Re: [PATCH for-5.0 0/8] ppc: Consolidate QOM links and pointers to the same object

[Greg Kurz <groug@kaod.org>]

On Fri, 15 Nov 2019 13:16:22 +0100
Cédric Le Goater <clg@kaod.org> wrote:

> On 15/11/2019 12:53, Greg Kurz wrote:
> > There's a recurring pattern in the code where a const link is added to a
> > newly instanciated object and the link is then used in the object's realize
> > function to keep a pointer to the QOM entity which the link points to.
> > 
> > void create_obj_B(Object *obj_a)
> > {
> >     Object *obj_b;
> > 
> >     obj_b = object_new(TYPE_B);
> >     object_property_add_const_link(obj_b, "link-to-a", obj_a, &error_abort);
> > }
> > 
> > void object_B_realize(DeviceState *dev, Error **errp)
> > {
> >     Object *obj_a;
> > 
> >     obj_a = object_property_get_link(OBJECT(dev), "link-to-a", errp);
> >     if (!obj_a) {
> >         return;
> >     }
> > 
> >     obj_b->obj_a = A(obj_a); // If obj_b->obj_a is changed, the link property
> >                              // still points to the original obj_a that was
> >                              // passed to object_property_add_const_link()
> > }
> > 
> > Confusing bugs could arise if the pointer and the link go out of sync for
> > some reason. This can be avoided if the property is defined to directly use
> > the pointer with object_property_add_link() and object_property_set_link().
> > 
> > This series just does that for all occurences of the fragile pattern in
> > the XIVE and PNV code.
> 
> Can we use DEFINE_PROP_LINK() instead ?
> 

Heh this seems to be even better indeed. I'll give a try.

> C. 
> 
> 
> > 
> > --
> > Greg
> > 
> > ---
> > 
> > Greg Kurz (8):
> >       xive: Link "cpu" property to XiveTCTX::cs pointer
> >       xive: Link "xive" property to XiveSource::xive pointer
> >       xive: Link "xive" property to XiveEndSource::xrtr pointer
> >       ppc/pnv: Link "psi" property to PnvLpc::psi pointer
> >       ppc/pnv: Link "psi" property to PnvOCC::psi pointer
> >       ppc/pnv: Link "chip" property to PnvHomer::chip pointer
> >       ppc/pnv: Link "chip" property to PnvCore::chip pointer
> >       ppc/pnv: Link "chip" property to PnvXive::chip pointer
> > 
> > 
> >  hw/intc/pnv_xive.c        |   29 +++++++++-----------
> >  hw/intc/spapr_xive.c      |    8 +++---
> >  hw/intc/xive.c            |   65 ++++++++++++++++++++++-----------------------
> >  hw/ppc/pnv.c              |   32 +++++++++++-----------
> >  hw/ppc/pnv_core.c         |   18 +++++++-----
> >  hw/ppc/pnv_homer.c        |   24 +++++++++--------
> >  hw/ppc/pnv_lpc.c          |   23 ++++++++--------
> >  hw/ppc/pnv_occ.c          |   23 ++++++++--------
> >  hw/ppc/pnv_psi.c          |    3 +-
> >  include/hw/ppc/pnv.h      |    2 +
> >  include/hw/ppc/pnv_core.h |    2 +
> >  11 files changed, 115 insertions(+), 114 deletions(-)
> > 
>