[PATCH v2 0/2] Hwmon driver for MAX31827 temperature switch

[PATCH v2 0/2] Hwmon driver for MAX31827 temperature switch

[Daniel Matyas]

There are new functionalities: max_alarm, min_alarm and update_interval.

Modified enable attribute: it switches between 1Hz periodic conversions
and shutdown mode.

When requesting a temperature read in shutdown mode 1shot is triggered,
the driver waits until the conversion is completed and then displays the
read value.

Added new write_alarm_val function which puts the device in shutdown
mode, modifies the value of an alarm attribute and the reenables the
device with the previous configurations. I used more bitwise operations
in this functions instead of regmap_update_bits, because this way only 2
write and 2 read operations are performed. With regmap_update_bits 3
write operations and 2 read operations would be performed.

Added support for the other 2 chips from the datasheet: max31828,
max31829.

Added documentation for the driver. 

Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/max31827-max31829.pdf

*** BLURB HERE ***

Daniel Matyas (2):
  dt-bindings: hwmon: add MAX31827
  hwmon: max31827: add MAX31827 driver

 .../bindings/hwmon/adi,max31827.yaml          |  51 +++
 Documentation/hwmon/max31827.rst              |  88 +++++
 MAINTAINERS                                   |   9 +
 drivers/hwmon/Kconfig                         |  11 +
 drivers/hwmon/Makefile                        |   1 +
 drivers/hwmon/max31827.c                      | 324 ++++++++++++++++++
 6 files changed, 484 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
 create mode 100644 Documentation/hwmon/max31827.rst
 create mode 100644 drivers/hwmon/max31827.c

-- 
2.34.1

[PATCH v2 1/2] [PATCH v1 1/2] dt-bindings: hwmon: add MAX31827

[Daniel Matyas]

MAX31827 is a low-power temperature switch with I2C interface.

The device is a ±1°C accuracy from -40°C to +125°C
(12 bits) local temperature switch and sensor with I2C/SM-
Bus interface. The combination of small 6-bump wafer-lev-
el package (WLP) and high accuracy makes this temper-
ature sensor/switch ideal for a wide range of applications.

Signed-off-by: Daniel Matyas <daniel.matyas@analog.com>
---
 .../bindings/hwmon/adi,max31827.yaml          | 51 +++++++++++++++++++
 MAINTAINERS                                   |  7 +++
 2 files changed, 58 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/adi,max31827.yaml

diff --git a/Documentation/devicetree/bindings/hwmon/adi,max31827.yaml b/Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
new file mode 100644
index 000000000000..37177eb9c039
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
@@ -0,0 +1,51 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/hwmon/adi,max31827.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices MAX31827, MAX31828, MAX31829 Low-Power Temperature Switch
+
+maintainers:
+  - Daniel Matyas <daniel.matyas@analog.com>
+
+description: |
+  Analog Devices MAX31827, MAX31828, MAX31829 Low-Power Temperature Switch with
+  I2C Interface
+  https://www.analog.com/media/en/technical-documentation/data-sheets/MAX31827-MAX31829.pdf
+
+properties:
+  compatible:
+    enum:
+      - adi,max31827
+      - adi,max31828
+      - adi,max31829
+
+  reg:
+    maxItems: 1
+
+  vref-supply:
+    description:
+      Must have values in the interval (1.6V; 3.6V) in order for the device to
+      function correctly.
+
+required:
+  - compatible
+  - reg
+  - vref-supply
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        temperature-sensor@42 {
+            compatible = "adi,max31827";
+            reg = <0x42>;
+            vref-supply = <&reg_vdd>;
+        };
+    };
+...
diff --git a/MAINTAINERS b/MAINTAINERS
index 0e64787aace8..8af1296ff1a0 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12535,6 +12535,13 @@ F:	Documentation/userspace-api/media/drivers/max2175.rst
 F:	drivers/media/i2c/max2175*
 F:	include/uapi/linux/max2175.h
 
