Hi,

It needs the graphics driver work done. The backlight control is done by
the driver on these chips, via acpi but not entirely implemented within
acpi.

A
On Jul 5, 2016 10:13 AM, "Marin Bernard" <li...@olivarim.com> wrote:

>
>
> Hi,
>
> I just bought a Lenovo Thinkpad T450 laptop and installed FreeBSD on top
> of it. It runs fine except I'm not able to change the display backlight.
> The laptop embeds a Core i5-5300U CPU with an Intel Graphics 5500 adapter
> (Broadwell). I know the adapter is not yet supported, but I hoped to have
> backlight control working anyway!
>
> Backlight control is working fine with OpenBSD 5.9, Linux 4.1+ and
> Windows, which is not very surprising as those OSes also support the
> display adapter. It's not working on FreeBSD 10.3-RELEASE nor 11.0-ALPHA6.
>
> What I have tried:
>   - I tried to load acpi_ibm and acpi_video kernel modules and tweak the
> sysctl they provide: I was able to modify the systctl values, but backlight
> remained the same.
>   - I also tried to install graphics/intel-backlight. There again: I was
> able to change values, but it didn't change the backlight.
>   - I tried to load the i915kms intel modul, just in case backlight
> control needed this to work properly. As before, no effect. I think the
> module is just ignoring my adapter as it does not support it.
>
> I'm ready to cope with the VESA driver for some time but I'd really like
> to get backlight control working. Do you have suggestions ? Is there
> anything I can do to help ?
>
> I use the UEFI framebuffer with vt in graphics mode. I did not try to run
> Xorg yet. Should I do it ?
>
> Thanks,
>
> --Marin
>
>
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