On Tue, Feb 10, 2026 at 10:12:38AM +0000, Daniel P. Berrangé wrote: > On Tue, Feb 10, 2026 at 11:23:27AM +0800, Zhao Liu wrote: > > Hi, > > > > This is the v2 trying to introduce property flags to detect user's > > property setting (from CLI/QMP/HMP). I dropped RFC tag since previous > > RFC v1 [1]. > > This says what the series is proposing, but IMHO what is more important > here is explaining why this either desirable or appropriate to add as > general facility in QOM. > > The idea that code should take different action for a given fixed value, > based on whether the value was set by the user, or left on the default, > makes me very uncomfortable. > > There have been a number of situations where something that was initially > a boolean flag, actually needed to be a tri-state instead, to provide > semantics like "On", "Off", "Auto".
But "auto" is exactly a property specific way to work around this. With this, we could allow "auto" for any property (except strings I guess) without per property code. > This "user set" flag could support such behaviour indirectly, but since > "user set" is an internal concept we'd still be only exposing a boolean > externally, while using a tri-state internally. That does not give the > full flexibility of a tri-state, because internally if we wanted to > have the default to be "yes", it offers no way for the mgmt app to > put it back to "auto". I do not get it. Of course user set is an external concept. It is user controllable! > For properties that are not booleans, it is much less obvious to me > whether we actually need a distinct "not set" concept at all. > > > So overall, at a conceptual level, I don't think that QOM should care > about /how/ a value came to be set. It should have no direct awareness > of the "user input", rather it just represents the configuration of the > system at a given point in time, however that came to pass. > > > With regards, > Daniel > -- > |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| > |: https://libvirt.org -o- https://fstop138.berrange.com :| > |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
