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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2012-02-09 at 15:32 +0000, Stefano Stabellini wrote:
> 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!!

And no one I know is able to describe, accurately, exactly what the
state diagram for even one of those actually looks like or indeed should
look like. It became quite evident in these threads about hotplug script
handling etc that no one really knows for sure what (is supposed to)
happens when.

Justin just posted a good description for blkif.h which included a state
machine description. We need the same for pciif.h, netif.h etc etc.

Ian.


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