[Devel] Missing _BQC method

[Devel] Missing _BQC method

[Anthony Jenkins]

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What may the OSPM assume/do about a missing _BQC (Brightness Query
Current level) method?  The last two HP ENVY laptops I owned do not have
this method, and FreeBSD's acpi_video driver (currently) requires it to
control screen brightness - unless I can assume _only_ the OSPM can set
the screen brightness.  My current workaround is a patch to the DSDT to
add a simple method that copies and returns a variable used by _BCM
(Brightness Control Method).

Thanks in advance,

-- 
Anthony Jenkins

Re: [Devel] Missing _BQC method

[Zhang Rui]

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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. 

thanks,
rui
>   The last two HP ENVY laptops I owned do not have
> this method, and FreeBSD's acpi_video driver (currently) requires it
> to
> control screen brightness - unless I can assume _only_ the OSPM can
> set
> the screen brightness.  My current workaround is a patch to the DSDT
> to
> add a simple method that copies and returns a variable used by _BCM
> (Brightness Control Method).
> 
> Thanks in advance,
>