Mark Cave-Ayland <mark.cave-ayl...@ilande.co.uk> writes:
> On 27/03/2023 17:12, Alex Bennée wrote:
>
>> Mark Cave-Ayland <mark.cave-ayl...@ilande.co.uk> writes:
>>
>>> On 27/03/2023 14:15, Alex Bennée wrote:
>>>
>>>> I'm still not sure how I achieve by use case of the parent class
>>>> defining the following properties:
>>>> static Property vud_properties[] = {
>>>> DEFINE_PROP_CHR("chardev", VHostUserDevice, chardev),
>>>> DEFINE_PROP_UINT16("id", VHostUserDevice, id, 0),
>>>> DEFINE_PROP_UINT32("num_vqs", VHostUserDevice, num_vqs, 1),
>>>> DEFINE_PROP_END_OF_LIST(),
>>>> };
>>>> But for the specialisation of the class I want the id to default to
>>>> the actual device id, e.g.:
>>>> static Property vu_rng_properties[] = {
>>>> DEFINE_PROP_UINT16("id", VHostUserDevice, id, VIRTIO_ID_RNG),
>>>> DEFINE_PROP_UINT32("num_vqs", VHostUserDevice, num_vqs, 1),
>>>> DEFINE_PROP_END_OF_LIST(),
>>>> };
>>>> And so far the API for doing that isn't super clear.
>>>> Signed-off-by: Alex Bennée <alex.ben...@linaro.org>
>>>> ---
>>>> include/hw/qdev-core.h | 9 +++++++++
>>>> 1 file changed, 9 insertions(+)
>>>> diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
>>>> index bd50ad5ee1..d4bbc30c92 100644
>>>> --- a/include/hw/qdev-core.h
>>>> +++ b/include/hw/qdev-core.h
>>>> @@ -776,6 +776,15 @@ BusState *sysbus_get_default(void);
>>>> char *qdev_get_fw_dev_path(DeviceState *dev);
>>>> char *qdev_get_own_fw_dev_path_from_handler(BusState *bus, DeviceState
>>>> *dev);
>>>> +/**
>>>> + * device_class_set_props(): add a set of properties to an device
>>>> + * @dc: the parent DeviceClass all devices inherit
>>>> + * @props: an array of properties, terminate by DEFINE_PROP_END_OF_LIST()
>>>> + *
>>>> + * This will add a set of properties to the object. It will fault if
>>>> + * you attempt to add an existing property defined by a parent class.
>>>> + * To modify an inherited property you need to use????
>>>> + */
>>>> void device_class_set_props(DeviceClass *dc, Property *props);
>>>> /**
>>>
>>> Hmmm that's an interesting one. Looking at the source in
>>> hw/core/qdev-properties.c you could possibly get away with something
>>> like this in vu_rng_class_init():
>>>
>>> ObjectProperty *op = object_class_property_find(klass, "id");
>>> object_property_set_default_uint(op, VIRTIO_ID_RNG);
>>>
>>> Of course this is all completely untested :)
>> Sadly we assert on the existing prop->defval:
>> static void object_property_set_default(ObjectProperty *prop,
>> QObject *defval)
>> {
>> assert(!prop->defval);
>> assert(!prop->init);
>> prop->defval = defval;
>> prop->init = object_property_init_defval;
>> }
>> Maybe the assert is too aggressive or we need a different helper,
>> maybe
>> a:
>> void object_property_update_default_uint(ObjectProperty *prop,
>> uint64_t value)
>> ?
>
> It seems in that case once the default has been set, it is impossible
> to change. The only other immediate option I can think of is to define
> a specific DEFINE_VHOST_PROPERTIES macro in a similar way to
> DEFINE_AUDIO_PROPERTIES which you can use to set the common properties
> for all VHostUserDevice devices, including providing the default ID.
I tried this: allow the default to change
modified qom/object.c
@@ -1557,11 +1557,16 @@ static void object_property_init_defval(Object *obj,
ObjectProperty *prop)
static void object_property_set_default(ObjectProperty *prop, QObject *defval)
{
- assert(!prop->defval);
- assert(!prop->init);
+ if (prop->init == object_property_init_defval) {
+ fprintf(stderr, "%s: updating existing defval\n", __func__);
+ prop->defval = defval;
+ } else {
+ assert(!prop->defval);
+ assert(!prop->init);
- prop->defval = defval;
- prop->init = object_property_init_defval;
+ prop->defval = defval;
+ prop->init = object_property_init_defval;
+ }
}
>
>
> ATB,
>
> Mark.
--
Alex Bennée
Virtualisation Tech Lead @ Linaro
