[PATCH v1 0/2] Add MAX22530-MAX22532 ADC Support

[PATCH v1 0/2] Add MAX22530-MAX22532 ADC Support

[Abhinav Jain]

Hello iio/maintainers,

This patch series adds initial support for the Analog Devices Maxim family
of MAX22530-MAX22532 ADCs. These are galvanically isolated, 4-channel,
multiplexed, 12-bit, analog-to-digital converters (ADC) in the MAXSafe™
family product line. An integrated, isolated, DC-DC converter powers all
fieldside circuitry, and this allows field-side diagnostics even when no
input signal is present.

The first patch adds the device tree documentation for the ADC. The DT
binding has been verified with DT_BINDING_CHECK. The second patch adds the
read functionality for raw and average ADC values from registers.

The code was tested with Raspberry Pi5 and MAX22531_EVKIT_A. With the
current driver version, it is possible to do single-shot read of ADC
sample data. On a preliminary version of the max22531 driver with
debugfs_reg_access callbacks, it was also possible to read/write from/to
different device registers and obtain the expected results.

Details of the test setup can be found at
https://wiki.analog.com/resources/tools-software/linux-drivers/iio-adc/max22531

This code was developed as part of the GSoC project for Linux
Foundation. Many thanks to my mentors Marcelo Schmitt, Ceclan Dumitru,
Jonathan Santos & Dragos Bogdan for their guidance and reviews
throughout the course of this programme.

Abhinav Jain (2):
  dt-bindings: iio: adc: Add device tree binding for MAX22531 ADC
  iio: adc: Add initial support for MAX22531 ADC

 .../bindings/iio/adc/adi,max22531.yaml        |  75 +++++++
 MAINTAINERS                                   |   8 +
 drivers/iio/adc/Kconfig                       |  10 +
 drivers/iio/adc/Makefile                      |   1 +
 drivers/iio/adc/max22531.c                    | 191 ++++++++++++++++++
 5 files changed, 285 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,max22531.yaml
 create mode 100644 drivers/iio/adc/max22531.c


base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494
-- 
2.34.1

[PATCH v1 1/2] dt-bindings: iio: adc: Add device tree binding for MAX22531 ADC

[Abhinav Jain]

Add device tree documentation for MAX22530-MAX22532 family of ADCs.
The MAX22530–MAX22532 are galvanically isolated, 4-channel, multiplexed,
12-bit, analog-to-digital converters (ADC) in the MAXSafe™ family product
line. An integrated, isolated, DC-DC converter powers all fieldside
circuitry, and this allows field-side diagnostics even when no input
signal is present.

Signed-off-by: Abhinav Jain <jain.abhinav177@gmail.com>
---
 .../bindings/iio/adc/adi,max22531.yaml        | 75 +++++++++++++++++++
 MAINTAINERS                                   |  7 ++
 2 files changed, 82 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,max22531.yaml

diff --git a/Documentation/devicetree/bindings/iio/adc/adi,max22531.yaml b/Documentation/devicetree/bindings/iio/adc/adi,max22531.yaml
new file mode 100644
index 000000000000..16bf4a1d0926
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/adi,max22531.yaml
@@ -0,0 +1,75 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright 2025 Abhinav Jain
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/adi,max22531.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices MAX22530-MAX22532 12-bit Field Isolated ADCs
+
+maintainers:
+  - Abhinav Jain <jain.abhinav177@gmail.com>
+
+description:
+  Bindings for the Analog Devices Max22530-MAX22532 Field-Side Self-Powered,
+  4-Channel, 12-bit, Isolated ADCs.
+
+  Datasheet can be found here
+    https://www.analog.com/media/en/technical-documentation/data-sheets/max22530-max22532.pdf
+
+$ref: /schemas/spi/spi-peripheral-props.yaml#
+
+properties:
+  compatible:
+    enum:
+      - adi,max22530
+      - adi,max22531
+      - adi,max22532
+
+  reg:
+    maxItems: 1
+
+  spi-max-frequency:
+    maximum: 10000000
+    description: Maximum SPI frequency (Hz)
+
+  vddl-supply:
+    description:
+      Logic power supply.
+
+  vddpl-supply:
+    description:
+      Isolated DC-DC converter power supply.
+
+  interrupts:
+    items:
+      - description: |
+          Interrupt for signaling when conversion results exceed the upper
+          threshold for ADC readings or fall below the lower threshold. The
+          interrupt source must be attached to one of COUT1 to COUT4 pins.
+      - description: |
+          Alert output that asserts low during a number of different error
+          conditions. The interrupt source must be attached to INT pin.
+
+required:
+  - compatible
+  - reg
+  - vddl-supply
+  - vddpl-supply
+
+additionalProperties: false
+
+examples:
+  - |
+    spi {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      max22531: adc@0 {
+        compatible = "adi,max22531";
+        reg = <0>;
+        spi-max-frequency = <5000000>;
+        vddl-supply = <&vddl>;
+        vddpl-supply = <&vddpl>;
+      };
+    };
diff --git a/MAINTAINERS b/MAINTAINERS
index a92290fffa16..6f26db9cf742 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14702,6 +14702,13 @@ F:	Documentation/userspace-api/media/drivers/max2175.rst
 F:	drivers/media/i2c/max2175*
 F:	include/uapi/linux/max2175.h
 
