for Clevo mail LED driver
>> This one has a loose end: when you call brightness_set on a led with
>> hardware flash acceleration, you will leave the trigger armed, BUT the led
>> won't blink anymore.  That's just wrong.
> 
> Agreed.

My only question is that do you know any LED hardware which can blink _and_
can set the brightness independently? If there would be such a LED I could
imagine that the brightness can be changed while the LED remains blinking at
some low frequency. For example a simple LED with brightness set possibility and
blinking directed by software is an example where the blinking and the brightness
setting are completely independent.

I agree, however, that if the brightness is set to LED_OFF, the trigger
should be also removed.

>> Either we should always remove *any* (hardware accelerated or not!) active
>> trigger when a write to brightness_set is done, or the stuff about "calling
>> brightness_set will disable the hardware accelerated blink" has to go.
>>
>> I personally prefer that we would always remove any active trigger if
>> brightness_set is to be called.  IMHO, it is neater, and it is also the
>> least-surprise-behaviour from an user perspective with the LED_OFF:LED_FULL
>> triggers we have right now.
> 
> Even without the hardware acceleration, a user write to set_brightness
> leaves any active trigger active and isn't really intuitive or right
> either. 
> 
>> Which one will be?  If it is "remove any active trigger", I'd not mind
>> writing the patch.

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