Re: [Qemu-devel] BB name vs. BDS name in the QAPI schema

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Mon, Sep 15, 2014 at 10:59:01AM +0200, Kevin Wolf wrote:
> Am 15.09.2014 um 03:31 hat Fam Zheng geschrieben:
> > On Sat, 09/13 19:04, Markus Armbruster wrote:
> > I remember at the time of introducing node-name, it was in a separate
> > namespace, but now it's not. Then why should the user care *whether* a name is
> > "device" or "node-name"?
> 
> When you reconfigure the graph (e.g. by taking a live snapshot), the BB
> name always stays at the root (i.e. points to the new BDS), whereas the
> node-name always stays at the same node (which was at the root, but
> isn't any more), that's probably important for the user. Maybe a bit
> like branches and tags in git.
> 
> So yes, they are somewhat different, but in the end they all resolve to
> a BDS and it makes sense to allow accessing them in a uniform way (just
> like 'git show <tag-name>' works the same as 'git show <branch-name>').
> 
> Which leads me to this conclusion: One mandatory string argument per
> command is enough, and also results in a cleaner interface than having
> two optional arguments that aren't truly optional because you need to
> specify the one xor the other.

I have slightly different taste - preferring to keep things explicit
instead of implicit - but I don't think the choice matters a great deal.
After all, we need to keep existing commands working (and Markus has
enumerated the combinations) so we cannot do anything radical.

If we use a single argument for new commands, it should be named
appropriately ("blockref"?) to indicate that it is not limited to just
BB or just BDS.

Stefan

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