Re: [Qemu-devel] [PATCH v2 6/7] qom: add a object_property_add_enum helper method

["Daniel P. Berrange" <berrange@redhat.com>]

On Thu, Apr 30, 2015 at 04:46:37PM +0100, Daniel P. Berrange wrote:
> A QOM property can be parsed as enum using the visit_type_enum()
> helper method, but this forces callers to use the more complex
> generic object_property_add() method when registering it. It
> also requires that users of that object have access to the
> string map when they want to read the property value.
> 
> This patch introduces a specialized object_property_add_enum()
> method which simplifies the use of enum properties, so the
> setters/getters directly get passed the int value.
> 
>   typedef enum {
>      MYDEV_TYPE_FROG,
>      MYDEV_TYPE_ALLIGATOR,
>      MYDEV_TYPE_PLATYPUS,
> 
>      MYDEV_TYPE_LAST
>   } MyDevType;
> 
> Then provide a table of enum <-> string mappings
> 
>   static const char *const mydevtypemap[MYDEV_TYPE_LAST + 1] = {
>      [MYDEV_TYPE_FROG] = "frog",
>      [MYDEV_TYPE_ALLIGATOR] = "alligator",
>      [MYDEV_TYPE_PLATYPUS] = "platypus",
>      [MYDEV_TYPE_LAST] = NULL,
>   };
> 
> Assuming an object struct of
> 
>    typedef struct {
>       Object parent;
>       MyDevType devtype;
>       ...other fields...
>    } MyDev;
> 
> The property can then be registered as follows:
> 
>    static int mydev_prop_get_devtype(Object *obj,
>                                      Error **errp G_GNUC_UNUSED)
>    {
>        MyDev *dev = MYDEV(obj);
> 
>        return dev->devtype;
>    }
> 
>    static void mydev_prop_set_devtype(Object *obj,
>                                       int value,
>                                       Error **errp G_GNUC_UNUSED)
>    {
>        MyDev *dev = MYDEV(obj);
> 
>        dev->endpoint = value;
>    }
> 
>    object_property_add_enum(obj, "devtype",
>                             mydevtypemap, "MyDevType",
>                             mydev_prop_get_devtype,
>                             mydev_prop_set_devtype,
>                             NULL);
> 
> Note there is no need to check the range of 'value' in
> the setter, because the string->enum conversion code will
> have already done that and reported an error as required.
> 
> Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> ---
>  include/qom/object.h       | 19 ++++++++++++
>  qom/object.c               | 58 ++++++++++++++++++++++++++++++++++++
>  tests/check-qom-proplist.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 151 insertions(+)


> diff --git a/tests/check-qom-proplist.c b/tests/check-qom-proplist.c
> index 9a02e4d..15f4933 100644
> --- a/tests/check-qom-proplist.c
> +++ b/tests/check-qom-proplist.c
> +static void test_dummy_badenum(void)
> +{
> +    Error *err = NULL;
> +    DummyObject *dobj = DUMMY_OBJECT(
> +        object_new_propv(TYPE_DUMMY,
> +                         "/objects",
> +                         "dummy0",
> +                         &err,
> +                         "bv", "yes",
> +                         "sv", "Hiss hiss hiss",
> +                         "av", "yeti",
> +                         NULL));

Opps, this won't compile as I forgot to update the 2nd arg. Will
send a v3

Regards,
Daniel
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