This does not occur on Linux Mint 19.1 Cinnamon and Ubuntu 18.04.1 Desktop. It also disables the brightness keys when we are at the login screen. Note for T420s users: Using the workarounds listed below (except the chmod workaround) in Linux Mint 19.1 MATE introduces a weird bug, whereby the brightness is reset every time the power cord is plugged or unplugged.
After applying the workarounds, you will be able to use brightness up Fn Home and brightness down Fn End to increase and decrease the LCD brightness as normal. There are a number of workarounds for this problem. To make matters worse, the ACPI video module in kernels up to 2.6.19.1 has a hideous bug that gets many ACPI video events wrong, and this is the probable cause for the "tries to switch video output" effect some users observed, which can cause serious problems in certain configurations, like X server hangs.
The Linux kernel handling for the ACPI video event brighness up is not implemented by the ACPI video module before Linux 2.6.20-rc?, which results in the brightness up key not working, even if the event is handled correctly. But from 15, the brightness level will go down to 13, 11, 9, 7, 5, 3, 1, then 0. For example, starting from 0, the brightness level will go up to 2, 4, 6, 8, 10, 12, 14, then 15. It will seem to the user, that the brightness up/down keys work in steps of 2.
One problem is that when the brightness up Fn Home or brightness down Fn End key is pressed, that event is processed twice. This made ThinkPad users suffer from a bug in the Linux kernel handling of ACPI video events.
0 kommentar(er)
