iio: temperature: tmp117: improve fallback capabilities

Don't error if the device-id found don't match the device-id for the
TMP117 sensor since other TMPxxx might be compatible to the TMP117. The
fallback mechanism tries to gather the required information from the
of_device_id or from the i2c_client information.

The commit also prepares the driver for adding new devices more easily
by making use of switch-case at the relevant parts.
Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Link: https://lore.kernel.org/r/20230228090518.529811-3-m.felsch@pengutronix.deSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/temperature/tmp117.c

@@ -16,6 +16,7 @@
 #include <linux/types.h>
 #include <linux/kernel.h>
 #include <linux/limits.h>
+#include <linux/property.h>
 
 #include <linux/iio/iio.h>
 
@@ -115,23 +116,40 @@ static const struct iio_info tmp117_info = {
 
 static int tmp117_identify(struct i2c_client *client)
 {
+	const struct i2c_device_id *id;
+	unsigned long match_data;
 	int dev_id;
 
 	dev_id = i2c_smbus_read_word_swapped(client, TMP117_REG_DEVICE_ID);
 	if (dev_id < 0)
 		return dev_id;
-	if (dev_id != TMP117_DEVICE_ID) {
-		dev_err(&client->dev, "TMP117 not found\n");
-		return -ENODEV;
+
+	switch (dev_id) {
+	case TMP117_DEVICE_ID:
+		return dev_id;
 	}
-	return 0;
+
+	dev_info(&client->dev, "Unknown device id (0x%x), use fallback compatible\n",
+		 dev_id);
+
+	match_data = (uintptr_t)device_get_match_data(&client->dev);
+	if (match_data)
+		return match_data;
+
+	id = i2c_client_get_device_id(client);
+	if (id)
+		return id->driver_data;
+
+	dev_err(&client->dev, "Failed to identify unsupported device\n");
+
+	return -ENODEV;
 }
 
 static int tmp117_probe(struct i2c_client *client)
 {
 	struct tmp117_data *data;
 	struct iio_dev *indio_dev;
-	int ret;
+	int ret, dev_id;
 
 	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA))
 		return -EOPNOTSUPP;
@@ -140,6 +158,8 @@ static int tmp117_probe(struct i2c_client *client)
 	if (ret < 0)
 		return ret;
 
+	dev_id = ret;
+
 	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
 	if (!indio_dev)
 		return -ENOMEM;
@@ -148,24 +168,28 @@ static int tmp117_probe(struct i2c_client *client)
 	data->client = client;
 	data->calibbias = 0;
 
-	indio_dev->name = "tmp117";
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->info = &tmp117_info;
 
-	indio_dev->channels = tmp117_channels;
-	indio_dev->num_channels = ARRAY_SIZE(tmp117_channels);
+	switch (dev_id) {
+	case TMP117_DEVICE_ID:
+		indio_dev->channels = tmp117_channels;
+		indio_dev->num_channels = ARRAY_SIZE(tmp117_channels);
+		indio_dev->name = "tmp117";
+		break;
+	}
 
 	return devm_iio_device_register(&client->dev, indio_dev);
 }
 
 static const struct of_device_id tmp117_of_match[] = {
-	{ .compatible = "ti,tmp117", },
+	{ .compatible = "ti,tmp117", .data = (void *)TMP117_DEVICE_ID },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, tmp117_of_match);
 
 static const struct i2c_device_id tmp117_id[] = {
-	{ "tmp117", 0 },
+	{ "tmp117", TMP117_DEVICE_ID },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, tmp117_id);