+MAX22531 ADC DRIVER
+M:	Abhinav Jain <jain.abhinav177@gmail.com>
+L:	linux-iio@vger.kernel.org
+S:	Maintained
+W:	https://ez.analog.com/linux-software-drivers
+F:	Documentation/devicetree/bindings/iio/adc/adi,max22531.yaml
+
 MAX31335 RTC DRIVER
 M:	Antoniu Miclaus <antoniu.miclaus@analog.com>
 L:	linux-rtc@vger.kernel.org
-- 
2.34.1

[PATCH v1 2/2] iio: adc: Add initial support for MAX22531 ADC

[Abhinav Jain]

Add device support for MAX22530-MAX22531.
Implement scale and read functionality for raw/filtered ADC readings.

Signed-off-by: Abhinav Jain <jain.abhinav177@gmail.com>
---
 MAINTAINERS                |   1 +
 drivers/iio/adc/Kconfig    |  10 ++
 drivers/iio/adc/Makefile   |   1 +
 drivers/iio/adc/max22531.c | 191 +++++++++++++++++++++++++++++++++++++
 4 files changed, 203 insertions(+)
 create mode 100644 drivers/iio/adc/max22531.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 6f26db9cf742..8a63faf1bde7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14708,6 +14708,7 @@ L:	linux-iio@vger.kernel.org
 S:	Maintained
 W:	https://ez.analog.com/linux-software-drivers
 F:	Documentation/devicetree/bindings/iio/adc/adi,max22531.yaml
+F:	drivers/iio/adc/max22531.c
 
 MAX31335 RTC DRIVER
 M:	Antoniu Miclaus <antoniu.miclaus@analog.com>
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index ea3ba1397392..a35c3c945e27 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -933,6 +933,16 @@ config MAX1363
 	  To compile this driver as a module, choose M here: the module will be
 	  called max1363.
 
