Re: [virtio-comment] [PATCH v6] virtio-i2c: add the device specification

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

On 2021/1/7 2:11, Stefan Hajnoczi wrote:
> On Thu, Dec 24, 2020 at 04:10:43PM +0800, Jie Deng wrote:
> > +\begin{lstlisting}
> > +struct virtio_i2c_out_hdr {
> > +        le16 addr;
> > +        le16 padding;
> > +        le32 flags;
> > +};
> > +\end{lstlisting}
> > +
> > +\begin{lstlisting}
> > +struct virtio_i2c_in_hdr {
> > +        u8 status;
> > +};
> > +\end{lstlisting}
> > +
> > +\begin{lstlisting}
> > +struct virtio_i2c_req {
> > +        struct virtio_i2c_out_hdr out_hdr;
> > +        u8 write_buf[];
> > +        u8 read_buf[];
> > +        struct virtio_i2c_in_hdr in_hdr;
> > +};
> > +\end{lstlisting}
> I didn't notice that the written and read fields were removed. Does this
> mean that struct virtio_i2c_req can either be read or write, but not
> read+write?

It can be read, write or read+write.

written/read are removed according to Michael's suggest. He preferred to 
directly use the read/write flags in descriptors.

Please refer to 
https://lists.oasis-open.org/archives/virtio-comment/202012/msg00045.html

> This makes sense if virtqueue buffers can be grouped together so
> bi-directional transfers can be described using multiple buffers. Just
> wanted to check if I understand this correctly.
>
> Thanks,
> Stefan