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Ambrevar

Member

Registered: 2011-08-14

Posts: 212

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HP EliteBook 2530p / Intel GS45 backlight issue

A classic: I can set the backlight via /sys/class/backlight/intel_backlight/brightness but the Fn buttons fail. I know I can remap the buttons, but I'd like to solve this properly.

Using the stock kernel and kernel parameters, sysfs exposes:

$ ls /sys/class/backlight
acpi_video0 intel_backlight

I've tried many things from the wiki (intel and backlight articles) and the web, including:

1. Kernel parameters

acpi_backlight=vendor
acpi_backlight=native
acpi_backlight=video
acpi_osi=
acpi_osi= acpi_backlight=vendor
acpi_osi="!Windows 2012"
acpi_osi="!Windows 2012" acpi_backlight=vendor
acpi_osi=Linux
acpi_osi=Linux acpi_backlight=vendor
...

None of them work, however some of them (acpi_osi=...) allow systemd to restore the backlight on startup.
Beside, some of them remove the acpi_video0 interface, but this does not solve the issue.

2. Xorg configuration

If I use the following settings,

Section "Device"
        Identifier  "card0"
        Driver      "intel"
        Option      "Backlight"  "intel_backlight"
        BusID       "PCI:0:2:0"
EndSection

Xorg fails to fire up with the following error:

[   708.357] (II) LoadModule: "intel"
[   708.357] (WW) Warning, couldn't open module intel
[   708.357] (II) UnloadModule: "intel"
[   708.357] (II) Unloading intel
[   708.357] (EE) Failed to load module "intel" (module does not exist, 0)
[   708.357] (EE) No drivers available.
[   708.357] (EE) 
Fatal server error:
[   708.357] (EE) no screens found(EE) 

If I change "intel" to "i915" (?), X starts but the backlight issue remains.

3. BIOS

The BIOS is very poor is does not provide anything related to ACPI / backlight.

4. dmesg

I've got a few errors on startup, I haven't managed to fix them yet, and I am not sure whether they relate to the backlight issue:

[    2.586785] tpm_tis 00:01: [Hardware Error]: Adjusting reported timeouts: A 750->750000us B 2000->2000000us C 750->750000us D 750->750000us
[    2.952670] ACPI Error: Method parse/execution failed [\_SB.PCI0.GFX0._DOD] (Node ffff8801370a9c80), AE_AML_PACKAGE_LIMIT (20150930/psparse-542)
[    4.498446] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe B FIFO underrun

Any clue?

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