[bisby]

My dad and I have the same Samsung laptop from 2012-ish. It came with Windows 7, and after upgrading to windows 8, a lot of stuff stopped working. Samsung didnt have "special" drivers for windows 8, so a lot of stuff (like the backlight buttons) didnt work properly. Eventually they fixed the problem, but they were weird out of date drivers. Windows 10 had no drivers at all.

I moved my laptop to Linux full time around the Windows 8.1 transition (which had also re-broken the drivers somehow). Everything worked great in Linux for me until kernel 4.2 or something when backlight brightness stopped working. Then after a few weeks or searching, I found a parameter that made it work again.

After applying the fixes to my dad's laptop, and setting up a few of his "must have" programs under wine for him, he claims that Ubuntu runs better for him than Windows ever did.

[pawadu]

> Everything worked great in Linux for me until kernel 4.2 or something when backlight brightness stopped working.

Interestingly, this also happened to a lot of Vaios when people upgraded to Windows 10. Now, your Linux was eventually fixed while my Vaio is still running at 0% backlight with zero response from Sony.

[bisby]

I dont know what changed in linux at kernel 4.2 (or maybe it was 4.1 or 4.3? I dunno. it was early 4.x), but I was able to fix it with a kernel boot parameter (acpi_osi=linux acpi_backlight=video). This tells the GPU to control the backlight, and everything works. Theres a lot of different laptop configurations of who powers and who runs the backlight. linux has all these options set up, but it has to pick one by default. So my laptop didnt "just work" on a fresh installation, but I was able to fix it.

I think I know what happened in windows: windows itself has no backlight driver, and the standard GPU drivers have no backlight handling (or do, but its disabled by default). So previously, these laptops would ship with a special Windows 7 driver that would handle the backlight. But its "so much work" to port that driver to windows 10... so they don't. So in this scenario, my laptop originally worked. A fresh installation would require proprietary Samsung drivers, and samsung has stopped providing those for windows 10... literally no fix available (it's possible the windows 7 drivers still work? to be clear, Ive never checked if there are work arounds or other drivers available. I switched to linux before windows 10 came out, and my dad is happy with linux resolving his backlight issues, so Ive never had to look it up)