[PATCH 0/3] Subject: [PATCH v1 0/3] iio: dac: Add support for MAX22007 DAC

[PATCH 0/3] Subject: [PATCH v1 0/3] iio: dac: Add support for MAX22007 DAC

[Janani Sunil]

This patch series introduces support for the Analog Devices MAX22007, a
quad-channel, 12-bit digital-to-analog converter (DAC) with integrated
precision output amplifiers and configurable voltage/current output capability.

**Device Overview:**
The MAX22007 features four independent DAC channels that can each be configured
for either voltage output (0-12.5V) or current output (0-25mA) mode. The device
communicates via SPI interface with built-in CRC8 error checking for data integrity.

**Features Implemented:**
- Support for all 4 DAC channels with 12-bit resolution
- Per-channel voltage/current mode configuration via device tree
  property `adi,type = [voltage, current]`
- Independent power control for each channel (attribute)
- Hardware reset support via GPIO (during probe)
- CRC8 error checking for SPI communication

**Patch Summary:**
1. dt-bindings: Binding documentation with channel configuration
2. documentation: Driver documentation with usage examples
3. driver: Implement IIO DAC driver

**Testing:**
The driver was hardware tested on a Raspberry Pi4 on top of v6.12.y
kernel using the MAX22007EVKIT evaluation board.

Janani Sunil (3):
dt-bindings: iio: dac: Add max22007
iio: dac: Add MAX22007 DAC driver support
docs: iio: Add documentation for MAX22007 driver

.../bindings/iio/dac/adi,max22007.yaml       | 117 ++++
   Documentation/iio/index.rst                  |   1 +
   Documentation/iio/max22007.rst                | 170 ++++++
   drivers/iio/dac/Kconfig                       |  12 +
   drivers/iio/dac/Makefile                      |   1 +
   drivers/iio/dac/max22007.c                    | 522 ++++++++++++++++++
   6 files changed, 823 insertions(+)
   create mode 100644 Documentation/devicetree/bindings/iio/dac/adi,max22007.yaml
   create mode 100644 Documentation/iio/max22007.rst
   create mode 100644 drivers/iio/dac/max22007.c

---
To: Lars-Peter Clausen <lars@metafoo.de>
To: Michael Hennerich <Michael.Hennerich@analog.com>
To: Alexandru Ardelean <alexandru.ardelean@analog.com>
To: Jonathan Cameron <jic23@kernel.org>
To: Rob Herring <robh@kernel.org>
To: Krzysztof Kozlowski <krzk+dt@kernel.org>
To: Conor Dooley <conor+dt@kernel.org>
To: Jonathan Corbet <corbet@lwn.net>
Cc: linux-iio@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Signed-off-by: Janani Sunil <janani.sunil@analog.com>

---
Janani Sunil (3):
      dt-bindings: iio: dac: Add max22007
      docs: iio: Add documentation for MAX22007 driver
      iio: dac: Add MAX22007 DAC driver support

 .../devicetree/bindings/iio/dac/adi,max22007.yaml  | 116 +++++
 Documentation/iio/index.rst                        |   1 +
 Documentation/iio/max22007.rst                     | 145 ++++++
 MAINTAINERS                                        |   9 +
 drivers/iio/dac/Kconfig                            |  13 +
 drivers/iio/dac/Makefile                           |   1 +
 drivers/iio/dac/max22007.c                         | 487 +++++++++++++++++++++
 7 files changed, 772 insertions(+)
---
base-commit: a7b10f0963c651a6406d958a5f64b9c5594f84da
change-id: 20251219-max22007-dev-1aaf08db7890

Best regards,
-- 
Janani Sunil <janani.sunil@analog.com>

[PATCH 1/3] dt-bindings: iio: dac: Add max22007

[Janani Sunil]

Devicetree bindings for MAX22007 4-channel
12-bit DAC that drives a voltage or current
output on each channel

Signed-off-by: Janani Sunil <janani.sunil@analog.com>
---
 .../devicetree/bindings/iio/dac/adi,max22007.yaml  | 116 +++++++++++++++++++++
 MAINTAINERS                                        |   7 ++
 2 files changed, 123 insertions(+)

diff --git a/Documentation/devicetree/bindings/iio/dac/adi,max22007.yaml b/Documentation/devicetree/bindings/iio/dac/adi,max22007.yaml
new file mode 100644
index 000000000000..c2f65d9e42d4
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/dac/adi,max22007.yaml
@@ -0,0 +1,116 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/dac/adi,max22007.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices MAX22007 DAC device driver
+
+maintainers:
+  - Janani Sunil <janani.sunil@analog.com>
+
+description:
+  The MAX22007 is a quad-channel, 12-bit digital-to-analog converter (DAC)
+  with integrated precision output amplifiers and current output capability.
+  Each channel can be independently configured for voltage or current output.
+  Datasheet available at https://www.analog.com/en/products/max22007.html
+
+$ref: /schemas/spi/spi-peripheral-props.yaml#
+
+properties:
+  compatible:
+    const: adi,max22007
+
+  reg:
+    maxItems: 1
+
+  spi-max-frequency:
+    maximum: 500000
+
+  '#address-cells':
+    const: 1
+
+  '#size-cells':
+    const: 0
+
+  vdd-supply:
+    description: Low-Voltage Power Supply from +2.7V to +5.5V.
+
+  hvdd-supply:
+    description:
+      Positive High-Voltage Power Supply from +8V to (HVSS +24V) for
+      the Output Channels.
+
+  hvss-supply:
+    description:
+      Negative High-Voltage Power Supply from -2V to 0V for the Output Channels.
+
+  reset-gpios:
+    maxItems: 1
+    description:
+      GPIO used for hardware reset of the device.
+
+patternProperties:
+  "^channel@[0-3]$":
+    allOf:
+      - $ref: /schemas/iio/dac/dac.yaml#
+      - type: object
+        description:
+          Represents the external channels which are connected to the DAC.
+          Channels not specified in the device tree will be powered off.
+
+        properties:
+          reg:
+            description: Channel number
+            maxItems: 1
+
+          adi,type:
+            description: Channel output type.
+            $ref: /schemas/types.yaml#/definitions/string
+            enum: [voltage, current]
+
+        required:
+          - reg
+          - adi,type
+
+        unevaluatedProperties: false
+
+required:
+  - compatible
+  - reg
+
+anyOf:
+  - required: [channel@0]
+  - required: [channel@1]
+  - required: [channel@2]
+  - required: [channel@3]
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        dac@0 {
+            compatible = "adi,max22007";
+            reg = <0>;
+            spi-max-frequency = <500000>;
+            reset-gpios = <&gpio 19 GPIO_ACTIVE_LOW>;
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            channel@0 {
+                reg = <0>;
+                adi,type = "voltage";
+            };
+
+            channel@1 {
+                reg = <1>;
+                adi,type = "current";
+            };
+        };
+    };
+...
diff --git a/MAINTAINERS b/MAINTAINERS
index 29340394ac9d..e1addbd21562 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1593,6 +1593,13 @@ W:	https://ez.analog.com/linux-software-drivers
 F:	Documentation/devicetree/bindings/iio/dac/adi,ad9739a.yaml
 F:	drivers/iio/dac/ad9739a.c
 
