[PATCHv2-RFC,1/2] qdev: add bit property type

diff --git a/hw/qdev-properties.c b/hw/qdev-properties.c
index fb07279..3782609 100644
--- a/hw/qdev-properties.c
+++ b/hw/qdev-properties.c
@@ -9,6 +9,67 @@  void *qdev_get_prop_ptr(DeviceState *dev, Property *prop)
     return ptr;
 }
 
+static void *qdev_bit_prop_ptr(DeviceState *dev, Property *prop)
+{
+    void *ptr = dev;
+    assert(prop->info->type == PROP_TYPE_BIT);
+    ptr += prop->offset / 32;
+    return ptr;
+}
+
+static uint32_t qdev_bit_prop_mask(Property *prop)
+{
+    assert(prop->info->type == PROP_TYPE_BIT);
+    return 0x1 << (prop->offset % 32);
+}
+
+static void bit_prop_set(DeviceState *dev, Property *props, bool val)
+{
+    uint32_t *p = qdev_bit_prop_ptr(dev, props);
+    uint32_t mask = qdev_bit_prop_mask(props);
+    if (val)
+        *p |= ~mask;
+    else
+        *p &= ~mask;
+}
+
+static void qdev_prop_cpy(DeviceState *dev, Property *props, void *src)
+{
+    if (props->info->type == PROP_TYPE_BIT) {
+        bool *defval = src;
+        bit_prop_set(dev, props, *defval);
+    } else {
+        char *dst = qdev_get_prop_ptr(dev, props);
+        memcpy(dst, src, props->info->size);
+    }
+}
+
+/* Bit */
+static int parse_bit(DeviceState *dev, Property *prop, const char *str)
+{
+    if (!strncasecmp(str, "on", 2))
+        bit_prop_set(dev, prop, true);
+    else if (!strncasecmp(str, "off", 3))
+        bit_prop_set(dev, prop, false);
+    else
+        return -1;
+    return 0;
+}
+
+static int print_bit(DeviceState *dev, Property *prop, char *dest, size_t len)
+{
+    uint8_t *p = qdev_bit_prop_ptr(dev, prop);
+    return snprintf(dest, len, (*p & qdev_bit_prop_mask(prop)) ? "on" : "off");
+}
+
+PropertyInfo qdev_prop_bit = {
+    .name  = "on/off",
+    .type  = PROP_TYPE_BIT,
+    .size  = sizeof(uint32_t),
+    .parse = parse_bit,
+    .print = print_bit,
+};
+
 /* --- 8bit integer --- */
 
 static int parse_uint8(DeviceState *dev, Property *prop, const char *str)
@@ -506,7 +567,6 @@  int qdev_prop_parse(DeviceState *dev, const char *name, const char *value)
 void qdev_prop_set(DeviceState *dev, const char *name, void *src, enum PropertyType type)
 {
     Property *prop;
-    void *dst;
 
     prop = qdev_prop_find(dev, name);
     if (!prop) {
@@ -519,8 +579,7 @@  void qdev_prop_set(DeviceState *dev, const char *name, void *src, enum PropertyT
                 __FUNCTION__, dev->info->name, name);
         abort();
     }
-    dst = qdev_get_prop_ptr(dev, prop);
-    memcpy(dst, src, prop->info->size);
+    qdev_prop_cpy(dev, prop, src);
 }
 
 void qdev_prop_set_uint8(DeviceState *dev, const char *name, uint8_t value)
@@ -580,14 +639,11 @@  void qdev_prop_set_ptr(DeviceState *dev, const char *name, void *value)
 
 void qdev_prop_set_defaults(DeviceState *dev, Property *props)
 {
-    char *dst;
-
     if (!props)
         return;
     while (props->name) {
         if (props->defval) {
-            dst = qdev_get_prop_ptr(dev, props);
-            memcpy(dst, props->defval, props->info->size);
+            qdev_prop_cpy(dev, props, props->defval);
         }
         props++;
     }
diff --git a/hw/qdev.h b/hw/qdev.h
index bbcdba1..26853e0 100644
--- a/hw/qdev.h
+++ b/hw/qdev.h
@@ -82,6 +82,7 @@  enum PropertyType {
     PROP_TYPE_NETDEV,
     PROP_TYPE_VLAN,
     PROP_TYPE_PTR,
+    PROP_TYPE_BIT,
 };
 
 struct PropertyInfo {
@@ -173,6 +174,7 @@  void do_device_del(Monitor *mon, const QDict *qdict);
 
 /*** qdev-properties.c ***/
 
+extern PropertyInfo qdev_prop_bit;
 extern PropertyInfo qdev_prop_uint8;
 extern PropertyInfo qdev_prop_uint16;
 extern PropertyInfo qdev_prop_uint32;
@@ -202,6 +204,13 @@  extern PropertyInfo qdev_prop_pci_devfn;
             + type_check(_type,typeof_field(_state, _field)),           \
         .defval    = (_type[]) { _defval },                             \
         }
+#define DEFINE_PROP_BIT(_name, _state, _field, _bit, _defval) { \
+        .name      = (_name),                                             \
+        .info      = &(qdev_prop_bit),                                    \
+        .offset    = offsetof(_state, _field) * 32 + (_bit)                \
+            + type_check(uint32_t,typeof_field(_state, _field)),             \
+        .defval    = (bool[]) { (_defval) }, \
+        }
 
 #define DEFINE_PROP_UINT8(_n, _s, _f, _d)                       \
     DEFINE_PROP_DEFAULT(_n, _s, _f, _d, qdev_prop_uint8, uint8_t)