Re: [PATCH v7] i2c: virtio: add a virtio i2c frontend driver

[Jie Deng]

On 2021/3/12 14:10, Viresh Kumar wrote:
> I saw your email about wrong version being sent, I already wrote some
> reviews. Sending them anyway for FWIW :)
>
> On 12-03-21, 21:33, Jie Deng wrote:
> > +struct virtio_i2c {
> > +	struct virtio_device *vdev;
> > +	struct completion completion;
> > +	struct i2c_adapter adap;
> > +	struct mutex lock;
> As I said in the previous version (Yes, we were both waiting for
> Wolfram to answer that), this lock shouldn't be required at all.
>
> And since none of us have a use-case at hand where we will have a
> problem without this lock, we should really skip it. We can always
> come back and add it if we find an issue somewhere. Until then, better
> to keep it simple.
The problem is you can't guarantee that adap->algo->master_xfer
is only called from i2c_transfer. Any function who holds the adapter can 
call
adap->algo->master_xfer directly. I prefer to avoid potential issues 
rather than
find a issue then fix.
> > +
> > +static struct i2c_adapter virtio_adapter = {
> > +	.owner = THIS_MODULE,
> > +	.name = "Virtio I2C Adapter",
> > +	.class = I2C_CLASS_DEPRECATED,
> What happened to this discussion ?
>
> https://lore.kernel.org/lkml/20210305072903.wtw645rukmqr5hx5@vireshk-i7/

My understanding is that new driver sets this to warn users that the 
adapter doesn't support classes anymore.

I'm not sure if Wolfram can explain it more clear for you.

> > +	.algo = &virtio_algorithm,
> > +
> > +		return ret;
> > +
> > +	vi->adap = virtio_adapter;
> This is strange, why are you allocating memory for adapter twice ?
> Once for virtio_adapter and once for vi->adap ? Either fill the fields
> directly for v->adap here and remove virtio_adapter or make vi->adap a
> pointer.

Will make vi->adap a pointer. Thanks.