Re: [Qemu-devel] [RFC 04/34] qdev: Prepare "realized" property

[Eduardo Habkost]

On Mon, Nov 26, 2012 at 01:12:16AM +0100, Andreas Färber wrote:
> Based on earlier patches by Paolo and me, introduce the QOM realizefn at
> device level only, as requested by Anthony.
> 
> For now this just wraps the qdev initfn.
> 
> Signed-off-by: Paolo Bonzini <address@hidden>
> Signed-off-by: Andreas Färber <address@hidden>
> Cc: Anthony Liguori <address@hidden>
> ---
>  hw/qdev-core.h |    4 +++
>  hw/qdev.c      |  100 
> ++++++++++++++++++++++++++++++++++++++++++--------------
>  2 Dateien geändert, 80 Zeilen hinzugefügt(+), 24 Zeilen entfernt(-)
> 
> diff --git a/hw/qdev-core.h b/hw/qdev-core.h
> index f0d3a5e..580a811 100644
> --- a/hw/qdev-core.h
> +++ b/hw/qdev-core.h
> @@ -29,6 +29,8 @@ enum {
>  typedef int (*qdev_initfn)(DeviceState *dev);
>  typedef int (*qdev_event)(DeviceState *dev);
>  typedef void (*qdev_resetfn)(DeviceState *dev);
> +typedef void (*DeviceRealize)(DeviceState *dev, Error **err);
> +typedef void (*DeviceUnrealize)(DeviceState *dev, Error **err);
>  
>  struct VMStateDescription;
>  
> @@ -47,6 +49,8 @@ typedef struct DeviceClass {
>      const struct VMStateDescription *vmsd;
>  
>      /* Private to qdev / bus.  */
> +    DeviceRealize realize;
> +    DeviceUnrealize unrealize;
>      qdev_initfn init;
>      qdev_event unplug;
>      qdev_event exit;
> diff --git a/hw/qdev.c b/hw/qdev.c
> index bce6ad5..d7b6320 100644
> --- a/hw/qdev.c
> +++ b/hw/qdev.c
> @@ -147,37 +147,30 @@ DeviceState *qdev_try_create(BusState *bus, const char 
> *type)
>     Return 0 on success.  */
>  int qdev_init(DeviceState *dev)
>  {
> -    DeviceClass *dc = DEVICE_GET_CLASS(dev);
> -    int rc;
> +    Error *local_err = NULL;
>  
>      assert(!dev->realized);
>  
> -    rc = dc->init(dev);
> -    if (rc < 0) {
> +    object_property_set_bool(OBJECT(dev), true, "realized", &local_err);
> +    if (local_err != NULL) {
> +        error_free(local_err);
>          object_delete(OBJECT(dev));
> -        return rc;
> +        return -1;
>      }
> +    return 0;
> +}
>  
> -    if (!OBJECT(dev)->parent) {
> -        static int unattached_count = 0;
> -        gchar *name = g_strdup_printf("device[%d]", unattached_count++);
> -
> -        object_property_add_child(container_get(qdev_get_machine(),
> -                                                "/unattached"),
> -                                  name, OBJECT(dev), NULL);
> -        g_free(name);
> -    }
> +static void device_realize(DeviceState *dev, Error **err)
> +{
> +    DeviceClass *dc = DEVICE_GET_CLASS(dev);
>  
> -    if (qdev_get_vmsd(dev)) {
> -        vmstate_register_with_alias_id(dev, -1, qdev_get_vmsd(dev), dev,
> -                                       dev->instance_id_alias,
> -                                       dev->alias_required_for_version);
> -    }
> -    dev->realized = true;
> -    if (dev->hotplugged) {
> -        device_reset(dev);
> +    if (dc->init) {
> +        int rc = dc->init(dev);
> +        if (rc < 0) {
> +            error_setg(err, "Device initialization failed.");
> +            return;
> +        }
>      }
> -    return 0;
>  }
[...]
> +static void device_class_init(ObjectClass *oc, void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(oc);
> +    dc->realize = device_realize;
> +}
> +
[...]

Stupid question: what exactly is the difference in capabilities and
semantics between DeviceClass.init() and DeviceClass.realize()? They
look exactly the same to me, from a first look. On which cases would
somebody use the former instead of the latter, and why?

-- 
Eduardo