Re: [Qemu-devel] [PATCH for-3.1 2/2] acpi: Decouple ACPI hotplug callbacks from HotplugHandler

[Igor Mammedov <imammedo@redhat.com>]

On Tue, 24 Jul 2018 21:14:48 +0300
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Tue, Jul 24, 2018 at 05:28:44PM +0200, Igor Mammedov wrote:
> > On Tue, 24 Jul 2018 09:39:16 -0300
> > Eduardo Habkost <ehabkost@redhat.com> wrote:
> >   
> > > On Tue, Jul 24, 2018 at 02:29:49PM +0200, Igor Mammedov wrote:  
> > > > On Mon, 23 Jul 2018 16:31:45 -0300
> > > > Eduardo Habkost <ehabkost@redhat.com> wrote:
> > > >     
> > > > > The ACPI hotplug callbacks get a HotplugHandler object as
> > > > > argument.  This has two problems:
> > > > > 
> > > > > 1) The functions require a TYPE_ACPI_DEVICE_IF object, but the
> > > > >    function prototype doesn't indicate that.  It's possible to
> > > > >    pass an object that would make the function crash.
> > > > > 2) The function does not require the object to implement
> > > > >    TYPE_HOTPLUG_HANDLER at all, but the function prototype
> > > > >    imposes that for no reason.
> > > > > 
> > > > > Change the argument type to AcpiDeviceIf instead of
> > > > > HotplugHandler.    
> > > > What is the motivation for this patch,
> > > > do you actually get crashes?    
> > > 
> > > I didn't get crashes, but the idea for the change came when
> > > Michael asked me how to get the HotplugHandler object.  I was
> > > going to suggest current_machine (which is also a hotplug
> > > handler), when I noticed he actually needed an AcpiDeviceIf
> > > object.
> > > 
> > > The main motivation, however, is to simply make the function
> > > prototypes make sense.  Is there a single reason to make the ACPI
> > > functions get a HotplugHandler argument instead of AcpiDeviceIf?  
> > I'd rather to keep current *_cb() functions as is,
> > as we might actually need access to hotplug handler there and in
> > that case keeping more generic hotplug handler would be better
> > and it also sort of documents better what is being passed in.
> > 
> > Also we won't have to rewrite it back from AcpiDeviceIf to
> > HotplugHandler again if it's needed.  
> 
> Personally I think type-safety is important, changing APIs
> isn't such a big deal. So I'd rather take Eduardo's patch unless
> the patches that would need to change it back are just
> round the corner. what's the status there?
I don't have any patches for this part nor any plan to work on it.
Ok, let's go ahead with Eduardo's patches. We can always change it
back if need arises.