Re: [PATCH V2] virtio: i2c: Allow zero-length transactions

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

On Tue, Aug 17, 2021 at 09:23:24AM +0530, Viresh Kumar wrote:
> On 16-08-21, 10:45, Michael S. Tsirkin wrote:
> > On Mon, Aug 16, 2021 at 03:17:23PM +0530, Viresh Kumar wrote:
> > > The I2C protocol allows zero-length requests with no data, like the
> > > SMBus Quick command, where the command is inferred based on the
> > > read/write flag itself.
> > 
> > So I wonder. What if we allow zero-length buffers in virtio? Would that
> > address the need?
> 
> There are three things this patch does, all of which are important
> IMO:
> 
> 1. Drop the need of passing both write and read buffers, as that isn't
>    required really since we already have another way of linking
>    different transfers using the fail-next flag.
> 
> 2. Make the buffer optional, for zero-length transfers.
> 
> 3. Pass the r/w flag separately, which is kind of relevant because of
>    2 (zero-length transfers) only.
> 
> 
> I think (1) can be done separately anyway, and we may be able to solve
> (2) and (3) if we allow zero-length buffers in virtio itself.

OK, so yea. Let's split this up please.

> -- 
> viresh