Loading drivers via kldload

John Baldwin jhb at freebsd.org
Tue Aug 16 19:09:11 UTC 2011

On Tuesday, August 16, 2011 12:26:11 pm Andriy Gapon wrote:
> The following are pure speculations, I'd rather let David speak, but just in case;
> on 16/08/2011 18:45 John Baldwin said the following:
> > Well, that would seem odd, still.  It only returns BUS_PROBE_GENERIC (not 0), so
> > David's driver's probe routine should still be called to get a chance to attach to
> > the device.
> Maybe it doesn't do that exactly because device and vendor ID are zeroes as David
> described earlier.

Eh?  device_probe_and_attach()'s loop to probe drivers is not PCI-specific, it
has no idea if a given device is PCI device or not let alone if it has non-zero
subvendor IDs.  Also, ata_pci_probe() doesn't look at the subvendor IDs at all.

> > Also, the ATA driver only allocates its BAR once, so it shouldn't
> > trigger the panic in question in that case (the panic is only triggered when you
> > try to double-allocate a BAR).
> This makes only if the BAR has sane values.  Not sure what happens if the BAR has
> some junk that duplicates other PCI device, or something like that.

The panic in question is due to a resource that was reserved by the parent
bus (i.e. either ACPI or PCI) using resource_list_reserve(), then a driver
called resource_list_alloc() on it once successfully, and
resource_list_alloc() is being called a second time to allocate an already-
allocated resource.  That won't happen due to junk in a BAR (and BARs are
all standard config header registers anyway).

John Baldwin

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