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Date: Wed, 23 Aug 2017 14:17:49 -0300
From: Eduardo Habkost <ehabkost@redhat.com>
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Subject: Re: [Qemu-devel] [RFC v4 12/13] usb: enumerate_slots implementation
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To: Gerd Hoffmann <kraxel@redhat.com>
Cc: Eric Blake <eblake@redhat.com>, qemu-devel@nongnu.org, Markus Armbruster <armbru@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>, Marcel Apfelbaum <marcel@redhat.com>, Laine Stump <laine@redhat.com>

On Mon, Aug 21, 2017 at 01:44:19PM +0200, Gerd Hoffmann wrote:
>   Hi,
>=20
> -ENOCONTEXT
>=20
> What is the use case?

I want to let libvirt know what are the available
slots/ports/addresses for devices in a machine, before it uses
device_add or -device.  This is useful when the machine creates
some devices implicitly, when different machine-types provide
different bus topologies, or when a device was created with no
explicit slot/port/address options.

Currently libvirt work around the lack of such interface by
hardcoding information on the implicitly-created devices/buses
and available slots for each machine-type.  See, for example,
src/qemu/qemu_domain_address.c in the libvirt source tree.

>=20
> > +=A0=A0=A0=A0QTAILQ_FOREACH(port, l, next) {
> > +=A0=A0=A0=A0=A0=A0=A0=A0DeviceSlotInfo *slot =3D make_slot(BUS(bus))=
;
> > +=A0=A0=A0=A0=A0=A0=A0=A0/*
> > +=A0=A0=A0=A0=A0=A0=A0=A0=A0* TODO: should the "bus" option be includ=
ed, or is
> > +=A0=A0=A0=A0=A0=A0=A0=A0=A0* "port" enough to identify the USB bus +=
 port?
> > +=A0=A0=A0=A0=A0=A0=A0=A0=A0*/
>=20
> Yes, bus must be included, port alone isn't enough in case multiple usb
> host adapters are present.

Thanks!

--=20
Eduardo