+MAX31827 TEMPERATURE SWITCH DRIVER
+M:	Daniel Matyas <daniel.matyas@analog.com>
+L:	linux-hwmon@vger.kernel.org
+S:	Supported
+W:	http://ez.analog.com/community/linux-device-drivers
+F:	Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
+
 MAX6650 HARDWARE MONITOR AND FAN CONTROLLER DRIVER
 L:	linux-hwmon@vger.kernel.org
 S:	Orphan
-- 
2.34.1

[PATCH v2 2/2] [PATCH v1 2/2] hwmon: max31827: add MAX31827 driver

[Daniel Matyas]

MAX31827 is a low-power temperature switch with I2C interface.

The device is a ±1°C accuracy from -40°C to +125°C
(12 bits) local temperature switch and sensor with I2C/SM-
Bus interface. The combination of small 6-bump wafer-lev-
el package (WLP) and high accuracy makes this temper-
ature sensor/switch ideal for a wide range of applications.

Signed-off-by: Daniel Matyas <daniel.matyas@analog.com>
---
 Documentation/hwmon/max31827.rst |  88 +++++++++
 MAINTAINERS                      |   2 +
 drivers/hwmon/Kconfig            |  11 ++
 drivers/hwmon/Makefile           |   1 +
 drivers/hwmon/max31827.c         | 324 +++++++++++++++++++++++++++++++
 5 files changed, 426 insertions(+)
 create mode 100644 Documentation/hwmon/max31827.rst
 create mode 100644 drivers/hwmon/max31827.c

diff --git a/Documentation/hwmon/max31827.rst b/Documentation/hwmon/max31827.rst
new file mode 100644
index 000000000000..fe4d5bae8785
--- /dev/null
+++ b/Documentation/hwmon/max31827.rst
@@ -0,0 +1,88 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Kernel driver max31827
+======================
+
+Supported chips:
+
+  * Maxim MAX31827
+
+    Prefix: 'max31827'
+
+    Addresses scanned: I2C 0x40 - 0x5f
+
+    Datasheet: Publicly available at the Analog Devices website
+
+  * Maxim MAX31828
+
+    Prefix: 'max31828'
+
+    Addresses scanned: I2C 0x40 - 0x5f
+
+    Datasheet: Publicly available at the Analog Devices website
+
+  * Maxim MAX31829
+
+    Prefix: 'max31829'
+
+    Addresses scanned: I2C 0x40 - 0x5f
+
+    Datasheet: Publicly available at the Analog Devices website
+
+
+Authors:
+	- Daniel Matyas <daniel.matyas@analog.com>
+
+Description
+-----------
+
+The chips supported by this driver are quite similar. The only difference
+between them is found in the default power-on behaviour of the chips. While the
+MAX31827's fault queue is set to 1, the other two chip's fault queue is set to
+4. Besides this, the MAX31829's alarm active state is high, while the other two
+chip's alarms are active on low. It is important to note that the chips can be
+configured to operate in the same manner with 1 write operation to the
+configuration register. From here on, we will refer to all these chips as
+MAX31827.
+
+MAX31827 implemets a temperature sensor with a 6 WLP packaging scheme. This
+sensor measures the temperature of the chip itself.
+
+MAX31827 has low and over temperature alarms with an effective value and a
+hysteresis value: -40 and -30 degrees for under temperature alarm and +100 and
++90 degrees for over temperature alarm.
+
+The alarm can be configured in comparator (default) and interrupt mode. In
+Comparator mode, the OT/UT status bits have a value of 1 when the temperature
+rises above the TH value or falls below TL, which is also subject to the Fault
+Queue selection. OT status returns to 0 when the temperature drops below the
+TH_HYST value or when shutdown mode is entered. Similarly, UT status returns to
+0 when the temperature rises above TL_HYST value or when shutdown mode is
+entered.
+
+In Interrupt mode exceeding TH also sets OT status to 1, which remains set until
+a read operation is performed on the configuration/status register; at this
+point, it returns to 0. Once OT status is set to 1 from exceeding TH and reset,
+it is set to 1 again only when the temperature drops below TH_HYST. The output
+remains asserted until it is reset by a read. It is set again if the temperature
+rises above TH, and so on. The same logic applies to the operation of the UT
+status bit.
+
+Putting the MAX31827 into shutdown mode also resets the OT/UT status bits. Note
+that if the mode is changed while OT/UT status bits are set, an OT/UT status
+reset may be required before it begins to behave normally. To prevent this,
+it is recommended to perform a read of the configuration/status register to
+clear the status bits before changing the operating mode.
+
+The conversions can be manuel with the one-shot functionality and automatic with
+a set frequency. When powered on, the chip measures temperatures with 1 conv/s.
+The conversion time varies depending on the resolution. The conversion time
+doubles with every bit of increased resolution. For 10 bit resolution
+35ms are needed, while for 12 bit resolution (default) 140ms.
+
+
+Notes
+-----
+
+Currently fault queue, alarm polarity and resolution cannot be modified.
+PEC is not implemented either.
diff --git a/MAINTAINERS b/MAINTAINERS
index 8af1296ff1a0..cfb15f3f4606 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12541,6 +12541,8 @@ L:	linux-hwmon@vger.kernel.org
 S:	Supported
 W:	http://ez.analog.com/community/linux-device-drivers
 F:	Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
+F:	Documentation/hwmon/max31827.rst
+F:	drivers/hwmon/max31827.c
 
