Re: [Qemu-devel] [PATCH v2] qom: Introduce object_realize_nofail()

[Andreas Färber]

Am 12.04.2012 17:41, schrieb Anthony Liguori:
> On 04/12/2012 09:04 AM, Andreas Färber wrote:
>> Am 12.04.2012 16:59, schrieb Paolo Bonzini:
>>> Il 12/04/2012 16:47, Anthony Liguori ha scritto:
>>>>
>>>>> Wrap setting of Object::realized property, error reporting and exit(1)
>>>>> into a helper function. It is the equivalent of qdev_init_nofail().
>>>>
>>>> I don't like this.
>>>>
>>>> If for no reason other than, a much more specific justification is
>>>> needed for this.  I absolutely don't want to repeat the error handling
>>>> mistakes of qdev.  I would rather we refactor all of the users of
>>>> qdev_init_nofail() to propagate errors.
>>>
>>> I agree about this in general, but for a different reason.  There
>>> should be
>>> only one call to object_realize_nofail, in vl.c, which might as well be
>>> inlined---I'll include it in my series.  All calls to qdev_init_nofail
>>> and qdev_init should disappear from boards that are properly converted
>>> to QOM.
>>
>> We had talked about this on IRC and found that it won't work for
>> selecting the type of an object.
> 
> Can you be more specific?
> 
> Selecting the type of an object should be done by having a link<>
> property and letting the user create an object and setup the link.

No, that's not what a link does. A link<> property lets the user
associate one instance, not a type that can be used for multiple
instances. We'd need a template<> or clone<> mechanism for that!

For example, the user specifies -cpu cortex-a9,+neon,-fpu and we have a
dual-core exynos4210 SoC.

I originally had a patch on my qom-cpu-sh4 v1 series where exactly such
a link got criticized by Peter:

http://patchwork.ozlabs.org/patch/146669/

And I agree, it was an ugly workaround around the missing two-stage
constructor support. Therefore I had posted my object_realize() series!

https://github.com/afaerber/qemu-cpu/commit/32e4dd701694fffcf312d111c79eedad243be2b3

Andreas

-- 
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg