Re: [Qemu-devel] [RFC] extensions to the -m memory option

[Peter Crosthwaite]

On Wed, Jun 3, 2015 at 5:31 AM, Liviu Ionescu <address@hidden> wrote:
>
>> On 01 Jun 2015, at 23:36, Liviu Ionescu <address@hidden> wrote:
>>
>> ... I just pushed a preliminary version where all STM32 MCUs and STM32 
>> related boards use the new framework.
>
> please disregard the current version, I'm already re-working the code to be 
> more compliant with the (quite complicated) object infrastructure.
>
> btw, except from various other pieces of code, more or less up-to-date, is 
> there any document explaining what is the recommended way of using these 
> objects?
>
> at least the confusing 'realize' mechanism is it explained somewhere?
>

http://wiki.qemu.org/QOMConventions

but that doesn't really cover your question.

Some of my rules of thumb.

1: For container objects, realize is often just a recursive call of
realize for the contained. It may set properties on the way. see
hw/arm/xlnx-zynqmp for a recent example.
2: Data structure creation should generally go in the init. If it
depends on a property (e.g. to size an array) then you can delay to
realize or do it in a property setter callback.
3: If it has a user visible failure path it goes in realize
4: When in doubt and if it is possible. do things in init, not realize.
5: External interface connection is usually realize (e.g. connecting a
uart or network)
6: Do not have any device state modifications in realize. A common
mistake is to put hardware reset behavior in realize (e.g. initing
registers to their reset value). Use the DeviceClass::reset callback
for this.
7: When I say init, I mean the object instance_init callback, do not
use the depracated SysBusDevice::init callback.

Regards,
Peter

>
> regards,
>
> Liviu
>
>