backlight(8) and Thinkpad special keys

hey there,
i've noticed that on my lenovo thinkpad that when loading the drm-510-kmod driver
the my usual way of managing screen brightness via hw.acpi.video.lcd.brightness
does not work (the sysctl knob is not available).  when loading the drm-54-kmod
it is available.  while debugging this i've noticed that using both drivers i am
able to adjust things via the backlight(8) utility - thanks manu!

the one drawback with this is that it seems like acpi_ibm(4) is no longer able
to manage screen brightness.  i.e. i can no longer use the special brightness
function keys to increase/descrase screen brightness.

so couple questions:

1. has anyone sucessfully tied their "special" keys to the backlight utility?
2. if not is the best approach to map the screen brightness keys to special events
   via devd that would call backlight(8) directly?  my reading of the acpi_ibm
   man page seems to indicate it prefers to operate directly via sysctl which
   doesn't seem to work for me under the 5.10 drm driver.

cheers,
-pete

-- 
Pete Wright
pete@nomadlogic.org