+ANALOG DEVICES INC MAX22007 DRIVER
+M:	Janani Sunil <janani.sunil@analog.com>
+L:	linux-iio@vger.kernel.org
+S:	Supported
+W:	https://ez.analog.com/linux-software-drivers
+F:	Documentation/devicetree/bindings/iio/dac/adi,max22007.yaml
+
 ANALOG DEVICES INC ADA4250 DRIVER
 M:	Antoniu Miclaus <antoniu.miclaus@analog.com>
 L:	linux-iio@vger.kernel.org

-- 
2.43.0

[PATCH 2/3] docs: iio: Add documentation for MAX22007 driver

[Janani Sunil]

Add documentation for MAX22007 driver which describes how the user
can access the driver using dtoverlays

Signed-off-by: Janani Sunil <janani.sunil@analog.com>
---
 Documentation/iio/index.rst    |   1 +
 Documentation/iio/max22007.rst | 145 +++++++++++++++++++++++++++++++++++++++++
 MAINTAINERS                    |   1 +
 3 files changed, 147 insertions(+)

diff --git a/Documentation/iio/index.rst b/Documentation/iio/index.rst
index 315ae37d6fd4..7601bc2882e7 100644
--- a/Documentation/iio/index.rst
+++ b/Documentation/iio/index.rst
@@ -37,4 +37,5 @@ Industrial I/O Kernel Drivers
    adxl345
    bno055
    ep93xx_adc
+   max22007
    opt4060
diff --git a/Documentation/iio/max22007.rst b/Documentation/iio/max22007.rst
new file mode 100644
index 000000000000..e04c563f1fd0
--- /dev/null
+++ b/Documentation/iio/max22007.rst
@@ -0,0 +1,145 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+
+===============
+MAX22007 driver
+===============
+
+Device driver for Analog Devices Inc. MAX22007 quad-channel industrial DAC.
+The module name is ``max22007``.
+
+Supported devices
+=================
+
+* `MAX22007 <https://www.analog.com/en/products/max22007.html>`_
+
+Wiring connections
+==================
+
+The MAX22007 uses a standard SPI interface.
+
+Device Tree Configuration
+=========================
+
+The device supports both global and per-channel configuration through device tree.
+
+Global Properties:
+
+* ``reset-gpios``: GPIO pin for hardware reset (optional, falls back to
+  software reset if not specified)
+* ``vdd-supply``: Low-Voltage Power Supply from +2.7V to +5.5V (optional)
+* ``hvdd-supply``: Positive High-Voltage Power Supply from +8V to (HVSS +24V)
+  for the Output Channels (optional)
+* ``hvss-supply``: Negative High-Voltage Power Supply from -2V to 0V for the
+  Output Channels (optional)
+
+Per-channel properties:
+
+* ``adi,type``: Specify the channel output type - must be either "voltage" or "current" (mandatory)
+
+Note: The driver operates in transparent mode (immediate register-to-output updates).
+Channel mode is determined by the ``adi,type`` property:
+
+* ``adi,type = "current"``: the channel operates in current mode
+* ``adi,type = "voltage"``: the channel operates in voltage mode
+
+Device attributes
+=================
+
+The MAX22007 driver provides IIO DAC interfaces that vary based on the
+configured channel mode. Each channel appears as a separate IIO device
+attribute:
+
+* ``out_voltage_raw`` (voltage mode channels)
+* ``out_current_raw`` (current mode channels)
+* ``out_voltage_scale`` / ``out_current_scale`` (channel scaling factors)
+* ``out_voltage_powerdown`` / ``out_current_powerdown`` (channel power control)
+
+The driver automatically configures the IIO channel type based on the configured
+channel mode from device tree.
+
+Power Mode Control
+==================
+
+Each channel provides standard IIO ``powerdown`` attributes for runtime power
+control:
+
+* Write ``1`` to power down (disable) the channel output
+* Write ``0`` to power up (enable) the channel output
+* Read the attribute to get the current power state (1=powered down, 0=powered up)
+
+This allows individual channels to be powered on/off independently for power
+management and safety purposes.
+
+Usage Examples
+==============
+
+Setting DAC output values:
+
+.. code-block:: bash
+
+   # Set channel 0 (voltage mode) to raw value 655 (≈2V)
+   # Output is updated immediately in transparent mode
+   echo 655 > /sys/bus/iio/devices/iio:deviceX/out_voltage0_raw
+
+   # Set channel 1 (current mode)
+   # Output is updated immediately in transparent mode
+   echo 1024 > /sys/bus/iio/devices/iio:deviceX/out_current1_raw
+
+Controlling channel power modes:
+
+.. code-block:: bash
+
+   # Enable channel 0 (power up)
+   echo 0 > /sys/bus/iio/devices/iio:deviceX/out_voltage0_powerdown
+
+   # Disable channel 1 (power down)
+   echo 1 > /sys/bus/iio/devices/iio:deviceX/out_current1_powerdown
+
+   # Check current power state (0=powered up, 1=powered down)
+   cat /sys/bus/iio/devices/iio:deviceX/out_voltage0_powerdown
+
+Reading channel values and scale factors:
+
+.. code-block:: bash
+
+   # Read raw DAC value
+   cat /sys/bus/iio/devices/iio:deviceX/out_voltage0_raw
+
+   # Read scale factor (volts per LSB)
+   cat /sys/bus/iio/devices/iio:deviceX/out_voltage0_scale
+
+Check available channels:
+
+.. code-block:: bash
+
+   ls /sys/bus/iio/devices/iio:deviceX/out_*_raw
+
+Scale Calculations
+==================
+
+The driver provides accurate scale factors based on the hardware configuration:
+
+**Voltage Mode:**
+
+- Scale = (5 × 2.5V) / 4096 = 0.003051757 V per LSB
+- Range: 0V to 12.5V over 12-bit (0-4095)
+- Formula: Output = Raw_Value × Scale
+
+**Current Mode:**
+
+- Scale = (2.5V / (2 × 50Ω)) / 4096 = 0.000006103515625 A per LSB
+- Range: 0A to 0.025A over 12-bit (0-4095)
+- Formula: Output = Raw_Value × Scale
+
+Driver Architecture
+===================
+
+The driver implements:
+
+* **CRC8 Error Checking**: Always-enabled CRC8 for SPI data integrity
+* **Channel Configuration**: Supports per-channel mode and power configuration
+
+Channel configuration (voltage/current mode) is set via the ``adi,type``
+device tree property and cannot be changed dynamically The driver requires
+proper device tree configuration with mandatory ``adi,type`` property for each
+channel.
diff --git a/MAINTAINERS b/MAINTAINERS
index e1addbd21562..6561455732c9 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1599,6 +1599,7 @@ L:	linux-iio@vger.kernel.org
 S:	Supported
 W:	https://ez.analog.com/linux-software-drivers
 F:	Documentation/devicetree/bindings/iio/dac/adi,max22007.yaml
+F:	Documentation/iio/max22007.rst
 
