dt-bindings: hwmon: Add nct7802 bindings

This change allows LTD and RTD inputs to be configured via device tree bindings. If the DT bindings are not present or invalid, the input configuration is not modified and left at HW defaults.

Signed-off-by Oskar Senft <[email protected]>

---
 drivers/hwmon/nct7802.c | 133 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 129 insertions(+), 4 deletions(-)

drivers/hwmon/nct7802.c +129 -5

index 604af2f6103a..e28f8eaf9f0f 100644
@@ -51,6 +51,23 @@ static const u8 REG_VOLTAGE_LIMIT_MSB_SHIFT[2][5] = {
 #define REG_CHIP_ID            0xfe
 #define REG_VERSION_ID         0xff
 
+/*
+ * Resistance temperature detector (RTD) modes according to 7.2.32 Mode
+ * Selection Register
+ */
+#define RTD_MODE_CURRENT       0x1
+#define RTD_MODE_THERMISTOR    0x2
+#define RTD_MODE_VOLTAGE       0x3
+
+#define MODE_RTD_MASK          0x3
+#define MODE_LTD_EN            0x40
+
+/*
+ * Bit offset for sensors modes in REG_MODE.
+ * Valid for index 0..2, indicating RTD1..3.
+ */
+#define MODE_BIT_OFFSET_RTD(index) ((index) * 2)
+
 /*
  * Data structures and manipulation thereof
  */

@@ -1038,7 +1055,116 @@ static const struct regmap_config nct7802_regmap_config = {
        .volatile_reg = nct7802_regmap_is_volatile,
 };
 
-static int nct7802_init_chip(struct nct7802_data *data)
+static int nct7802_get_channel_config(struct device *dev,
+                                     struct device_node *node, u8 *mode_mask,
+                                     u8 *mode_val)
+{
+       u32 reg;
+       const char *type_str, *md_str;
+       u8 md;
+
+       if (!node->name || of_node_cmp(node->name, "channel"))
+               return 0;
+
+       if (of_property_read_u32(node, "reg", &reg)) {
+               dev_err(dev, "Could not read reg value for '%s'\n",
+                       node->full_name);
+               return -EINVAL;
+       }
+
+       if (reg > 3) {
+               dev_err(dev, "Invalid reg (%u) in '%s'\n", reg,
+                       node->full_name);
+               return -EINVAL;
+       }
+
+       if (reg == 0) {
+               if (!of_device_is_available(node))
+                       *mode_val &= ~MODE_LTD_EN;
+               else
+                       *mode_val |= MODE_LTD_EN;
+               *mode_mask |= MODE_LTD_EN;
+               return 0;
+       }
+
+       /* At this point we have reg >= 1 && reg <= 3 */
+
+       if (!of_device_is_available(node)) {
+               *mode_val &= ~(MODE_RTD_MASK << MODE_BIT_OFFSET_RTD(reg - 1));
+               *mode_mask |= MODE_RTD_MASK << MODE_BIT_OFFSET_RTD(reg - 1);
+               return 0;
+       }
+
+       if (of_property_read_string(node, "sensor-type", &type_str)) {
+               dev_err(dev, "No type for '%s'\n", node->full_name);
+               return -EINVAL;
+       }
+
+       if (!strcmp(type_str, "voltage")) {
+               *mode_val |= (RTD_MODE_VOLTAGE & MODE_RTD_MASK)
+                            << MODE_BIT_OFFSET_RTD(reg - 1);
+               *mode_mask |= MODE_RTD_MASK << MODE_BIT_OFFSET_RTD(reg - 1);
+               return 0;
+       }
+
+       if (strcmp(type_str, "temperature")) {
+               dev_err(dev, "Invalid type '%s' for '%s'\n", type_str,
+                       node->full_name);
+               return -EINVAL;
+       }
+
+       if (reg == 3) {
+               /* RTD3 only supports thermistor mode */
+               md = RTD_MODE_THERMISTOR;
+       } else {
+               if (of_property_read_string(node, "temperature-mode",
+                                           &md_str)) {
+                       dev_err(dev, "No mode for '%s'\n", node->full_name);
+                       return -EINVAL;
+               }
+
+               if (!strcmp(md_str, "thermal-diode"))
+                       md = RTD_MODE_CURRENT;
+               else if (!strcmp(md_str, "thermistor"))
+                       md = RTD_MODE_THERMISTOR;
+               else {
+                       dev_err(dev, "Invalid mode '%s' for '%s'\n", md_str,
+                               node->full_name);
+                       return -EINVAL;
+               }
+       }
+
+       *mode_val |= (md & MODE_RTD_MASK) << MODE_BIT_OFFSET_RTD(reg - 1);
+       *mode_mask |= MODE_RTD_MASK << MODE_BIT_OFFSET_RTD(reg - 1);
+
+       return 0;
+}
+
+static int nct7802_configure_channels(struct device *dev,
+                                     struct nct7802_data *data)
+{
+       bool found_channel_config = false;
+       u8 mode_mask = 0, mode_val = 0;
+       struct device_node *node;
+       int err;
+
+       /* Enable local temperature sensor by default */
+       mode_val |= MODE_LTD_EN;
+       mode_mask |= MODE_LTD_EN;
+
+       if (dev->of_node) {
+               for_each_child_of_node(dev->of_node, node) {
+                       err = nct7802_get_channel_config(dev, node, &mode_mask,
+                                                        &mode_val);
+                       if (err)
+                               return err;
+               }
+       }
+
+       return regmap_update_bits(data->regmap, REG_MODE, mode_mask, mode_val);
+}
+
+static int nct7802_init_chip(struct device *dev, struct nct7802_data *data)
 {
        int err;
 

