linux-kernel - Re: i915 backlight

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Date:	Thu, 01 Aug 2013 17:07:03 +0800
From:	Aaron Lu <aaron.lu@...el.com>
To:	Borislav Petkov <bp@...en8.de>
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 08/01/2013 04:12 PM, Borislav Petkov wrote:
> 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

Yes, so the event is correctly sent out.

> 
>> 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.

Err...we have the event sent out on hotkey press and the interface also
works, but still, using hotkey to adjust brightness level is broken...

I just found an old acer laptop that has similar issue(or even worse: on
X starts, an almost black screen is shown and hotkey adjust doesn't
work), I'll look into this.

> 
> 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

Yes, different interface has different brightness ranges and a value in
one range may turn out to be the same actual brightness level of another
value in another range.

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

:-)

> 
> Thanks guys.
> 
Thanks,
Aaron
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