Re: [virtio-comment] [PATCH 1/1] RFC: virtio-bt: add virtio BT device specification

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Mar 15, 2023 at 05:20:09PM +0100, Cornelia Huck wrote:
> On Wed, Mar 15 2023, "Michael S. Tsirkin" <mst@redhat.com> wrote:
> 
> > On Wed, Mar 15, 2023 at 04:55:59PM +0100, Cornelia Huck wrote:
> >> On Fri, Mar 10 2023, Igor Skalkin <Igor.Skalkin@opensynergy.com> wrote:
> >> > +\subsection{Feature bits}\label{sec:Device Types / BT Device / Feature bits}
> >> > +
> >> > +\begin{description}
> >> > +\item[VIRTIO_BT_F_VND_HCI (0)]  Indicates vendor command support.
> >> > +\item[VIRTIO_BT_F_MSFT_EXT (1)] Indicates MSFT vendor support.
> >> > +\item[VIRTIO_BT_F_AOSP_EXT (2)] Indicates AOSP vendor support.
> >> > +\item[VIRTIO_BT_F_CONFIG_V2 (3)] The device uses the second version of the
> >> > +configuration space structure.
> >> > +\end{description}
> >> > +
> >> > +\devicenormative{\subsubsection}{Feature bits}{Device Types / BT Device / Feature bits}
> >> > +
> >> > +The device MUST require the driver to accept the VIRTIO_BT_F_CONFIG_V2 feature
> >> > +bit, i.e. not set FEATURES_OK without it, and use the second version
> >> > +(struct virtio_bt_config_v2) of the configuration layout, because the
> >> > +first one (struct virtio_bt_config) is unaligned, which violates the
> >> > +specification.
> >> 
> >> Did we have a device or driver that didn't use v2? I'm not sure we want
> >> to add a feature for that, other than for backwards compatibility.
> >
> > Linux drivers use a different layout, yes.
> 
> Oh, indeed.
> 
> >
> > I think it should be possible to implement device without
> > VIRTIO_BT_F_CONFIG_V2 if someone wants to be compatible.
> 
> So, do we need to downgrade the requirements for this feature to SHOULD?
> 
> >
> > And hmm we need to get back to addressing the negotiation mess ...

For devices I would downgrade it to MAY even.

-- 
MST