https://bugzilla.kernel.org/show_bug.cgi?id=60659
--- Comment #9 from Alexey Brodkin alexey.brodkin@gmail.com --- I have exactly the same laptop - HP Elitebook 8560w with a nVidia Quadro 1000M, NVC1 (GF108) in nouveau slang - and used to suffer from similar issue.
But I've just tried Fedora 20 image for Graphics test day (http://fedorapeople.org/groups/qa/201310-Graphics_Test-mini-x86_64.iso) and with "acpi_backlight=vendor" specified I may confirm that in Gnome environment (it's 3.10) backlight controls work properly.
Indeed without "acpi_backlight=vendor" (which is a default situation) Gnome shows brightness change animation and "/sys/class/backlight/acpi_video0/brightness" changes properly, but real screen brightness doesn't change.
Here's my kernel version information: ========== Linux localhost 3.11.6-300.fc20.x86_64 #1 SMP Fri Oct 18 22:31:53 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux ==========
Boot command-line (from beginning of dmesg output) is: ========== Command line: initrd=initrd0.img root=live:CDLABEL=LIVE rootfstype=vfat ro rd.live.image quiet rhgb rd.luks=0 rd.md=0 rd.dm=0 acpi_backlight=vendor BOOT_IMAGE=vmlinuz0 ==========
So I assume this bug might be closed now as resolved. Let me know if there's a need for some more information/testing.