Re: [virtio-dev] [PATCH 09/14] legacy feature bits: confirmance statements

[Rusty Russell <rusty@au1.ibm.com>]

"Michael S. Tsirkin" <mst@redhat.com> writes:
> On Tue, Feb 25, 2014 at 01:07:40PM +1030, Rusty Russell wrote:
>> > +Transitional devices MUST offer, and if offered by the device
>> > +traditional drivers MUST negotiate the following:
>> > +\begin{description}
>> >  \item[VIRTIO_F_ANY_LAYOUT (27)] This feature indicates that the device
>> >    accepts arbitrary descriptor layouts, as described in Section
>> >    \ref{sec:Basic Facilities of a Virtio Device / Virtqueues / Message Framing / Legacy Interface: Message Framing}~\nameref{sec:Basic Facilities of a Virtio Device / Virtqueues / Message Framing / Legacy Interface: Message Framing}.
>> 
>> s/traditional/transitional/
>> 
>> s/if offered by the device traditional drivers MUST negotiate/
>> transitional drivers MUST accept/ ?
>> 
>> This requirement seems like a SHOULD, not a MUST to me though.
>
> I made it a MUST because it creates a way for device to detect
> that driver is new and might use arbitrary layout.
> I'm worried that since everything seems to work without it,
> people will ignore the SHOULD requirement.

OK, but I don't know how much it will help in practice.  If a driver is
supporting legacy it might as well handle the !ANY_LAYOUT case.

Cheers,
Rusty.