>Many BIOS ACPI tables from years ago simply _assumed_ that you have
>hardcoded irq 14/15, even... Their irq descriptors for 14/15 would be
>absent or completely non-functional.
>
>Or maybe its the $pirq table I'm recalling. One of the two, anyway.
For x86, the ACPI interrupt configuration process is to identity-map
the IOAPIC entries below 16 1:1 PIC:IOAPIC,
unless there are interrupt source overrides
(such as commonly done to swizzle IRQ0 from a different pin)
This makes legacy-mode ATA happy. Hard code ATA to 14/15 and
off you go.
But there is a gray area where the ATA controller registers
as a PCI device, but Linux goes off and looks in the ACPI PRT
for that PCI-dev and finds no entry. So if you didn't
have the hard-coded 14/15, you'd be dead.
Then there are cases where the PRT specifies something
_other_ than 14/15 for ATA, and in that cases the hard-coded
default is the wrong thing to do; and the workaround is
to use BIOS SETUP options to be sure that ATA is set up
in legacy mode.
I suspect Linux could be smarter here. The 14/15 should be
the backup default for when the tables
don't give us anything else; not the only option.
-Len
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
