--- Comment #26 from Antony J.R firstname.lastname@example.org --- (In reply to Takashi Iwai from comment #25)
OK, then you're hitting multiple issues, as it seems.
The inconsistent value read from sysfs was addressed by my patch. But, I suppose that the main reason of the non-functional backlight is that the driver misdetected the backlight control over aux.
I refreshed again the KMP with a hack patch to disable the aux support. Please give it a try later again. This will show a line "XXX ext_caps=0x..." in kernel log.
Thank you for your time. I can now control the brightness with Fn Keys or the OS Slider in OpenSUSE.
So the problem was with the aux detection.
I know this is not a proper fix but it works. I hope you upstream this work to the mainline kernel or OpenSUSE patches??