Re: [PATCH]: ACPI: Skip the power state check in power transition

[Matthew Garrett <mjg59@srcf.ucam.org>]

On Thu, May 14, 2009 at 09:47:39AM +0800, yakui_zhao wrote:
> On Wed, 2009-05-13 at 21:08 +0800, Matthew Garrett wrote:
> > The default behaviour should be to be compatible with Windows, 
> > regardless of what the spec says. There's an argument for providing a 
> > strict interpretation of the spec for testing purposes, but I don't
> > see 
> > any reason for it to be split up into dozens of individual kernel 
> > parameters
> The ACPI 1.0 spec is followed by windows XP. And the power state is not
> checked in power transition under windows XP.
> But we don't know whether it is still skipped on the new version
> windows.(For example: Windows 7).
>
> If the module param is removed, we must delete the source code related
> with power state check. And if the power state is checked in power
> transition on windows 7, what we should do? It is not reasonable to add
> them again.

If Windows 7 changes the behaviour then the correct approach is to key 
this behaviour on whether the system firmware requests the Windows 7 OSI 
string. The code can be #if 0ed out until then, or placed under an 
acpi.strict kernel option that turns on all standards-compliant but 
windows-incompatible code.

> Maybe it is better to determine whether the power state check is skipped
> in power transition.

We have a stated policy that Linux will default to being Windows 
compatible. You've demonstrated that in this case Linux isn't Windows 
compatible, which means that it's a bug. The correct behaviour for Linux 
here is to ignore the _STA value (or, indeed, not to call _STA at all in 
this path).

-- 

Matthew Garrett | mjg59@srcf.ucam.org