From: Devel [mailto:email@example.com] On Behalf Of Zheng, Lv
Sent: Thursday, October 31, 2013 10:41 AM
To: Stefan Demharter; devel(a)acpica.org
Subject: Re: [Devel] Advice for in-kernel acpi patching
> From: Devel [mailto:firstname.lastname@example.org] On Behalf Of Stefan
> Sent: Thursday, October 31, 2013 5:32 AM
> To: devel(a)acpica.org
> Subject: [Devel] Advice for in-kernel acpi patching
> Hi all,
> I have a laptop (acer 3820tg) with muxed intel + radeon graphic cards
which has the following problem:
> If I use the intel as primary card and switch the radeon card off an
on, the mux wronlgy changes to the discrete card.
> This is particularily bad if you want to enable dynamic-power-off for
the radeon card.
> I identifed the problem to be a specific STORE-call in the method
PEGP._ON in the table SSDT1.
> I also wrote a module which patches the SSDT1 table on the fly. The
function which does the real patching is attached.
> As of now I think it's a somewhat hacky solution which should be
> At first I have the following questions:
> - Is there already an easy way to patch acpi methods within the linux
> - Do you agree that solving such stuff within the kernel is the right
way to go?
There are means in the Linux kernel can be used to achieve such kind of
namespace patching, please find the documentation at:
Plus, Documentation/acpi/method_customizing.txt introduces a way to override a control
method at runtime, without rebuilding the kernel, please check if it helps.
I think the latter might be able to fit your requirement.
> Any other advice would be appreciated, too.
> Best Regards,
> PS: I don't think loading a user-patched SSDT1 table at kernel start
is the right way to go because:
> - It doesn't work out of the box for new linux installations on the
> - If you change the bios setting for the graphic cards from
> to intel-only or radeon-only the patched SSDT1 table would be wrong.
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