* Markus Armbruster (armbru@xxxxxxxxxx) wrote: > Philippe Mathieu-Daudé <philmd@xxxxxxxxxx> writes: > > > Hi Daniel, Dave, Markus & Thomas. > > > > On 4/6/24 06:58, Markus Armbruster wrote: > >> "Dr. David Alan Gilbert" <dave@xxxxxxxxxxx> writes: > >>> * Daniel P. Berrangé (berrange@xxxxxxxxxx) wrote: > >>>> On Fri, May 31, 2024 at 06:47:45AM +0200, Thomas Huth wrote: > >>>>> On 30/05/2024 09.45, Philippe Mathieu-Daudé wrote: > >>>>>> We are trying to unify all qemu-system-FOO to a single binary. > >>>>>> In order to do that we need to remove QAPI target specific code. > >>>>>> > >>>>>> @dump-skeys is only available on qemu-system-s390x. This series > >>>>>> rename it as @dump-s390-skey, making it available on other > >>>>>> binaries. We take care of backward compatibility via deprecation. > >>>>>> > >>>>>> Philippe Mathieu-Daudé (4): > >>>>>> hw/s390x: Introduce the @dump-s390-skeys QMP command > >>>>>> hw/s390x: Introduce the 'dump_s390_skeys' HMP command > >>>>>> hw/s390x: Deprecate the HMP 'dump_skeys' command > >>>>>> hw/s390x: Deprecate the QMP @dump-skeys command > >>>>> > >>>>> Why do we have to rename the command? Just for the sake of it? I think > >>>>> renaming HMP commands is maybe ok, but breaking the API in QMP is something > >>>>> you should consider twice. > > > > I'm looking at how to include this command in the new "single binary". > > > > Markus explained in an earlier series, just expanding this command as > > stub to targets that don't implement it is not backward compatible and > > breaks QMP introspection. Currently on s390x we get a result, on other > > targets the command doesn't exist. If we add a stubs, then other targets > > return something (even if it is an empty list), confusing management > > interface. > > Loss of introspection precision is a concern, not a hard "no". > > We weigh all the concerns, and pick a solution we hate the least :) > > > So this approach use to deprecate process to include a new command > > which behaves differently on non-s390x targets. > > > > If we don't care for this particular case, better. However I'd still > > like to discuss this approach for other target-specific commands. > > > >> PRO rename: the command's tie to S390 is them immediately obvious, which > >> may be useful when the command becomes available in qemu-systems capable > >> of running other targets. > >> > >> CON rename: users need to adapt. > >> > >> What are the users? Not libvirt, as far as I can tell. > > > > Years ago we said, "all HMP must be based on QMP". > > In practice, it's closer to "HMP must be base on QMP when the > functionality does or should exist in QMP." > > > Now we realize HMP > > became stable because QMP-exposed, although not consumed externally... > > I'm afraid I didn't get this part. > > > Does the concept of "internal QMP commands" makes sense for HMP debug > > ones? (Looking at a way to not expose them). We could use the "x-" > > prefix to not care about stable / backward compat, but what is the point > > of exposing to QMP commands that will never be accessed there? > > > >>>> That was going to be my question too. Seems like its possible to simply > >>>> stub out the existing command for other targets. > >> > >> That's going to happen whether we rename the commands or not. > >> > >>> Are these commands really supposed to be stable, or are they just debug > >>> commands? If they are debug, then add the x- and don't worry too much. > > > > OK. > > > >> docs/devel/qapi-code-gen.rst: > >> > >> Names beginning with ``x-`` used to signify "experimental". This > >> convention has been replaced by special feature "unstable". > >> > >> Feature "unstable" is what makes something unstable, and is what > >> machines should check. > > > > What I mentioned earlier could be 'Feature "internal" or "debug"'. > > What's the difference to "unstable"? It should be clear *why* something is marked x- - something that's marked 'x-' because the feature is still in development is expected to shake out at some point, and the interface designed so it can. (and at some point the developer should get a prod to be asked whethere the x- can be removed). That's different from it permenantly being x- because it's expected to change as the needs of the people debugging change. Dave > >> An "x-" prefix may still be useful for humans. Machines should *not* > >> key on the prefix. It's unreliable anyway: InputBarrierProperties > >> member @x-origin is stable despite it's name. Renames to gain or lose > >> the prefix may or may not be worth the bother. > > > > Could follow the rules and be renamed as "origin-coordinate-x". > > I don't think it's worth the trouble. The "x-" prefix is now strictly > for humans, and humans can figure out what the x- in @x-origin, > @y-origin means. > > [...] > -- -----Open up your eyes, open up your mind, open up your code ------- / Dr. David Alan Gilbert | Running GNU/Linux | Happy \ \ dave @ treblig.org | | In Hex / \ _________________________|_____ http://www.treblig.org |_______/
