[ltp] [patch 10/11] ibm-acpi: workaround for EC 0x2f initialization bug

[Henrique de Moraes Holschuh]

On Mon, 09 Oct 2006, Shem Multinymous wrote:
> On 10/9/06, Henrique de Moraes Holschuh <hmh@hmh.eng.br> wrote:
> >The workaround flags the status and level as "unknown" on module 
> >load/kernel
> >boot, until we are certain at least one fan control command was issued.
> 
> If we ever see the status changing, we can also trust the new value.

Indeed we can.  I like the idea, I will implement this.

> Maybe we can even trust any value other than 0x07?

That would require people with a wide range of ThinkPad models to report
back on my call for fan bug testers, to know for sure.

> OTOH, what happens after resume from suspend to disk?

The ACPI DSDT usually sets the fan to auto.  In fact, we wouldn't know of
the bug if the stupid things set the fan to something on startup as well
(in _INI methods).

> Also, should we save the fan status on suspend and restore it on resume?

No, we cannot do this, except as a model-specific quirk to work around ACPI
DSDT bugs.

> (My take: no. Thermal conditions may have changed, it's best to leave
> it at the default.)

Exactly.

-- 
  "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