On Thu, May 04, 2017 at 03:42:54PM +0300, Lars Noodén wrote:
> I've also tried adding "acpi_backlight=vendor" to the kernel boot options.

Try:
acpi-backlight=vendor
instead of
acpi_backlight=vendor

If that still doesn't work, then try:
acpi-backlight=vendor acpi_osi=Linux

Greg


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