@@ -1047,8 +1173,7 @@ static int nct7802_init_chip(struct nct7802_data *data)
        if (err)
                return err;
 
-       /* Enable local temperature sensor */
-       err = regmap_update_bits(data->regmap, REG_MODE, 0x40, 0x40);
+       err = nct7802_configure_channels(dev, data);
        if (err)
                return err;
 

@@ -1074,7 +1199,7 @@ static int nct7802_probe(struct i2c_client *client)
        mutex_init(&data->access_lock);
        mutex_init(&data->in_alarm_lock);
 
-       ret = nct7802_init_chip(data);
+       ret = nct7802_init_chip(dev, data);
        if (ret < 0)
                return ret;
 
--

2.33.0.882.g93a45727a2-goog

This change allows LTD and RTD inputs to be configured via device tree bindings. If the DT bindings are not present or invalid, the input configuration is not modified and left at HW defaults.

Signed-off-by Oskar Senft <[email protected]>

---

  drivers/hwmon/nct7802.c | 133 ++++++++++++++++++++++++++++++++++++++--
  1 file changed, 129 insertions(+), 4 deletions(-)

drivers/hwmon/nct7802.c +96 -1

index 604af2f6103a..e28f8eaf9f0f 100644
@@ -51,6 +51,23 @@ static const u8 REG_VOLTAGE_LIMIT_MSB_SHIFT[2][5] = {
  #define REG_CHIP_ID		0xfe
  #define REG_VERSION_ID		0xff
 
+/*
+ * Resistance temperature detector (RTD) modes according to 7.2.32 Mode
+ * Selection Register
+ */
+#define RTD_MODE_CURRENT	0x1
+#define RTD_MODE_THERMISTOR	0x2
+#define RTD_MODE_VOLTAGE	0x3
+
+#define MODE_RTD_MASK		0x3
+#define MODE_LTD_EN		0x40
+
+/*
+ * Bit offset for sensors modes in REG_MODE.
+ * Valid for index 0..2, indicating RTD1..3.
+ */
+#define MODE_BIT_OFFSET_RTD(index) ((index) * 2)
+
  /*
   * Data structures and manipulation thereof
   */

@@ -1038,7 +1055,116 @@ static const struct regmap_config nct7802_regmap_config = {
  	.volatile_reg = nct7802_regmap_is_volatile,
  };
 
