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

["Daniel P. Berrangé" <berrange@redhat.com>]

On Wed, Apr 24, 2019 at 03:20:36PM -0300, Eduardo Habkost wrote:
> 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 <ehabkost@redhat.com>
> > > ---
> > >  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.

I've no objection to expanding it to capture other info - we'll
want to change the 'deprecated' field to an enum though. Also,
in some cases there won't be any real alternative so lets just
call it 'hint' instead. How about

    { 'enum':  "SupportStatus",
      'data': { 'production',  # Secure for use in hostile production env
                'development', # No security guarentee, friendly dev only
		'deprecated',  # To be removed in the future
    } }

    { 'struct': "SupportStatusInfo",
       'data': { 'status': 'SupportStatus',
                 '*info': 'str',
		 '*hint': 'str' } }

Regards,
Daniel
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