qdev instance_init vs realize split

[Damien Hedde]

Hi,

I'm wondering if there are rules or convention about what we put in the 
instance_init() vs realize() for simple devices ? (For complex ones we 
generally have no choice to put everything in realize())

For example we can declare irqs and mmios in instance_init() or 
realize() if they do not depend on some property.

This is not a big deal, but given how works the help message generation 
in the monitor, there are difference if the device is user-creatable.

If we leave irqs and mmios declaration in the instance_init(). They 
appear in the help message.
> (qemu) device_add ibex-timer,help
> ibex-timer options:
>   ibex-timer[0]=<child<memory-region>>
>   sysbus-irq[0]=<link<irq>>
>   timebase-freq=<uint32> -  (default: 10000)

If we delay the declaration in realize(), we only have the declared 
qdev-properties (which is maybe more what we expect at this point):

> (qemu) device_add ibex-timer,help
> ibex-timer options:
>   timebase-freq=<uint32> -  (default: 10000)

Any comments ?

Thanks,
Damien