suspend/resume on Lenovo X1 (regression from reports on wiki)

[Jung-uk Kim]

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On 2013-09-04 18:47:47 -0400, Jung-uk Kim wrote:
> On 2013-09-04 18:39:07 -0400, Bengt Ahlgren wrote:
>> The value of hw.acpi.video.lcd0.brightness changes when the
>> screen brightness keys (Fn+Home/End) are pressed, but nothing
>> happens with the screen.  Same goes for changing the value with
>> sysctl.  After a fresh boot it works with one issue.  The screen
>> brightness level seems to lag behind one keypress.  Without
>> acpi_video, screen brightness changes without the lag.
> 
>> hw.acpi.video.lcd0.active is always stuck at 0 - can't change
>> with sysctl (regardless if the screen is on after a fresh boot,
>> or black after a text console suspend/resume):
> 
>> [root at bit ~]# sysctl hw.acpi.video.lcd0.active=1 
>> hw.acpi.video.lcd0.active: 0 -> 0
> 
>> Again, for my old X40 with non-KMS Xorg intel driver has 
>> (curiously, the screen blinks when issuing this sysctl command):
> 
>> [bengta at P142 ~]$ sysctl hw.acpi.video hw.acpi.video.lcd0.active:
>> 1 hw.acpi.video.crt0.active: 0
> 
> Then, KMS probably breaks acpi_video(4), too. :-(

kib let me know that there is a way to make it work but it was not
well-integrated to i915kms.ko.  If you are interested in fixing it,
dev/drm2/i915/intel_opregion.c is the source and you can download the
specification from here:

https://01.org/linuxgraphics/sites/default/files/documentation/acpi_igd_opregion_spec.pdf

Jung-uk Kim
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