-static int nct7802_init_chip(struct nct7802_data *data)
+static int nct7802_get_channel_config(struct device *dev,
+				      struct device_node *node, u8 *mode_mask,
+				      u8 *mode_val)
+{
+	u32 reg;
+	const char *type_str, *md_str;
+	u8 md;
+
+	if (!node->name || of_node_cmp(node->name, "channel"))
+		return 0;
+
+	if (of_property_read_u32(node, "reg", &reg)) {
+		dev_err(dev, "Could not read reg value for '%s'\n",
+			node->full_name);
+		return -EINVAL;
+	}
+
+	if (reg > 3) {
+		dev_err(dev, "Invalid reg (%u) in '%s'\n", reg,
+			node->full_name);
+		return -EINVAL;
+	}
+
+	if (reg == 0) {
+		if (!of_device_is_available(node))
+			*mode_val &= ~MODE_LTD_EN;
+		else
+			*mode_val |= MODE_LTD_EN;
+		*mode_mask |= MODE_LTD_EN;
+		return 0;
+	}
+
+	/* At this point we have reg >= 1 && reg <= 3 */
+
+	if (!of_device_is_available(node)) {
+		*mode_val &= ~(MODE_RTD_MASK << MODE_BIT_OFFSET_RTD(reg - 1));
+		*mode_mask |= MODE_RTD_MASK << MODE_BIT_OFFSET_RTD(reg - 1);
+		return 0;
+	}
+
+	if (of_property_read_string(node, "sensor-type", &type_str)) {
+		dev_err(dev, "No type for '%s'\n", node->full_name);
+		return -EINVAL;
+	}
+
+	if (!strcmp(type_str, "voltage")) {
+		*mode_val |= (RTD_MODE_VOLTAGE & MODE_RTD_MASK)
+			     << MODE_BIT_OFFSET_RTD(reg - 1);
+		*mode_mask |= MODE_RTD_MASK << MODE_BIT_OFFSET_RTD(reg - 1);
+		return 0;
+	}
+
+	if (strcmp(type_str, "temperature")) {
+		dev_err(dev, "Invalid type '%s' for '%s'\n", type_str,
+			node->full_name);
+		return -EINVAL;
+	}
+
+	if (reg == 3) {
+		/* RTD3 only supports thermistor mode */
+		md = RTD_MODE_THERMISTOR;
+	} else {
+		if (of_property_read_string(node, "temperature-mode",
+					    &md_str)) {
+			dev_err(dev, "No mode for '%s'\n", node->full_name);
+			return -EINVAL;
+		}
+
+		if (!strcmp(md_str, "thermal-diode"))
+			md = RTD_MODE_CURRENT;
+		else if (!strcmp(md_str, "thermistor"))
+			md = RTD_MODE_THERMISTOR;
+		else {
+			dev_err(dev, "Invalid mode '%s' for '%s'\n", md_str,
+				node->full_name);
+			return -EINVAL;
+		}
+	}
+

drivers/hwmon/nct7802.c +15 -3

+	if (dev->of_node) {
+		for_each_child_of_node(dev->of_node, node) {
+			err = nct7802_get_channel_config(dev, node, &mode_mask,
+							 &mode_val);
+			if (err)
+				return err;
+		}
+	}
+
+	return regmap_update_bits(data->regmap, REG_MODE, mode_mask, mode_val);
+}
+
+static int nct7802_init_chip(struct device *dev, struct nct7802_data *data)
  {
  	int err;
 

@@ -1047,8 +1173,7 @@ static int nct7802_init_chip(struct nct7802_data *data)
  	if (err)
  		return err;
 
-	/* Enable local temperature sensor */
-	err = regmap_update_bits(data->regmap, REG_MODE, 0x40, 0x40);
+	err = nct7802_configure_channels(dev, data);
  	if (err)
  		return err;
 

@@ -1074,7 +1199,7 @@ static int nct7802_probe(struct i2c_client *client)
  	mutex_init(&data->access_lock);
  	mutex_init(&data->in_alarm_lock);
 
-	ret = nct7802_init_chip(data);
+	ret = nct7802_init_chip(dev, data);
  	if (ret < 0)
  		return ret;
 

Quoted 1 line

+ bool found_channel_config = false;

now unused, as 0-day points out.

drivers/hwmon/nct7802.c static const struct regmap_config nct7802_regmap_config = { · line 1154

Quoted 4 lines

drivers/hwmon/nct7802.c +4 -0

+     /* Enable local temperature sensor by default */
+     mode_val |= MODE_LTD_EN;
+     mode_mask |= MODE_LTD_EN;
+

Either make it = and drop the initialization above, or better initialize the variables with MODE_LTD_EN right away.

