Re: [Qemu-devel] [PATCH 1/3] qapi: SupportStatusInfo struct

[Eduardo Habkost]

On Wed, Apr 24, 2019 at 09:26:52AM +0100, Daniel P. Berrangé wrote:
> On Tue, Apr 23, 2019 at 06:22:44PM -0300, Eduardo Habkost wrote:
> > This struct will be used to represent support and deprecation
> > status of QEMU features.
> > 
> > Signed-off-by: Eduardo Habkost <address@hidden>
> > ---
> >  qapi/common.json | 24 ++++++++++++++++++++++++
> >  1 file changed, 24 insertions(+)
> > 
> > diff --git a/qapi/common.json b/qapi/common.json
> > index 99d313ef3b..b59d0dc66b 100644
> > --- a/qapi/common.json
> > +++ b/qapi/common.json
> > @@ -193,3 +193,27 @@
> >               'ppc64', 'riscv32', 'riscv64', 's390x', 'sh4',
> >               'sh4eb', 'sparc', 'sparc64', 'tricore', 'unicore32',
> >               'x86_64', 'xtensa', 'xtensaeb' ] }
> > +
> > +##
> > +# @SupportStatusInfo:
> > +#
> > +# Information on support status of a given feature
> > +# (e.g. machine type)
> > +#
> > +# @deprecated: if true, the given feature is deprecated and may be removed
> > +#              in future versions of QEMU according to the QEMU deprecation
> > +#              policy.
> > +#
> > +# @status-message: Human readable message describing support status
> > +#                  of the feature.
> > +#
> > +# @suggested-alternative: Optional.  Suggested alternative for a deprecated
> > +#                         feature.  For machine types, this should be the 
> > name
> > +#                         of an available machine-type.
> > +#
> > +# Since: 4.1
> > +##
> > +{ 'struct': 'SupportStatusInfo',
> > +  'data': { 'deprecated': 'bool',
> > +            '*status-message': 'str',
> > +            '*suggested-alternative': 'str' } }
> 
> I see status-message has to be optional, since you're embedding the
> struct into another struct and want deprecated==false by default.
> 
> I'd be inclined to change it to embed a pointer to the struct and
> drop the deprecated field, and make both status-message and
> suggested-alternative be mandatory. ie a struct  "DeprecationInfo" 
> the pointer to which is NULL if not deprecated.

That could be a simple solution if we were sure we would only
track deprecation info.  But I would like us to track additional
support status on that struct eventually.

Also, I'd like to explicitly differentiate "information is not
available because QEMU is old" from "information is available and
machine type is not deprecated".

-- 
Eduardo