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Re: [Qemu-devel] [PATCH 01/18] qom: add new dynamic property infrastruct

From: Anthony Liguori
Subject: Re: [Qemu-devel] [PATCH 01/18] qom: add new dynamic property infrastructure based on Visitors
Date: Thu, 01 Dec 2011 19:08:00 -0600
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20110831 Lightning/1.0b2 Thunderbird/3.1.13

On 12/01/2011 09:52 AM, Kevin Wolf wrote:
Am 30.11.2011 22:03, schrieb Anthony Liguori:
qdev properties are settable only during construction and static to classes.
This isn't flexible enough for QOM.

This patch introduces a property interface for qdev that provides dynamic
properties that are tied to objects, instead of classes.  These properties are
Visitor based instead of string based too.

Signed-off-by: Anthony Liguori<address@hidden>
  hw/qdev.c |   99 +++++++++++++++++++++++++++++++++++++++++++++++++++
  hw/qdev.h |  118 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  qerror.c  |    4 ++
  qerror.h  |    3 ++
  4 files changed, 224 insertions(+), 0 deletions(-)

diff --git a/hw/qdev.c b/hw/qdev.c
index 106407f..ad2d44f 100644
--- a/hw/qdev.c
+++ b/hw/qdev.c
@@ -390,12 +390,33 @@ void qdev_init_nofail(DeviceState *dev)

+static void qdev_property_del_all(DeviceState *dev)
+    while (dev->properties) {
+        GSList *i = dev->properties;
+        DeviceProperty *prop = i->data;
+        dev->properties = i->next;
+        if (prop->release) {
+            prop->release(dev, prop->name, prop->opaque);
+        }
+        g_free(prop->name);
+        g_free(prop->type);
+        g_free(prop);
+        g_free(i);
+    }
  /* Unlink device from bus and free the structure.  */
  void qdev_free(DeviceState *dev)
      BusState *bus;
      Property *prop;

+    qdev_property_del_all(dev);
      if (dev->state == DEV_STATE_INITIALIZED) {
          while (dev->num_child_bus) {
              bus = QLIST_FIRST(&dev->child_bus);
@@ -962,3 +983,81 @@ char* qdev_get_fw_dev_path(DeviceState *dev)

      return strdup(path);
+void qdev_property_add(DeviceState *dev, const char *name, const char *type,
+                       DevicePropertyEtter *get, DevicePropertyEtter *set,
+                       DevicePropertyRelease *release, void *opaque,
+                       Error **errp)

How about letting the caller pass in a DeviceProperty for improved
readability and usability? Instead of memorizing the order of currently
eight parameters (could probably become more in the future) you can use
proper C99 initializers then.

Yeah, instead of taking a void *opaque, it could then just take the DeviceProperty and use container_of adding a good bit more type safety. I like it, thanks for the suggestion.

@@ -45,6 +82,7 @@ struct DeviceState {
      QTAILQ_ENTRY(DeviceState) sibling;
      int instance_id_alias;
      int alias_required_for_version;
+    GSList *properties;

Why GSList instead of qemu-queue.h macros that would provide type safety?

You're clearly thwarting my attempts at slowly introducing GSList as a replacement for qemu-queue ;-)

I really dislike qemu-queue. I think it's a whole lot more difficult to use in practice. The glib data structures are much more rich than qemu-queue.

I don't think a property can belong to multiple devices, can it?
qdev_property_add only refers to a single device, and nothing else adds
elements to the list.

Yes, you are correct.


Anthony Liguori


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