Re: [Qemu-devel] [PATCH 27/28] sysbus: apic: ioapic: convert to QEMU Object Model

[Anthony Liguori <anthony@codemonkey.ws>]

On 01/25/2012 02:37 AM, Jan Kiszka wrote:
> On 2012-01-25 00:03, Anthony Liguori wrote:
>> They're exactly the same size (16 lines).  If you embed TypeInfo into
>> DeviceTypeInfo, and introduce a Device specific type registration
>> function, then you could do:
>>
>> static DeviceTypeInfo my_device_type_info = {
>>      .type.name = TYPE_MY_DEVICE,
>>      .type.parent = TYPE_PARENT_DEVICE,
>>      .reset = my_device_reset,
>
> And if you introduce some
>
> #define TYPE_UNIMPLEMENTED (void *)&dummy_variable

(void *) isn't compatible with integers or function pointers (at least not in a 
portable way).

You would need to use type specific unimplemented mechanisms.

>
> you can easily express
>
> [.field = NULL]         =>  use parent
>   .field = UNIMPLEMENTED =>  don't run any handler
>
>> };
>>
>> static void register_devices(void)
>> {
>>      device_type_register_static(&my_device_type_info);
>> }
>>
>> Which admittedly saves 6 lines, but also is a big step backwards IMHO.
>> Now you've got a lot of one-off functions which means you loose the
>> advantage of having everything work through the same infrastructure.
>
> Can't follow. Four lines
>
> [static inline] void device_type_register_static(DeviceTypeInfo *dt)
> {
>      type_register_static(&dt->type);
> }
>
> are neither ugly nor complex. Rather, this helps concentrating effort at
> _central_ places instead of decentralizing and duplicating lines like in
> your imperative approach. That's the whole point: keep the common case
> (derived classes) compact.

Send a patch.  The infrastructure available should be enough to do whatever you 
need to.

I'm not being dismissive, I've already spent a lot of time trying to make it 
work and have convinced myself that it isn't workable.

If you can show a mechanism that works, I don't mind scripting a mass 
conversion.  I'm also fairly confident that a workable solution is going to be 
better than what we have.

Regards,

Anthony Liguori

>
> Jan
>