Garrett: Why ACPI?

Matthew Garrett explains
why ACPI exists and why it is not as bad a thing as some think.

There's an alternative universe where we decided to teach the
kernel about every piece of hardware it should run on. Fortunately
(or, well, unfortunately) we've seen that in the ARM world. Most
device-specific simply never reaches mainline, and most users are
stuck running ancient kernels as a result. Imagine every x86 device
vendor shipping their own kernel optimised for their hardware, and
now imagine how well that works out given the quality of their
firmware. Does that really seem better to you?