Re: [Etherboot-developers] Re: [Etherboot-users] pci.c patch

[Donald J C. <dj...@ci...>]

"Eric W. Biederman" wrote:
> 
> Ken Yap <ke...@bi...> writes:
> 
> > >For the last case reported on this list, this code won't solve it.
> > >The problem there was serverworks has 2 parrallel pci buses.  I'm
> > >not certain if they are even bridged.
> > >
> > >Unless there is a performace problem setting busses = 256, and
> > >scanning all potential PCI busses should be much more reliable.
> >
> > Do you know how Linux does it?
...
> Seriously if we make scan bus have busses = 256.  And then never
> increment the bus count we will be fine, and the code will be simple.
> 
> 255 is the maximum possible bus number, and etherboot already tests
> for the presence of a pci device in the slot, so it should ignore an
> unused bus pretty quickly.  It already correctly ignores an unused
> bus or the previous patch wouldn't have worked.  Plus etherboot has an
> early out mechanism, so we shouldn't even get past the first pci bus
> on most machines.

Maybe this should be a Config option.  Since only a very few people
seem to run into it, leave the default as is and allow a simple change
to Config to select whatever number of busses the user wants to examine.
rom-o-matic could offer the option, as well (although I don't want to
speak for Marty, he is about the most helpful person I've come across
recently.)

Of course, if there is no problem with the above analysis, then just
checking all possible busses might be fine.  I am a little leary that
some machine somewhere will puke if you go poking around for busses
that aren't there (but then I know about as much about PCI as I know
about quantum physics.)

-Don

--
Don Christensen    Senior Software Development Engineer
  dj...@ci...    MMABU - Mid-Market Access Business Unit
  Cisco Systems    ComLOB - Commercial Line of Business
   San Jose, CA    "So much relies on the course that you take
                   The fool and the wise man both burn at the stake"