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Re: [Qemu-devel] [PATCH] qom: helper macro for adding read-only properti

From: Michael S. Tsirkin
Subject: Re: [Qemu-devel] [PATCH] qom: helper macro for adding read-only properties
Date: Mon, 16 Sep 2013 19:07:21 +0300

On Mon, Sep 16, 2013 at 08:32:13AM +0200, Andreas Färber wrote:
> Am 15.09.2013 19:23, schrieb Michael S. Tsirkin:
> > Add a helper macro for adding read-only properties, that works in the
> > common case where the value is a constant.
> > 
> > Signed-off-by: Michael S. Tsirkin <address@hidden>
> > ---
> > 
> > I'm using this patch in my acpi work - any objections
> > to applying it on my tree?
> Actually yes: Apart from the clang issues raised and the disturbing
> upper-casing of arguments,

BTW there are no upper casing of arguments:
internal variable names in macros must include
macro name otherwise you get hard to debug collisions:

#define SQUARE_ME(x) \
        do { \
                int var = x; \
                x = var * x; \
        } while (0) \

int v = 2;

// v is 4

int var = 2;

// BUG: var is still 2

> this is hardcoding "int" type and NULL errp,
> so I don't think it deserves to live in object.h as is. I do agree that
> we could use more helper functions to deal with dynamic properties.
> So what about taking bool/string property helpers as example and putting
> intX_t getters into object.c, using a passed-through opaque argument to
> obtain the value? We could then have real object_property_add_int32()
> etc. functions using the appropriate type name, with field/value pointer
> and Error** arguments. A pointer can be assumed to hold up to uint32_t
> values or, to keep the API more general, use a local static const
> variable for non-field values.
> It does touch on the issue I brought up on a KVM call a couple weeks ago
> of how dynamic and static properties are supposed to relate. I
> personally welcome making dynamic properties more easy to deal with; an
> alternative might be to extend qdev-properties.c with
> DEFINE_PROP_READONLY_UINT32() etc. CC'ing Igor, who has dealt with
> dynamic-vs.-static properties for X86CPU.
> Regards,
> Andreas

OK this makes you happy?
All calls pass NULL as Error so I omitted
it for now.
We can add later if anyone has a use for it.

diff --git a/include/qom/object.h b/include/qom/object.h
index 1a7b71a..90dce59 100644
--- a/include/qom/object.h
+++ b/include/qom/object.h
@@ -795,6 +795,27 @@ void object_property_add(Object *obj, const char *name, 
const char *type,
 void object_property_del(Object *obj, const char *name, struct Error **errp);
+ * object_property_add_uint8_t_ptr:
+ * object_property_add_uint16_t_ptr:
+ * object_property_add_uint32_t_ptr:
+ * object_property_add_uint64_t_ptr:
+ * @obj: the object to add a property to
+ * @name: the name of the property
+ * @v: pointer to value
+ *
+ * Add an integer property in memory.  This function will add a
+ * property of the appropriate type.
+ */
+void object_property_add_uint8_t_ptr(Object *obj, const char *name,
+                                     const uint8_t *v);
+void object_property_add_uint16_t_ptr(Object *obj, const char *name,
+                                      const uint16_t *v);
+void object_property_add_uint32_t_ptr(Object *obj, const char *name,
+                                      const uint32_t *v);
+void object_property_add_uint64_t_ptr(Object *obj, const char *name,
+                                      const uint64_t *v);
  * object_property_find:
  * @obj: the object
  * @name: the name of the property

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