Lenovo Z500 Screen Brightness Problem Fixed, but Why?

General
1

I’m running Cachy on a Lenovo Z500 Ideapad, i5-3230M, Intel graphics, 8 GB of RAM, 500 GB drive. Abruptly, the screen brightness dropped by over half. All the various screen brightness controls in KDE were set to max, but none would affect the brightness. At first, I thought I had a hardware problem, but I did a search and found this, exactly my problem on exactly my laptop:

https://forums.linuxmint.com/viewtopic.php?p=1091121

"so essentially you’d go to the command line and do

sudo gedit /etc/default/grub

then look for

GRUB_CMDLINE_LINUX_DEFAULT=“quiet splash”

and set it to

GRUB_CMDLINE_LINUX_DEFAULT=“quiet splash acpi_backlight=video”

then do

sudo grub-mkconfig -o /boot/grub/grub.cfg

and restart."

This worked; my screen brightness is now back to normal. So as a bit of a newbie to Arch, I’m asking:

1.) Why did this happen in the first place? Why did the screen brightness spontaneously get cut in half?

2.) How did this fix it?

Thanks to anyone who can shed some light. Just trying to learn something.

2

For point 1:
The management of hardware is made bu the driver inside kernel of linux. Sometimes, it is necessary to set argument (ie : parameters) to set properly the management by the kernel. if not, hardwa may have unexpected running, or it ( as IT pending) but not manage, so not control and stop the boot.

for the point 2:
you have add the parameter and generate a new image with update. This is fine. what else ?

3

Thanks, maclinuxbravo! After your post, I did some digging through the Arch wiki, and figured out that one reason this happens on some laptops and not others is the difference in BIOS/UEFI. The interface to the kernel can be different, and at least in this case, that’s the issue more so than the kernel driver itself.