RE: [PATCH v5] introduce vfio-user protocol specification

[Thanos Makatos]

> > >   * *Error* in a reply message indicates the command being
> acknowledged
> > had
> > >     an error. In this case, the *Error* field will be valid.
> > >
> > > * *Error* in a reply message is a UNIX errno value. It is reserved in a
> > command message.
> >
> > I'm not quite following why we need a bit flag and an error field. Do you
> > anticipate a failure, but with errno==0?
> 
> Indeed, the Error bit seems redundant. John, is there a reason why we need
> the
> error bit?

I haven't heard back from John yet; however I think it makes sense to maintain
an error bit and not necessarily require errno to be set, since there can be
errors that no errno value makes sense. I'll update the spec.