> From: Jason Gunthorpe <jgg@xxxxxxxxxx> > Sent: Thursday, November 18, 2021 9:33 PM > > > In concept a singleton group is different from a > > multi-devices group which has only one device bound to driver... > > Really? Why? I don't see it that way.. > > A singleton group is just a multi-device group that hasn't been > hotplugged yet. > > We don't seem to have the concept of a "true" singleton group which is > permanently single due to HW features. > > > This series aims to avoid conflict having both user and kernel drivers > > mixed in a multi-devices group. Well, the difference is just in literal. I don't know the background why the existing iommu_attach_device() users want to do it this way. But given the condition in iommu_attach_device() it could in theory imply some unknown hardware-level side effect which may break the desired functionality once the group size grows beyond singleton. Is it a real case? I don't know... You are now redefining that condition from singleton group to multi-devices group with single driver bound. As long as no object from existing driver users, I'm fine with it. But still want to raise awareness as it does change the existing semantics (though might be considered as an imperfect way). Thanks Kevin