 ANALOG DEVICES INC ADA4250 DRIVER
 M:	Antoniu Miclaus <antoniu.miclaus@analog.com>

-- 
2.43.0

[PATCH 3/3] iio: dac: Add MAX22007 DAC driver support

[Janani Sunil]

Add support for the MAX22007 4 channel DAC
that drives a voltage or current output on each channel.

Signed-off-by: Janani Sunil <janani.sunil@analog.com>
---
 MAINTAINERS                |   1 +
 drivers/iio/dac/Kconfig    |  13 ++
 drivers/iio/dac/Makefile   |   1 +
 drivers/iio/dac/max22007.c | 487 +++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 502 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 6561455732c9..7efd5cf98023 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1600,6 +1600,7 @@ S:	Supported
 W:	https://ez.analog.com/linux-software-drivers
 F:	Documentation/devicetree/bindings/iio/dac/adi,max22007.yaml
 F:	Documentation/iio/max22007.rst
+F:	drivers/iio/dac/max22007.c
 
 ANALOG DEVICES INC ADA4250 DRIVER
 M:	Antoniu Miclaus <antoniu.miclaus@analog.com>
diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
index 7cd3caec1262..4a31993f5b14 100644
--- a/drivers/iio/dac/Kconfig
+++ b/drivers/iio/dac/Kconfig
@@ -482,6 +482,19 @@ config MAX517
 	  This driver can also be built as a module.  If so, the module
 	  will be called max517.
 
