Alex Williamson <alex.williamson@xxxxxxxxxx> writes: > On Wed, 2010-06-16 at 10:23 +0200, Markus Armbruster wrote: >> Alex Williamson <alex.williamson@xxxxxxxxxx> writes: >> >> > On Tue, 2010-06-15 at 12:28 +0100, Paul Brook wrote: >> >> > > Alex proposed to disambiguate by adding "identified properties of the >> >> > > immediate parent bus and device" to the path component. For PCI, these >> >> > > are dev.fn. Likewise for any other bus where devices have unambigous >> >> > > bus address. The driver name carries no information! >> >> > >> >> > From user POV, driver names are very handly to address a device >> >> > intuitively - except for the case you have tones of devices on the same >> >> > bus that are handled by the same driver. For that case we need to >> >> > augment the device name with a useful per-bus ID, derived from the bus >> >> > address where available, otherwise based on instance numbers. >> >> >> >> This is where I think you're missing a trick. We don't need to augment the >> >> name, we just need to allow the bus id to be used instead. >> > >> > For the case of a hot remove, I agree. If the user specifies "pci_del >> > pci.0/03.0", that's completely sufficient because we don't care what's >> > in that slot, just remove it. However, I still see some use cases for >> > device names in the path. Take for example: >> > >> > (A): /i440FX-pcihost/pci.0/e1000.05.0 >> > >> > vs >> > >> > (B): /pci.0/05.0 >> > >> > (removing both the root bridge driver name and the device driver name) >> >> / is the main system bus. System bus defines no bus address at the >> moment. Therefore, you have to use the driver name i440FX-pcihost. > > So is the general rule "If a device's parent bus does not provide an > address, print device name"? I think the general rule for constructing a *canonical* qdev path should be: * If it's the main system bus, the path is /. * If it's another bus, the path is P/B, where P is the canonical path of the device providing the bus, and B is the bus name. Unambiguous, since no device ever defines two buses with the same name. * If it's a device, the path is P/D, where P is the canonical path of the bus. If the bus defines bus addresses, then D is @A, where A is the device's bus address. We haven't made up our minds whether the else case exists, or what to do if it does. The simple "else D is the device model driver's name" works only if the bus can't take multiple device models with the same driver. The canonical path is not the only path. For instance, a qdev ID is a valid path, but it's not canonical. /i440FX-pcihost/pci.0/e1000 is another valid, non-canonical path. [...] -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
