linux-kernel - Re: [PATCH 5/7] platform/x86: fujitsu-laptop: do not update ACPI device power status

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Date:   Thu, 22 Jun 2017 16:58:43 -0700
From:   Darren Hart <dvhart@...radead.org>
To:     Michał Kępień <kernel@...pniu.pl>
Cc:     Jonathan Woithe <jwoithe@...t42.net>,
        Andy Shevchenko <andy@...radead.org>,
        platform-driver-x86@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/7] platform/x86: fujitsu-laptop: do not update ACPI
 device power status

On Thu, Jun 22, 2017 at 11:02:35PM +0200, Michał Kępień wrote:
> > On Fri, Jun 16, 2017 at 06:40:56AM +0200, Michał Kępień wrote:
> > > Calling acpi_bus_update_power() for ACPI devices FUJ02B1 and FUJ02E3 is
> > > pointless as they are not power manageable (neither _PS0 nor _PR0 is
> > > defined for any of them), which causes their power state to be inherited
> > > from their parent devices.  Given the ACPI paths of these two devices
> > > (\_SB.PCI0.LPCB.FJEX, \_SB.FEXT), their parent devices are also not
> > > power manageable.  These parent devices will thus have their power state
> > > initialized to ACPI_STATE_D0, which in turn causes the power state for
> > > both FUJ02B1 and FUJ02E3 to always be ACPI_STATE_D0 ("on").
> > > 
> > 
> > How confident are we that all implementations of these two ACPI devices lack
> > _PS0 and _PR0 ?
> 
> I looked at DSDT dumps of four different Fujitsu laptops released in the
> past ten years or so for which at least one of these two ACPI devices is
> present and found no traces of either of these methods being defined for
> them.  I do not think we have a way of ensuring that the above holds
> true for every other model out there, but I will point out that
> fujitsu-laptop is the only user of acpi_bus_update_power() outside of
> drivers/acpi.

OK, thanks. Queueing to testing.

-- 
Darren Hart
VMware Open Source Technology Center