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

[Luca Tettamanti]

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.

Luca