[PATCH v5 4/4] hwmon: (pmbus/max20830): add support for max20830c and max20840c

[Alexis Czezar Torreno <alexisczezar.torreno@analog.com>]

Add support for MAX20830C and MAX20840 step-down DC-DC switching
regulator with PMBus interface. MAX20830C is a different packaging
for MAX20830, and MAX20840C supports 40A regulation compared to
MAX20830 that is only 30A.

Signed-off-by: Alexis Czezar Torreno <alexisczezar.torreno@analog.com>
---
 Documentation/hwmon/max20830.rst | 27 ++++++++++++++++++++++-----
 drivers/hwmon/pmbus/Kconfig      |  4 ++--
 drivers/hwmon/pmbus/max20830.c   | 36 +++++++++++++++++++++++-------------
 3 files changed, 47 insertions(+), 20 deletions(-)

diff --git a/Documentation/hwmon/max20830.rst b/Documentation/hwmon/max20830.rst
index 936e409dcc5c0898dde27d782308d4a7e1357e73..b850f3b6e40d1f1d0cec944be40af02265aced59 100644
--- a/Documentation/hwmon/max20830.rst
+++ b/Documentation/hwmon/max20830.rst
@@ -13,6 +13,22 @@ Supported chips:
 
     Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/max20830.pdf
 
+  * Analog Devices MAX20830C
+
+    Prefix: 'max20830c'
+
+    Addresses scanned: -
+
+    Datasheet:
+
+  * Analog Devices MAX20840C
+
+    Prefix: 'max20840c'
+
+    Addresses scanned: -
+
+    Datasheet:
+
 Author:
 
   - Alexis Czezar Torreno <alexisczezar.torreno@analog.com>
@@ -21,12 +37,13 @@ Author:
 Description
 -----------
 
-This driver supports hardware monitoring for Analog Devices MAX20830
-Step-Down Switching Regulator with PMBus Interface.
+This driver supports hardware monitoring for Analog Devices MAX20830, MAX20830C
+and MAX20840C. These are Step-Down Switching Regulator with PMBus Interface.
 
-The MAX20830 is a 2.7V to 16V, 30A fully integrated step-down DC-DC switching
-regulator. Through the PMBus interface, the device can monitor input/output
-voltages, output current and temperature.
+MAX20830, and MAX20830C are 2.7V to 16V, 30A fully integrated step-down DC-DC
+switching regulators. MAX20840C is similar but can reach 40A. Through the PMBus
+interface, these devices can monitor input/output voltages, output current and
+temperature.
 
 The driver is a client driver to the core PMBus driver. Please see
 Documentation/hwmon/pmbus.rst for details on PMBus client drivers.
diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
index ae003a6eac30a7b0a022c5f7f467d8f81736c3f7..5d435e81fc808c42576e5d1733f8a3e1ef32c023 100644
--- a/drivers/hwmon/pmbus/Kconfig
+++ b/drivers/hwmon/pmbus/Kconfig
@@ -394,10 +394,10 @@ config SENSORS_MAX20751
 	  be called max20751.
 
 config SENSORS_MAX20830
-	tristate "Analog Devices MAX20830"
+	tristate "Analog Devices MAX20830 and compatibles"
 	help
 	  If you say yes here you get hardware monitoring support for Analog
-	  Devices MAX20830.
+	  Devices MAX20830, MAX20830C, and MAX20840C.
 
 	  This driver can also be built as a module. If so, the module will
 	  be called max20830.
diff --git a/drivers/hwmon/pmbus/max20830.c b/drivers/hwmon/pmbus/max20830.c
index ddead72a8db5d6f8491cbfbf356db0f8de64da03..94433deda0113aa7bf0fc2b3f7807553f3014320 100644
--- a/drivers/hwmon/pmbus/max20830.c
+++ b/drivers/hwmon/pmbus/max20830.c
@@ -21,6 +21,12 @@ struct max20830_data {
 	u32 vout_rfb2;
 };
 
+static const char * const supported_chip_ids[] = {
+	"MAX20830",
+	"MAX20830C",
+	"MAX20840C",
+};
+
 /*
  * MAX20830 only supports READ_VOUT for VOUT monitoring.
  *
@@ -82,7 +88,7 @@ static int max20830_probe(struct i2c_client *client)
 {
 	u8 buf[I2C_SMBUS_BLOCK_MAX + 1] = {};
 	struct max20830_data *data;
-	int ret;
+	int i, ret;
 
 	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
 	if (!data)
@@ -104,13 +110,12 @@ static int max20830_probe(struct i2c_client *client)
 	 * which do not support SMBus block reads.
 	 */
 	if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_BLOCK_DATA)) {
-		/* Reads 9 Data bytes from MAX20830 */
 		ret = i2c_smbus_read_block_data(client, PMBUS_IC_DEVICE_ID, buf);
 		if (ret < 0)
 			return dev_err_probe(&client->dev, ret,
 					     "Failed to read IC_DEVICE_ID\n");
 	} else {
-		/* Reads 1 length byte + 9 Data bytes from MAX20830 */
+		/* Reads 1 length byte + data bytes */
 		ret = i2c_smbus_read_i2c_block_data(client, PMBUS_IC_DEVICE_ID,
 						    MAX20830_IC_DEVICE_ID_LENGTH + 1,
 						    buf);
@@ -126,20 +131,25 @@ static int max20830_probe(struct i2c_client *client)
 		ret = ret - 1;
 	}
 
-	/*
-	 * MAX20830 IC_DEVICE_ID sends string data "MAX20830\0".
-	 * Return value should at least be 9 bytes of data.
-	 */
+	/* Verify we read the expected number of bytes */
 	if (ret < MAX20830_IC_DEVICE_ID_LENGTH)
 		return dev_err_probe(&client->dev, -ENODEV,
-				     "IC_DEVICE_ID too short: expected at least 9 bytes, got %d\n",
-				     ret);
+				     "IC_DEVICE_ID too short: expected %d bytes, got %d\n",
+				     MAX20830_IC_DEVICE_ID_LENGTH, ret);
+
+	/* Null-terminate the string */
+	buf[ret] = '\0';
+
+	/* Verify the device ID matches what we expect */
+	for (i = 0; i < ARRAY_SIZE(supported_chip_ids); i++) {
+		if (!strcmp(buf, supported_chip_ids[i]))
+			break;
+	}
 
-	/* 9 bytes of data, buf[0]-buf[7] = "MAX20830", buf[8] = '\0' */
-	buf[MAX20830_IC_DEVICE_ID_LENGTH - 1] = '\0';
-	if (strncmp(buf, "MAX20830", MAX20830_IC_DEVICE_ID_LENGTH - 1))
+	/* No match found - unsupported device */
+	if (i == ARRAY_SIZE(supported_chip_ids))
 		return dev_err_probe(&client->dev, -ENODEV,
-				     "Unsupported device: '%s'\n", buf);
+				     "Unsupported device: '%*pE'\n", ret, buf);
 
 	return pmbus_do_probe(client, &data->info);
 }

-- 
2.34.1