Re: [Qemu-devel] [RfC PATCH 0/2] qdev/prop: type checking.

[Gerd Hoffmann <kraxel@redhat.com>]

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On 07/13/09 17:36, Paul Brook wrote:
>> The second helps a bunch of helper macros to help creating property
>> declarations and converts pci.c as example.  I'm not that happy with
>> that one yet.  Especially I'd like to check somehow that
>> typeof(_state->_field) == _type.  But couldn't figure out a way to do
>> so.  As we are setting up static data structures we are quite limited in
>> what we can do here.  The typechecking trick used by the linux kernel
>> min/max macros can't be used for example.
>
> Could we use a union rather than an opaque pointer for the default value?

See patch (not functional, just to show the macros).

Improves things only a little bit.  We still don't have any type 
checking for the struct element we are writing to.  We have the field 
offset and the type it is supposed to be.  But no actual check.

cheers,
   Gerd

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>From a770efe5a41de0bc841e935bf0a102ba643db031 Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Mon, 13 Jul 2009 14:00:18 +0200
Subject: [PATCH] qdev/prop: helper macros.

---
 hw/pci.c       |    5 +++++
 hw/qdev-addr.h |    3 +++
 hw/qdev.h      |   32 +++++++++++++++++++++++++++++++-
 3 files changed, 39 insertions(+), 1 deletions(-)

diff --git a/hw/pci.c b/hw/pci.c
index 4c61d63..e689d35 100644
--- a/hw/pci.c
+++ b/hw/pci.c
@@ -56,6 +56,7 @@ static struct BusInfo pci_bus_info = {
     .print_dev  = pcibus_dev_print,
     .add_dev    = pci_create,
     .props      = (Property[]) {
+#if 0
         {
             .name   = "devfn",
             .info   = &qdev_prop_uint32,
@@ -63,6 +64,10 @@ static struct BusInfo pci_bus_info = {
             .defval = (uint32_t[]) { -1 },
         },
         {/* end of list */}
+#else
+        DEFINE_PROP_UINT32("devfn", PCIDevice, devfn, -1),
+        DEFINE_PROP_END_OF_LIST()
+#endif
     }
 };
 
diff --git a/hw/qdev-addr.h b/hw/qdev-addr.h
index f02bd7a..e135a96 100644
--- a/hw/qdev-addr.h
+++ b/hw/qdev-addr.h
@@ -1,2 +1,5 @@
+#define DEFINE_PROP_TADDR(_n, _s, _f)           \
+    DEFINE_PROP(_n, _s, _f, qdev_prop_taddr)
+
 extern PropertyInfo qdev_prop_taddr;
 void qdev_prop_set_taddr(DeviceState *dev, const char *name, target_phys_addr_t value);
diff --git a/hw/qdev.h b/hw/qdev.h
index ed0ae83..e7f2367 100644
--- a/hw/qdev.h
+++ b/hw/qdev.h
@@ -51,7 +51,12 @@ struct Property {
     const char   *name;
     PropertyInfo *info;
     int          offset;
-    void         *defval;
+    void         *defval; /* FIXME: delete */
+    union {
+        uint16_t *uint16_t;
+        uint32_t *uint32_t;
+        void     *any;
+    } def;
 };
 
 enum PropertyType {
@@ -144,6 +149,31 @@ extern PropertyInfo qdev_prop_hex32;
 extern PropertyInfo qdev_prop_ptr;
 extern PropertyInfo qdev_prop_mac;
 
+#define DEFINE_PROP(_name, _state, _field, _prop) { \
+        .name      = (_name),                                    \
+        .info      = &(_prop),                                   \
+        .offset    = offsetof(_state, _field),                   \
+        }
+#define DEFINE_PROP_DEFAULT(_name, _state, _field, _defval, _prop, _type) { \
+        .name      = (_name),                                           \
+        .info      = &(_prop),                                          \
+        .offset    = offsetof(_state, _field),                          \
+        .def._type = (_type[]) { _defval },                             \
+        }
+
+#define DEFINE_PROP_UINT16(_n, _s, _f, _d)                      \
+    DEFINE_PROP_DEFAULT(_n, _s, _f, _d, qdev_prop_uint16, uint16_t)
+#define DEFINE_PROP_UINT32(_n, _s, _f, _d)                      \
+    DEFINE_PROP_DEFAULT(_n, _s, _f, _d, qdev_prop_uint32, uint32_t)
+#define DEFINE_PROP_HEX32(_n, _s, _f, _d)                       \
+    DEFINE_PROP_DEFAULT(_n, _s, _f, _d, qdev_prop_hex32, uint32_t)
+#define DEFINE_PROP_PTR(_n, _s, _f)             \
+    DEFINE_PROP(_n, _s, _f, qdev_prop_ptr)
+#define DEFINE_PROP_MAC(_n, _s, _f)             \
+    DEFINE_PROP(_n, _s, _f, qdev_prop_mac)
+#define DEFINE_PROP_END_OF_LIST()               \
+    {}
+
 /* Set properties between creation and init.  */
 void *qdev_get_prop_ptr(DeviceState *dev, Property *prop);
 int qdev_prop_parse(DeviceState *dev, const char *name, const char *value);
-- 
1.6.2.5