Re: [Qemu-devel] Re: [RFC PATCH 0/5] Introduce canonical device hierarchy string

[Alex Williamson <alex.williamson@redhat.com>]

On Tue, 2010-06-15 at 10:53 +0200, Markus Armbruster wrote:
> Alex Williamson <alex.williamson@redhat.com> writes:
> 
> > On Mon, 2010-06-14 at 09:02 +0200, Gerd Hoffmann wrote:
> >> Hi,
> >> 
> >> > My premise with this attempt is that we walk the hierarchy and use the
> >> > names to create the base of the path.  As we get to the device,
> >> > particularly to the parent bus of the device, we need to start looking at
> >> > properties to ensure uniqueness.
> >> 
> >> You'll need that for every bus along the way down to the device.  Create 
> >> a virtual machine with two lsi scsi host adapters, then attach a disk 
> >> with scsi id 0 to each.  Just the scsi id isn't good enougth to identify 
> >> the device.  You'll need the lsi pci address too.
> >
> > Yep, see below.
> >
> >> > For now, the only properties I've tagged as path
> >> > properties are PCI bus addresses and MAC addresses.
> >> 
> >> mac address isn't needed here.  You need the property which specifies 
> >> the bus address.  For PCI this obviously is the PCI address.  For scsi 
> >> the scsi id.  For ISA you can use the I/O port base.  virtio-serial the 
> >> port number, ...
> >
> > PCI: addr
> > SCSI: scsi-id
> > ISA: serial/parallel = iobase, others??
> 
> If there's no iobase (pathological case), require ID.
> 
> > ide-drive: unit
> 
> Bus name is IDE, but it's clear enough what you mean :)

I put ide-drive here because the unit is a property of the device, not
the bus.

> > I2C: address
> >
> > virtio-serial doesn't seem to make a DeviceState per port, so I think it
> > can be skipped.
> 
> Really?
> 
> Anyway, its port number should do as bus address.

Maybe I'm not specifying it correctly.  I see a max_nr_ports property,
but I don't see that each port is a separate qdev.

> >                  I'm sure I'm still missing some...
> 
> s390-virtio
> SSI
> System

I'll need some help coming up with useful properties to key on for
these.  I had hoped there's only one System bus.

> USB

usb-storage seems to have a useful drive property that lets me
distinguish these devices:

/i440FX-pcihost/pci.0/piix3-usb-uhci.01.2/usb.0/usb-storage.usb0/scsi.0/scsi-disk.0
/i440FX-pcihost/pci.0/piix3-usb-uhci.01.2/usb.0/usb-storage.usb1/scsi.0/scsi-disk.0
                                                            ^^^^ drive

But otherwise USB is disappointingly devoid of useful properties at the
bus level.

Alex