> > We are talking memory-mapped io here, so it cannot just be "re-used", it > is wat it is. I guess the PCI BAR could be released and then the physical > address the resource was at could be re-used for another piece of MMIo, > but AFAIK outside of PI=CI hotplug we never release BARs. > > Maybe we need to ref-count resources and have the aprent free only be > a deref and not release the resource until the child resource also > is free-ed doing another deref? > > I must say that to me it sometimes just seems like always allowing unbind > is a bad idea. Another example of this is things like virtio, where > we can have a filesystem based on virtio-block, but the virtio interface > between the hypervisor and the guest-kernel is a PCI-device and in theory > the user could unbind the virtio driver from that PCI-device, after which > the whole house comes crashing down. > > I also know that the extcon framework in its current incarnaton > does not deal with unbind properly... > > Maybe it is time that we allow drivers to block unbind instead of > trying to support unbind in really complex situations where normal > use-cases will never need it ? > > I do realize unbind is very useful for driver developent without > rebooting. > Hey, i did not want to trigger an eartquake in the basement of the kernel ;-) My intention was to prevent some crashes, and help developers to find their bugs. I think my patch exactly does this. > 1) make resources refcounted, have child resources take a ref on the parent > 2) Disallow unbind on devices with bound child-devices? > Exactly what i was thinking of in first attempts. But i fear that would break even more use cases. Hans, directly regarding the driver: The problem i see is that the xhci_intel_unregister_pdev which is added as an action with devm_add_action_or_reset() is called late by the framework, later than the usb_hcd_pci_remove() in xhci_pci_remove. Is there any chance to trigger this before? This is what Greg meant with "right order". Anyway, i really appreciate these discussions, thanks for all your patience. Best Regards Carsten
