RE: [PATCH v6 1/2] virtio-crypto: Add virtio crypto device specification

["Zeng, Xin" <xin.zeng@intel.com>]

On Thu, Friday, August 05, 2016 3:56 AM, Michael S. Tsirkin wrote:
> -----Original Message-----
> From: Michael S. Tsirkin [mailto:mst@redhat.com]
> Sent: Friday, August 05, 2016 3:56 AM
> To: Gonglei (Arei)
> Cc: Zeng, Xin; qemu-devel@nongnu.org; virtio-dev@lists.oasis-open.org;
> Huangpeng (Peter); Luonengjun; cornelia.huck@de.ibm.com;
> stefanha@redhat.com; denglingli@chinamobile.com; Jani Kokkonen;
> Ola.Liljedahl@arm.com; Varun.Sethi@freescale.com; Keating, Brian A; Ma,
> Liang J; Griffin, John; Hanweidong (Randy); Huangweidong (C)
> Subject: Re: [PATCH v6 1/2] virtio-crypto: Add virtio crypto device
> specification
> 
> On Thu, Aug 04, 2016 at 11:24:26AM +0000, Gonglei (Arei) wrote:
> > > > +The first driver-read-only field, \field{version} specifies the
> > > > +virtio crypto's version, which is reserved for back-compatibility
> > > > +in future.It's currently defined for the version field:
> > > > +
> > > > +\begin{lstlisting}
> > > > +#define VIRTIO_CRYPTO_VERSION_1  (1)
> > >
> > > Suggest to remove this macro,
> > > Do you think a version which is composed of major version and minor
> > > version is better?
> > >
> >
> > I think we should tell the developer how to set the value of version
> > field, but I have no idea about which value or form is better, so I
> > used 1 as the first version. What's your opinion?
> 
> My opinion is that you should drop this completely. We do feature bits, not
> version numbers in virtio. We do not want each device doing its own thing for
> compatibility.
> 

But as I mentioned before,  considering the bug fix case, if each backend device 
release need a feature bit meaning "some bugs are fixed", are the feature bits
enough? 
Physical devices usually have a revision ID to mark its version, could we have a
revision Id field for each virtio device to distinguish the the virtio devices which 
have the same feature sets but have different version? 

> --
> MST