Brightness control not working on Ubuntu 12.04(mac)

[Lunarts]

On imac 2011(12,1) 21,1 inches; using the keyboard brightness keys shows the brightness increasing or decreasing; but the brightness itself does not change in any way; by default brightness will be set to full by ubuntu.

I was only able to change brightness with AMD catalyst or xrandr --output LVDS --brightness 0.9.

Ubuntu also does not recognize the imac auto-brightness hardware I guess.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Onno Steenbergen (osteenbergen)]

Same problem on MacBrookPro4.1 Have tried the nvidiabl module, but no luck yet. It did work in 11.10 and other previous version

[Lunarts (lunartsbr-gmail)]

At Ubuntu 12.10, the brightness work, IF I load Ubuntu without using rEFInd at all. By using rEFInd it seems brightness does not work. Tested under 0.4.6 rEFInd.

If someone can test if using the pre rEFInd entry(press alt at startup, load 'windows' option) provided by a grub installed to the hd root(sda) the brightness work, and using post rEFInd interference linux entry which the brightness does not work; it can confirm the issue is rEFInd, not ubuntu.

[Yoyo (l3c5o9chqwzc)]

I am using Ubuntu 18.04 and this problem has still not been fixed nor has anybody looked at it, I would like it fixed because I don't want to go back to Mac OS X, but I might have to because this is just ridiculously bright...