Messages in this thread |  | | Subject | pci_assign_resource() inconsistency | From | Benjamin Herrenschmidt <> | Date | Mon, 11 Dec 2006 14:47:55 +1100 |
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Hi !
pci_assign_resource() was recently marked as much check the result code (which I find annoying since it alread contains a printk if it fails but anyway ... ).
So we do have a call to in in arch/powerpc/kernel/pci_32.c and I went to fix the warning and ... wondered what should we do there ? So I looked at other users and found it a bit strange...
So at first, an unassigned resource has the IORESOURCE_UNSET flag set (or is supposed to). pci_assign_resource() itself will clear that flag if it succeeds.
However, pretty much nothing else checks that flag, so it's mostly useful.
Now, we have drivers/pci/setup-bus.c doing:
if (pci_assign_resource(list->dev, idx)) { res->start = 0; res->end = 0; res->flags = 0; }
So it basically destroys the resource content utterly when pci_assign_resource() fails...
There are questions raised here:
- Shouldn't we instead fix things so that instead, we properly test for IORESOURCE_UNSET in pci_request_* & friends and just have pci_assign_resource() continue as it's doing now, that is not clear that flag if the assignment fails ?
- setup-bus.c is a bit violent: As soon as it hits a p2p bridge, it will bluntly re-assign everybody, not trying to check wether a resource was already correctly assigned by the firmware or not. However, it never sets IORESOURCE_UNSET. Thus if we do the above, we should probably have it always set that bit before calling pci_assign_resource()...
Now the question is, what should I do in pci_32.c ... right now, we unconditionally clear IORESOURCE_UNSET, which isn't very correct, then call pci_assign_resource().
Should I do like the setup-bus.c and just completely wipe the resource if pci_assign_resource() fail ? Or should I just stop clearing IORESOURCE_UNSET (and thus rely on pci_assign_resource() to clear it only if it succeeds, which seems to work) in which case I see no point in making that function much check since there is nothing useful to do when it fails and it does printk already.
Ben.
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