Re: [PULL 25/41] rust: qom: put class_init together from multiple ClassInitImpl<>

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 7/1/25 17:03, Paolo Bonzini wrote:
> On Tue, Jan 7, 2025 at 4:37 PM Zhao Liu <zhao1.liu@intel.com> wrote:
>>> If anybody wants to do it as an exercise, I am happy to help, otherwise I
>>> can prepare a patch too.
>>
>> If possible and if no one else wants to practice, I would also like to
>> give it a try (I'll add it to my list).
> 
> Hmm, thinking more about it, it does require a bit that is slightly
> more complicated than I anticipated, which is a binding to
> object_class_dynamic_cast(). I placed something completely untested
> (except it compiles...) in rust-next. It uses a new trait
> InterfaceType that can be used as
> 
>      ResettableClass::interface_init::<T, DeviceState>(dc);
> 
> but I don't really like the two parameters and also I don't like that
> class_init is called differently for classes and interfaces. It's
> probably possible to design a better API, but I didn't spend too much
> time on it because it may require rethinking how classes are declared
> (not a huge deal, as we have only four of them).

Are you saying this is not a problem related to QDev Reset, but
a limitation with any QOM interface, and we can not instantiate
any type implementing TYPE_INTERFACE? As in:

   .interfaces = (InterfaceInfo[]) {
     ...
   },

> Feel free to give it a try, but it seems like a relatively low
> priority item compared to upstreaming timers (i.e. HPET) and
> MemoryRegionOps; or figuring out logging.
> 
> Paolo
>