Re: [virtio-dev] Re: [virtio-comment] [PATCH v4] virtio-i2c: add the device specification

[Jie Deng <jie.deng@intel.com>]

On 2020/11/17 16:23, Gerd Hoffmann wrote:
> On Tue, Nov 17, 2020 at 02:55:14PM +0800, Jie Deng wrote:
> > On 2020/11/16 16:16, Paolo Bonzini wrote:
> > > On 16/11/20 03:12, Jie Deng wrote:
> > > > Fore example, the frontend may kick the sequence "write read read
> > > > ..." to the backend at a time.
> > > >
> > > > The segments can be aggregated into "i2c_msg list" and sent to the
> > > > hardware at a time by the backend.
> > > >
> > > > The host native drivers will finally send these segments using the
> > > > methods they support.
> > > If so, the spec needs to specify what the backend must/should/may
> > > aggregate into a single host-side transaction.
> > >
> > > What my proposal does is essentially saying that the backend MUST
> > > aggregate a write and a read segment into a single transaction if it is
> > > sent with a single virtio-i2c request.
> > >
> > > Paolo
> > This may depend on the host hardware. I can add a host feature bit to
> > indicate it.
> That is not enough.  You also need that for the transactions.  If the
> driver sends a write and a read message the device needs to know
> whenever that is one or two transactions.  So if you want continue
> with the i2c_msg list idea you need some way to group your messages
> into transactions.
Can the "kick" be used for grouping ? I mean when a write and a read 
are sent
by one kick at a time, they will be treated as one transaction by 
default if the host
has such a feature bit.

Thanks.


> Or you go with paolos idea which looks simpler to me.
>
> take care,
>    Gerd
>
>
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