Re: [PATCH 4/4] i2c: stm32f7: Add SMBus-specific protocols support

[Alain Volmat <alain.volmat@st.com>]

On Sat, May 23, 2020 at 01:01:40PM +0200, Wolfram Sang wrote:
> 
> > +static int stm32f7_i2c_reg_client(struct i2c_client *client)
> > +{
> > +	struct stm32f7_i2c_dev *i2c_dev = i2c_get_adapdata(client->adapter);
> > +	int ret;
> > +
> > +	if (client->flags & I2C_CLIENT_HOST_NOTIFY) {
> > +		/* Only enable on the first device registration */
> > +		if (atomic_inc_return(&i2c_dev->host_notify_cnt) == 1) {
> > +			ret = stm32f7_i2c_enable_smbus_host(i2c_dev);
> > +			if (ret) {
> > +				dev_err(i2c_dev->dev,
> > +					"failed to enable SMBus host notify (%d)\n",
> > +					ret);
> > +				return ret;
> > +			}
> > +		}
> > +	}
> > +
> > +	return 0;
> > +}
> 
> So, as mentioned in the other review, I'd like to evaluate other
> possibilities for the above:
> 
> - One option is to enable it globally in probe(). Then you lose the
>   possibility to have a device at address 0x08.

I'd prefer avoid this solution to not lose the address 0x08.

> - Enable it in probe() only if there is a generic binding "host-notify".

Do you mean having the adapter walk through childs node and see if at least
one of them have the host-notify property ? This mean that such solution
wouldn't work for device relying on platform data rather than DT nodes.

> - Let the core scan for a device with HOST_NOTIFY when registering an
>   adapter and then call back into the driver somehow?

You mean at adapter registration time only ? Not device probing time ?
At probing time, we could have the core (i2c_device_probe) check for the flag
HOST_NOTIFY and if setted call a dedicated host-notify reg callback ?

> 
> Other ideas?
>