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

[Paolo Bonzini]

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