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

[Jan Kiszka <jan.kiszka@web.de>]

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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

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.

Jan


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