Re: [Qemu-devel] [PATCH v4 24/26] qidl: add QAPI-based code generator

[Michael Roth <mdroth@linux.vnet.ibm.com>]

On Mon, Oct 15, 2012 at 03:08:51PM +0200, Paolo Bonzini wrote:
> Il 15/10/2012 10:12, Paolo Bonzini ha scritto:
> > Il 12/10/2012 23:11, Michael Roth ha scritto:
> >> +        elif field['type'].startswith('enum '):
> >> +            typename = 'int'
> > 
> > Note that there is support for enum properties in qdev.  Please consider
> > adding it, though it can be done as a follow-up.
> > 
> > I'm going to play a bit with the series and convert 1 or 2 devices
> > myself to see how it looks, then I'll give my acked-by.
> 
> Ok, so now I played with it a bit.  My main comments, which can all be
> tackled as a follow-up, are:
> 
> - immutable/derived/broken/elsewhere (and the default, let's call it
> serialized) are really five cases of the same QIDL property.  Perhaps
> this could be enforced in the extended syntax like this:
> 
>     #define q_immutable QIDL(serialize(immutable))
>     #define q_derived QIDL(serialize(derived))
>     #define q_broken QIDL(serialize(broken))
>     #define q_elsewhere QIDL(serialize(elsewhere))
> 
> I would also make it possible to explicitly specify the fifth state, if
> only for symmetry.

Agreed, that's a more proper grouping. Though, for consistency with
QIDL(property, ...), I would do QIDL(serialize, ...)

> 
> I'm not sure what your plans are for q_derived vs. VMState.  If a field
> X is set in pre_save hooks based on field Y, how should the fields be
> set?  X is usually not up-to-date, so it should be q_derived.  But Y
> cannot be serialized as is, so it should be q_elsewhere.  One of the
> two is wrong, which one? :)
> 
> - q_properties are also always q_immutable.  I think this should be
> enforced in the code generator.

Agreed.

> 
> - it would be _much_ better if you could automatically derive properties
> information for embedded structs.  For example, Notifiers and qemu_irqs
> are always q_immutable.  NotifierLists probably are always q_elsewhere,
> because the owner of the notifiers should add themselves back.

q_inherit maybe? Otherwise we're overriding "q_default" in subtle
ways that may not always be desired.

> 
> In general, if struct X is QIDL_DECLAREd and only has q_immutable
> fields, it can be taken as q_immutable.  Hence for example the base
> class should not need any decoration; ISADevice will be seen as
> q_immutable, but PCIDevice will be seen as serialized.  But even if a
> struct is not QIDL_DECLAREd, it  should be possible to apply a tag to a
> typedef, and have it always applied to the members.

I'd prefer to stick with a common declaration macro to handle tagging.
How about QIDL_DECLARE(MyImmutableType, q_immutable) to apply a tag to
all members?

> 
> Paolo
>