Matthew Garrett <mjg59@xxxxxxxxxxxxx> writes:
> BIOS authors don't always program all the features of hardware. This is
> often the case for Intel IDE controllers, which are usually able to run
> in AHCI mode but are rarely configured to do so. Reprogramming them is
> easy enough other than the requirement for some MMIO space. If the BIOS
> hasn't allocated this, it's necessary for us to do so manually.
Traditionally we've had bad experiences forcing hardware to do something
the BIOS didn't consider. e.g. occasionally the BIOS has good reasons
to not allow it; maybe it knows about some errata or other problem
the kernel doesn't.
If you do this then don't make it default at least, but only allow
to force it use an option.