[PATCH 1/1] QEMU: support USB cdrom devices

[Peter Krempa]

On Mon, Sep 07, 2020 at 12:48:21 +0100, Daniel Berrange wrote:
> On Mon, Sep 07, 2020 at 01:45:09PM +0200, Gerd Hoffmann wrote:
> >   Hi,

[...]

> > > 1. doing this transparently with a controller per device, just like the
> > > usb-storage controller does internally (ok - it's just a scsi-cd there),
> > > even if the usb-bot supports multiple LUNs. Guess multiple LUNs would
> > > act like an USB hub?
> > 
> > usb-storage simply doesn't support multiple LUNs, so when going that
> > route you can completely ignore the multiple LUN case.
> > 
> > > 2. invalidating the cdrom with USB addresses configurations and exposing
> > > the controller in the XML. This seems easier from the libvirt code POV,
> > > like:
> > > 
> > >     <controller type='scsi' model='usb-bot'>
> > >       <address type='usb' port='1'/>
> > >     </controller>
> > 
> > Yep, that is the other obvious approach.
> > 
> > > So I still would like to see my much simpler solution merged.
> > 
> > See above, but I'm not a libvirt maintainer so that's not for me to
> > judge.  I'm just pointing out that this can be fixed without switching
> > back to the old -drive syntax.
> 
> Switching back to -drive is out of the question. We've worked very hard
> to eliminate its usage and get to an exclusively -blockdev based solution
> because supporting both approaches in parallel complicates too much.

Yes, indeed.

We theoretically can emulate a complex device consisting of a USB-bot
device including the cdrom for this including the hotplug operations in
a single step. I will need to investigate this, but I'm backed up on my
email as I was on vacation.