29/06/2017 09:56, Jan Blunck: > On Wed, Jun 28, 2017 at 7:03 PM, Thomas Monjalon <tho...@monjalon.net> wrote: > > 27/06/2017 20:55, Jan Blunck: > >> On Wed, Jun 21, 2017 at 1:30 AM, Gaetan Rivet <gaetan.ri...@6wind.com> > >> wrote: > >> > /** > >> > + * Find a bus capable of identifying a device. > >> > + * > >> > + * @param str > >> > + * A device identifier (PCI address, virtual PMD name, ...). > >> > + * > >> > + * @return > >> > + * A valid bus handle if found. > >> > + * NULL if no bus is able to parse this device. > >> > + */ > >> > +struct rte_bus *rte_bus_from_dev(const char *str); > >> > >> I still don't agree with this. The bus name should be passed > >> explicitly by the user of the API. > >> > >> NAK. > > > > Please explain why you think the bus name should be explicit. > > If the bus is ambiguous, it can be explicited by the user. > > > > I see some good benefits in being tolerant with the bus/device > > representation. It provides a smooth transition to the bus model. > > > > We build libraries. The applications we build with the help of those > libraries get notified by the OS about device events. Those devices > are chields of their parent bus. At the time the event is fired the OS > already knows about: > > - the bus name (parent) > - the device name (child) > - additional event parameters (environment) > > Blame me that I probably spent too much time with Kay Sievers and > GregKH to understand that device naming is easy to get wrong. Just > look at the hyperv device names and how they switched to the UUID > scheme. I don't think that hyperv is the only bus that uses UUID as > device identification. We should not codify a policy of how to deduce > a bus name from a given device name if that is knowledge that is > already present externally. Otherwise I fear this part of the EAL will > be subject to constant churn.
OK I understand your point that it is a weak identification. It is as weak as what we have currently. It works at least when we have only PCI and VDEV. However it does not prevent to use a strong identification with bus and parent names. I see rte_bus_from_dev() as a helper to transition to the new strong identification model. So we could remove it in few releases. Does it make sense?