This change documents the device tree bindings for the Nuvoton NCT7802Y driver.

Signed-off-by Oskar Senft <[email protected]>

---
 .../bindings/hwmon/nuvoton,nct7802.yaml       | 142 ++++++++++++++++++
 1 file changed, 142 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/nuvoton,nct7802.yaml

Documentation/devicetree/bindings/hwmon/nuvoton,nct7802.yaml new file +142 -1

new file mode 100644
index 000000000000..ff99f40034f2
@@ -0,0 +1,142 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+
+$id: http://devicetree.org/schemas/hwmon/nuvoton,nct7802.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Nuvoton NCT7802Y Hardware Monitoring IC
+
+maintainers:
+  - Guenter Roeck <[email protected]>
+
+description: |
+  The NCT7802Y is a hardware monitor IC which supports one on-die and up to
+  5 remote temperature sensors with SMBus interface.
+
+  Datasheets:
+    https://www.nuvoton.com/export/resource-files/Nuvoton_NCT7802Y_Datasheet_V12.pdf
+
+properties:
+  compatible:
+    enum:
+      - nuvoton,nct7802
+
+  reg:
+    maxItems: 1
+
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 0
+
+  channel@0:
+    type: object
+    description: Local Temperature Sensor ("LTD")
+    properties:
+      reg:
+        const: 0
+    required:
+      - reg
+
+  channel@1:
+    type: object
+    description: Remote Temperature Sensor or Voltage Sensor ("RTD1")
+    properties:
+      reg:
+        const: 1
+      sensor-type:
+        items:
+          - enum:
+              - temperature
+              - voltage
+      temperature-mode:
+        items:
+          - enum:
+              - thermistor
+              - thermal-diode
+    required:
+      - reg
+      - sensor-type
+
+  channel@2:
+    type: object
+    description: Remote Temperature Sensor or Voltage Sensor ("RTD2")
+    properties:
+      reg:
+        const: 2
+      sensor-type:
+        items:
+          - enum:
+              - temperature
+              - voltage
+      temperature-mode:
+        items:
+          - enum:
+              - thermistor
+              - thermal-diode
+    required:
+      - reg
+      - sensor-type
+
+  channel@3:
+    type: object
+    description: Remote Temperature Sensor or Voltage Sensor ("RTD3")
+    properties:
+      reg:
+        const: 3
+      sensor-type:
+        items:
+          - enum:
+              - temperature
+              - voltage
+    required:
+      - reg
+      - sensor-type
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        nct7802@28 {
+            compatible = "nuvoton,nct7802";
+            reg = <0x28>;
+
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            channel@0 { /* LTD */
+              reg = <0>;
+              status = "okay";
+            };
+
+            channel@1 { /* RTD1 */
+              reg = <1>;
+              status = "okay";
+              sensor-type = "temperature";
+              temperature-mode = "thermistor";
+            };
+
+            channel@2 { /* RTD2 */
+              reg = <2>;
+              status = "okay";
+              sensor-type = "temperature";
+              temperature-mode = "thermal-diode";
+            };
+
+            channel@3 { /* RTD3 */
+              reg = <3>;
+              status = "okay";
+              sensor-type = "voltage";
+            };
+        };
+    };
--

2.33.0.882.g93a45727a2-goog

This change documents the device tree bindings for the Nuvoton NCT7802Y driver.

Signed-off-by Oskar Senft <[email protected]>

---

  .../bindings/hwmon/nuvoton,nct7802.yaml       | 142 ++++++++++++++++++
  1 file changed, 142 insertions(+)

create mode 100644 Documentation/devicetree/bindings/hwmon/nuvoton,nct7802.yaml

Documentation/devicetree/bindings/hwmon/nuvoton,nct7802.yaml new file +6 -0

new file mode 100644
index 000000000000..ff99f40034f2
@@ -0,0 +1,142 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+
+$id: http://devicetree.org/schemas/hwmon/nuvoton,nct7802.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#