 MAX6650 HARDWARE MONITOR AND FAN CONTROLLER DRIVER
 L:	linux-hwmon@vger.kernel.org
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 5b3b76477b0e..80c44a787d42 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -2401,4 +2401,15 @@ config SENSORS_ASUS_EC
 
 endif # ACPI
 
+config MAX31827
+	tristate "MAX31827 low-power temperature switch"
+	depends on I2C
+	select REGMAP_I2C
+	help
+	  If you say yes here you get support for MAX31827
+	  low-power temperature switch and sensor connected with I2C.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called max31827.
+
 endif # HWMON
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 88712b5031c8..d00f0a1e73f6 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -224,3 +224,4 @@ obj-$(CONFIG_PMBUS)		+= pmbus/
 
 ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
 
+obj-$(CONFIG_MAX31827) += max31827.o
diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c
new file mode 100644
index 000000000000..8eb708adac49
--- /dev/null
+++ b/drivers/hwmon/max31827.c
@@ -0,0 +1,324 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * max31827.c - Support for Maxim Low-Power Switch
+ *
+ * Copyright (c) 2023 Daniel Matyas <daniel.matyas@analog.com>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/delay.h>
+#include <linux/hwmon.h>
+#include <linux/i2c.h>
+#include <linux/regmap.h>
+
+#define MAX31827_T_REG 0x0
+#define MAX31827_CONFIGURATION_REG 0x2
+#define MAX31827_TH_REG 0x4
+#define MAX31827_TL_REG 0x6
+#define MAX31827_TH_HYST_REG 0x8
+#define MAX31827_TL_HYST_REG 0xA
+
+#define MAX31827_CONFIGURATION_1SHOT_MASK BIT(0)
+#define MAX31827_CONFIGURATION_CNV_RATE_MASK GENMASK(3, 1)
+#define MAX31827_CONFIGURATION_U_TEMP_STAT_MASK BIT(14)
+#define MAX31827_CONFIGURATION_O_TEMP_STAT_MASK BIT(15)
+
+#define MAX31827_12_BIT_CNV_TIME 140
+
+#define MAX31827_DEVICE_ENABLE(x) ((x) ? 0xA : 0x0)
+
+enum chips { max31827, max31828, max31829 };
+
+struct max31827_state {
+	struct regmap *regmap;
+	bool enable;
+};
+
+static const struct regmap_config max31827_regmap = {
+	.reg_bits = 8,
+	.val_bits = 16,
+	.max_register = 0xA,
+};
+
+static int write_alarm_val(struct max31827_state *st, unsigned int reg,
+			   unsigned int val)
+{
+	unsigned int cfg;
+	unsigned int tmp;
+	int ret;
+
+	if (!st->enable)
+		return regmap_write(st->regmap, reg, val);
+
+	ret = regmap_read(st->regmap, MAX31827_CONFIGURATION_REG, &cfg);
+	if (ret)
+		return ret;
+
+	tmp = cfg & ~(MAX31827_CONFIGURATION_1SHOT_MASK |
+		      MAX31827_CONFIGURATION_CNV_RATE_MASK);
+	ret = regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, tmp);
+	if (ret)
+		return ret;
+
+	ret = regmap_write(st->regmap, reg, val);
+	if (ret)
+		return ret;
+
+	ret = regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, cfg);
+
+	return ret;
+}
+
+static umode_t max31827_is_visible(const void *state,
+				   enum hwmon_sensor_types type, u32 attr,
+				   int channel)
+{
+	if (type == hwmon_temp) {
+		switch (attr) {
+		case hwmon_temp_enable:
+		case hwmon_temp_max:
+		case hwmon_temp_min:
+		case hwmon_temp_max_hyst:
+		case hwmon_temp_min_hyst:
+			return 0644;
+		case hwmon_temp_input:
+		case hwmon_temp_min_alarm:
+		case hwmon_temp_max_alarm:
+			return 0444;
+		}
+	} else if (type == hwmon_chip) {
+		if (attr == hwmon_chip_update_interval)
+			return 0644;
+	}
+
+	return 0;
+}
+
+static int max31827_read(struct device *dev, enum hwmon_sensor_types type,
+			 u32 attr, int channel, long *val)
+{
+	struct max31827_state *st = dev_get_drvdata(dev);
+	unsigned int uval;
+	int ret;
+
+	switch (type) {
+	case hwmon_temp:
+		switch (attr) {
+		case hwmon_temp_enable:
+			ret = regmap_read(st->regmap,
+					  MAX31827_CONFIGURATION_REG, &uval);
+			uval = FIELD_GET(MAX31827_CONFIGURATION_1SHOT_MASK |
+					 MAX31827_CONFIGURATION_CNV_RATE_MASK,
+					 uval);
+			if (uval)
+				uval = 1;
+			break;
+		case hwmon_temp_input:
+			if (!st->enable) {
+				ret = regmap_update_bits(st->regmap,
+							 MAX31827_CONFIGURATION_REG,
+							 MAX31827_CONFIGURATION_1SHOT_MASK,
+							 1);
+				if (ret)
+					return ret;
+
+				msleep(MAX31827_12_BIT_CNV_TIME);
+			}
+			ret = regmap_read(st->regmap, MAX31827_T_REG, &uval);
+
+			break;
+		case hwmon_temp_max:
+			ret = regmap_read(st->regmap, MAX31827_TH_REG, &uval);
+			break;
+		case hwmon_temp_max_hyst:
+			ret = regmap_read(st->regmap, MAX31827_TH_HYST_REG,
+					  &uval);
+			break;
+		case hwmon_temp_max_alarm:
+			ret = regmap_read(st->regmap,
+					  MAX31827_CONFIGURATION_REG, &uval);
+			uval = FIELD_GET(MAX31827_CONFIGURATION_O_TEMP_STAT_MASK,
+					 uval);
+			break;
+		case hwmon_temp_min:
+			ret = regmap_read(st->regmap, MAX31827_TL_REG, &uval);
+			break;
+		case hwmon_temp_min_hyst:
+			ret = regmap_read(st->regmap, MAX31827_TL_HYST_REG,
+					  &uval);
+			break;
+		case hwmon_temp_min_alarm:
+			ret = regmap_read(st->regmap,
+					  MAX31827_CONFIGURATION_REG, &uval);
+			uval = FIELD_GET(MAX31827_CONFIGURATION_U_TEMP_STAT_MASK,
+					 uval);
+			break;
+		default:
+			ret = -EOPNOTSUPP;
+		}
+		break;
+
+	case hwmon_chip:
+		if (attr == hwmon_chip_update_interval) {
+			ret = regmap_read(st->regmap,
+					  MAX31827_CONFIGURATION_REG, &uval);
+			uval = FIELD_GET(MAX31827_CONFIGURATION_CNV_RATE_MASK,
+					 uval);
+		}
+		break;
+
+	default:
+		ret = -EOPNOTSUPP;
+	}
+
+	if (ret)
+		return ret;
+
+	*val = (short)uval;
+
+	return 0;
+}
+
+static int max31827_write(struct device *dev, enum hwmon_sensor_types type,
+			  u32 attr, int channel, long val)
+{
+	struct max31827_state *st = dev_get_drvdata(dev);
+
+	switch (type) {
+	case hwmon_temp:
+		switch (attr) {
+		case hwmon_temp_enable:
+			if (val >> 1)
+				return -EOPNOTSUPP;
+
+			st->enable = val;
+
+			return regmap_update_bits(st->regmap,
+						  MAX31827_CONFIGURATION_REG,
+						  MAX31827_CONFIGURATION_1SHOT_MASK |
+						  MAX31827_CONFIGURATION_CNV_RATE_MASK,
+						  MAX31827_DEVICE_ENABLE(val));
+
+		case hwmon_temp_max:
+			return write_alarm_val(st, MAX31827_TH_REG, val);
+
+		case hwmon_temp_max_hyst:
+			return write_alarm_val(st, MAX31827_TH_HYST_REG, val);