+config MAX22531
+        tristate "Analog Devices MAX22531 ADC Driver"
+        depends on SPI
+        help
+          Say yes here to build support for field-side self-powered 12-bit
+	   isolated Maxim ADCs. (max22530, max22531, max22532).
+
+	   To compile this driver as a module, choose M here: the module will be
+	   called max22531.
+
 config MAX34408
 	tristate "Maxim max34408/max344089 ADC driver"
 	depends on I2C
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 09ae6edb2650..0429d9da571f 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -83,6 +83,7 @@ obj-$(CONFIG_MAX11205) += max11205.o
 obj-$(CONFIG_MAX11410) += max11410.o
 obj-$(CONFIG_MAX1241) += max1241.o
 obj-$(CONFIG_MAX1363) += max1363.o
+obj-$(CONFIG_MAX22531) += max22531.o
 obj-$(CONFIG_MAX34408) += max34408.o
 obj-$(CONFIG_MAX77541_ADC) += max77541-adc.o
 obj-$(CONFIG_MAX9611) += max9611.o
diff --git a/drivers/iio/adc/max22531.c b/drivers/iio/adc/max22531.c
new file mode 100644
index 000000000000..fb035225e426
--- /dev/null
+++ b/drivers/iio/adc/max22531.c
@@ -0,0 +1,191 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * MAX22531 SPI ADC Driver
+ *
+ * Copyright (C) 2025 Abhinav Jain
+ *
+ * Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/max22530-max22532.pdf
+ */
+
+#include <linux/module.h>
+#include <linux/unaligned.h>
+#include <linux/spi/spi.h>
+#include <linux/iio/iio.h>
+#include <linux/regulator/consumer.h>
+
+#define MAX22531_REG_PROD_ID		0x00
+#define MAX22531_REG_ADC_CHAN(x)	((x) + 1)
+#define MAX22531_REG_FADC_CHAN(x)	((x) + 1)
+
+#define MAX22531_VREF_MV		1800
+#define MAX22531_DEVICE_REV_MSK		GENMASK(6, 0)
+#define MAX22531_DEVICE_REV		0x01
+
+#define MAX22531_REG_ADDR_MASK		GENMASK(7, 2)
+#define MAX22531_REG_WRITE_MASK		BIT(1)
+
+enum max22531_id {
+	max22530,
+	max22531,
+	max22532,
+};
+
+struct max22531_chip_info {
+	const char *name;
+};
+
+static struct max22531_chip_info max22531_chip_info_tbl[] = {
+	[max22530] = {
+		.name = "max22530",
+	},
+	[max22531] = {
+		.name = "max22531",
+	},
+	[max22532] = {
+		.name = "max22532",
+	},
+};
+
+struct max22531 {
+	struct spi_device *spi_dev;
+	const struct max22531_chip_info *chip_info;
+};
+
+#define MAX22531_CHANNEL(ch)						\
+	{								\
+		.type = IIO_VOLTAGE,					\
+		.indexed = 1,						\
+		.channel = (ch),					\
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |		\
+				BIT(IIO_CHAN_INFO_AVERAGE_RAW),         \
+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
+	}
+
+static const struct iio_chan_spec max22531_channels[] = {
+	MAX22531_CHANNEL(0),
+	MAX22531_CHANNEL(1),
+	MAX22531_CHANNEL(2),
+	MAX22531_CHANNEL(3),
+};
+
+static int max22531_reg_read(struct max22531 *adc, unsigned int reg,
+			     unsigned int *readval)
+{
+	u8 cmd;
+
+	cmd = FIELD_PREP(MAX22531_REG_ADDR_MASK, reg);
+	*readval = spi_w8r16be(adc->spi_dev, cmd);
+	if (*readval < 0)
+		return *readval;
+
+	return 0;
+}
+
+static int max22531_read_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int *val, int *val2, long mask)
+{
+	struct max22531 *adc = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = max22531_reg_read(adc, MAX22531_REG_ADC_CHAN(chan->channel), val);
+		if (ret)
+			return ret;
+	return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_AVERAGE_RAW:
+		ret = max22531_reg_read(adc, MAX22531_REG_FADC_CHAN(chan->channel), val);
+		if (ret)
+			return ret;
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_SCALE:
+		*val = MAX22531_VREF_MV;
+		*val2 = 12;
+
+		return IIO_VAL_FRACTIONAL_LOG2;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info max22531_info = {
+	.read_raw = max22531_read_raw,
+};
+
+static int max22531_probe(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev;
+	struct max22531 *adc;
+	unsigned int prod_id;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*adc));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	adc = iio_priv(indio_dev);
+	adc->spi_dev = spi;
+	adc->chip_info = spi_get_device_match_data(spi);
+	if (!adc->chip_info)
+		return dev_err_probe(&spi->dev, -EINVAL,
+				"no chip info\n");
+
+	indio_dev->name = adc->chip_info->name;
+	indio_dev->info = &max22531_info;
+	indio_dev->channels = max22531_channels;
+	indio_dev->num_channels = ARRAY_SIZE(max22531_channels);
+
+	ret = devm_regulator_get_enable(&spi->dev, "vddl");
+	if (ret)
+		return dev_err_probe(&spi->dev, ret,
+		       "Failed to retrieve power logic supply.\n");
+
+	ret = devm_regulator_get_enable(&spi->dev, "vddpl");
+	if (ret)
+		return dev_err_probe(&spi->dev, ret,
+		       "Failed to retrieve isolated DC-DC supply.\n");
+
+	ret = max22531_reg_read(adc, MAX22531_REG_PROD_ID, &prod_id);
+	if (ret ||
+	    FIELD_GET(MAX22531_DEVICE_REV_MSK, prod_id) != MAX22531_DEVICE_REV)
+		dev_warn(&spi->dev, "PROD_ID verification failed\n");
+
+	return devm_iio_device_register(&spi->dev, indio_dev);
+}
+
+static const struct spi_device_id max22531_id[] = {
+	{ "max22530", (kernel_ulong_t)&max22531_chip_info_tbl[max22530] },
+	{ "max22531", (kernel_ulong_t)&max22531_chip_info_tbl[max22531] },
+	{ "max22532", (kernel_ulong_t)&max22531_chip_info_tbl[max22532] },
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, max22531_id);
+
+static const struct of_device_id max22531_spi_of_id[] = {
+	{ .compatible = "adi,max22530",
+		.data = &max22531_chip_info_tbl[max22530], },
+	{ .compatible = "adi,max22531",
+		.data = &max22531_chip_info_tbl[max22531], },
+	{ .compatible = "adi,max22532",
+		.data = &max22531_chip_info_tbl[max22532], },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, max22531_spi_of_id);
+
+static struct spi_driver max22531_driver = {
+	.driver = {
+		.name = "max22531",
+		.of_match_table = max22531_spi_of_id,
+	},
+	.probe		= max22531_probe,
+	.id_table	= max22531_id,
+};
+module_spi_driver(max22531_driver);
+
+MODULE_AUTHOR("Abhinav Jain <jain.abhinav177@gmail.com>");
+MODULE_DESCRIPTION("MAX22531 ADC");
+MODULE_LICENSE("GPL");
-- 
2.34.1

