Jan Kiszka <jan.kis...@siemens.com> writes: > Markus Armbruster wrote: >> Jan Kiszka <jan.kis...@web.de> writes: >> >>> From: Jan Kiszka <jan.kis...@siemens.com> >>> >>> We allow to address a bus only using its local name. This is ambiguous >>> but unfortunately so handy that people (specifically libvirt) will >>> likely complain if bus=pci.0 needs to be replaced with >>> bus=/i440FX-pcihost/pci.0 all over the place. So keep this for now but >>> drop at least support for starting a qtree walks with an abbreviated bus >>> name. >>> >>> Signed-off-by: Jan Kiszka <jan.kis...@siemens.com> >> >> Again, affects only -device and device_add option bus. >> >> Before, an argument started either with '/' (path anchored at root) or a >> bus name (path anchored at that bus). >> >> Now, an argument started either with '/' (path anchored at root) or it >> is a bus name. >> >> If we decide to add sane relative paths to qdev, i.e. paths anchored at >> unique ID, we get a slight anomaly here: >> >> bus=a bus name, not a relative path >> bus=a/b relative path anchored at node with unique ID a. >> >> Works for me. > > If we allow ID-anchoring, we are in ambiguous land again unless we > reject IDs that happen to match any bus name in the system. Even then, > the problem will be that the aliases based on bus names need to be > auto-generated (for backward compatibility) while IDs are user-assigned. > If the user comes first, auto-generation will innocently produce an ugly > conflict and we will either have to reject bus instantiation or live > with the conflict.
No. For backward compatibility, we need bus=a to be interpreted as bus name, not as qdev path. In other words, we overload bus to be either bus name or qdev path. It's a wart, but unavoidable unless we restrict bus to bus names and add a separate option for paths. As long as we require all qdev paths to be absolute, the wart is relatively small. The rule to resolve the overloading is simple: if the value starts with '/', then it's a qdev path, else it's a bus name. With relative qdev paths, the wart becomes more a bit more prominent. The rule to resolve the overloading becomes: if the value contains '/', it's a qdev path, else it's a bus name. I can't see ambiguity here.
