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SubjectPCI bookkeeping
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Is there something (other than the kernel sources)
that I can read in order to understand the background
to the current state of PCI handling? I'm asking
because I (think I) have found an interrupt handling
bug that derives from uncoordinated management of
PCI config info, but I don't want to proclaim that
Linux is broken if the real problem is just a lack
of understanding on my part.

Here's what I'm tryng to understand: in 2.2.X
in pcibios_fixup_devices() [and apparently in
pcibios_fixup_irqs() in 2.4.0test8 as well] we run
through the list of PCI devices (as represented
by the in-kernel data structures) looking in each
device structure for its IRQ, if any. We then
calculate new IRQ values (suitable for use with the
I/O-APIC?) and write those new values back into
the corresponding structure. Later on, various
drivers use code like pcibios_read_config_byte()
to query the IRQ value for use during setup of
their interrupt handlers.

The problem I'm seeing is that at least one driver
has signed up to handle the wrong IRQ because,
when it queried that PCI config value, it went
back and got it from PCI config space rather
than from the in-kernel data structures where the
(correct) recalculated value had been stored. So,
I'm wondering if our Official Approach is to always
query the in-kernel data structures which have
been setup so nicely for us, or are we supposed
to obtain (some or all of) that sort of info from
PCI space? Or is this all just a bleeding mess?

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