[Bug 208661] New: Backlight doesn't work with both nv_backlight and acpi_video

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=208661

            Bug ID: 208661
           Summary: Backlight doesn't work with both nv_backlight and
                    acpi_video
           Product: Drivers
           Version: 2.5
    Kernel Version: 5.7.0-1-amd64
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Video(DRI - non Intel)
          Assignee: drivers_video-dri at kernel-bugs.osdl.org
          Reporter: iknstudio at protonmail.com
        Regression: No

Created attachment 290457
  --> https://bugzilla.kernel.org/attachment.cgi?id=290457&action=edit
vbios.rom

Hi,

I'm trying to get backlight working on this laptop. I am using the nouveau
driver, and kernel 5.7.
I tried a few different parameters for acpi_osi=, like the following:
 - acpi_osi=linux
 - acpi_osi=! acpi_osi="Windows 2012"
 - acpi_osi=! acpi_osi="Windows 2015"
however, none of them worked. /sys/class/backlight/*/bl_power is 0 for both
devices at boot. acpi_video0 has a max_brightness of 10 while nv_backlight has
a max brightness of 100.

I am attaching the vbios. The graphics card is nVidia GT540M.

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