* Markus Armbruster (arm...@redhat.com) wrote: > "Dr. David Alan Gilbert" <dgilb...@redhat.com> writes: > > > * Markus Armbruster (arm...@redhat.com) wrote: > >> "Dr. David Alan Gilbert" <dgilb...@redhat.com> writes: > [...] > >> > I'm confused why we need a 'reset to default' - all we need is the > >> > ability > >> > to change each parameter, and for the new value of that parameter > >> > to be an empty string. > >> > >> You argue syntax, I'm arguing semantics. > >> > >> The command means "set parameter P to value V". *Except* when V is "", > >> it means something else, namely "reset parameter P to its default, > >> whatever that may be". > >> > >> This is (a) not general, because it won't do for cases where "" may > >> occur as value, and (b) ugly. > >> > >> Ugliness is the eye of the beholder. Lack of generality isn't. > > > > No, I'm questioning why it's defined as 'reset parameter P to its default'; > > why do we need a way to do that? > > Dan's commit message explains: > > Some of the migration parameters are strings, which default to NULL, > eg tls_hostname and tls_creds. > > The mgmt app will set the tls_creds parameter on both source and target > QEMU instances, in order to trigger use of TLS for migration. > > After performing a TLS encrypted migration though, migration might be > used for other reasons - for example, to save the QEMU state to a file. > We need TLS turned off when doing this, but the migrate-set-parameters > QAPI command does not provide any facility to clear/reset parameters > to their default state. > > If you simply ommit the tls_creds parameter in migrate-set-parameters, > then 'has_tls_creds' will be false and so no action will be taken. The > only option that works with migrate-set-parameters is to treat "" on > the wire as equivalent to requesting NULL. Failing that we would have > to create a new 'migrate-reset-parameters' method to explicitly put > a parameter back to its default value.
OK, I thought the default was empty string. IMHO the problem here is we're just being too clever; lets just make the default "" rather than NULL, and make that parameter always be a string. Dave -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
