Re: [PATCH 03/12] qom: Make object_class_property_add_uint*_ptr() get offset

[Igor Mammedov]

On Fri,  9 Oct 2020 12:01:13 -0400
Eduardo Habkost <ehabkost@redhat.com> wrote:

> The existing object_class_property_add_uint*_ptr() functions are
> not very useful, because they need a pointer to the property
> value, which can't really be provided before the object is
> created.
> 
> Replace the pointer parameter in those functions with a
> `ptrdiff_t offset` parameter.
> 
> Include a uint8 class property in check-qom-proplist unit tests,
> to ensure the feature is working.


Not sure I like approach, it's reinventing qdev pointer properties in QOM form.
I had an impression that Paolo wanted qdev pointer properties be gone
and replaced by something like link properties.

object_property_add_uintXX_ptr() were introduced as a quick hack,
when ACPI code generation was moved from Seabios, to avoid more
code shuffling in device models and adding more boiler plate in
form of custom setters/getters (the later didn't seem to bother
us everywhere else where we use object_[class_]property_add() ).
Then it spread little bit to another places.

I'd rather get rid of object_property_add_uintXX_ptr() API altogether
in favor of object_[class_]property_add() like it is used in other places
to handle intXX properties.
Adding helpers similar to object_property_add_bool() for intXX
could reduce boiler plate need for converting current instances of
_ptr(), and such helpers would also help with reducing boilerplate
for the rest of instances where object_[class_]property_add()
currently is used for dealing with integers.


> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: "Daniel P. Berrangé" <berrange@redhat.com>
> Cc: Eduardo Habkost <ehabkost@redhat.com>
> Cc: qemu-devel@nongnu.org
> ---
>  include/qom/object.h       |  8 ++++----
>  qom/object.c               | 36 +++++++++++++++++++++++-------------
>  tests/check-qom-proplist.c | 10 ++++++++--
>  3 files changed, 35 insertions(+), 19 deletions(-)
> 
> diff --git a/include/qom/object.h b/include/qom/object.h
> index d378f13a11..1634294e4f 100644
> --- a/include/qom/object.h
> +++ b/include/qom/object.h
> @@ -1747,7 +1747,7 @@ ObjectProperty *object_property_add_uint8_ptr(Object 
> *obj, const char *name,
>  
>  ObjectProperty *object_class_property_add_uint8_ptr(ObjectClass *klass,
>                                           const char *name,
> -                                         const uint8_t *v,
> +                                         ptrdiff_t offset,
>                                           ObjectPropertyFlags flags);
>  
>  /**
> @@ -1768,7 +1768,7 @@ ObjectProperty *object_property_add_uint16_ptr(Object 
> *obj, const char *name,
>  
>  ObjectProperty *object_class_property_add_uint16_ptr(ObjectClass *klass,
>                                            const char *name,
> -                                          const uint16_t *v,
> +                                          ptrdiff_t offset,
>                                            ObjectPropertyFlags flags);
>  
>  /**
> @@ -1789,7 +1789,7 @@ ObjectProperty *object_property_add_uint32_ptr(Object 
> *obj, const char *name,
>  
>  ObjectProperty *object_class_property_add_uint32_ptr(ObjectClass *klass,
>                                            const char *name,
> -                                          const uint32_t *v,
> +                                          ptrdiff_t offset,
>                                            ObjectPropertyFlags flags);
>  
>  /**
> @@ -1810,7 +1810,7 @@ ObjectProperty *object_property_add_uint64_ptr(Object 
> *obj, const char *name,
>  
>  ObjectProperty *object_class_property_add_uint64_ptr(ObjectClass *klass,
>                                            const char *name,
> -                                          const uint64_t *v,
> +                                          ptrdiff_t offset,
>                                            ObjectPropertyFlags flags);
>  
>  /**
> diff --git a/qom/object.c b/qom/object.c
> index 17692ed5c3..bb32f5d3ad 100644
> --- a/qom/object.c
> +++ b/qom/object.c
> @@ -2450,13 +2450,22 @@ static char *object_get_type(Object *obj, Error 
> **errp)
>  }
>  
>  typedef struct {
> -    /* Pointer to property value */
> -    void *ptr;
> +    bool is_offset;
> +    union {
> +        /* Pointer to property value.  Valid if is_offset=false */
> +        void *ptr;
> +        /* Offset in Object struct.  Valid if is_offset=true */
> +        ptrdiff_t offset;
> +    };
>  } PointerProperty;
>  
>  static void *pointer_property_get_ptr(Object *obj, PointerProperty *prop)
>  {
> -    return prop->ptr;
> +    if (prop->is_offset) {
> +        return (void *)obj + prop->offset;
> +    } else {
> +        return prop->ptr;
> +    }
>  }
>  
>  static void property_get_uint8_ptr(Object *obj, Visitor *v, const char *name,
> @@ -2573,10 +2582,11 @@ object_class_property_add_uint_ptr(ObjectClass *oc, 
> const char *name,
>                                     ObjectPropertyAccessor getter,
>                                     ObjectPropertyAccessor setter,
>                                     ObjectPropertyFlags flags,
> -                                   void *ptr)
> +                                   ptrdiff_t offset)
>  {
>      PointerProperty *prop = g_new0(PointerProperty, 1);
> -    prop->ptr = ptr;
> +    prop->is_offset = true;
> +    prop->offset = offset;
>      return object_class_property_add(oc, name, type,
>                                       (flags & OBJ_PROP_FLAG_READ) ? getter : 
> NULL,
>                                       (flags & OBJ_PROP_FLAG_WRITE) ? setter 
> : NULL,
> @@ -2597,13 +2607,13 @@ object_property_add_uint8_ptr(Object *obj, const char 
> *name,
>  
>  ObjectProperty *
>  object_class_property_add_uint8_ptr(ObjectClass *klass, const char *name,
> -                                    const uint8_t *v,
> +                                    ptrdiff_t offset,
>                                      ObjectPropertyFlags flags)
>  {
>      return object_class_property_add_uint_ptr(klass, name, "uint8",
>                                                property_get_uint8_ptr,
>                                                property_set_uint8_ptr,
> -                                              flags, (void *)v);
> +                                              flags, offset);
>  }
>  
>  ObjectProperty *
> @@ -2620,13 +2630,13 @@ object_property_add_uint16_ptr(Object *obj, const 
> char *name,
>  
>  ObjectProperty *
>  object_class_property_add_uint16_ptr(ObjectClass *klass, const char *name,
> -                                     const uint16_t *v,
> +                                     ptrdiff_t offset,
>                                       ObjectPropertyFlags flags)
>  {
>      return object_class_property_add_uint_ptr(klass, name, "uint16",
>                                                property_get_uint16_ptr,
>                                                property_set_uint16_ptr,
> -                                              flags, (void *)v);
> +                                              flags, offset);
>  }
>  
>  ObjectProperty *
> @@ -2643,13 +2653,13 @@ object_property_add_uint32_ptr(Object *obj, const 
> char *name,
>  
>  ObjectProperty *
>  object_class_property_add_uint32_ptr(ObjectClass *klass, const char *name,
> -                                     const uint32_t *v,
> +                                     ptrdiff_t offset,
>                                       ObjectPropertyFlags flags)
>  {
>      return object_class_property_add_uint_ptr(klass, name, "uint32",
>                                                property_get_uint32_ptr,
>                                                property_set_uint32_ptr,
> -                                              flags, (void *)v);
> +                                              flags, offset);
>  }
>  
>  ObjectProperty *
> @@ -2666,13 +2676,13 @@ object_property_add_uint64_ptr(Object *obj, const 
> char *name,
>  
>  ObjectProperty *
>  object_class_property_add_uint64_ptr(ObjectClass *klass, const char *name,
> -                                     const uint64_t *v,
> +                                     ptrdiff_t offset,
>                                       ObjectPropertyFlags flags)
>  {
>      return object_class_property_add_uint_ptr(klass, name, "uint64",
>                                                property_get_uint64_ptr,
>                                                property_set_uint64_ptr,
> -                                              flags, (void *)v);
> +                                              flags, offset);
>  }
>  
>  typedef struct {
> diff --git a/tests/check-qom-proplist.c b/tests/check-qom-proplist.c
> index 1b76581980..fba30c20b2 100644
> --- a/tests/check-qom-proplist.c
> +++ b/tests/check-qom-proplist.c
> @@ -61,6 +61,7 @@ struct DummyObject {
>      bool bv;
>      DummyAnimal av;
>      char *sv;
> +    uint8_t u8v;
>  };
>  
>  struct DummyObjectClass {
> @@ -141,6 +142,9 @@ static void dummy_class_init(ObjectClass *cls, void *data)
>                                     &dummy_animal_map,
>                                     dummy_get_av,
>                                     dummy_set_av);
> +    object_class_property_add_uint8_ptr(cls, "u8v",
> +                                        offsetof(DummyObject, u8v),
> +                                        OBJ_PROP_FLAG_READWRITE);
>  }
>  
>  
> @@ -385,12 +389,14 @@ static void test_dummy_createlist(void)
>                     "bv", "yes",
>                     "sv", "Hiss hiss hiss",
>                     "av", "platypus",
> +                   "u8v", "42",
>                     NULL));
>  
>      g_assert(err == NULL);
>      g_assert_cmpstr(dobj->sv, ==, "Hiss hiss hiss");
>      g_assert(dobj->bv == true);
>      g_assert(dobj->av == DUMMY_PLATYPUS);
> +    g_assert_cmpint(dobj->u8v, ==, 42);
>  
>      g_assert(object_resolve_path_component(parent, "dummy0")
>               == OBJECT(dobj));
> @@ -531,7 +537,7 @@ static void test_dummy_iterator(void)
>  {
>      const char *expected[] = {
>          "type",                 /* inherited from TYPE_OBJECT */
> -        "sv", "av",             /* class properties */
> +        "sv", "av", "u8v",      /* class properties */
>          "bv"};                  /* instance property */
>      Object *parent = object_get_objects_root();
>      DummyObject *dobj = DUMMY_OBJECT(
> @@ -552,7 +558,7 @@ static void test_dummy_iterator(void)
>  
>  static void test_dummy_class_iterator(void)
>  {
> -    const char *expected[] = { "type", "av", "sv" };
> +    const char *expected[] = { "type", "av", "sv", "u8v" };
>      ObjectPropertyIterator iter;
>      ObjectClass *klass = object_class_by_name(TYPE_DUMMY);
>