+
+		case hwmon_temp_min:
+			return write_alarm_val(st, MAX31827_TL_REG, val);
+
+		case hwmon_temp_min_hyst:
+			return write_alarm_val(st, MAX31827_TL_HYST_REG, val);
+
+		default:
+			return -EOPNOTSUPP;
+		}
+
+	case hwmon_chip:
+		if (attr == hwmon_chip_update_interval) {
+			val = FIELD_PREP(MAX31827_CONFIGURATION_CNV_RATE_MASK,
+					 val);
+			return regmap_update_bits(st->regmap,
+						  MAX31827_CONFIGURATION_REG,
+						  MAX31827_CONFIGURATION_CNV_RATE_MASK,
+						  val);
+		}
+		break;
+
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return -EOPNOTSUPP;
+}
+
+static int max31827_init_client(struct max31827_state *st)
+{
+	st->enable = true;
+
+	return regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG,
+				  MAX31827_CONFIGURATION_1SHOT_MASK |
+				  MAX31827_CONFIGURATION_CNV_RATE_MASK,
+				  MAX31827_DEVICE_ENABLE(1));
+}
+
+static const struct hwmon_channel_info *max31827_info[] = {
+	HWMON_CHANNEL_INFO(temp, HWMON_T_ENABLE | HWMON_T_INPUT | HWMON_T_MIN |
+			   HWMON_T_MIN_HYST | HWMON_T_MIN_ALARM | HWMON_T_MAX |
+			   HWMON_T_MAX_HYST | HWMON_T_MAX_ALARM),
+	HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL),
+	NULL,
+};
+
+static const struct hwmon_ops max31827_hwmon_ops = {
+	.is_visible = max31827_is_visible,
+	.read = max31827_read,
+	.write = max31827_write,
+};
+
+static const struct hwmon_chip_info max31827_chip_info = {
+	.ops = &max31827_hwmon_ops,
+	.info = max31827_info,
+};
+
+static int max31827_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct device *hwmon_dev;
+	struct max31827_state *st;
+	int err;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA))
+		return -EOPNOTSUPP;
+
+	st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL);
+	if (!st)
+		return -ENOMEM;
+
+	st->regmap = devm_regmap_init_i2c(client, &max31827_regmap);
+	if (IS_ERR(st->regmap))
+		return dev_err_probe(dev, PTR_ERR(st->regmap),
+				     "Failed to allocate regmap.\n");
+
+	err = max31827_init_client(st);
+	if (err)
+		return err;
+
+	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, st,
+							 &max31827_chip_info,
+							 NULL);
+
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct i2c_device_id max31827_i2c_ids[] = {
+	{ "max31827", max31827 },
+	{ "max31828", max31828 },
+	{ "max31829", max31829 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max31827_i2c_ids);
+
+static const struct of_device_id max31827_of_match[] = {
+	{ .compatible = "adi,max31827" },
+	{ .compatible = "adi,max31828" },
+	{ .compatible = "adi,max31829" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, max31827_of_match);
+
+static struct i2c_driver max31827_driver = {
+	.class = I2C_CLASS_HWMON,
+	.driver = {
+		.name = "adi,max31827",
+		.of_match_table = max31827_of_match,
+	},
+	.probe_new = max31827_probe,
+	.id_table = max31827_i2c_ids,
+};
+module_i2c_driver(max31827_driver);
+
+MODULE_AUTHOR("Daniel Matyas <daniel.matyas@analog.com>");
+MODULE_DESCRIPTION("Maxim MAX31827 low-power temperature switch driver");
+MODULE_LICENSE("GPL");
-- 
2.34.1

