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) ? -- Alex Bennée Virtualisation Tech Lead @ Linaro