Re: [Qemu-devel] [PATCH v2] machine: Move acpi_nvdimm_state into struct MachineState

[Eduardo Habkost <ehabkost@redhat.com>]

On Thu, Mar 07, 2019 at 10:48:59AM +0100, Igor Mammedov wrote:
[...]
> > +static void machine_set_nvdimm_persistence(Object *obj, const char *value,
> > +                                               Error **errp)
> > +{
> > +    MachineState *ms = MACHINE(obj);
> > +    AcpiNVDIMMState *nvdimms_state = &ms->nvdimms_state;
> > +
> > +    if (strcmp(value, "cpu") == 0)
> > +        nvdimms_state->persistence = 3;
> we probably should use QAPI enum magic to handle description to value conversion
> but I don't know how to (CCed Markus).

QEMU is not very consistent in this.  I have found at least 3
different methods for registering enum properties:

1) qdev PropertyInfo using set_enum/get_enum.  Examples:
   DEFINE_PROP_ON_OFF_AUTO, DEFINE_PROP_LOSTTICKPOLICY.
2) object_property_add() + visit_type_...().  Examples:
   machine_set_kernel_irqchip(), pc_machine_set_vmport(),
   pc_machine_set_smm().
3) object_property_add_add_enum() and object_class_property_add_enum().  Examples:
   qauthz_list_prop_set_policy(), host_memory_backend_set_policy(),
   qcrypto_secret_prop_set_format(), netfilter_set_direction().

> But since it's just moving existing code, it do not insist and it could be
> done on top later on.

Agreed, but I think we should at least add a TODO comment
indicating the code is not a good example to be followed.

-- 
Eduardo