Re: [PATCH 0/3] Fix backlight issues on some Windows 8 systems

Yves-Alexis Perez
2013-06-25T21:46:08Z

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On mar., 2013-06-25 at 22:33 +0100, Matthew Garrett wrote:
> > I was referring to “standardize the behaviour by leaving up to
> > userspace”. A lot of thinkpads (for example) (all the pre-windows 8
> > ones) have a perfectly working ACPI backlight interface.
>
> And this patchset won't alter their behaviour.

Sorry if I was unclear and if my mail implied that. It was about your
remark later in the thread (and the mail from Daniel Vetter)
>
> > Also, if the kernel has no way of knowing which levels work, I fail to
> > see how userspace can do better.
>
> It can't. That's why this patchset disables the ACPI interface on
> Windows 8 systems.
>
> > I understand that switching to intel_backlight instead of acpi_video0
> > follows what Windows 8 recommends but for me it looks orthogonal to the
> > fact ACPI methods now have some awkward (Lenovo) or broken (Dell). I
> > mean, it's not the first time firmware people break some kernel
> > behavior. I know it's usually not easy to contact them, but shouldn't
> > those methods be fixed, instead of somehow blindly switching to graphic
> > drivers?
>
> No. The correct answer to all firmware issues is "Are we making the same
> firmware calls as the version of Windows that this hardware thinks it's
> running". If Windows 8 doesn't make these calls, we shouldn't make these
> calls.

But if that introduce regressions, shouldn't workarounds be found then?
Sorry if I keep repeating that but brightness keys handling in-kernel is
quite a useful feature and losing it (because of the “behave exactly
like Windows 8 kernel” policy) is indeed a regression.
--
Yves-Alexis

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