Re: [Qemu-devel] [PATCH v3 14/14] pci: Tidy up PCI host bridges

From: Paolo Bonzini <pbonzini@redhat.com>
To: "Andreas Färber" <afaerber@suse.de>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
	jbaron@redhat.com, "Alexander Graf" <agraf@suse.de>,
	qemu-devel@nongnu.org, "Andreas Färber" <andreas.faerber@web.de>,
	"\"list@suse.de\"@zmta06.collab.prod.int.phx2.redhat.com:New
	World" <qemu-ppc@nongnu.org>,
	anthony@codemonkey.ws, open@suse.de
Subject: Re: [Qemu-devel] [PATCH v3 14/14] pci: Tidy up PCI host bridges
Date: Thu, 05 Jul 2012 11:53:48 +0200	[thread overview]
Message-ID: <4FF5642C.5070506@redhat.com> (raw)
In-Reply-To: <4FF4C4EC.2090404@suse.de>

Il 05/07/2012 00:34, Andreas Färber ha scritto:
>> > Just to clarify: replacing upcasts which are always safe
>> > with downcasts which can fail is what I consider especially ugly.
> As per Anthony the parent field in the QOM instance structs is not
> supposed to be touched (cf. object.h). We mark it /*< private >*/ so
> that it doesn't even show up in gtk-doc documentation. If it is unused,
> its name becomes irrelevant and could even be "reserved" if we so
> wanted. Renaming it to whatever proves that all old references are gone.

I disagree with removing static checks whenever possible.

> Background is that qdev and QOM work differently with regards to
> inheritance: as mentioned in the preceding patch, for qdev the parent
> was (had to be) identified by name and could be anywhere in the struct;

Not entirely true, being at the beginning of the struct is already
enforced by using DO_UPCAST (which is admittedly a strange name for a
downcast macro) instead of container_of.

> for QOM the parent is a subset of the struct from the start and it's
> supposed to be accessed through the struct type that provides the
> fields, the usual way to get such a pointer is through
> OBJECT_CHECK()-derived cast macros.

Paolo