[haiku-development] Re: acpi_backlight_support
- From: Fredrik Holmqvist <fredrik.holmqvist@xxxxxxxxx>
- To: haiku-development@xxxxxxxxxxxxx
- Date: Sun, 3 Apr 2011 23:04:53 +0200
2011/4/3 Clemens <clemens.zeidler@xxxxxxxxxxxxxx>:
> On Sat, 02 Apr 2011 11:41:43 +1300, Brecht Machiels <brecht@xxxxxxxxxxx>
> wrote:
>> [..]
>> Basically, I need to check whether
>> the _BCL method is available for a specific device. Is this possible to
>> check for a particular method in acpi_backlight_support?
>>
> [..]
> Otherwise I see no other way than scan through the complete acpi namespace
> tree and check for this method.
ACPI Spec 4.0, Section B: ACPI Extensions for Display Adapters doesn't
mention where in the tree it should live and it can actually be
several displays attached. Example from spec show LCD, TV and CRT. So
I think the correct way is to scan for it.
I'm not sure if we expose the tree walking methods of ACPICA in public
headers, but it's not hard to do if needed. (ACPICA/Haiku OS could
need some reworking for cleaner integration). The ACPICA docs have all
the info needed: http://www.acpica.org/documentation/ on walking the
tree with high level calls or low level iteration. I'd recommend you
to read it anyway.
Keep in mind that we are still a one or two releases behind latest
ACPICA release, so the docs might be small inconsistencies to our
ACPICA version.
/Fredrik Holmqvist,TQH
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