iio: mcp9600: Recognize chip id for mcp9601

The current driver works with mcp9601, but emits a warning because it
does not recognize the chip id.

MCP9601 is a superset of MCP9600. The drivers works without changes
on this chipset.

However, the 9601 chip supports open/closed-circuit detection if wired
properly, so we'll need to be able to differentiate between them.

Moved "struct mcp9600_data" up in the file since a later patch will
need it and chip_info before the declarations.

Signed-off-by: Ben Collins <[e-mail]>
Reviewed-by: David Lechner <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/temperature/Kconfig

···
 	  will be called max31865.
 
 config MCP9600
-	tristate "MCP9600 thermocouple EMF converter"
+	tristate "MCP9600 and similar thermocouple EMF converters"
 	depends on I2C
 	help
-	  If you say yes here you get support for MCP9600
-	  thermocouple EMF converter connected via I2C.
+	  If you say yes here you get support for...
+	  - MCP9600
+	  - MCP9601
+	  ...thermocouple EMF converters connected via I2C.
 
 	  This driver can also be built as a module. If so, the module
 	  will be called mcp9600.

drivers/iio/temperature/mcp9600.c

···
 
 /* MCP9600 device id value */
 #define MCP9600_DEVICE_ID_MCP9600	0x40
+#define MCP9600_DEVICE_ID_MCP9601	0x41
 
 #define MCP9600_ALERT_COUNT		4
 
···
 				 BIT(IIO_EV_INFO_VALUE) |
 				 BIT(IIO_EV_INFO_HYSTERESIS),
 	},
+};
+
+struct mcp_chip_info {
+	u8 chip_id;
+	const char *chip_name;
+};
+
+struct mcp9600_data {
+	struct i2c_client *client;
 };
 
 #define MCP9600_CHANNELS(hj_num_ev, hj_ev_spec_off, cj_num_ev, cj_ev_spec_off) \
···
 	MCP9600_CHANNELS(1, 0, 2, 0), /* Alerts: 1 - 3 4 */
 	MCP9600_CHANNELS(1, 1, 2, 0), /* Alerts: - 2 3 4 */
 	MCP9600_CHANNELS(2, 0, 2, 0), /* Alerts: 1 2 3 4 */
-};
-
-struct mcp9600_data {
-	struct i2c_client *client;
 };
 
 static int mcp9600_read(struct mcp9600_data *data,
···
 
 static int mcp9600_probe(struct i2c_client *client)
 {
+	struct device *dev = &client->dev;
+	const struct mcp_chip_info *chip_info;
 	struct iio_dev *indio_dev;
 	struct mcp9600_data *data;
-	int ret, ch_sel;
+	int ch_sel, dev_id;
 
-	ret = i2c_smbus_read_byte_data(client, MCP9600_DEVICE_ID);
-	if (ret < 0)
-		return dev_err_probe(&client->dev, ret, "Failed to read device ID\n");
-	if (ret != MCP9600_DEVICE_ID_MCP9600)
-		dev_warn(&client->dev, "Expected ID %x, got %x\n",
-				MCP9600_DEVICE_ID_MCP9600, ret);
+	chip_info = i2c_get_match_data(client);
+	if (!chip_info)
+		return dev_err_probe(dev, -ENODEV,
+				     "No chip-info found for device\n");
 
-	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+	dev_id = i2c_smbus_read_byte_data(client, MCP9600_DEVICE_ID);
+	if (dev_id < 0)
+		return dev_err_probe(dev, dev_id, "Failed to read device ID\n");
+
+	switch (dev_id) {
+	case MCP9600_DEVICE_ID_MCP9600:
+	case MCP9600_DEVICE_ID_MCP9601:
+		if (dev_id != chip_info->chip_id)
+			dev_warn(dev,
+				 "Expected id %02x, but device responded with %02x\n",
+				 chip_info->chip_id, dev_id);
+		break;
+
+	default:
+		dev_warn(dev, "Unknown id %x, using %x\n", dev_id,
+			 chip_info->chip_id);
+	}
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
 	if (!indio_dev)
 		return -ENOMEM;
 
···
 		return ch_sel;
 
 	indio_dev->info = &mcp9600_info;
-	indio_dev->name = "mcp9600";
+	indio_dev->name = chip_info->chip_name;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->channels = mcp9600_channels[ch_sel];
 	indio_dev->num_channels = ARRAY_SIZE(mcp9600_channels[ch_sel]);
 
-	return devm_iio_device_register(&client->dev, indio_dev);
+	return devm_iio_device_register(dev, indio_dev);
 }
 
+static const struct mcp_chip_info mcp9600_chip_info = {
+	.chip_id   = MCP9600_DEVICE_ID_MCP9600,
+	.chip_name = "mcp9600",
+};
+
+static const struct mcp_chip_info mcp9601_chip_info = {
+	.chip_id   = MCP9600_DEVICE_ID_MCP9601,
+	.chip_name = "mcp9601",
+};
+
 static const struct i2c_device_id mcp9600_id[] = {
-	{ "mcp9600" },
+	{ "mcp9600", .driver_data = (kernel_ulong_t)&mcp9600_chip_info },
+	{ "mcp9601", .driver_data = (kernel_ulong_t)&mcp9601_chip_info },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, mcp9600_id);
 
 static const struct of_device_id mcp9600_of_match[] = {
-	{ .compatible = "microchip,mcp9600" },
+	{ .compatible = "microchip,mcp9600", .data = &mcp9600_chip_info },
+	{ .compatible = "microchip,mcp9601", .data = &mcp9601_chip_info },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, mcp9600_of_match);