libpciaccess bogus bridge data - commit 2bda5b73

Bryce Harrington bryce at
Mon Dec 6 11:38:24 PST 2010

On Mon, Dec 06, 2010 at 09:35:48AM -0800, Jesse Barnes wrote:
> On Wed, 1 Dec 2010 18:54:22 -0800
> Bryce Harrington <bryce at> wrote:
> > Jesse,
> > 
> > I have a question about change 2bda5b73 that you did to libpciaccess
> > last year, to stop pci_device_get_bridge_buses() from looking at bus
> > data if the bridge data was not read.
> > 
> > A ubuntu bug reporter says that this check is preventing his device from
> > getting detected properly - see
> > 
> >
> > 
> > Looking at the code I see that for case 0x04 there's already a check for
> > NULL, where it attempts to re-read the bridge info, so presumably there
> > are at least some situations where NULL bridge.pci is expected?
> > 
> > What I'm wondering is if the check should be less strict in cases of
> > multi-function cards, or if somewhere else in the code needs updated to
> > read these devices properly.
> The multifunction check is probably ok, but there should still be a
> bridge above the device regardless, even if it's just a host bridge I
> think, so we should figure out why that's not getting set...

In the discussion on 681207, it seems the portion of the data structure
being tested by this patch for null is always going to be null when it's
cast.  So the original reporter finds this check always results in the
function exiting early, and suggests the patch should be reverted.  What
are your thoughts?


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