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Date: Wed, 28 Jun 2017 22:02:19 +0800
From: Fam Zheng <famz@redhat.com>
Message-ID: <20170628140219.GI14166@lemon.lan>
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Subject: Re: [Qemu-devel] [PATCH 4/7] qdev: Introduce DEFINE_PROP_LINK
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org, Andreas =?iso-8859-1?Q?F=E4rber?= <afaerber@suse.de>, "Dr . David Alan Gilbert" <dgilbert@redhat.com>, Markus Armbruster <armbru@redhat.com>

On Wed, 06/28 15:38, Paolo Bonzini wrote:
> 
> 
> On 28/06/2017 14:48, Fam Zheng wrote:
> > 
> > It's implemented by creating a wrapper property that basically forwards
> > operations to a QOM "link-FOO" property, which handles the check
> > callback and flags. The feature that is missing from QOM is the dynamic
> > child pointer which is done in the added code with the usual "offset"
> > approach.
> 
> Would it be possible to add a ".create" field to PropertyInfo?  Then
> there's no need to introduce the wrapper.

QOM setter/getter want a LinkProperty opaque pointer, but qdev uses a Property
pointer. I don't see a way to adapt that with .create(). Can you elaborate?

> 
> Also, I think _check and _flags can be always
> qdev_prop_allow_set_link_before_realize and
> OBJ_PROP_LINK_UNREF_ON_RELEASE for DEFINE_PROP_LINK.

A quick grep gave me some object_property_add_link() callers using different
parameters, but I don't know if they should use DEFINE_PROP_LINK.

Fam