static ssize_t show_read(struct device *dev, char *buf)
static ssize_t show_read(struct device *dev, struct device_attribute *attr, char *buf)
static ssize_t show_read(struct device *dev, char *buf){	struct i2c_client *client = to_i2c_client(dev);	struct pcf8574_data *data = i2c_get_clientdata(client);	data->read = i2c_smbus_read_byte(client); 	return sprintf(buf, "%u\n", data->read);}