linux-kernel - Re: [PATCH] acpi/video: Add Lenovo IdeaPad Yoga 13 to acpi video detect blacklist

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Message-ID: <20131014034927.GA3638@tango.0pointer.de>
Date:	Mon, 14 Oct 2013 05:49:28 +0200
From:	Lennart Poettering <mzxreary@...inter.de>
To:	Aaron Lu <aaron.lu@...el.com>
Cc:	Len Brown <lenb@...nel.org>, "Rafael J. Wysocki" <rjw@...k.pl>,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	platform-driver-x86@...r.kernel.org
Subject: Re: [PATCH] acpi/video: Add Lenovo IdeaPad Yoga 13 to acpi video
  detect blacklist

On Mon, 14.10.13 10:36, Aaron Lu (aaron.lu@...el.com) wrote:

> > - Backlight control doesn't work via ACPI without acpi_osi="!Windows 2012"
> > - Backlight control doesn't work via ACPI with acpi_osi="!Windows 2012"
> > - Backlight control doesn't work via EC commands from ideapad-laptop.c
> > 
> > The only way backlight handling is supported on the Yoga 13 is via the
> > intel video driver.
> 
> Since I don't have access to the acpidump of this system, my only
> question is, does the firmware has a _OSI("Windows 2012") query in DSDT
> table?

Yes, it appears to do that as part of _OSC.

The disassembled DSDT table is here:

http://0pointer.de/public/yoga13-dsdt.dsl

> > Or in other words: the situation for the Yoga 13 is *unrelated* to the
> > Windows 8 issues, and your patch.
> 
> I think they are related...
> If the firmware is compatible to Windows 8, then my patch will disable
> ACPI video backlight interface to prefer GPU's interface.

OK, that might indeed work.

> > I'll soon send another patch which also blacklists the thing in the
> > ideapad driver, so that only the intel backlight driver is enabled on
> > Yoga 13 systems, at which point everything will work fine.
> 
> Right, that is needed. And if going with my patch, the ideapad driver
> will need to be patched similarly like thinkpad_acpi to add a check of
> acpi_video_backlight_support before it decides to register its own
> backlight interface.

The ideapad driver currently skips registration of the backlight device
if acpi_video_backlight_support() returns true. is that all you need?

Hmm, regarding your patch series, do you plan to skip the registration
of the acpi backlight device if the "raw" device is supported? I mean,
the intel driver could be compiled as a module (and generally is on the
popular distros), so at the time the ACPI subsystem wants to register
the backlight device and know if a raw backlight device is around it
never will be, so what is the point of that? Or am I missing something?

Lennart

-- 
Lennart Poettering - Red Hat, Inc.
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