On 27/03/2023 17:12, Alex Bennée wrote:
Mark Cave-Ayland <[email protected]> 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 <[email protected]>
---
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.
ATB,
Mark.