Re: [PATCH v1 2/2] iio: adc: Add initial support for MAX22531 ADC

[kernel test robot]

Hi Abhinav,

kernel test robot noticed the following build errors:

[auto build test ERROR on 19272b37aa4f83ca52bdf9c16d5d81bdd1354494]

url:    https://github.com/intel-lab-lkp/linux/commits/Abhinav-Jain/dt-bindings-iio-adc-Add-device-tree-binding-for-MAX22531-ADC/20250826-052702
base:   19272b37aa4f83ca52bdf9c16d5d81bdd1354494
patch link:    https://lore.kernel.org/r/edc52c93e0d4e08619ba8a98674aeb7d49e6dd1b.1756115378.git.jain.abhinav177%40gmail.com
patch subject: [PATCH v1 2/2] iio: adc: Add initial support for MAX22531 ADC
config: m68k-allyesconfig (https://download.01.org/0day-ci/archive/20250826/202508262023.u2lGZ2mB-lkp@intel.com/config)
compiler: m68k-linux-gcc (GCC) 15.1.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250826/202508262023.u2lGZ2mB-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202508262023.u2lGZ2mB-lkp@intel.com/

All errors (new ones prefixed by >>):

   drivers/iio/adc/max22531.c: In function 'max22531_reg_read':
>> drivers/iio/adc/max22531.c:76:15: error: implicit declaration of function 'FIELD_PREP' [-Wimplicit-function-declaration]
      76 |         cmd = FIELD_PREP(MAX22531_REG_ADDR_MASK, reg);
         |               ^~~~~~~~~~
   drivers/iio/adc/max22531.c: In function 'max22531_probe':
>> drivers/iio/adc/max22531.c:154:13: error: implicit declaration of function 'FIELD_GET' [-Wimplicit-function-declaration]
     154 |             FIELD_GET(MAX22531_DEVICE_REV_MSK, prod_id) != MAX22531_DEVICE_REV)
         |             ^~~~~~~~~


