[RFC PATCH 1/5] pci/p2p: add a function to test peer to peer capability

[Greg Kroah-Hartman]

On Tue, Jan 29, 2019 at 11:24:09AM -0700, Logan Gunthorpe wrote:
> 
> 
> On 2019-01-29 10:47 a.m., jglisse at redhat.com wrote:
> > +bool pci_test_p2p(struct device *devA, struct device *devB)
> > +{
> > +	struct pci_dev *pciA, *pciB;
> > +	bool ret;
> > +	int tmp;
> > +
> > +	/*
> > +	 * For now we only support PCIE peer to peer but other inter-connect
> > +	 * can be added.
> > +	 */
> > +	pciA = find_parent_pci_dev(devA);
> > +	pciB = find_parent_pci_dev(devB);
> > +	if (pciA == NULL || pciB == NULL) {
> > +		ret = false;
> > +		goto out;
> > +	}
> > +
> > +	tmp = upstream_bridge_distance(pciA, pciB, NULL);
> > +	ret = tmp < 0 ? false : true;
> > +
> > +out:
> > +	pci_dev_put(pciB);
> > +	pci_dev_put(pciA);
> > +	return false;
> > +}
> > +EXPORT_SYMBOL_GPL(pci_test_p2p);
> 
> This function only ever returns false....

I guess it was nevr actually tested :(

I feel really worried about passing random 'struct device' pointers into
the PCI layer.  Are we _sure_ it can handle this properly?

thanks,

greg k-h