FreeBSD on macbook & backlight module

Rui Paulo rpaulo at FreeBSD.org
Mon Jan 14 08:01:40 PST 2008


I have the backlight module ready to be committed (needs approval
first), but it would be great if we could create a general backlight
API. I have some initial ideas, but needs a bit more thought. 

Also, xrandr on (7.3 with "intel" video driver) seems to be able to
control the LCD backlight on MacBooks, but it seems bogus:

% xrandr --prop
Screen 0: minimum 320 x 200, current 1280 x 800, maximum 1280 x 1280
VGA disconnected (normal left inverted right x axis y axis)
LVDS connected 1280x800+0+0 (normal left inverted right x axis y axis) 286mm x 179mm
        EDID_DATA:
                00ffffffffffff0006105b9c00000000
                0e100103801d12780a87f594574f8c27
                27505400000001010101010101010101
                010101010101bc1b00a0502017303020
                36001eb3100000190000000100061020
                00000000000000000a20000000fe004c
                544e31333357310000000a20000000fc
                00436f6c6f72204c43440a20202000c6
        BACKLIGHT: 296 (0x00000128) range:  (0,296)

I don't really know about how exactly this control works, because:

1) the range is wrong.
2) setting values with xrandr --output LVDS --set BACKLIGHT <value>,
doesn't seem to be doing anything good. It just sets a high and low
value for the backlight brigthness.

If anyone knows anything about this, I would appreciate if you could
step forward.

There's another problem: xv (try it with mplayer -vo xv) seems to be
setting the backlight value on initialization. So, if you start Xorg
with backlight value of 50, then reduce it to 20 and after that try
to play a video with mplayer, the backlight value seems to come back
to 50. There are very strange interactions between xrandr and my own
backlight control kernel module. It would be great to disable xrandr's
backlight control, at least.

Regards.
--
Rui Paulo
I have the backlight module ready to be committed (needs approval
first), but it would be great if we could create a general backlight
API. I have some initial ideas, but needs a bit more thought. 

Also, xrandr on (7.3 with "intel" video driver) seems to be able to
control the LCD backlight on MacBooks, but it seems bogus:

% xrandr --prop
Screen 0: minimum 320 x 200, current 1280 x 800, maximum 1280 x 1280
VGA disconnected (normal left inverted right x axis y axis)
LVDS connected 1280x800+0+0 (normal left inverted right x axis y axis) 286mm x 179mm
        EDID_DATA:
                00ffffffffffff0006105b9c00000000
                0e100103801d12780a87f594574f8c27
                27505400000001010101010101010101
                010101010101bc1b00a0502017303020
                36001eb3100000190000000100061020
                00000000000000000a20000000fe004c
                544e31333357310000000a20000000fc
                00436f6c6f72204c43440a20202000c6
        BACKLIGHT: 296 (0x00000128) range:  (0,296)

I don't really know about how exactly this control works, because:

1) the range is wrong.
2) setting values with xrandr --output LVDS --set BACKLIGHT <value>,
doesn't seem to be doing anything good. It just sets a high and low
value for the backlight brigthness.

If anyone knows anything about this, I would appreciate if you could
step forward.

There's another problem: xv (try it with mplayer -vo xv) seems to be
setting the backlight value on initialization. So, if you start Xorg
with backlight value of 50, then reduce it to 20 and after that try
to play a video with mplayer, the backlight value seems to come back
to 50. There are very strange interactions between xrandr and my own
backlight control kernel module. It would be great to disable xrandr's
backlight control, at least.

Regards.
--
Rui Paulo


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