linux-kernel - Re: 2.6.22-rc1-mm1 [cannot change thermal trip points]

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Message-ID: <20070517215203.GB7336@elf.ucw.cz>
Date:	Thu, 17 May 2007 23:52:03 +0200
From:	Pavel Machek <pavel@....cz>
To:	Len Brown <lenb@...nel.org>
Cc:	Chuck Ebbert <cebbert@...hat.com>, len.brown@...el.com,
	Maciej Rutecki <maciej.rutecki@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	torvalds@...ux-foundation.org
Subject: Re: 2.6.22-rc1-mm1 [cannot change thermal trip points]

Hi!

> > >     ACPI: thermal trip points are read-only
> > 
> > What was the rationale? Can we get this one reverted? 
> > 
> > Some machines (HP omnibook xe3) have broken trip points -- too high --
> > so machine will overheat and trigger hw shutdown before starting
> > passive cooling.
> > 
> > That's really broken, and write to trip points is reasonable way to
> > 'fix' that. (I'd understand if you only ever let trip points to
> > decrease... but otoh root should be able to shoot himself....)
> 
> No, writing trip-points is neither a fix, nor it is reasonable.
> It is a workaround at best, and it is a dangerous and mis-leading hack.
> 
> The OS has no capability to actually change the ACPI trip points
> that are used by the BIOS.  Changing the OS copy of them
> to make the user think that trip events will actually
> happen when the temperature crosses the OS copy is crazy.

Aha... wait. It seemed to work for me when I enabled thermal
polling...

Slowing cpu down / shutdown / turn the fan on is done in the os after
all. Should we just start polling temperatures when user writes custom
trip points? 

> If there are systems with broken thermals and the
> ACPI thermal control needs and over-ride to turn
> on the fan, then that is fine -- but using
> fake trip-points and giving the user the impression
> that they are real is not viable.

They become real when we fake _TSP, too, ..?
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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