vim +/FIELD_PREP +76 drivers/iio/adc/max22531.c

    70	
    71	static int max22531_reg_read(struct max22531 *adc, unsigned int reg,
    72				     unsigned int *readval)
    73	{
    74		u8 cmd;
    75	
  > 76		cmd = FIELD_PREP(MAX22531_REG_ADDR_MASK, reg);
    77		*readval = spi_w8r16be(adc->spi_dev, cmd);
    78		if (*readval < 0)
    79			return *readval;
    80	
    81		return 0;
    82	}
    83	
    84	static int max22531_read_raw(struct iio_dev *indio_dev,
    85				     struct iio_chan_spec const *chan,
    86				     int *val, int *val2, long mask)
    87	{
    88		struct max22531 *adc = iio_priv(indio_dev);
    89		int ret;
    90	
    91		switch (mask) {
    92		case IIO_CHAN_INFO_RAW:
    93			ret = max22531_reg_read(adc, MAX22531_REG_ADC_CHAN(chan->channel), val);
    94			if (ret)
    95				return ret;
    96		return IIO_VAL_INT;
    97	
    98		case IIO_CHAN_INFO_AVERAGE_RAW:
    99			ret = max22531_reg_read(adc, MAX22531_REG_FADC_CHAN(chan->channel), val);
   100			if (ret)
   101				return ret;
   102			return IIO_VAL_INT;
   103	
   104		case IIO_CHAN_INFO_SCALE:
   105			*val = MAX22531_VREF_MV;
   106			*val2 = 12;
   107	
   108			return IIO_VAL_FRACTIONAL_LOG2;
   109	
   110		default:
   111			return -EINVAL;
   112		}
   113	}
   114	
   115	static const struct iio_info max22531_info = {
   116		.read_raw = max22531_read_raw,
   117	};
   118	
   119	static int max22531_probe(struct spi_device *spi)
   120	{
   121		struct iio_dev *indio_dev;
   122		struct max22531 *adc;
   123		unsigned int prod_id;
   124		int ret;
   125	
   126		indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*adc));
   127		if (!indio_dev)
   128			return -ENOMEM;
   129	
   130		adc = iio_priv(indio_dev);
   131		adc->spi_dev = spi;
   132		adc->chip_info = spi_get_device_match_data(spi);
   133		if (!adc->chip_info)
   134			return dev_err_probe(&spi->dev, -EINVAL,
   135					"no chip info\n");
   136	
   137		indio_dev->name = adc->chip_info->name;
   138		indio_dev->info = &max22531_info;
   139		indio_dev->channels = max22531_channels;
   140		indio_dev->num_channels = ARRAY_SIZE(max22531_channels);
   141	
   142		ret = devm_regulator_get_enable(&spi->dev, "vddl");
   143		if (ret)
   144			return dev_err_probe(&spi->dev, ret,
   145			       "Failed to retrieve power logic supply.\n");
   146	
   147		ret = devm_regulator_get_enable(&spi->dev, "vddpl");
   148		if (ret)
   149			return dev_err_probe(&spi->dev, ret,
   150			       "Failed to retrieve isolated DC-DC supply.\n");
   151	
   152		ret = max22531_reg_read(adc, MAX22531_REG_PROD_ID, &prod_id);
   153		if (ret ||
 > 154		    FIELD_GET(MAX22531_DEVICE_REV_MSK, prod_id) != MAX22531_DEVICE_REV)
   155			dev_warn(&spi->dev, "PROD_ID verification failed\n");
   156	
   157		return devm_iio_device_register(&spi->dev, indio_dev);
   158	}
   159	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v1 1/2] dt-bindings: iio: adc: Add device tree binding for MAX22531 ADC

[Conor Dooley]

[-- Attachment #1: Type: text/plain, Size: 2094 bytes --]

