[Qemu-devel] [PATCH 2/3] qdev: support properties which don't set a default value

[Peter Maydell <peter.maydell@linaro.org>]

In some situations it's useful to have a qdev property which doesn't
automatically set its default value when qdev_property_add_static is
called (for instance when the default value is not constant).

Support this by adding a flag to the Property struct indicating
whether to set the default value.  This replaces the existing test
for whether the PorpertyInfo set_default_value function pointer is
NULL, and we set the .set_default field to true for all those cases
of struct Property which use a PropertyInfo with a non-NULL
set_default_value, so behaviour remains the same as before.

We define two new macros DEFINE_PROP_SIGNED_NODEFAULT and
DEFINE_PROP_UNSIGNED_NODEFAULT, to cover the most plausible use cases
of wanting to set an integer property with no default value.

Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
Since the previous patch fixed the only case that was
using a default value but not explicitly setting .defval.[ui],
this patch is a bit easier to review: .set_default = true
is added in exactly the places that initialize .defval.[ui].
---
 include/hw/qdev-core.h       |  1 +
 include/hw/qdev-properties.h | 20 ++++++++++++++++++++
 hw/core/qdev.c               |  2 +-
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index 9d7c1c0..d110163 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -226,6 +226,7 @@ struct Property {
     PropertyInfo *info;
     ptrdiff_t    offset;
     uint8_t      bitnr;
+    bool         set_default;
     union {
         int64_t i;
         uint64_t u;
diff --git a/include/hw/qdev-properties.h b/include/hw/qdev-properties.h
index 36d040c..66816a5 100644
--- a/include/hw/qdev-properties.h
+++ b/include/hw/qdev-properties.h
@@ -43,15 +43,24 @@ extern PropertyInfo qdev_prop_arraylen;
         .info      = &(_prop),                                          \
         .offset    = offsetof(_state, _field)                           \
             + type_check(_type,typeof_field(_state, _field)),           \
+        .set_default = true,                                            \
         .defval.i  = (_type)_defval,                                    \
         }
 
+#define DEFINE_PROP_SIGNED_NODEFAULT(_name, _state, _field, _prop, _type) { \
+        .name      = (_name),                                           \
+        .info      = &(_prop),                                          \
+        .offset    = offsetof(_state, _field)                           \
+            + type_check(_type, typeof_field(_state, _field)),          \
+        }
+
 #define DEFINE_PROP_BIT(_name, _state, _field, _bit, _defval) {  \
         .name      = (_name),                                    \
         .info      = &(qdev_prop_bit),                           \
         .bitnr    = (_bit),                                      \
         .offset    = offsetof(_state, _field)                    \
             + type_check(uint32_t,typeof_field(_state, _field)), \
+        .set_default = true,                                     \
         .defval.u  = (bool)_defval,                              \
         }
 
@@ -60,15 +69,24 @@ extern PropertyInfo qdev_prop_arraylen;
         .info      = &(_prop),                                          \
         .offset    = offsetof(_state, _field)                           \
             + type_check(_type, typeof_field(_state, _field)),          \
+        .set_default = true,                                            \
         .defval.u  = (_type)_defval,                                    \
         }
 
+#define DEFINE_PROP_UNSIGNED_NODEFAULT(_name, _state, _field, _prop, _type) { \
+        .name      = (_name),                                           \
+        .info      = &(_prop),                                          \
+        .offset    = offsetof(_state, _field)                           \
+            + type_check(_type, typeof_field(_state, _field)),          \
+        }
+
 #define DEFINE_PROP_BIT64(_name, _state, _field, _bit, _defval) {       \
         .name      = (_name),                                           \
         .info      = &(qdev_prop_bit64),                                \
         .bitnr    = (_bit),                                             \
         .offset    = offsetof(_state, _field)                           \
             + type_check(uint64_t, typeof_field(_state, _field)),       \
+        .set_default = true,                                            \
         .defval.u  = (bool)_defval,                                     \
         }
 
@@ -77,6 +95,7 @@ extern PropertyInfo qdev_prop_arraylen;
         .info      = &(qdev_prop_bool),                          \
         .offset    = offsetof(_state, _field)                    \
             + type_check(bool, typeof_field(_state, _field)),    \
+        .set_default = true,                                     \
         .defval.u    = (bool)_defval,                            \
         }
 
@@ -110,6 +129,7 @@ extern PropertyInfo qdev_prop_arraylen;
                           _arrayfield, _arrayprop, _arraytype) {        \
         .name = (PROP_ARRAY_LEN_PREFIX _name),                          \
         .info = &(qdev_prop_arraylen),                                  \
+        .set_default = true,                                            \
         .defval.u = 0,                                                  \
         .offset = offsetof(_state, _field)                              \
             + type_check(uint32_t, typeof_field(_state, _field)),       \
diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 849952a..96965a7 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -793,7 +793,7 @@ void qdev_property_add_static(DeviceState *dev, Property *prop,
                                     prop->info->description,
                                     &error_abort);
 
-    if (prop->info->set_default_value) {
+    if (prop->set_default) {
         prop->info->set_default_value(obj, prop);
     }
 }
-- 
2.7.4