Re: [parisc-linux] RFC: I/O tree design

[Grant Grundler <grundler@cup.hp.com>]

Ryan Bradetich wrote:
> Here is my proposal for phase 2 of the I/O tree for parisc-linux.

Overall, this sounds ok to me.
Just a nit WRT to terminology.

...
> This proposal also calls for a special "root" node at
> index 0 of the device array.  The root node is the starting
> point of the I/O tree and does not have a parent, nor any
> siblings.  The root node has a single child pointer which
> points to the head of the sibling list for the system
> bus.

I would call the "root" node the "parent psuedo-bus adapter"
(or something like that) of the central bus. It's special because
it generally won't represent a physical PA I/O device. But it does
contain a "lower port address" - the fixed PA IO address your
previous bus-walk patch started with.

The idea here is you can pass "hp_device *" to your PA bus walk code
and not have seperate code for central bus or GSC bus. The bus walk
code could use the "lower port address" as a new starting point to
poke around.


thanks,
grant

Grant Grundler
parisc-linux {PCI|IOMMU|SMP} hacker
+1.408.447.7253