+config MAX22007
+	tristate "Analog Devices MAX22007 DAC Driver"
+	depends on SPI
+	select REGMAP_SPI
+	select CRC8
+	help
+	  Say Y here if you want to build a driver for Analog Devices MAX22007.
+
+	  MAX22007 is a quad-channel, 12-bit, voltage-output digital to
+	  analog converter (DAC) with SPI interface.
+
+	  If compiled as a module, it will be called max22007.
+
 config MAX5522
 	tristate "Maxim MAX5522 DAC driver"
 	depends on SPI_MASTER
diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
index e6ac4c67e337..0bbc6d09d22c 100644
--- a/drivers/iio/dac/Makefile
+++ b/drivers/iio/dac/Makefile
@@ -48,6 +48,7 @@ obj-$(CONFIG_LTC2664) += ltc2664.o
 obj-$(CONFIG_LTC2688) += ltc2688.o
 obj-$(CONFIG_M62332) += m62332.o
 obj-$(CONFIG_MAX517) += max517.o
+obj-$(CONFIG_MAX22007) += max22007.o
 obj-$(CONFIG_MAX5522) += max5522.o
 obj-$(CONFIG_MAX5821) += max5821.o
 obj-$(CONFIG_MCP4725) += mcp4725.o
diff --git a/drivers/iio/dac/max22007.c b/drivers/iio/dac/max22007.c
new file mode 100644
index 000000000000..0d57fee27367
--- /dev/null
+++ b/drivers/iio/dac/max22007.c
@@ -0,0 +1,487 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * max22007.c - MAX22007 DAC driver
+ *
+ * Driver for Analog Devices MAX22007 Digital to Analog Converter.
+ *
+ * Copyright (c) 2025 Analog Devices Inc.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bits.h>
+#include <linux/crc8.h>
+#include <linux/dev_printk.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/gpio/consumer.h>
+#include <linux/iio/iio.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+#include <linux/spi/spi.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/unaligned.h>
+
+#define MAX22007_NUM_CHANNELS				4
+#define MAX22007_REV_ID_REG				0x00
+#define MAX22007_STAT_INTR_REG				0x01
+#define MAX22007_INTERRUPT_EN_REG			0x02
+#define MAX22007_CONFIG_REG				0x03
+#define MAX22007_CONTROL_REG				0x04
+#define MAX22007_CHANNEL_MODE_REG			0x05
+#define MAX22007_SOFT_RESET_REG				0x06
+#define MAX22007_DAC_CHANNEL_REG(ch)			(0x07 + (ch))
+#define MAX22007_GPIO_CTRL_REG				0x0B
+#define MAX22007_GPIO_DATA_REG				0x0C
+#define MAX22007_GPI_EDGE_INT_CTRL_REG			0x0D
+#define MAX22007_GPI_INT_STATUS_REG			0x0E
+
+/* Channel mask definitions */
+#define     MAX22007_CH_MODE_CH_MASK(channel)		BIT(12 + (channel))
+#define     MAX22007_CH_PWR_CH_MASK(channel)		BIT(8 + (channel))
+#define     MAX22007_DAC_LATCH_MODE_MASK(channel)	BIT(12 + (channel))
+#define     MAX22007_LDAC_UPDATE_MASK(channel)		BIT(12 + (channel))
+#define     MAX22007_SW_RST_MASK			BIT(8)
+#define     MAX22007_SW_CLR_MASK			BIT(12)
+#define     MAX22007_SOFT_RESET_BITS_MASK		(MAX22007_SW_RST_MASK | \
+	    MAX22007_SW_CLR_MASK)
+#define     MAX22007_DAC_DATA_MASK			GENMASK(15, 4)
+#define     MAX22007_DAC_MAX_RAW			GENMASK(11, 0)
+#define     MAX22007_CRC8_POLYNOMIAL			0x8C
+#define     MAX22007_CRC_EN_MASK			BIT(0)
+#define     MAX22007_RW_MASK				BIT(0)
+#define     MAX22007_CRC_OVERHEAD			1
+
+/* Field value preparation macros with masking */
+#define     MAX22007_CH_PWR_VAL(channel, val)	(((val) & 0x1) << (8 + (channel)))
+#define     MAX22007_CH_MODE_VAL(channel, val)	(((val) & 0x1) << (12 + (channel)))
+#define     MAX22007_DAC_LATCH_MODE_VAL(channel, val)	(((val) & 0x1) << (12 + (channel)))
+
+static u8 max22007_crc8_table[256];
+
+enum max22007_channel_mode {
+	MAX22007_VOLTAGE_MODE,
+	MAX22007_CURRENT_MODE
+};
+
+enum max22007_channel_power {
+	MAX22007_CH_POWER_OFF,
+	MAX22007_CH_POWER_ON,
+};
+
+struct max22007_state {
+	struct spi_device *spi;
+	struct regmap *regmap;
+	struct iio_chan_spec *iio_chan;
+	u8 tx_buf[4] __aligned(IIO_DMA_MINALIGN);
+	u8 rx_buf[4];
+};
+
+static int max22007_spi_read(void *context, const void *reg, size_t reg_size,
+			     void *val, size_t val_size)
+{
+	struct max22007_state *st = context;
+	u8 calculated_crc, received_crc;
+	u8 crc_data[3];
+	int ret;
+	struct spi_transfer xfer = {
+		.tx_buf = st->tx_buf,
+		.rx_buf = st->rx_buf,
+	};
+
+	xfer.len = reg_size + val_size + MAX22007_CRC_OVERHEAD;
+
+	memcpy(st->tx_buf, reg, reg_size);
+
+	ret = spi_sync_transfer(st->spi, &xfer, 1);
+	if (ret) {
+		dev_err(&st->spi->dev, "SPI transfer failed: %d\n", ret);
+		return ret;
+	}
+
+	crc_data[0] = st->tx_buf[0];
+	crc_data[1] = st->rx_buf[1];
+	crc_data[2] = st->rx_buf[2];
+
+	calculated_crc = crc8(max22007_crc8_table, crc_data, 3, 0x00);
+	received_crc = st->rx_buf[3];
+
+	if (calculated_crc != received_crc) {
+		dev_err(&st->spi->dev, "CRC mismatch on read register %02x:\n", *(u8 *)reg);
+		return -EIO;
+	}
+
+	/* Ignore the dummy byte 0 */
+	memcpy(val, &st->rx_buf[1], val_size);
+
+	return 0;
+}
+
+static int max22007_spi_write(void *context, const void *data, size_t count)
+{
+	struct max22007_state *st = context;
+	struct spi_transfer xfer = {
+		.tx_buf = st->tx_buf,
+		.rx_buf = st->rx_buf,
+	};
+
+	memset(st->tx_buf, 0, sizeof(st->tx_buf));
+
+	xfer.len = count + MAX22007_CRC_OVERHEAD;
+
+	memcpy(st->tx_buf, data, count);
+	st->tx_buf[count] = crc8(max22007_crc8_table, st->tx_buf,
+				 sizeof(st->tx_buf) - 1, 0x00);
+
+	return spi_sync_transfer(st->spi, &xfer, 1);
+}
+
+static bool max22007_reg_readable(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case MAX22007_REV_ID_REG:
+	case MAX22007_STAT_INTR_REG:
+	case MAX22007_CONFIG_REG:
+	case MAX22007_CONTROL_REG:
+	case MAX22007_CHANNEL_MODE_REG:
+	case MAX22007_SOFT_RESET_REG:
+	case MAX22007_GPIO_CTRL_REG:
+	case MAX22007_GPIO_DATA_REG:
+	case MAX22007_GPI_EDGE_INT_CTRL_REG:
+	case MAX22007_GPI_INT_STATUS_REG:
+		return true;
+	case MAX22007_DAC_CHANNEL_REG(0) ... MAX22007_DAC_CHANNEL_REG(MAX22007_NUM_CHANNELS - 1):
+		return true;
+	default:
+		return false;
+	}
+}
+
+static bool max22007_reg_writable(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case MAX22007_CONFIG_REG:
+	case MAX22007_CONTROL_REG:
+	case MAX22007_CHANNEL_MODE_REG:
+	case MAX22007_SOFT_RESET_REG:
+	case MAX22007_GPIO_CTRL_REG:
+	case MAX22007_GPIO_DATA_REG:
+	case MAX22007_GPI_EDGE_INT_CTRL_REG:
+		return true;
+	case MAX22007_DAC_CHANNEL_REG(0) ... MAX22007_DAC_CHANNEL_REG(MAX22007_NUM_CHANNELS - 1):
+		return true;
+	default:
+		return false;
+	}
+}
+
+static const struct regmap_bus max22007_regmap_bus = {
+	.read = max22007_spi_read,
+	.write = max22007_spi_write,
+	.read_flag_mask = MAX22007_RW_MASK,
+	.reg_format_endian_default = REGMAP_ENDIAN_BIG,
+	.val_format_endian_default = REGMAP_ENDIAN_BIG,
+};
+
+static const struct regmap_config max22007_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 16,
+	.reg_shift = -1,
+	.readable_reg = max22007_reg_readable,
+	.writeable_reg = max22007_reg_writable,
+	.max_register = 0x0E,
+};
+
+static int max22007_write_channel_data(struct max22007_state *state, unsigned int channel,
+				       unsigned int data)
+{
+	unsigned int reg_val;
+
+	if (data > MAX22007_DAC_MAX_RAW)
+		return -EINVAL;
+
+	reg_val = FIELD_PREP(MAX22007_DAC_DATA_MASK, data);
+
+	return regmap_write(state->regmap, MAX22007_DAC_CHANNEL_REG(channel), reg_val);
+}
+
+static int max22007_read_channel_data(struct max22007_state *state, unsigned int channel,
+				      int *data)
+{
+	int ret;
+	unsigned int reg_val;
+
+	ret = regmap_read(state->regmap, MAX22007_DAC_CHANNEL_REG(channel), &reg_val);
+	if (ret)
+		return ret;
+
+	*data = FIELD_GET(MAX22007_DAC_DATA_MASK, reg_val);
+
+	return 0;
+}
+
+static int max22007_read_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int *val, int *val2, long mask)
+{
+	struct max22007_state *st = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = max22007_read_channel_data(st, chan->channel, val);
+		if (ret)
+			return ret;
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		if (chan->type == IIO_VOLTAGE) {
+			*val = 5 * 2500;  /* 5 * Vref(2.5V) in mV */
+			*val2 = 12;  /* 12-bit DAC resolution (2^12) */
+		} else {
+			*val = 25;  /* Vref / (2 * Rsense) = 2500mV / 100 */
+			*val2 = 12;  /* 12-bit DAC resolution (2^12) */
+		}
+		return IIO_VAL_FRACTIONAL_LOG2;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int max22007_write_raw(struct iio_dev *indio_dev,
+			      struct iio_chan_spec const *chan,
+			      int val, int val2, long mask)
+{
+	struct max22007_state *st = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		return max22007_write_channel_data(st, chan->channel, val);
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info max22007_info = {
+	.read_raw = max22007_read_raw,
+	.write_raw = max22007_write_raw,
+};
+
+static ssize_t max22007_read_dac_powerdown(struct iio_dev *indio_dev,
+					   uintptr_t private,
+					   const struct iio_chan_spec *chan,
+					   char *buf)
+{
+	struct max22007_state *st = iio_priv(indio_dev);
+	unsigned int reg_val;
+	bool powerdown;
+	int ret;
+
+	ret = regmap_read(st->regmap, MAX22007_CHANNEL_MODE_REG, &reg_val);
+	if (ret)
+		return ret;
+
+	powerdown = !(reg_val & MAX22007_CH_PWR_CH_MASK(chan->channel));
+
+	return sysfs_emit(buf, "%d\n", powerdown);
+}
+
+static ssize_t max22007_write_dac_powerdown(struct iio_dev *indio_dev,
+					    uintptr_t private,
+					    const struct iio_chan_spec *chan,
+					    const char *buf, size_t len)
+{
+	struct max22007_state *st = iio_priv(indio_dev);
+	bool powerdown;
+	int ret;
+
+	ret = kstrtobool(buf, &powerdown);
+	if (ret)
+		return ret;
+
+	if (powerdown)
+		ret = regmap_update_bits(st->regmap, MAX22007_CHANNEL_MODE_REG,
+					 MAX22007_CH_PWR_CH_MASK(chan->channel),
+					 MAX22007_CH_PWR_VAL(chan->channel, MAX22007_CH_POWER_OFF));
+	else
+		ret = regmap_update_bits(st->regmap, MAX22007_CHANNEL_MODE_REG,
