[PATCH] drm/radeon: add new AMD ACPI header and update relevant code

[Alex Deucher]

On Thu, Aug 2, 2012 at 12:31 PM, Luca Tettamanti <kronos.it at gmail.com> wrote:
> On Thu, Aug 2, 2012 at 5:03 PM, Alex Deucher <alexdeucher at gmail.com> wrote:
>> I admit I'm not really an ACPI expert, but thinking about this more,
>> I'm wondering if maybe we should just send the appropriate brightness
>> change, switch display, etc. event to userspace rather than handling
>> it directly in the radeon driver, then let userspace callback down via
>> the bl interface, etc.  With backlight for example, does handling it
>> in the kernel driver as per your patch prevent userspace from seeing
>> the brightness up/down event?  Wouldn't that break things like OSD
>> brightness displays and such?
>
> No, the event is sent to userspace by the standard ACPI video driver,
> it works as before.
> Changing brightness usually goes like this:
> 1) user presses a hotkey
> 2) a notification is generated (0x86 or 0x87)
> 3) video.ko handles the notification and calls into ACPI to change the
> level (_BCM) and firmware does its magic
> 4) a key press (brightness up/down) is sent to userspace
>
> With ATIF step 3 does not actually change the brightness, it just send
> out another event (VIDEO_PROBE, or one of the device specific ones) so
> we need to take care of that too. The rest of the process, including
> the delivery of the key presses, stays the same.

Excellent!  thanks for clarifying.

Alex