Comment 20 for bug 257827

SRU Justification:

Impact: Bad brightness handling on a wide range of laptops, plus boot crashes on a number of Samsung laptop.

Fix Description: direct backport of a group of ACPI changes which sort out backlight handling plus prevent non-existant display devices being detected as real.

Patch:
    http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-intrepid.git;a=commit;h=6620210fc1da8a39db88281290a0271d46e57283
    http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-intrepid.git;a=commit;h=ff8ad74bf82886a50cdc6b5ca0671dbe63e7f435
    http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-intrepid.git;a=commit;h=7279cb0e60d00b9fe0ca4292aacd6372f83c495e
    http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-intrepid.git;a=commit;h=2871e0ac9a33e81e9b4c68dd7e10c01ec452360f
    http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-intrepid.git;a=commit;h=971f09bdfb75a9923c61d99af3db1e006a8bc354
    http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-intrepid.git;a=commit;h=78da909520bf8169b7aa57729f5daade4daf76ef
    http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-intrepid.git;a=commit;h=56b51fa2eaf86599058dc905139d810fd847ea58
    http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-intrepid.git;a=commit;h=e525a3ca3b31b63144f177470dcf823bca381327
    http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-intrepid.git;a=commit;h=926f8037764bb44f52005f7ab7f946a62b005c91
    http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-intrepid.git;a=commit;h=4d7a929d3df4589ccb3c23f5ffb2774112c80a82

Risks: testing by a number of affected users has demonstrated successful boot and improvements in brightness handling.

TEST CASE: see bug report.