Intel i915 backlight

[Henry Hu]

On Fri, May 9, 2014 at 6:19 PM, Xīcò <xico at atelo.org> wrote:

> Dear freebsd-x11,
>
> I am running /stable/10 (with i915kms and newcons) on a Vaio VPCZ21
> with a SandyBridge.  Unfortunately backlight is not working out of the
> box.
>
> I played a bit with the existing acpi modules (including acpi_sony and
> acpi_video), and wrote a bit of code to modify the backlight level,
> through sony acpi, but it does not seem quite effective. Basically, the
> (sony) acpi reports 16 backlight levels, iirc, but modifying them does
> not influence the actual brightness.
>
> On linux, backlight level is controlled through the graphic card. So,
> basically I am investigating how to do so on FreeBSD. I am quite unsure
> of how it works, probably xbacklight relies on xf86-video-intel. There
> is some code in sys/dev/drm2/i915/intel_panel.c which looks appropriate
> to handle the backlight, but I fail to understand how it is called by
> xorg, for instance.
>
> Well, I assume someone here will have a better understanding of all
> that, and possible on how the intel backlight works, and whether it is
> only a pwm. For now, I am relying on software xrandr --brightness to set
> an adequate luminosity, before further investigating the issue.
>

I'm using an ASUS UX51VZ, with an integrated intel display adapter, and a
NVidia card.

Now I'm using intel-backlight tool from intel-gpu-tools (
http://cgit.freedesktop.org/xorg/app/intel-gpu-tools/). It works fairly
well.

There are several ACPI functions which seem to set the brightness, but most
of them don't work, including \_SB.ATKD.SPLV.

Settings in sysctls hw.acpi.video do not work for me, although I can see
brightness levels being reported. I think that some code is absent in the
i915 module, because in sys/dev/drm2/i915/intel_opregion.c, there is a big
block of code surrounded by #ifdef CONFIG_ACPI which only works for Linux.

I've seen a patch which exposed some sysctls to adjust brightness, and it
calls intel_panel_set_backlight()/intel_panel_get_max_backlight().


> Best,
>
> --
> Xīcò
> _______________________________________________
> freebsd-x11 at freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-x11
> To unsubscribe, send any mail to "freebsd-x11-unsubscribe at freebsd.org"




-- 
Cheers,
Henry