FN hotkeys not working after kernel loads (Was: Dell Latitude 5400 + plasma - keyboard?)

[Hans <hans.ullrich@loop.de>]

Still hasseling with this problem....

I am now believing, that the reason of the problem is either a BIOS issue or a 
kernel issue.

Tested several things and I the issue appears as soon as the kernel is 
started. In the internet I found informations, that if the BIOS does not see 
Windows, it may disable several functions. 

Here a kernel parameter like acpi_osi=Linux or similar should help. Tried 
several combonations, lie acpi_osi=Linux or acpi_osi=!Windows 2022 or 
acpi_backlight=vendor and combinations of this - but got no success.

However, it is clear, the functions like screen brightness etc. stop working, 
as soon as the kernel loads. When grub is active (active here means: boot grub 
menu, where to chose the kernel to start), the brightness of the screen can be 
changed. But as soon I press enter, and the kernel loads,  it stops working.

At that moment /usr amd /var are still not mounted (as I have to open the 
encrypotion manually). This means: No configuration is involved and no other 
binaries.

Thus let me conclude: It is a kernel issue with the BIOS and the only way I 
see, will be to enter some parameters like described above.

However, though reading a lot of manuals, I am lost, what to set and how to 
start. And in the internet I saw many many people as lost at me with the same 
issue. 

I have the hope, some kernel developer might read here or some specialist or 
someone got into the same issue than me.

I will work on and try harder, but at the moment I am stuck.

Thanks for reading this.

Best

Hans