linux-kernel - Re: ACPI OSI disaster on latest HP laptops

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Date:	Sat, 2 Aug 2008 16:41:14 +0100
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
Cc:	Len Brown <lenb@...nel.org>, Thomas Renninger <trenn@...e.de>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	linux-acpi <linux-acpi@...r.kernel.org>,
	"Moore, Robert" <robert.moore@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andi Kleen <ak@...ux.intel.com>,
	Christian Kornacker <ckornacker@...e.de>
Subject: Re: ACPI OSI disaster on latest HP laptops - critical temperature shutdown

On Sat, Aug 02, 2008 at 11:38:33AM -0300, Henrique de Moraes Holschuh wrote:

> Yes.  IBM ThinkPads store the result of each version test separately, and I
> recall I saw at least one DSDT code path that didn't test all of them in
> order to select a branch of code to run.

As an example, here's a section from the T61:

                    If (\_OSI ("Windows 2001"))
                    {
                        Store (0x01, \WNTF)
                        Store (0x01, \WXPF)
                        Store (0x00, \WSPV)
                    }

                    If (\_OSI ("Windows 2001 SP1"))
                    {
                        Store (0x01, \WSPV)
                    }

                    If (\_OSI ("Windows 2001 SP2"))
                    {
                        Store (0x02, \WSPV)
                    }

And then later:

           If (LAnd (\WXPF, LGreaterEqual (\WSPV, 0x01)))
            {
                PPMS (0x02)
            }

The only way WXPF can be non-zero and WSPV can be greater or equal to 
one is if more than one of those tests succeeded.

> > Not all BIOSes would support this, so we'd need to support the Windows 
> > workarounds anyway. At that point, there's no real benefit in having 
> > multiple codepaths.
> 
> Sorry, but I will disagree.
> 
> Anything that can help in the future with the vendors that are better at
> Linux support is a good thing.  You are right that we will still have to
> deal with the others, but there are such things as vendor-specific windows
> workarounds (they didn't want to change their firmware, or they couldn't, or
> the others didn't care to add the workaround, etc).  If that vendor uses the
> "NotWindows" OSI correctly, we would not need to take any special action.

Allowing vendors to special-case Linux means that we have to have a 
special-case path for the minority of vendors who ask for this. It's 
added complexity and we don't actually gain anything from it.

-- 
Matthew Garrett | mjg59@...f.ucam.org
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