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

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Message-ID: <20081106152255.GA23717@x61>
Date:	Thu, 6 Nov 2008 16:22:55 +0100
From:	Tino Keitel <tino.keitel@...ei.de>
To:	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 Thu, Nov 06, 2008 at 12:11:21 -0200, Henrique de Moraes Holschuh wrote:

[...]

> fulll-speed > 7 > AUTO.
> 
> > Correction: I just tested a bit further, and it doesn't work. If I set
> > fan level to 3, suspend, resume, set fan level to auto, and
> > resume/suspend again, fan level is restored to 3. This is because
> > fan_control_desired_level isn't updated by fan_update_desired_level()
> 
> Fan level should NEVER be restored to 3, it should end up set to auto,
> full-speed, or 7 when the box finishes resuming.  If it can be restored to
> 3, something is hideously broken.

Then it seems I misunderstood the whole fan state resume stuff. I
thought that it restores the value that was set before suspend, unless
it was set to some emergency value meanwhile. I think I should not look
into this further, as there are too many restrictions and/or side
effects involved. However, I think it's a good idea to document all
that in the source code in the future, so that other people can really
understand this. I think it's also a good idea to collect all the
quirks, safety nets and fallbacks in a central place, so that the
context is clear.

> Maybe something in the hwmon class is also trying to keep values across
> sleep/suspend?

This happened only with my first (broken) patch, so no need to bother
about this.

Regards,
Tino
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