Why ACPI?

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?

It's understandable why ACPI has a poor reputation. But it's also hard to figure out what would work better in the real world. We could have built something similar on top of Open Firmware instead but the distinction wouldn't be terribly meaningful - we'd just have Forth instead of the ACPI bytecode language. Longing for a non-ACPI world without presenting something that's better and actually stands a reasonable chance of adoption doesn't make the world a better place.

Matthew Garrett with the usual paragraphs of wisdom.