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Date: Wed, 11 Mar 2015 14:49:44 +0100
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] uapi/virtio_scsi: allow overriding
	CDB/SENSE size
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org

On Wed, Mar 11, 2015 at 02:31:51PM +0100, Paolo Bonzini wrote:
> 
> 
> On 11/03/2015 14:19, Michael S. Tsirkin wrote:
> > QEMU wants to use virtio scsi structures with
> > a different VIRTIO_SCSI_CDB_SIZE/VIRTIO_SCSI_SENSE_SIZE,
> > let's add ifdefs to allow overriding them.
> > 
> > Keep the old defines under new names:
> > VIRTIO_SCSI_CDB_DEFAULT_SIZE/VIRTIO_SCSI_SENSE_DEFAULT_SIZE,
> > since that's what these values really are:
> > defaults for cdb/sense size fields.
> > 
> > Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> 
> QEMU will then use a zero-element array instead of a flexible array
> member.  That's okay.

Or a flex array member: just do
#define VIRTIO_SCSI_CDB_SIZE 
#define VIRTIO_SCSI_SENSE_SIZE 
before including this header.


> Acked-by: Paolo Bonzini <pbonzini@redhat.com>
> 
> Paolo
> 
> > ---
> >  include/uapi/linux/virtio_scsi.h | 12 ++++++++++--
> >  1 file changed, 10 insertions(+), 2 deletions(-)
> > 
> > diff --git a/include/uapi/linux/virtio_scsi.h b/include/uapi/linux/virtio_scsi.h
> > index 42b9370..cc18ef8 100644
> > --- a/include/uapi/linux/virtio_scsi.h
> > +++ b/include/uapi/linux/virtio_scsi.h
> > @@ -29,8 +29,16 @@
> >  
> >  #include <linux/virtio_types.h>
> >  
> > -#define VIRTIO_SCSI_CDB_SIZE   32
> > -#define VIRTIO_SCSI_SENSE_SIZE 96
> > +/* Default values of the CDB and sense data size configuration fields */
> > +#define VIRTIO_SCSI_CDB_DEFAULT_SIZE   32
> > +#define VIRTIO_SCSI_SENSE_DEFAULT_SIZE 96
> > +
> > +#ifndef VIRTIO_SCSI_CDB_SIZE
> > +#define VIRTIO_SCSI_CDB_SIZE VIRTIO_SCSI_CDB_DEFAULT_SIZE
> > +#endif
> > +#ifndef VIRTIO_SCSI_SENSE_SIZE
> > +#define VIRTIO_SCSI_SENSE_SIZE VIRTIO_SCSI_SENSE_DEFAULT_SIZE
> > +#endif
> >  
> >  /* SCSI command request, followed by data-out */
> >  struct virtio_scsi_cmd_req {
> >