Re: [PATCH v2 1/2] [PATCH v1 1/2] dt-bindings: hwmon: add MAX31827

[Krzysztof Kozlowski]

On 12/04/2023 17:33, Daniel Matyas wrote:
> MAX31827 is a low-power temperature switch with I2C interface.
> 
> The device is a ±1°C accuracy from -40°C to +125°C
> (12 bits) local temperature switch and sensor with I2C/SM-
> Bus interface. The combination of small 6-bump wafer-lev-
> el package (WLP) and high accuracy makes this temper-
> ature sensor/switch ideal for a wide range of applications.
> 
> Signed-off-by: Daniel Matyas <daniel.matyas@analog.com>
> ---
>  .../bindings/hwmon/adi,max31827.yaml          | 51 +++++++++++++++++++
>  MAINTAINERS                                   |  7 +++
>  2 files changed, 58 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
> 
> diff --git a/Documentation/devicetree/bindings/hwmon/adi,max31827.yaml b/Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
> new file mode 100644
> index 000000000000..37177eb9c039
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
> @@ -0,0 +1,51 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/hwmon/adi,max31827.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Analog Devices MAX31827, MAX31828, MAX31829 Low-Power Temperature Switch
> +
> +maintainers:
> +  - Daniel Matyas <daniel.matyas@analog.com>
> +
> +description: |
> +  Analog Devices MAX31827, MAX31828, MAX31829 Low-Power Temperature Switch with
> +  I2C Interface
> +  https://www.analog.com/media/en/technical-documentation/data-sheets/MAX31827-MAX31829.pdf
> +
> +properties:
> +  compatible:
> +    enum:
> +      - adi,max31827
> +      - adi,max31828
> +      - adi,max31829

Why suddenly these are all incompatible? This is not what I suggested.

> +
> +  reg:
> +    maxItems: 1
> +

Best regards,
Krzysztof

Unclear what to do with compatibility

[Daniel Matyas]

MAX31827 is a low-power temperature switch with I2C interface.

The device is a ±1°C accuracy from -40°C to +125°C
(12 bits) local temperature switch and sensor with I2C/SM-
Bus interface. The combination of small 6-bump wafer-lev-
el package (WLP) and high accuracy makes this temper-
ature sensor/switch ideal for a wide range of applications.

Signed-off-by: Daniel Matyas <daniel.matyas@analog.com>
---
 .../bindings/hwmon/adi,max31827.yaml          | 51 +++++++++++++++++++
 MAINTAINERS                                   |  7 +++
 2 files changed, 58 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/adi,max31827.yaml

diff --git a/Documentation/devicetree/bindings/hwmon/adi,max31827.yaml b/Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
new file mode 100644
index 000000000000..37177eb9c039
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
@@ -0,0 +1,51 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/hwmon/adi,max31827.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices MAX31827, MAX31828, MAX31829 Low-Power Temperature Switch
+
+maintainers:
+  - Daniel Matyas <daniel.matyas@analog.com>
+
+description: |
+  Analog Devices MAX31827, MAX31828, MAX31829 Low-Power Temperature Switch with
+  I2C Interface
+  https://www.analog.com/media/en/technical-documentation/data-sheets/MAX31827-MAX31829.pdf
+
+properties:
+  compatible:
+    enum:
+      - adi,max31827
+      - adi,max31828
+      - adi,max31829
+

I am really sorry, but I do not understand what I should do.

