Hello!

I don't like telling the user to grovel around lspci -t by hand.  It's
not many lines of code to add a new -P option to lspci to show the path
to each device instead of bus:dev.fn

I like the feature, but I have a couple of minor objections to the
implementation:

-static char options[] = "nvbxs:d:ti:mgp:qkMDQ" GENERIC_OPTIONS ;
+static char options[] = "nvbxs:d:tPi:mgp:qkMDQ" GENERIC_OPTIONS ;

Please update the help_msg, too.

+static void
+show_slot_path(struct pci_dev *p)
+{
+  struct pci_dev *d = NULL;
+
+  if (opt_path && p->bus)
+    {
+      for (d = p->access->devices; d; d = d->next) {
+	if (d->hdrtype == -1)
+	  d->hdrtype = pci_read_byte(d, PCI_HEADER_TYPE) & 0x7f;

Please do not modify the hdrtype field, it is private to libpci.

Instead, always read the PCI_HEADER_TYPE register. It will be fast since
lspci caches configuration space accesses.

+	if (d->hdrtype != PCI_HEADER_TYPE_BRIDGE &&
+	    d->hdrtype != PCI_HEADER_TYPE_CARDBUS)
+	  continue;
+	if (pci_read_byte(d, PCI_SECONDARY_BUS) > p->bus)
+	  continue;
+	if (pci_read_byte(d, PCI_SUBORDINATE_BUS) < p->bus)
+	  continue;

Beware, cardbus bridges use different registers for secondary and subordinate bus.

... the more I think about it, the more I am convinced that we want to
re-use the bus topology builder from ls-tree.c. I will give it a try,
stay tuned.

				Martin