[PATCH v3 7/9] qom: introduce qdev_new_dynamic()

["Daniel P. Berrangé" <berrange@redhat.com>]

qdev_new() has a failure scenario where it will assert() if given
an abstract type. Callers which are creating qdevs based on user
input, or unknown/untrusted type names, must manually check the
result of qdev_class_is_abstract() before calling qdev_new()
to propagate an Error, instead of asserting.

Introduce a qdev_new_dynamic() method which is a counterpart to
qdev_new() that directly returns an Error, instead of asserting.
This new method is to be used where the typename is specified
dynamically by code separate from the immediate caller.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 hw/core/qdev.c         |  5 +++++
 include/hw/qdev-core.h | 27 +++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 7fcbbe431b..eceba33222 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -149,6 +149,11 @@ DeviceState *qdev_new(const char *name)
     return DEVICE(object_new_dynamic(name, &error_abort));
 }
 
+DeviceState *qdev_new_dynamic(const char *name, Error **errp)
+{
+    return DEVICE(object_new_dynamic(name, errp));
+}
+
 static QTAILQ_HEAD(, DeviceListener) device_listeners
     = QTAILQ_HEAD_INITIALIZER(device_listeners);
 
diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index 020417d027..566c5ef277 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -435,14 +435,41 @@ compat_props_add(GPtrArray *arr,
  * qdev_new: Create a device on the heap
  * @name: device type to create (we assert() that this type exists)
  *
+ * This method should be used where @name is statically specified
+ * from a const string at build time, where the caller does not expect
+ * failure to be possible.
+ *
  * This only allocates the memory and initializes the device state
  * structure, ready for the caller to set properties if they wish.
  * The device still needs to be realized.
  *
+ * If an instance of @name is not permitted to be instantiated, an
+ * assert will be raised. This can happen if @name is abstract.
+ *
  * Return: a derived DeviceState object with a reference count of 1.
  */
 DeviceState *qdev_new(const char *name);
 
+/**
+ * qdev_new_dynamic: Create a device on the heap
+ * @name: device type to create (we assert() that this type exists)
+ * @errp: pointer to be filled with error details on failure
+ *
+ * This method must be used where @name is dynamically chosen
+ * at runtime, which has the possibility of unexpected choices leading
+ * to failures.
+ *
+ * This only allocates the memory and initializes the device state
+ * structure, ready for the caller to set properties if they wish.
+ * The device still needs to be realized.
+ *
+ * If an instance of @name is not permitted to be instantiated, an
+ * error will be reported. This can happen if @name is abstract.
+ *
+ * Return: a derived DeviceState object with a reference count of 1.
+ */
+DeviceState *qdev_new_dynamic(const char *name, Error **errp);
+
 /**
  * qdev_is_realized() - check if device is realized
  * @dev: The device to check.
-- 
2.46.0