https://bugzilla.novell.com/show_bug.cgi?id=578578
https://bugzilla.novell.com/show_bug.cgi?id=578578#c6
Michael Chang changed:
What |Removed |Added
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CC| |jlee@novell.com
--- Comment #6 from Michael Chang 2011-08-24 05:53:16 UTC ---
Hi Matthias,
Yes. This is related with "Intel backlight combination mode", that is the
backlight brightness level can be changed via LPBC (that is the PCI
configuration register your workaround uses) OR i915's BLC_PWM_CTL register. As
far as I know, we have to access both registers at the same time to guarantee a
reasonable dynamic backlight range (The LPBC is acts a multiplier of 255 with
BLC_PWM_CTL value).
This combination mode is used on older Intel graphics and yours is fall into
this category (GMA4500 is used in Montevina platform, we ever came across
similar issue on this hardware). For modern Intel graphics, the LPBC register
was obsoleted.
I also CC Joey Lee as he is maintainer of ACER acpi/wmi driver. This might also
be an ACPI issue as these function keys would trigger SCI events (Q event) to
execute corresponding ACPI method (Q method) an change the backlight (via the
opregion or whatever means) in it.
First, it would be good if you could help to provide dmesg while your are
changing the backlight, whith following kernel command-line parameter.
drm.debug=0x02
I would suggest a step, for example ..like
$ dmesg -c
$ xrandr --output LVDS1 --set BACKLIGHT 6
$ xrandr --output LVDS1 --set BACKLIGHT 9
$ dmesg > /tmp/xrandr-backlight.log
Thanks. :)
Thanks. :)
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