Bug 195116 - Display brightness control/resuming require acpi_video to be loaded after i915kms
Summary: Display brightness control/resuming require acpi_video to be loaded after i91...
Status: New
Alias: None
Product: Base System
Classification: Unclassified
Component: kern (show other bugs)
Version: CURRENT
Hardware: Any Any
: --- Affects Only Me
Assignee: freebsd-acpi (Nobody)
Keywords: i915
Depends on:
Reported: 2014-11-17 17:52 UTC by Lutz Bichler
Modified: 2019-01-22 09:12 UTC (History)
1 user (show)

See Also:

Info of affected system (15.40 KB, text/plain)
2019-01-22 09:07 UTC, shadow53
no flags Details

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Description Lutz Bichler 2014-11-17 17:52:18 UTC
On an Asus UX31A (Ivybridge) it is required to load the acpi_video module after the i915kms module to be able to control the brightness (hw.acpi.video.lcd0.brightness) or to successfully resume the machine. 

Therefore, it is not possible to directly load the acpi_video module at startup
(especially because loading the i915kms module from loader.conf leads to a black screen on this machine).
Comment 1 shadow53 2019-01-22 09:07:42 UTC
Created attachment 201323 [details]
Info of affected system

Text file contains the output of pciconf -lv, /var/run/dmesg.boot, freebsd-version, and uname -a in that order.

System uses a system and kernel built from source, using the default GENERIC configuration for amd64. Had this issue using the default binary updates as well.
Comment 2 shadow53 2019-01-22 09:12:19 UTC
New to bugzilla - didn't realize the attaching of files was its own comment.

The system described in the attachment has this same issue, where brightness cannot be controlled if acpi_video is loaded on boot but can be controlled if the module is unloaded and loaded again. The system is a laptop with an Intel Skylake i5 processor and Optimus graphics, using only the Intel card.

I have not run into issues with black screens, though that may be because I'm using the i915kms module from the drm-fbsd12.0-kmod package, loaded using kld_list in rc.conf.