linux-kernel - Re: [ibm-acpi-devel] Fan level 7 after resume wit 2.6.28-rc3

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Message-ID: <20081113072623.GA1574@ucw.cz>
Date:	Thu, 13 Nov 2008 08:26:23 +0100
From:	Pavel Machek <pavel@...e.cz>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	ibm-acpi-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [ibm-acpi-devel] Fan level 7 after resume wit 2.6.28-rc3

On Sun 2008-11-09 09:30:11, Henrique de Moraes Holschuh wrote:
> On Sat, 08 Nov 2008, Rafael J. Wysocki wrote:
> > > Meanwhile, I suggest you just remove the calls to fan_suspend and fan_resume
> > > as a workaround.
> > 
> > Speaking of which, last time I looked at fan_suspend and fan_resume, they
> > were hopelessly broken (I admit that was quite some time ago, though).
> 
> And they still were. I have the patch fixing it, and it reworked that path
> entirely.  Will send it soon.
> 
> > IMO, fan_suspend() is not necessary at all and the only thing fan_resume()
> > could do is to make the kernel's data structures reflect the actual state of
> > the fan.
> 
> There are NO kernel data structures to reflect the actual state of the fan.
> The fan BELONGS to the EC in the thinkpad.  We don't store any crap about it
> in the driver, except to -track- one quirk.  We query the EC for all the
> required data (which happens to be a single byte) every time we need the
> info.  If the user asks us to do something, we send that to the EC and then
> promptly forget about it.
> 
> So, I don't have to restore anything for things to just work.  The "feature"
> was added because people who set the fan to something different than AUTO
> wanted it to retain the state they set across sleep, which the box won't do
> by itself (the DSDT resets the fan on the WAK path).
> 
> OTOH, if I want to restore anything across sleep/resume, I have to store the
> state on sleep.
> 
> But there is no way I am slowing down the fan on resume: it could be in
> emergency mode due to thermal conditions.

Well... one part  of me says that if user explicitely asked for
overheat he should get that :-). 

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