Screen Brightness (Problem abandoned!)

[Howard]

I have two earlier versions of PCLOS on my Inspiron mini 10v as well as the LXDE 2012.06 that I'm currently using as default.  On both the older installations the F4 & F5 keys control the screen brightness as they should.  The more recent is an updated LXDE 2010 that I had to abandon mid 2012.  In this version a pop-up screen shows a brightness icon and a horizontal analogue bar.  But, in my current 2012.06 version these keys are dead.  I cannot find any differences between this and the 2010 version (which still works mostly) , the keyboard setting is US, Generic 101 key-PC  in both and there doesn't seem to be any missing software that's relevant.

(I haven't been able to make a working live CD of 2012.12 to check that - there seems to be something wrong with the mirror sites.)

[AnotherUser]

what kernel are you running? On my Inspiron 15R, I had to modify the kernel startup parameters to add acpi_backlight=vendor to get FN+F4 and FN+F5 to work.

[Howard]

Thanks.  According to synaptic it's kernel 2.6.38.8pclos3.bfs.  The older version definitely has a different kernel (but I don't know which), that's a difference I hadn't thought of.  I've never messed with kernel settings before - where do I find it?

[AnotherUser]

I don't know if it's the same in LXDE, but in the KDE version, it's under PCLinuxOS Control Center --> Boot --> Setup Boot System, then click NEXT to get the list of boot options. Click on the kernel you'd like to change the boot settings on, and click on the MODIFY button. Click on the APPEND line, and at the end add acpi_backlight=vendor to the end of it (make sure to have a space to separate this from the last thing on the line). Click OK, then FINISH, then reboot

[Howard]

Thanks Anotheruser - I see: it's just another way of editing menu.lst - I usually use an editor directly (e.g. Leafpad).  I tried that, but adding acpi_backlight=vendor didn't restore the activity of F4/F5.

This had me exploring a bit and I found some more info on:

https://wiki.archlinux.org/index.php/Backlight

I found that adding acpi_backlight=vendor did make some differences though, the folders in /sys/class/backlight/ were the dell_backlight ones (the same as in the older installation).  Without it the folder there was acpi_video0.

BUT I've just tested the LXDE 2012.12 live CD and the F4/F5 keys work with that so I'll install it when I can find time (it's half a day of customising.)   So I'll not bother with this any more.