you are right about Intel AHCI, I also had to change it once in BIOS for detecting some Intel's SSD drives. But I think that was again for boot time hardware initialization. Are you sure that these parameters are accessed from BIOS routines on a running Linux kernel?
Rajat
2010/11/5 Greg Freemyer <greg.freemyer@xxxxxxxxx>
2010/11/4 Rajat Sharma <fs.rajat@xxxxxxxxx>:
> As I can remember, Linux uses BIOS only at the bootup time, after that on aRajat,
> running kernel, there is no role of BIOS routines. Please refer to
> Understanding Linux Kernel for specific details. It also has one appendix on
> Linux Boot-up sequence which depends on BIOS. Linux has its own drivers for
> controlling IOAPIC and PCI drivers etc.
> Rajat
At least for the storage stack that is misleading because although
BIOS routines are not used, that does not mean the BIOS has no impact
on the kernel functionality.
There are configuration choices made in the bios that have a
fundamental impact on the kernels operation:
eg.
AHCI operation vs. Legacy
JBOD vs. fakeraid
etc.
fundamentally impact how the hardware work and actually cause entirely
different ATA drivers to be used because these selections impact the
PCI-ID reported by the hardware.
Then there are more detailed tuning parameters that are read by the
drivers to tune performance of the individual ATA drivers. For these
parameters, the storage drivers attempt to determine them on their
own, but in several scenarios the ATA controller is simply better able
to make an informed guess and the kernel simply reads those tuning
parameters and uses them.
Greg
