Re: [PATCH 06/12] hw/xen: add get_frontend_path() method to XenDeviceClass

[David Woodhouse]

On Tue, 2023-10-24 at 13:42 +0100, Paul Durrant wrote:
> 
> > --- a/hw/xen/xen-bus.c
> > +++ b/hw/xen/xen-bus.c
> > @@ -711,8 +711,16 @@ static void xen_device_frontend_create(XenDevice 
> > *xendev, Error **errp)
> >    {
> >        ERRP_GUARD();
> >        XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));
> > +    XenDeviceClass *xendev_class = XEN_DEVICE_GET_CLASS(xendev);
> >    
> > -    xendev->frontend_path = xen_device_get_frontend_path(xendev);
> > +    if (xendev_class->get_frontend_path) {
> > +        xendev->frontend_path = xendev_class->get_frontend_path(xendev, 
> > errp);
> > +        if (!xendev->frontend_path) {
> > +            return;
> 
> I think you need to update errp here to note that you are failing to 
> create the frontend.

If xendev_class->get_frontend_path returned NULL it will have filled in errp.

As a general rule (I'll be doing a bombing run on xen-bus once I get my
patch queue down into single digits) we should never check 'if (*errp)'
to check if a function had an error. It should *also* return a success
or failure indication, and we should cope with errp being NULL.

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