Re: [Xen-devel] [PATCH 20 of 29 RFC] libxl: introduce libxl hotplug public API functions

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 9 Feb 2012, Ian Jackson wrote:
> Stefano Stabellini writes ("Re: [Xen-devel] [PATCH 20 of 29 RFC] libxl: 
> introduce libxl hotplug public API functions"):
> > On Thu, 9 Feb 2012, Ian Jackson wrote:
> > > Stefano Stabellini writes ("Re: [Xen-devel] [PATCH 20 of 29 RFC] libxl: 
> > > introduce libxl hotplug public API functions"):
> > > > - we can reuse the "state" based mechanism to establish a connection:
> > > > again not a great protocol, but very well known and understood.
> > > 
> > > I don't think we have, in general, a good understanding of these
> > > "state" based protocols ...
> > 
> > What?! We have netback, netfront, blkback, blkfront, pciback, pcifront,
> > kbdfront, fbfront, xenconsole, and these are only the ones in Linux!!
> 
> In many (most?) of these cases we don't know exactly what the state
> numbers mean

see xen/include/public/io/xenbus.h


> let alone exactly the details of the rest of the
> protocol.
 
The details of the rest of the protocol are a well known contract
between frontend, backend and the toolstack. In fact they work with
different toolstacks (xend, libxl, xapi), different backend
implementations (Linux, QEMU), different frontends (Linux, Windows PV
drivers). And the examples I mentioned are just the ones that I happen
to work with.

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