[Qemu-devel] [PATCH 07/18] qom: add link properties

[Anthony Liguori]

Links represent an ephemeral relationship between devices.  They are meant to
replace the qdev concept of busses by allowing more informal relationships
between devices.

Links are fairly limited in their usefulness without implementing QOM-style
subclassing and interfaces.

Signed-off-by: Anthony Liguori <address@hidden>
---
 hw/qdev.c |   69 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 hw/qdev.h |   23 ++++++++++++++++++++
 2 files changed, 92 insertions(+), 0 deletions(-)

diff --git a/hw/qdev.c b/hw/qdev.c
index b09d22a..658ed2c 100644
--- a/hw/qdev.c
+++ b/hw/qdev.c
@@ -1180,6 +1180,75 @@ void qdev_property_add_child(DeviceState *dev, const 
char *name,
     g_free(type);
 }
 
+static void qdev_get_link_property(DeviceState *dev, Visitor *v, void *opaque,
+                                   const char *name, Error **errp)
+{
+    DeviceState **child = opaque;
+    gchar *path;
+
+    if (*child) {
+        path = qdev_get_canonical_path(*child);
+        visit_type_str(v, &path, name, errp);
+        g_free(path);
+    } else {
+        path = (gchar *)"";
+        visit_type_str(v, &path, name, errp);
+    }
+}
+
+static void qdev_set_link_property(DeviceState *dev, Visitor *v, void *opaque,
+                                   const char *name, Error **errp)
+{
+    DeviceState **child = opaque;
+    bool ambiguous = false;
+    const char *type;
+    char *path;
+
+    type = qdev_property_get_type(dev, name, NULL);
+
+    visit_type_str(v, &path, name, errp);
+
+    if (strcmp(path, "") != 0) {
+        DeviceState *target;
+
+        target = qdev_resolve_path(path, &ambiguous);
+        if (target) {
+            gchar *target_type;
+
+            target_type = g_strdup_printf("link<%s>", target->info->name);
+            if (strcmp(target_type, type) == 0) {
+                *child = target;
+            } else {
+                error_set(errp, QERR_INVALID_PARAMETER_TYPE, name, type);
+            }
+
+            g_free(target_type);
+        } else {
+            error_set(errp, QERR_DEVICE_NOT_FOUND, path);
+        }
+    } else {
+        *child = NULL;
+    }
+
+    g_free(path);
+}
+
+void qdev_property_add_link(DeviceState *dev, const char *name,
+                            const char *type, DeviceState **child,
+                            Error **errp)
+{
+    gchar *full_type;
+
+    full_type = g_strdup_printf("link<%s>", type);
+
+    qdev_property_add(dev, name, full_type,
+                      qdev_get_link_property,
+                      qdev_set_link_property,
+                      NULL, child, errp);
+
+    g_free(full_type);
+}
+
 static gchar *qdev_get_path_in(DeviceState *parent, DeviceState *dev)
 {
     GSList *i;
diff --git a/hw/qdev.h b/hw/qdev.h
index 905a02c..e8c9e76 100644
--- a/hw/qdev.h
+++ b/hw/qdev.h
@@ -519,4 +519,27 @@ DeviceState *qdev_resolve_path(const char *path, bool 
*ambiguous);
 void qdev_property_add_child(DeviceState *dev, const char *name,
                              DeviceState *child, Error **errp);
 
+/**
+ * @qdev_property_add_link - Add a link property to a device
+ *
+ * Links establish relationships between devices.  Links are unidirection
+ * although two links can be combined to form a bidirectional relationship
+ * between devices.
+ *
+ * Links form the graph in the device model.
+ *
+ * @dev - the device to add a property to
+ *
+ * @name - the name of the property
+ *
+ * @type - the qdev type of the link
+ *
+ * @child - a pointer to where the link device reference is stored
+ *
+ * @errp - if an error occurs, a pointer to an area to store the area
+ */
+void qdev_property_add_link(DeviceState *dev, const char *name,
+                            const char *type, DeviceState **child,
+                            Error **errp);
+
 #endif
-- 
1.7.4.1