On Tue, Aug 26, 2025 at 02:55:24AM +0530, Abhinav Jain wrote:
> Add device tree documentation for MAX22530-MAX22532 family of ADCs.
> The MAX22530–MAX22532 are galvanically isolated, 4-channel, multiplexed,
> 12-bit, analog-to-digital converters (ADC) in the MAXSafe™ family product
> line. An integrated, isolated, DC-DC converter powers all fieldside
> circuitry, and this allows field-side diagnostics even when no input
> signal is present.
> 
> Signed-off-by: Abhinav Jain <jain.abhinav177@gmail.com>
> ---
>  .../bindings/iio/adc/adi,max22531.yaml        | 75 +++++++++++++++++++
>  MAINTAINERS                                   |  7 ++
>  2 files changed, 82 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,max22531.yaml
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,max22531.yaml b/Documentation/devicetree/bindings/iio/adc/adi,max22531.yaml
> new file mode 100644
> index 000000000000..16bf4a1d0926
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/adi,max22531.yaml
> @@ -0,0 +1,75 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +# Copyright 2025 Abhinav Jain
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/adc/adi,max22531.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Analog Devices MAX22530-MAX22532 12-bit Field Isolated ADCs
> +
> +maintainers:
> +  - Abhinav Jain <jain.abhinav177@gmail.com>
> +
> +description:
> +  Bindings for the Analog Devices Max22530-MAX22532 Field-Side Self-Powered,
> +  4-Channel, 12-bit, Isolated ADCs.
> +
> +  Datasheet can be found here
> +    https://www.analog.com/media/en/technical-documentation/data-sheets/max22530-max22532.pdf
> +
> +$ref: /schemas/spi/spi-peripheral-props.yaml#
> +
> +properties:
> +  compatible:
> +    enum:
> +      - adi,max22530
> +      - adi,max22531
> +      - adi,max22532

Generally this looks okay to me, but I would like you to mention what it
is that makes a fallback between these impossible in your commit
message. 

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Re: [PATCH v1 1/2] dt-bindings: iio: adc: Add device tree binding for MAX22531 ADC

[Krzysztof Kozlowski]

On 25/08/2025 23:25, Abhinav Jain wrote:
> Add device tree documentation for MAX22530-MAX22532 family of ADCs.
> The MAX22530–MAX22532 are galvanically isolated, 4-channel, multiplexed,
> 12-bit, analog-to-digital converters (ADC) in the MAXSafe™ family product
> line. An integrated, isolated, DC-DC converter powers all fieldside
> circuitry, and this allows field-side diagnostics even when no input
> signal is present.
> 
> Signed-off-by: Abhinav Jain <jain.abhinav177@gmail.com>


Please do not develop on old trees. You need to rebase your patchset and
test it on latest mainline kernel.

You CC-ed an address, which suggests you do not work on mainline kernel
or you do not use get_maintainers.pl/b4/patman. Please rebase and always
work on mainline or start using mentioned tools, so correct addresses
will be used.


Best regards,
Krzysztof

Re: [PATCH v1 2/2] iio: adc: Add initial support for MAX22531 ADC

[Jonathan Cameron]

On Tue, 26 Aug 2025 02:55:49 +0530
Abhinav Jain <jain.abhinav177@gmail.com> wrote:

> Add device support for MAX22530-MAX22531.
> Implement scale and read functionality for raw/filtered ADC readings.
> 
> Signed-off-by: Abhinav Jain <jain.abhinav177@gmail.com>
Hi Abhinav,

A few minor style related things and one question on FADC registers address.

Thanks,

Jonathan

>  M:	Antoniu Miclaus <antoniu.miclaus@analog.com>
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index ea3ba1397392..a35c3c945e27 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -933,6 +933,16 @@ config MAX1363
>  	  To compile this driver as a module, choose M here: the module will be
>  	  called max1363.
>  
> +config MAX22531
> +        tristate "Analog Devices MAX22531 ADC Driver"
> +        depends on SPI
> +        help
> +          Say yes here to build support for field-side self-powered 12-bit
> +	   isolated Maxim ADCs. (max22530, max22531, max22532).
Use a list
	  - max22530
	  - max22531
etc
because it means new parts being added create less fuzz.  We've gotten this wrong
in far too many drivers and ended up with messier follow up series as a result!

