Re: [Qemu-devel] [PATCH 23/35] acpi:piix4: make plug/unlug callbacks generic

[Michael S. Tsirkin]

On Mon, Apr 07, 2014 at 02:00:37PM +0200, Igor Mammedov wrote:
> On Mon, 7 Apr 2014 14:32:41 +0300
> "Michael S. Tsirkin" <address@hidden> wrote:
> 
> > On Fri, Apr 04, 2014 at 03:36:48PM +0200, Igor Mammedov wrote:
> > > ... and report error if plugged in device is not supported.
> > > Later generic callbacks will be used by memory hotplug.
> > > 
> > > Signed-off-by: Igor Mammedov <address@hidden>
> > 
> > 
> > OK in that case, how about teaching all hotplug callbacks about this?
> > 
> > There are two ATM:
> > shpc_device_hotplug_cb
> > pcie_cap_slot_hotplug_cb
> > 
> > Teach them both to fail gracefully if they get
> > an object that is not a pci device.
> > 
> > Afterwards, simply iterate over all objects of type
> > TYPE_HOTPLUG_HANDLER
> > and look for one that will accept your object.
> Then you would never know if any hotplug handler has actually
> handled event.

Why not? Check the error.
If no one accepts your object, return error to user.

> I think hotplug handler should return error if unsupported
> device passed in rather than ignore it. It makes catching
> wiring errors easier.

Absolutely.

> Dropping error so that we could not care which hotplug handler
> should be notified, looks like a wrong direction and makes
> system more fragile.

That's not what I was suggesting.

> It shouldn't be up to consumer to determine that event should
> be routed to it, but rather by external routing that knows
> what and when should be notified.

Yes. So

        for each hotplug handler (&err)
                handler->plug(device, &err)
                if (!err)
                        break;


        if (err)
                hotplug failed - destroy device


> > 
> > 
> > > ---
> > >  hw/acpi/piix4.c | 31 ++++++++++++++++++++++---------
> > >  1 file changed, 22 insertions(+), 9 deletions(-)
> > > 
> > > diff --git a/hw/acpi/piix4.c b/hw/acpi/piix4.c
> > > index 67dc075..4341f82 100644
> > > --- a/hw/acpi/piix4.c
> > > +++ b/hw/acpi/piix4.c
> > > @@ -310,19 +310,32 @@ static void piix4_pm_powerdown_req(Notifier *n, 
> > > void *opaque)
> > >      acpi_pm1_evt_power_down(&s->ar);
> > >  }
> > >  
> > > -static void piix4_pci_device_plug_cb(HotplugHandler *hotplug_dev,
> > > -                                     DeviceState *dev, Error **errp)
> > > +static void piix4_device_plug_cb(HotplugHandler *hotplug_dev,
> > > +                                 DeviceState *dev, Error **errp)
> > >  {
> > >      PIIX4PMState *s = PIIX4_PM(hotplug_dev);
> > > -    acpi_pcihp_device_plug_cb(&s->ar, s->irq, &s->acpi_pci_hotplug, dev, 
> > > errp);
> > > +
> > > +    if (object_dynamic_cast(OBJECT(dev), TYPE_PCI_DEVICE)) {
> > > +        acpi_pcihp_device_plug_cb(&s->ar, s->irq, &s->acpi_pci_hotplug, 
> > > dev,
> > > +                                  errp);
> > > +    } else {
> > > +        error_setg(errp, "acpi: device plug request for not supported 
> > > device"
> > > +                   " type: %s", object_get_typename(OBJECT(dev)));
> > > +    }
> > >  }
> > >  
> > > -static void piix4_pci_device_unplug_cb(HotplugHandler *hotplug_dev,
> > > -                                       DeviceState *dev, Error **errp)
> > > +static void piix4_device_unplug_cb(HotplugHandler *hotplug_dev,
> > > +                                   DeviceState *dev, Error **errp)
> > >  {
> > >      PIIX4PMState *s = PIIX4_PM(hotplug_dev);
> > > -    acpi_pcihp_device_unplug_cb(&s->ar, s->irq, &s->acpi_pci_hotplug, 
> > > dev,
> > > -                                errp);
> > > +
> > > +    if (object_dynamic_cast(OBJECT(dev), TYPE_PCI_DEVICE)) {
> > > +        acpi_pcihp_device_unplug_cb(&s->ar, s->irq, 
> > > &s->acpi_pci_hotplug, dev,
> > > +                                    errp);
> > > +    } else {
> > > +        error_setg(errp, "acpi: device unplug request for not supported 
> > > device"
> > > +                   " type: %s", object_get_typename(OBJECT(dev)));
> > > +    }
> > >  }
> > >  
> > >  static void piix4_update_bus_hotplug(PCIBus *pci_bus, void *opaque)
> > > @@ -553,8 +566,8 @@ static void piix4_pm_class_init(ObjectClass *klass, 
> > > void *data)
> > >       */
> > >      dc->cannot_instantiate_with_device_add_yet = true;
> > >      dc->hotpluggable = false;
> > > -    hc->plug = piix4_pci_device_plug_cb;
> > > -    hc->unplug = piix4_pci_device_unplug_cb;
> > > +    hc->plug = piix4_device_plug_cb;
> > > +    hc->unplug = piix4_device_unplug_cb;
> > >  }
> > >  
> > >  static const TypeInfo piix4_pm_info = {
> > > -- 
> > > 1.9.0