Re: [Qemu-devel] [PATCH v6 02/27] bootindex: add del_boot_device_path function

[Eduardo Habkost <ehabkost@redhat.com>]

On Thu, Sep 04, 2014 at 03:01:41AM +0000, Gonglei (Arei) wrote:
> Hi,
> 
> > From: Eduardo Habkost [mailto:ehabkost@redhat.com]
> > Sent: Thursday, September 04, 2014 2:13 AM
> > Subject: Re: [PATCH v6 02/27] bootindex: add del_boot_device_path function
> > 
> > On Wed, Sep 03, 2014 at 06:45:56AM +0000, Gonglei (Arei) wrote:
> > [...]
> > > > > 4. When we hotplug the virtio-net-pci device, only pass virtio-net-pci's
> > pointer
> > > > to
> > > > > del_boot_device_path(). But virtio-net-pci != virtio-net-device, so I add a
> > > > function
> > > > > named is_same_fw_dev_path() to handle this situation.
> > > >
> > > > When hot-unplugging virtio-net-pci I'd expect we free both
> > > > virtio-net-pci and virtio-net-device (and therefore call
> > > > del_boot_device_path twice, once for each device).  Can you check that?
> > > >
> > > Yes, I can.
> > >
> > > The del_boot_device_path() is called only once, just for virtio-net-pci.
> > > For its child, virtio-net-devcie's resource is cleaned by qbus->child unrealizing
> > > process, will not call device_finalize().
> > 
> > Then we need to fix this to make sure there's a corresponding
> > del_boot_device_path() call (with the same pointer) to every
> > add_boot_device_path() call, instead of adding a hack to
> > del_boot_device_path().
> > 
> Good idea. We can add functions named $device_finalize_bootindex(), such as:
> 
> static void virtio_net_set_bootindex(Object *obj, Visitor *v, void *opaque,
>                                      const char *name, Error **errp)
> {
>     VirtIONet *n = VIRTIO_NET(obj);
>     
>     set_bootindex(&n->nic_conf, v, name, errp);
>     add_boot_device_path(n->nic_conf.bootindex,
>                          DEVICE(obj), "/ethernet-phy@0"); 
> }
> 
> static void virtio_net_finalize_bootindex(Object *obj, const char *name,
>                                           void *opaque)
> {
>     del_boot_device_path(DEVICE(obj));
> }
> ...
> object_property_add(obj, "bootindex", "int",
>                         virtio_net_get_bootindex, 
>                         virtio_net_set_bootindex,
>                         virtio_net_finalize_bootindex, dev, NULL);
> 
> as the previous email, we lay add_boot_device_path() in $device_set_bootindex,
> and lay del_boot_device_path() in $device_finalize_bootindex is a good idea IMO.

Whatever the approach we use, can we have a wrapper to reduce code
duplication? e.g. a:
  void device_add_bootindex_property(DeviceState *dev, int32_t *field, const char *suffix)
function.

Then instead of reimplementing set/get/finalize functions, device code
could just call something like:
  device_add_bootindex_property(dev, &n->nic_conf.bootindex,
                                "/ethernet-phy@0");

-- 
Eduardo