[RFC v2 4/5] bus: factorize device selection

[Bruce Richardson]

On Fri, Feb 27, 2026 at 03:17:27PM +0100, David Marchand wrote:
> On Thu, 26 Feb 2026 at 17:32, Bruce Richardson
> <bruce.richardson at intel.com> wrote:
> > > +RTE_EXPORT_INTERNAL_SYMBOL(rte_bus_is_ignored_device)
> > > +bool
> > > +rte_bus_is_ignored_device(const struct rte_bus *bus, const struct rte_devargs *devargs)
> > > +{
> > > +     switch (bus->conf.scan_mode) {
> > > +     case RTE_BUS_SCAN_ALLOWLIST:
> > > +             if (devargs && devargs->policy == RTE_DEV_ALLOWED)
> > > +                     return false;
> > > +             break;
> > > +     case RTE_BUS_SCAN_UNDEFINED:
> > > +     case RTE_BUS_SCAN_BLOCKLIST:
> > > +             if (devargs == NULL || devargs->policy != RTE_DEV_BLOCKED)
> > > +                     return false;
> > > +             break;
> > > +     }
> > > +     return true;
> > > +}
> >
> > I think this could do with more comments. Am I right in thinking that
> > devargs is NULL on input if the device in question is not referenced by any
> > devargs passed to the app? This seems a little obscure form of input
> > parameter, so I definitely think it needs documenting.
> 
> Yes the handling of a NULL devargs is implicit, I can add a comment.
> 
> 
> > Is there any way the search for the device name that returns the devargs
> > null/non-null pointer can be similarly generalized?
> 
> I also wondered about that and it would be better, but I stopped
> quickly when I looked at the bus specific devargs_lookup functions,
> preparing the v2.
> 
> For example with the pci bus, names for pci devices can take various
> forms, so the pci bus uses its device specific representation for
> identifying the devargs.
>         rte_pci_device_name(&dev->addr,
>                         dev->name, sizeof(dev->name));
>         devargs = pci_devargs_lookup(&dev->addr);
> 
> And:
>         RTE_EAL_DEVARGS_FOREACH("pci", devargs) {
>                 devargs->bus->parse(devargs->name, &addr);
>                 if (!rte_pci_addr_cmp(pci_addr, &addr))
>                         return devargs;
>         }
> 
> I suspect vmbus is the same, with this uuid stuff.
> 
> And others bus need investigation too.
> I could try to normalize the devargs names for this lookup.. ?
> 

That's a nice to have, IMHO. I think if the NULL/non-NULL is properly
commented it's good enough for this set. You can probably note the cleanup
as a TODO in the code as a further reminder.

/Bruce