Documentation/devicetree/bindings/hwmon/nuvoton,nct7802.yaml new file +35 -0

+  Datasheets:
+    https://www.nuvoton.com/export/resource-files/Nuvoton_NCT7802Y_Datasheet_V12.pdf
+
+properties:
+  compatible:
+    enum:
+      - nuvoton,nct7802
+
+  reg:
+    maxItems: 1
+
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 0
+
+  channel@0:
+    type: object
+    description: Local Temperature Sensor ("LTD")
+    properties:
+      reg:
+        const: 0
+    required:
+      - reg
+
+  channel@1:
+    type: object
+    description: Remote Temperature Sensor or Voltage Sensor ("RTD1")
+    properties:
+      reg:
+        const: 1
+      sensor-type:
+        items:
+          - enum:

Documentation/devicetree/bindings/hwmon/nuvoton,nct7802.yaml new file +81 -0

+
+  channel@2:
+    type: object
+    description: Remote Temperature Sensor or Voltage Sensor ("RTD2")
+    properties:
+      reg:
+        const: 2
+      sensor-type:
+        items:
+          - enum:
+              - temperature
+              - voltage
+      temperature-mode:
+        items:
+          - enum:
+              - thermistor
+              - thermal-diode
+    required:
+      - reg
+      - sensor-type
+
+  channel@3:
+    type: object
+    description: Remote Temperature Sensor or Voltage Sensor ("RTD3")
+    properties:
+      reg:
+        const: 3
+      sensor-type:
+        items:
+          - enum:
+              - temperature
+              - voltage
+    required:
+      - reg
+      - sensor-type
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        nct7802@28 {
+            compatible = "nuvoton,nct7802";
+            reg = <0x28>;
+
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            channel@0 { /* LTD */
+              reg = <0>;
+              status = "okay";
+            };
+
+            channel@1 { /* RTD1 */
+              reg = <1>;
+              status = "okay";
+              sensor-type = "temperature";
+              temperature-mode = "thermistor";
+            };
+
+            channel@2 { /* RTD2 */
+              reg = <2>;
+              status = "okay";
+              sensor-type = "temperature";
+              temperature-mode = "thermal-diode";
+            };
+
+            channel@3 { /* RTD3 */
+              reg = <3>;
+              status = "okay";
+              sensor-type = "voltage";
+            };
+        };
+    };

Quoted 2 lines

Signed-off-by Oskar Senft <[email protected]>

---

change log goes here.

Documentation/devicetree/bindings/hwmon/nuvoton,nct7802.yaml line 16

Quoted 4 lines

Documentation/devicetree/bindings/hwmon/nuvoton,nct7802.yaml new file +4 -0

+description: |
+  The NCT7802Y is a hardware monitor IC which supports one on-die and up to
+  5 remote temperature sensors with SMBus interface.
+

Just noticed: 5 remote temperature sensors ? Shouldn't that be 3 ?

Documentation/devicetree/bindings/hwmon/nuvoton,nct7802.yaml line 61

Quoted 13 lines

Documentation/devicetree/bindings/hwmon/nuvoton,nct7802.yaml new file +13 -0

+      sensor-type:
+        items:
+          - enum:
+              - temperature
+              - voltage
+      temperature-mode:
+        items:
+          - enum:
+              - thermistor
+              - thermal-diode
+    required:
+      - reg
+      - sensor-type

If I understand correctly, "temperature-mode" is implemented as mandatory for channels 1 and 2 if sensor-type is "temperature" (which makes sense). No idea though if it is possible to express that in yaml.
If not, can it be mentioned as comment ?

Quoted 83 lines

Documentation/devicetree/bindings/hwmon/nuvoton,nct7802.yaml new file +81 -0

+
+  channel@2:
+    type: object
+    description: Remote Temperature Sensor or Voltage Sensor ("RTD2")
+    properties:
+      reg:
+        const: 2
+      sensor-type:
+        items:
+          - enum:
+              - temperature
+              - voltage
+      temperature-mode:
+        items:
+          - enum:
+              - thermistor
+              - thermal-diode
+    required:
+      - reg
+      - sensor-type
+
+  channel@3:
+    type: object
+    description: Remote Temperature Sensor or Voltage Sensor ("RTD3")
+    properties:
+      reg:
+        const: 3
+      sensor-type:
+        items:
+          - enum:
+              - temperature
+              - voltage
+    required:
+      - reg
+      - sensor-type
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        nct7802@28 {
+            compatible = "nuvoton,nct7802";
+            reg = <0x28>;
+
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            channel@0 { /* LTD */
+              reg = <0>;
+              status = "okay";
+            };
+
+            channel@1 { /* RTD1 */
+              reg = <1>;
+              status = "okay";
+              sensor-type = "temperature";
+              temperature-mode = "thermistor";
+            };
+
+            channel@2 { /* RTD2 */
+              reg = <2>;
+              status = "okay";
+              sensor-type = "temperature";
+              temperature-mode = "thermal-diode";
+            };
+
+            channel@3 { /* RTD3 */
+              reg = <3>;
+              status = "okay";
+              sensor-type = "voltage";
+            };
+        };
+    };

