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

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

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.


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