+					 MAX22007_CH_PWR_CH_MASK(chan->channel),
+					 MAX22007_CH_PWR_VAL(chan->channel, MAX22007_CH_POWER_ON));
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static const struct iio_chan_spec_ext_info max22007_ext_info[] = {
+	{
+		.name = "powerdown",
+		.read = max22007_read_dac_powerdown,
+		.write = max22007_write_dac_powerdown,
+		.shared = IIO_SEPARATE,
+	},
+	{ },
+};
+
+static const struct iio_chan_spec max22007_channel_template = {
+	.output = 1,
+	.indexed = 1,
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
+	.ext_info = max22007_ext_info,
+};
+
+static int max22007_parse_channel_cfg(struct max22007_state *st, u8 *num_channels)
+{
+	struct device *dev = &st->spi->dev;
+	struct iio_chan_spec *iio_chan;
+	int ret, num_chan = 0, i = 0;
+	u32 reg;
+
+	num_chan = device_get_child_node_count(dev);
+	if (!num_chan)
+		return dev_err_probe(dev, -ENODEV, "no channels configured\n");
+
+	st->iio_chan = devm_kcalloc(dev, num_chan, sizeof(*st->iio_chan), GFP_KERNEL);
+	if (!st->iio_chan)
+		return -ENOMEM;
+
+	device_for_each_child_node_scoped(dev, child) {
+		const char *channel_type_str;
+		enum max22007_channel_mode mode;
+
+		ret = fwnode_property_read_u32(child, "reg", &reg);
+		if (ret)
+			return dev_err_probe(dev, ret,
+					     "failed to read reg property of %pfwP\n", child);
+
+		if (reg >= MAX22007_NUM_CHANNELS)
+			return dev_err_probe(dev, -EINVAL,
+					     "reg out of range in %pfwP\n", child);
+
+		iio_chan = &st->iio_chan[i];
+
+		*iio_chan = max22007_channel_template;
+		iio_chan->channel = reg;
+
+		ret = fwnode_property_read_string(child, "adi,type", &channel_type_str);
+		if (ret)
+			return dev_err_probe(dev, ret,
+					     "missing adi,type property for %pfwP\n", child);
+
+		if (strcmp(channel_type_str, "current") == 0) {
+			mode = MAX22007_CURRENT_MODE;
+			iio_chan->type = IIO_CURRENT;
+		} else if (strcmp(channel_type_str, "voltage") == 0) {
+			mode = MAX22007_VOLTAGE_MODE;
+			iio_chan->type = IIO_VOLTAGE;
+		} else {
+			return dev_err_probe(dev, -EINVAL,
+					     "invalid adi,type '%s' for %pfwP\n",
+					     channel_type_str, child);
+		}
+
+		ret = regmap_update_bits(st->regmap, MAX22007_CHANNEL_MODE_REG,
+					 MAX22007_CH_MODE_CH_MASK(reg),
+					 MAX22007_CH_MODE_VAL(reg, mode));
+		if (ret)
+			return ret;
+
+		/* Set DAC to transparent mode (immediate update) */
+		ret = regmap_update_bits(st->regmap, MAX22007_CONFIG_REG,
+					 MAX22007_DAC_LATCH_MODE_MASK(reg),
+					 MAX22007_DAC_LATCH_MODE_VAL(reg, 1));
+		if (ret)
+			return ret;
+
+		i++;
+	}
+
+	*num_channels = num_chan;
+
+	return 0;
+}
+
+static int max22007_probe(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev;
+	struct max22007_state *state;
+	struct gpio_desc *reset_gpio;
+	u8 num_channels;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*state));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	state = iio_priv(indio_dev);
+	state->spi = spi;
+
+	crc8_populate_lsb(max22007_crc8_table, MAX22007_CRC8_POLYNOMIAL);
+
+	state->regmap = devm_regmap_init(&spi->dev, &max22007_regmap_bus, state,
+					 &max22007_regmap_config);
+	if (IS_ERR(state->regmap))
+		return dev_err_probe(&spi->dev, PTR_ERR(state->regmap),
+				     "Failed to initialize regmap\n");
+
+	reset_gpio = devm_gpiod_get_optional(&spi->dev, "reset", GPIOD_OUT_LOW);
+	if (IS_ERR(reset_gpio))
+		return dev_err_probe(&spi->dev, PTR_ERR(reset_gpio),
+				     "Failed to get reset GPIO\n");
+
+	if (reset_gpio) {
+		gpiod_set_value_cansleep(reset_gpio, 0);
+	} else {
+		ret = regmap_write(state->regmap, MAX22007_SOFT_RESET_REG,
+				   MAX22007_SOFT_RESET_BITS_MASK);
+		if (ret)
+			return ret;
+	}
+
+	ret = regmap_update_bits(state->regmap, MAX22007_CONFIG_REG,
+				 MAX22007_CRC_EN_MASK,
+				 MAX22007_CRC_EN_MASK);
+	if (ret)
+		return ret;
+
+	ret = max22007_parse_channel_cfg(state, &num_channels);
+	if (ret)
+		return ret;
+
+	indio_dev->info = &max22007_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = state->iio_chan;
+	indio_dev->num_channels = num_channels;
+	indio_dev->name = "max22007";
+
+	return devm_iio_device_register(&spi->dev, indio_dev);
+}
+
+static const struct spi_device_id max22007_id[] = {
+	{ "max22007" },
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, max22007_id);
+
+static const struct of_device_id max22007_of_match[] = {
+	{ .compatible = "adi,max22007" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, max22007_of_match);
+
+static struct spi_driver max22007_driver = {
+	.driver = {
+		.name = "max22007",
+		.of_match_table = max22007_of_match,
+	},
+	.probe = max22007_probe,
+	.id_table = max22007_id,
+};
+module_spi_driver(max22007_driver);
+
+MODULE_AUTHOR("Janani Sunil <janani.sunil@analog.com>");
+MODULE_DESCRIPTION("Analog Devices MAX22007 DAC");
+MODULE_LICENSE("GPL");

