Re: qdev instance_init vs realize split

[Philippe Mathieu-Daudé]

On 15/2/22 11:19, Damien Hedde wrote:
> 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())

See Peter's recommendations here:
https://www.mail-archive.com/qemu-devel@nongnu.org/msg723958.html

> 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