linux-kernel - Re: i915 backlight

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Date:	Thu, 1 Aug 2013 10:12:15 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Aaron Lu <aaron.lu@...el.com>
Cc:	intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
	lkml <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: i915 backlight

On Thu, Aug 01, 2013 at 09:13:35AM +0800, Aaron Lu wrote:
> Can you please run acpi_listen and then press the Fn-Fx key, see if the
> events are correctly sent out?

Like this?

# acpi_listen
video/brightnessdown BRTDN 00000087 00000000
video/brightnessup BRTUP 00000086 00000000
video/brightnessdown BRTDN 00000087 00000000
video/brightnessup BRTUP 00000086 00000000
video/brightnessdown BRTDN 00000087 00000000
video/brightnessup BRTUP 00000086 00000000
video/brightnessdown BRTDN 00000087 00000000
video/brightnessup BRTUP 00000086 00000000
video/brightnessdown BRTDN 00000087 00000000
^C

> From the bug page:
> https://bugzilla.kernel.org/show_bug.cgi?id=51231#c80
> I got the impression that both the acpi_video interface and the vendor
> interface thinkpad_screen are broken. So adding this cmdline here works
> suggests that either thinkpad_screen works or thinkpad vendor driver
> doesn't get loaded or doesn't create that interface for some reason.
> 
> Alternatively, if the intel_backlight interface works(highly possible),
> you can use xorg.conf to specify the that backlight interface for X.
> 
> Section "Device"
>         Option     "Backlight"	"intel_backlight"
> 	Identifier  "Card0"
> 	Driver      "intel"
> 	BusID       "PCI:0:2:0"
> EndSection

Yeah, that didn't work *but* manually writing to both:

/sys/class/backlight/acpi_video0/brightness

and

/sys/class/backlight/intel_backlight/brightness

works.

The ranges are different, though:

intel_backlight/actual_brightness:1000
intel_backlight/bl_power:0
intel_backlight/brightness:1000
intel_backlight/max_brightness:4437
intel_backlight/type:raw

acpi_video0/actual_brightness:41
acpi_video0/bl_power:0
acpi_video0/brightness:41
acpi_video0/max_brightness:100
acpi_video0/type:firmware

I guess I need to write me a dirty script for now ... :-)

Thanks guys.
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