On Sun, 2017-01-01 at 17:01 -0500, Anthony Jenkins wrote:
What may the OSPM assume/do about a missing _BQC (Brightness Query
Current level) method?
_BQC is optional according to the latest ACPI spec.
I don't know about the others, but in Linux, the brightness level is
set to 100% during boot if _BQC is missing, and a cached value is used
to save the current brightness level.
The last two HP ENVY laptops I owned do not have
this method, and FreeBSD's acpi_video driver (currently) requires it
control screen brightness - unless I can assume _only_ the OSPM can
the screen brightness. My current workaround is a patch to the DSDT
add a simple method that copies and returns a variable used by _BCM
(Brightness Control Method).
Thanks in advance,