Comment 8 for bug 1173725

Sorry, I don't think the backlight problem on the V5-171 is a regression. I've never had it work as expected.

I've now tried the acpi_osi="!Windows 2012" test, to see if this machine could be added to the temporary blacklist. I.e. whether my bug was a regression caused when Linux added the "Windows 2012" OSI string.[1] Unfortunately that boot option didn't help.

[1] https://bugzilla.kernel.org/show_bug.cgi?id=51231#c137

The result from testing v3.11-rc2 is that it does fix the problem. And as expected, the revert in v3.11-rc3 breaks it again.

To answer the question about firmware upgrades, I'm not going to try that unless it helps upstream. It's not worth reflashing "at my own risk" just to avoid passing acpi_backlight=vendor.