Re: [Qemu-devel] [PATCH 11/35] scsi-disk: support READ DVD STRUCTURE

[Paolo Bonzini <pbonzini@redhat.com>]

On 10/21/2011 03:32 PM, Kevin Wolf wrote:
> 2) let ide-cd create its own SCSI bus and act as an adaptor, similar to
> >  USB devices.  There would still be duplication for commands that do DMA
> >  in multiple steps; I think READ CD is the only one.
> >
> >  3) create a separate API just for the purpose of sharing code between
> >  ATAPI and SCSI (your "can we share some parts even now", basically).
> >
> >  I think I'm leaning towards (3), but I don't think it makes sense to do
> >  it now unless someone is interested in implementing for example CD
> >  burning support.  However, I'm leaning towards that also because I
> >  honestly have no idea how hard (2) would be.
>
> Which gives me the impression that your feeling is (as well as mine)
> that (2) would give us the nicer result and is probably the Right Thing
> to do long-term.

Long term, yes.  Now, probably not (not until the QOM situation becomes 
clearer, that is).

It would also get you CD recorder passthrough, by composing scsi-generic 
or scsi-block within the IDE drive.

> Though at the same time I agree that I don't have an idea of how hard
> this would be and if it would be worth the effort. And with the current
> qdev that doesn't allow device composition it might even get really ugly.
>
> It's a hard question, but ignoring it is probably not a solution.

I agree.  On the other hand, the ATAPI code is changed rarely.  If it 
had been kept in sync in the past, I would not have touched it at all. 
I have never tried using >4.7 GB DVD images, but perhaps they just work 
and besides burning, they would be the only interesting use case.

Paolo