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

[Daniel P . Berrangé]

On Tue, Apr 30, 2019 at 09:42:36AM -0300, Eduardo Habkost wrote:
> On Tue, Apr 30, 2019 at 11:10:06AM +0100, Daniel P. Berrangé wrote:
> > 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 <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.
> > 
> > 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
> >     } }
> 
> "secure for production" and "deprecated" are independent
> variables.  There are deprecated features that are still secure,
> and deprecated features that were never supposed to be used in
> production in the first place.

Good point - we should track  quality status separately. So still
need a boolean deprecation flag too i guess. 

> 
> > 
> >     { 'struct': "SupportStatusInfo",
> >        'data': { 'status': 'SupportStatus',
> >                  '*info': 'str',
> >              '*hint': 'str' } }
> 
> "hint" seems nicer than "suggested" or "recommended".  I like it.
> 
> -- 
> Eduardo

Regards,
Daniel
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