Re: [PATCH] i2c: virtio: Add support for zero-length requests

[Michael S. Tsirkin]

On Fri, Oct 22, 2021 at 02:51:10PM +0800, Jie Deng wrote:
> 
> On 2021/10/21 17:47, Viresh Kumar wrote:
> > The virtio specification received a new mandatory feature
> > (VIRTIO_I2C_F_ZERO_LENGTH_REQUEST) for zero length requests. Fail if the
> > feature isn't offered by the device.
> > 
> > For each read-request, set the VIRTIO_I2C_FLAGS_M_RD flag, as required
> > by the VIRTIO_I2C_F_ZERO_LENGTH_REQUEST feature.
> > 
> > This allows us to support zero length requests, like SMBUS Quick, where
> > the buffer need not be sent anymore.
> > 
> > Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> > ---
> > Hi Wolfram,
> > 
> > Please do not apply this until the spec changes [1] are merged, sending it early
> > to get review done. I will ping you later once the spec is merged.
> > 
> > [1] https://lists.oasis-open.org/archives/virtio-dev/202110/msg00109.html
> > 
> >   drivers/i2c/busses/i2c-virtio.c | 56 ++++++++++++++++++---------------
> >   include/uapi/linux/virtio_i2c.h |  6 ++++
> >   2 files changed, 36 insertions(+), 26 deletions(-)
> > 
> 
> Acked-by: Jie Deng<jie.deng@xxxxxxxxx>  once the spec is merged.


There's supposed to be space before < btw. and one puts # before any
comments this way tools can process the ack automatically:

Acked-by: Jie Deng<jie.deng@xxxxxxxxx> # once the spec is merged.

> 
> 
> > +	if (!virtio_has_feature(vdev, VIRTIO_I2C_F_ZERO_LENGTH_REQUEST)) {
> > +		dev_err(&vdev->dev, "Zero-length request feature is mandatory\n");
> > +		return -EINVAL;
> 
> 
> It might be better to return -EOPNOTSUPP ?
>