[Qemu-devel] Re: [PATCH 2/2] Introduce macro for defining qdev properties

[Gerd Hoffmann <kraxel@redhat.com>]

On 07/17/09 16:41, Anthony Liguori wrote:
> This patch introduces macros for defining qdev properties.  The default macro
> is clever enough to infer the type of the structure field and to automatically
> generate a name for the property.  Additional macros are provided that allow
> infered values to be overridden along with a set of macros to define properties
> with default values.

> +#define TYPEOF_FIELD(type, field) typeof(((type *)0)->field)

Hmm, tried to create something simliar.  Didn't work, looks like I did 
something wrong :-(

> +#define QDEV_PROP_TYPE_INFER(type, field)                          \
> +        CHOOSE(TYPES_COMPAT(TYPEOF_FIELD(type, field), uint16_t),  \
> +&qdev_prop_uint16,                                         \
> +        CHOOSE(TYPES_COMPAT(TYPEOF_FIELD(type, field), int16_t),   \
> +&qdev_prop_uint16,                                         \
> +        CHOOSE(TYPES_COMPAT(TYPEOF_FIELD(type, field), uint32_t),  \
> +&qdev_prop_uint32,                                         \
> +        CHOOSE(TYPES_COMPAT(TYPEOF_FIELD(type, field), int32_t),   \
> +&qdev_prop_uint32,                                         \
> +        CHOOSE(TYPES_COMPAT(TYPEOF_FIELD(type, field), CharDriverState *), \
> +&qdev_prop_chrdev,                                         \
> +        /* force a build break when inference fails */             \
> +       (double)3.14159265)))))

You probably want to use something like 
&qdev_prop_not_found_for_this_type instead of pi to get a somewhat 
better error message.

Overall this looks pretty good to me.

cheers,
   Gerd