-- 
2.43.0

Re: [PATCH 1/3] dt-bindings: iio: dac: Add max22007

[Krzysztof Kozlowski]

On 19/12/2025 16:31, Janani Sunil wrote:
> Devicetree bindings for MAX22007 4-channel
> 12-bit DAC that drives a voltage or current
> output on each channel

Please wrap commit message according to Linux coding style / submission
process (neither too early nor over the limit):
https://elixir.bootlin.com/linux/v6.4-rc1/source/Documentation/process/submitting-patches.rst#L597

> 
> Signed-off-by: Janani Sunil <janani.sunil@analog.com>
> ---
>  .../devicetree/bindings/iio/dac/adi,max22007.yaml  | 116 +++++++++++++++++++++
>  MAINTAINERS                                        |   7 ++
>  2 files changed, 123 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/dac/adi,max22007.yaml b/Documentation/devicetree/bindings/iio/dac/adi,max22007.yaml
> new file mode 100644
> index 000000000000..c2f65d9e42d4
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/dac/adi,max22007.yaml
> @@ -0,0 +1,116 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/dac/adi,max22007.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Analog Devices MAX22007 DAC device driver

Bindings are for hardware, drop all device driver references.

> +
> +maintainers:
> +  - Janani Sunil <janani.sunil@analog.com>
> +
> +description:
> +  The MAX22007 is a quad-channel, 12-bit digital-to-analog converter (DAC)
> +  with integrated precision output amplifiers and current output capability.
> +  Each channel can be independently configured for voltage or current output.
> +  Datasheet available at https://www.analog.com/en/products/max22007.html
> +
> +$ref: /schemas/spi/spi-peripheral-props.yaml#
> +
> +properties:
> +  compatible:
> +    const: adi,max22007
> +
> +  reg:
> +    maxItems: 1
> +
> +  spi-max-frequency:
> +    maximum: 500000
> +
> +  '#address-cells':
> +    const: 1
> +
> +  '#size-cells':
> +    const: 0
> +
> +  vdd-supply:
> +    description: Low-Voltage Power Supply from +2.7V to +5.5V.
> +
> +  hvdd-supply:
> +    description:
> +      Positive High-Voltage Power Supply from +8V to (HVSS +24V) for
> +      the Output Channels.
> +
> +  hvss-supply:
> +    description:
> +      Negative High-Voltage Power Supply from -2V to 0V for the Output Channels.
> +
> +  reset-gpios:
> +    maxItems: 1
> +    description:
> +      GPIO used for hardware reset of the device.

Drop description, redundant, because not saying anything other than
schema already said. You could say whether it is active low for example
if you wanted to add something useful.

> +
> +patternProperties:
> +  "^channel@[0-3]$":
> +    allOf:
> +      - $ref: /schemas/iio/dac/dac.yaml#
> +      - type: object

Drop allOf. I don't get where did you get this syntax, it's not needed.

> +        description:
> +          Represents the external channels which are connected to the DAC.
> +          Channels not specified in the device tree will be powered off.
> +
> +        properties:
> +          reg:
> +            description: Channel number
> +            maxItems: 1
> +
> +          adi,type:
> +            description: Channel output type.
> +            $ref: /schemas/types.yaml#/definitions/string
> +            enum: [voltage, current]

Why would it matter if this is voltage or current? That's the first time
this property appears. Why none of existing fit?

> +
> +        required:
> +          - reg
> +          - adi,type
> +
> +        unevaluatedProperties: false
> +
> +required:
> +  - compatible
> +  - reg
> +
> +anyOf:
> +  - required: [channel@0]
> +  - required: [channel@1]
> +  - required: [channel@2]
> +  - required: [channel@3]
> +
> +unevaluatedProperties: false


Best regards,
Krzysztof

Re: [PATCH 1/3] dt-bindings: iio: dac: Add max22007

[Jonathan Cameron]

On Fri, 19 Dec 2025 16:31:15 +0100
Janani Sunil <janani.sunil@analog.com> wrote:

Hi Janani and welcome to IIO.


> Devicetree bindings for MAX22007 4-channel
> 12-bit DAC that drives a voltage or current
> output on each channel

This is a very short wrap. Aim for 75 characters in patch description lines
(so slightly shorter than 80 chars standard for everything else).

> 
> Signed-off-by: Janani Sunil <janani.sunil@analog.com>

> ---
>  .../devicetree/bindings/iio/dac/adi,max22007.yaml  | 116 +++++++++++++++++++++
>  MAINTAINERS                                        |   7 ++
>  2 files changed, 123 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/dac/adi,max22007.yaml b/Documentation/devicetree/bindings/iio/dac/adi,max22007.yaml
> new file mode 100644
> index 000000000000..c2f65d9e42d4
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/dac/adi,max22007.yaml

...

> +  vdd-supply:
> +    description: Low-Voltage Power Supply from +2.7V to +5.5V.
> +
> +  hvdd-supply:
> +    description:
> +      Positive High-Voltage Power Supply from +8V to (HVSS +24V) for
> +      the Output Channels.
> +
> +  hvss-supply:
> +    description:
> +      Negative High-Voltage Power Supply from -2V to 0V for the Output Channels.
> +
> +  reset-gpios:
> +    maxItems: 1
> +    description:
> +      GPIO used for hardware reset of the device.
> +
> +patternProperties:
> +  "^channel@[0-3]$":
> +    allOf:
> +      - $ref: /schemas/iio/dac/dac.yaml#
> +      - type: object
> +        description:
> +          Represents the external channels which are connected to the DAC.
> +          Channels not specified in the device tree will be powered off.
> +
> +        properties:
> +          reg:
> +            description: Channel number
> +            maxItems: 1

min / max?

> +
> +          adi,type:
> +            description: Channel output type.
> +            $ref: /schemas/types.yaml#/definitions/string
> +            enum: [voltage, current]
This is much more constrained (as only two types of channel) but we do have
precedence for adi,ch-func in adi,ad74115.yaml and adi,ad74413r.yaml

That's not a particularly pretty binding but we should probably stick to
it anyway.

adi,type is too vague a name for this property anyway.

> +
> +        required:
> +          - reg
> +          - adi,type
> +
> +        unevaluatedProperties: false
> +
> +required:
> +  - compatible

For supplies we document as required any that are needed for the device
to function, whether or not we happen to need to specify them on
a given board (given fallbacks that apply on assumption that fixes
always on supplies are in use).  So I'd expect to see at least some
of the supplies listed here.

