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

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Message-ID: <20081109113011.GB8329@khazad-dum.debian.net>
Date:	Sun, 9 Nov 2008 09:30:11 -0200
From:	Henrique de Moraes Holschuh <hmh@....eng.br>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	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 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.

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh
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