On Sat, May 23, 2020 at 01:01:40PM +0200, Wolfram Sang wrote:

quoted

+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?