Re: [Qemu-devel] [PATCH v2 9/9] tpm: Added support for TPM emulator

[Stefan Berger]

On 04/10/2017 12:14 PM, Stefan Berger wrote:
> On 04/10/2017 06:07 AM, Patrick Ohly wrote:
> > On Mon, 2017-04-10 at 09:54 +0000, Marc-André Lureau wrote:
> >
> > > By "public protocol", I mean qemu communication with a foreign
> > > project, swtpm or other.
> > >
> > > If qemu grows new needs, or if the protocol is found limited or buggy,
> > > it may change. Subtle interactions may break between various
> > > implementations.  The minimum would be some versioning or
> > > capabilities. A document describing the states and messages
> > > allowed/denied & effects would be quite necessary.
> > Stefan, is there any documentation besides the source?
>
> No.

I now started to describe the protocol on the Wiki:

https://github.com/stefanberger/swtpm/wiki/Control-Channel-Specification

However, there's also a description in an existing man page:

https://github.com/stefanberger/swtpm/blob/master/man/man3/swtpm_ioctls.pod

> > Just asking, I don't think it is needed because...
> >
> > > Otoh, there doesn't seem to be other users of this protocol, or other
> > > implementations. So it may make sense to make it qemu-specific, and
> > > thus "private": the protocol and implementation can evolve without
> > > risk to break other users. This gives us a lot more flexibility and
> > > control, and doesn't have to be very strictly documented (although it
> > > is still better to be strict, but requires more effort).
> > ... I suspect it falls into this camp. I can't think of any users of the
> > protocol besides swtpm itself and now qemu. Stefan, is that correct?
>
> Correct. Only swtpm client tools (swtpm_ioctl) and now your QEMU 
> patches are using the protocol.