Should I add oneOf or items to the compatibility property?

+  reg:
+    maxItems: 1
+
+  vref-supply:
+    description:
+      Must have values in the interval (1.6V; 3.6V) in order for the device to
+      function correctly.
+
+required:
+  - compatible
+  - reg
+  - vref-supply
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        temperature-sensor@42 {
+            compatible = "adi,max31827";
+            reg = <0x42>;
+            vref-supply = <&reg_vdd>;
+        };
+    };
+...
diff --git a/MAINTAINERS b/MAINTAINERS
index 0e64787aace8..8af1296ff1a0 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12535,6 +12535,13 @@ F:	Documentation/userspace-api/media/drivers/max2175.rst
 F:	drivers/media/i2c/max2175*
 F:	include/uapi/linux/max2175.h
 
+MAX31827 TEMPERATURE SWITCH DRIVER
+M:	Daniel Matyas <daniel.matyas@analog.com>
+L:	linux-hwmon@vger.kernel.org
+S:	Supported
+W:	http://ez.analog.com/community/linux-device-drivers
+F:	Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
+
 MAX6650 HARDWARE MONITOR AND FAN CONTROLLER DRIVER
 L:	linux-hwmon@vger.kernel.org
 S:	Orphan
-- 
2.34.1

Best regards,
Daniel

Re: Unclear what to do with compatibility

[Krzysztof Kozlowski]

On 13/04/2023 14:30, Daniel Matyas wrote:
> MAX31827 is a low-power temperature switch with I2C interface.

You sent a new patch. With a weird subject. I don't understand exactly
what is this.

> 
> The device is a ±1°C accuracy from -40°C to +125°C
> (12 bits) local temperature switch and sensor with I2C/SM-
> Bus interface. The combination of small 6-bump wafer-lev-
> el package (WLP) and high accuracy makes this temper-
> ature sensor/switch ideal for a wide range of applications.
> 
> Signed-off-by: Daniel Matyas <daniel.matyas@analog.com>
> ---
>  .../bindings/hwmon/adi,max31827.yaml          | 51 +++++++++++++++++++
>  MAINTAINERS                                   |  7 +++
>  2 files changed, 58 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
> 
> diff --git a/Documentation/devicetree/bindings/hwmon/adi,max31827.yaml b/Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
> new file mode 100644
> index 000000000000..37177eb9c039
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
> @@ -0,0 +1,51 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/hwmon/adi,max31827.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Analog Devices MAX31827, MAX31828, MAX31829 Low-Power Temperature Switch
> +
> +maintainers:
> +  - Daniel Matyas <daniel.matyas@analog.com>
> +
> +description: |
> +  Analog Devices MAX31827, MAX31828, MAX31829 Low-Power Temperature Switch with
> +  I2C Interface
> +  https://www.analog.com/media/en/technical-documentation/data-sheets/MAX31827-MAX31829.pdf
> +
> +properties:
> +  compatible:
> +    enum:
> +      - adi,max31827
> +      - adi,max31828
> +      - adi,max31829
> +
> 
> I am really sorry, but I do not understand what I should do.
> 
> Should I add oneOf or items to the compatibility property?

The devices should be marked as compatible with each other, so you can
drop useless match table entries.

https://elixir.bootlin.com/linux/v6.3-rc6/source/Documentation/devicetree/bindings/sound/nvidia,tegra210-ope.yaml#L31

and fix this in the driver.


Best regards,
Krzysztof