> +
> +	   To compile this driver as a module, choose M here: the module will be
> +	   called max22531.
Should be tab index + 2 spaces for whole help block. 
> +

> diff --git a/drivers/iio/adc/max22531.c b/drivers/iio/adc/max22531.c
> new file mode 100644
> index 000000000000..fb035225e426
> --- /dev/null
> +++ b/drivers/iio/adc/max22531.c
> @@ -0,0 +1,191 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * MAX22531 SPI ADC Driver
> + *
> + * Copyright (C) 2025 Abhinav Jain
> + *
> + * Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/max22530-max22532.pdf
> + */
> +
> +#include <linux/module.h>
> +#include <linux/unaligned.h>
> +#include <linux/spi/spi.h>
> +#include <linux/iio/iio.h>
> +#include <linux/regulator/consumer.h>

As per the build bot report, there are some headers that want to be here and
aren't. In general aim for following Include What You Use IWYU principles
for kernel code, subject to some fuzz around headers that are always used via
an other one.

> +
> +#define MAX22531_REG_PROD_ID		0x00
> +#define MAX22531_REG_ADC_CHAN(x)	((x) + 1)
> +#define MAX22531_REG_FADC_CHAN(x)	((x) + 1)

I'm confused. Why the same registers for both of these?  If they really
are the same, perhaps one macro is enough.

> +
> +#define MAX22531_VREF_MV		1800
> +#define MAX22531_DEVICE_REV_MSK		GENMASK(6, 0)
> +#define MAX22531_DEVICE_REV		0x01
> +
> +#define MAX22531_REG_ADDR_MASK		GENMASK(7, 2)
> +#define MAX22531_REG_WRITE_MASK		BIT(1)
> +
> +enum max22531_id {
> +	max22530,
> +	max22531,
> +	max22532,
> +};
> +
> +struct max22531_chip_info {
> +	const char *name;
> +};
> +
> +static struct max22531_chip_info max22531_chip_info_tbl[] = {
> +	[max22530] = {
> +		.name = "max22530",
> +	},
> +	[max22531] = {
> +		.name = "max22531",
> +	},
> +	[max22532] = {
> +		.name = "max22532",
> +	},
> +};

See below for reasoning. Split these into separate structures rather
than an array.

> +static int max22531_reg_read(struct max22531 *adc, unsigned int reg,
> +			     unsigned int *readval)
> +{
> +	u8 cmd;
> +
> +	cmd = FIELD_PREP(MAX22531_REG_ADDR_MASK, reg);
> +	*readval = spi_w8r16be(adc->spi_dev, cmd);

Rather than having side effect of leaving a negative in *readval, use
a local variable and only assign readval if all is good.

> +	if (*readval < 0)
> +		return *readval;
> +
> +	return 0;
> +}

> +static int max22531_probe(struct spi_device *spi)
> +{

> +	ret = max22531_reg_read(adc, MAX22531_REG_PROD_ID, &prod_id);
> +	if (ret ||
A failure to read is a bug that we should fail on, whereas the value
read not matching is indeed something were a warn or info makes sense.
So split this check 
	if (ret)
		return ret;

	if (FIELD_GET()...
		dev_warn

> +	    FIELD_GET(MAX22531_DEVICE_REV_MSK, prod_id) != MAX22531_DEVICE_REV)
> +		dev_warn(&spi->dev, "PROD_ID verification failed\n");
> +
> +	return devm_iio_device_register(&spi->dev, indio_dev);
> +}
> +
> +static const struct spi_device_id max22531_id[] = {
> +	{ "max22530", (kernel_ulong_t)&max22531_chip_info_tbl[max22530] },
> +	{ "max22531", (kernel_ulong_t)&max22531_chip_info_tbl[max22531] },
> +	{ "max22532", (kernel_ulong_t)&max22531_chip_info_tbl[max22532] },

Whilst this style used to be common, over time we've come to the conclusion
that an indexed array for these doesn't bring value. Instead
just have separate structures with names that indicate which chip they
are for.  max22532_chip_info etc  That allows the enum to be dropped which
has the advantage of removing the temptation to use it for anything else
(which is usually a bad idea)

> +	{ }
> +};
> +MODULE_DEVICE_TABLE(spi, max22531_id);
> +
> +static const struct of_device_id max22531_spi_of_id[] = {
> +	{ .compatible = "adi,max22530",
> +		.data = &max22531_chip_info_tbl[max22530], },
> +	{ .compatible = "adi,max22531",
> +		.data = &max22531_chip_info_tbl[max22531], },
> +	{ .compatible = "adi,max22532",
> +		.data = &max22531_chip_info_tbl[max22532], },
> +	{ }