Re: [PATCH 4/4] xen/version: Introduce non-truncating XENVER_* subops

[Julien Grall <julien@xxxxxxx>]

On 03/01/2023 21:22, Andrew Cooper wrote:
> On 03/01/2023 8:47 pm, Julien Grall wrote:
> > On 03/01/2023 20:09, Andrew Cooper wrote:
> > > diff --git a/xen/include/public/version.h b/xen/include/public/version.h
> > > index c8325219f648..cf2d2ef38b54 100644
> > > --- a/xen/include/public/version.h
> > > +++ b/xen/include/public/version.h
> > > @@ -19,12 +19,20 @@
> > >    /* arg == NULL; returns major:minor (16:16). */
> > >    #define XENVER_version      0
> > >    -/* arg == xen_extraversion_t. */
> > > +/*
> > > + * arg == xen_extraversion_t.
> > > + *
> > > + * This API/ABI is broken.  Use XENVER_extraversion2 instead.
> > I read this as newer tools should never try to call
> > XENVER_extraversion. But I don't think this is what you intend to say,
> > correct? If so, I would say that an OS should first try
> > XENVER_extraversion2 and then fallback to XENVER_extraversion if it
> > returns -ENOSYS.
> >
> > Same goes for the new hypercalls.
> Right, but that's sufficiently basic that it goes without saying.
It never hurts to be obvious. I couldn't say the same for the other way 
around.
> This is not a "my first introduction to writing code" tutorial.
That's the first introduction to Xen for an OS developer. Adding a few 
words (maybe with the first version introducing it) would likely be 
welcomed by any developer.
This avoids any misinterpretation and/or losing time playing the git 
blame game...
Cheers,

--
Julien Grall