linux-kernel - Re: CPU LED trigger: add hooks to generic code so that it works on x86

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Message-ID: <20150527084718.GA4991@amd>
Date:	Wed, 27 May 2015 10:47:18 +0200
From:	Pavel Machek <pavel@....cz>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	mingo@...hat.com, linux-kernel@...r.kernel.org, cooloney@...il.com,
	rpurdie@...ys.net, j.anaszewski@...sung.com,
	linux-leds@...r.kernel.org
Subject: Re: CPU LED trigger: add hooks to generic code so that it works on
 x86

On Wed 2015-05-27 10:08:31, Peter Zijlstra wrote:
> On Wed, May 27, 2015 at 09:47:57AM +0200, Pavel Machek wrote:
> > On Wed 2015-05-27 09:43:43, Peter Zijlstra wrote:
> > > On Wed, May 27, 2015 at 08:57:12AM +0200, Pavel Machek wrote:
> > > > 
> > > > CPU LED trigger hooks are currently hidden in arm-specific code, which
> > > > means that this trigger only works on arm. Add it to the generic
> > > > code, so that it works on x86, too.
> > > 
> > > And why do we want to go and slow down the idle loop for everyone?
> > 
> > If the trigger is not configured, this is not slowing down anyone.
> > 
> > If the trigger is configured, well, then the user requested the
> > functionality. So we are not slowing down _everyone_, just the people
> > that want the blinking.
> 
> What kind of x86 hardware will support this? If its _everything_ distros
> will have to enable this and it suddenly becomes a lot of people.

It needs directly connected leds. It is useful on thinkpad t40p, for
example.

Distros should not enable this, IMO. But I don't think overhead is
that big in either case.

But I wanted to enable it, and result was trigger that can be
configured, enabled, and just plain does not work (which is nasty).
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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