Hi Guenter

Thanks again for your review!

Quoted 4 lines

Quoted 2 lines

Signed-off-by Oskar Senft <[email protected]>

---

change log goes here.

This might be a silly question: I'm using "git send-email", but I don't think there's a way to edit the e-mail before it goes out. Do I just add "---\n[Change log]" manually in the commit description?

Quoted 6 lines

Documentation/devicetree/bindings/hwmon/nuvoton,nct7802.yaml line 16

Quoted 4 lines

Documentation/devicetree/bindings/hwmon/nuvoton,nct7802.yaml new file +4 -0

+description: |
+  The NCT7802Y is a hardware monitor IC which supports one on-die and up to
+  5 remote temperature sensors with SMBus interface.
+

Just noticed: 5 remote temperature sensors ? Shouldn't that be 3 ?

This includes 2 temperature sensors that are queried via PECI (i.e. SMBus). I generated the description from the "general description" section in the datasheet. I think the driver doesn't implement the 2 PECI sensors at this time, but the statement about the HW is still true.

Quoted 14 lines

Documentation/devicetree/bindings/hwmon/nuvoton,nct7802.yaml line 61

Quoted 13 lines

Documentation/devicetree/bindings/hwmon/nuvoton,nct7802.yaml new file +13 -0

+      sensor-type:
+        items:
+          - enum:
+              - temperature
+              - voltage
+      temperature-mode:
+        items:
+          - enum:
+              - thermistor
+              - thermal-diode
+    required:
+      - reg
+      - sensor-type

Quoted 4 lines

If I understand correctly, "temperature-mode" is implemented as mandatory for channels 1 and 2 if sensor-type is "temperature" (which makes sense). No idea though if it is possible to express that in yaml.
If not, can it be mentioned as comment ?

After doing a bit more searching, I found the amazing "if: then:
else:" construct that allows to express this properly and eliminates the code duplication. I'll follow up in PATCH v6.

Thanks
Oskar.

Quoted 84 lines

Quoted 83 lines

Documentation/devicetree/bindings/hwmon/nuvoton,nct7802.yaml new file +81 -0

+
+  channel@2:
+    type: object
+    description: Remote Temperature Sensor or Voltage Sensor ("RTD2")
+    properties:
+      reg:
+        const: 2
+      sensor-type:
+        items:
+          - enum:
+              - temperature
+              - voltage
+      temperature-mode:
+        items:
+          - enum:
+              - thermistor
+              - thermal-diode
+    required:
+      - reg
+      - sensor-type
+
+  channel@3:
+    type: object
+    description: Remote Temperature Sensor or Voltage Sensor ("RTD3")
+    properties:
+      reg:
+        const: 3
+      sensor-type:
+        items:
+          - enum:
+              - temperature
+              - voltage
+    required:
+      - reg
+      - sensor-type
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        nct7802@28 {
+            compatible = "nuvoton,nct7802";
+            reg = <0x28>;
+
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            channel@0 { /* LTD */
+              reg = <0>;
+              status = "okay";
+            };
+
+            channel@1 { /* RTD1 */
+              reg = <1>;
+              status = "okay";
+              sensor-type = "temperature";
+              temperature-mode = "thermistor";
+            };
+
+            channel@2 { /* RTD2 */
+              reg = <2>;
+              status = "okay";
+              sensor-type = "temperature";
+              temperature-mode = "thermal-diode";
+            };
+
+            channel@3 { /* RTD3 */
+              reg = <3>;
+              status = "okay";
+              sensor-type = "voltage";
+            };
+        };
+    };