> +  - reg
> +
> +anyOf:
> +  - required: [channel@0]
> +  - required: [channel@1]
> +  - required: [channel@2]
> +  - required: [channel@3]

Interesting. I'm not sure we have never bothered to document this before and there
are other devices for which some sort of channel config is pretty much needed.
What is the justification to have this explicitly listed here?

> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +    spi {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        dac@0 {
> +            compatible = "adi,max22007";
> +            reg = <0>;
> +            spi-max-frequency = <500000>;
> +            reset-gpios = <&gpio 19 GPIO_ACTIVE_LOW>;
> +            #address-cells = <1>;
> +            #size-cells = <0>;
> +
> +            channel@0 {
> +                reg = <0>;
> +                adi,type = "voltage";
> +            };
> +
> +            channel@1 {
> +                reg = <1>;
> +                adi,type = "current";
> +            };
> +        };
> +    };
> +...

Re: [PATCH 2/3] docs: iio: Add documentation for MAX22007 driver

[Jonathan Cameron]

On Fri, 19 Dec 2025 16:31:16 +0100
Janani Sunil <janani.sunil@analog.com> wrote:

> Add documentation for MAX22007 driver which describes how the user
> can access the driver using dtoverlays
> 
> Signed-off-by: Janani Sunil <janani.sunil@analog.com>

Hi Janani,

We've recently had a few comments on whether driver specific docs add value
(for particular drivers, sometimes they definitely do!).  From what I'm
seeing here, I'm not thinking this one needs a document.  Not most drivers
don't have such a file because they make use of standard ABI that is well
documented.  DT stuff always belongs in the dt-binding rather than these
files.  With both those elements gone there isn't much value to this file.
So I'd drop it.  We can easily add a file if something complex shows up
in later patches, that justifies this.

Thanks,

Jonathan

> ---
>  Documentation/iio/index.rst    |   1 +
>  Documentation/iio/max22007.rst | 145 +++++++++++++++++++++++++++++++++++++++++
>  MAINTAINERS                    |   1 +
>  3 files changed, 147 insertions(+)
> 
> diff --git a/Documentation/iio/index.rst b/Documentation/iio/index.rst
> index 315ae37d6fd4..7601bc2882e7 100644
> --- a/Documentation/iio/index.rst
> +++ b/Documentation/iio/index.rst
> @@ -37,4 +37,5 @@ Industrial I/O Kernel Drivers
>     adxl345
>     bno055
>     ep93xx_adc
> +   max22007
>     opt4060
> diff --git a/Documentation/iio/max22007.rst b/Documentation/iio/max22007.rst
> new file mode 100644
> index 000000000000..e04c563f1fd0
> --- /dev/null
> +++ b/Documentation/iio/max22007.rst
> @@ -0,0 +1,145 @@
> +.. SPDX-License-Identifier: GPL-2.0-only
> +
> +===============
> +MAX22007 driver
> +===============
> +
> +Device driver for Analog Devices Inc. MAX22007 quad-channel industrial DAC.
> +The module name is ``max22007``.
> +
> +Supported devices
> +=================
> +
> +* `MAX22007 <https://www.analog.com/en/products/max22007.html>`_
> +
> +Wiring connections
> +==================
> +
> +The MAX22007 uses a standard SPI interface.
I'd not bother with this section.  Most SPI devices after all use
the standard interface, so we can document this by not documenting anything
else :)

> +
> +Device Tree Configuration
> +=========================

Anything here should be in the dt-binding. As such this section isn't useful.

> +
> +The device supports both global and per-channel configuration through device tree.
> +
> +Global Properties:
> +
> +* ``reset-gpios``: GPIO pin for hardware reset (optional, falls back to
> +  software reset if not specified)
> +* ``vdd-supply``: Low-Voltage Power Supply from +2.7V to +5.5V (optional)
> +* ``hvdd-supply``: Positive High-Voltage Power Supply from +8V to (HVSS +24V)
> +  for the Output Channels (optional)
> +* ``hvss-supply``: Negative High-Voltage Power Supply from -2V to 0V for the
> +  Output Channels (optional)
> +
> +Per-channel properties:
> +
> +* ``adi,type``: Specify the channel output type - must be either "voltage" or "current" (mandatory)
> +
> +Note: The driver operates in transparent mode (immediate register-to-output updates).
> +Channel mode is determined by the ``adi,type`` property:
> +
> +* ``adi,type = "current"``: the channel operates in current mode
> +* ``adi,type = "voltage"``: the channel operates in voltage mode
> +
> +Device attributes
> +=================
> +
> +The MAX22007 driver provides IIO DAC interfaces that vary based on the
> +configured channel mode. Each channel appears as a separate IIO device
> +attribute:
> +
> +* ``out_voltage_raw`` (voltage mode channels)
> +* ``out_current_raw`` (current mode channels)
> +* ``out_voltage_scale`` / ``out_current_scale`` (channel scaling factors)
> +* ``out_voltage_powerdown`` / ``out_current_powerdown`` (channel power control)
> +
> +The driver automatically configures the IIO channel type based on the configured
> +channel mode from device tree.
This bit feels very standard and so not in need of extra documentation.

> +
> +Power Mode Control
> +==================
> +
> +Each channel provides standard IIO ``powerdown`` attributes for runtime power
> +control:
> +
> +* Write ``1`` to power down (disable) the channel output
> +* Write ``0`` to power up (enable) the channel output
> +* Read the attribute to get the current power state (1=powered down, 0=powered up)
> +
> +This allows individual channels to be powered on/off independently for power
> +management and safety purposes.

Likewise, this is very standard.

> +
> +Usage Examples
> +==============
> +
> +Setting DAC output values:
> +
> +.. code-block:: bash
> +
> +   # Set channel 0 (voltage mode) to raw value 655 (≈2V)
> +   # Output is updated immediately in transparent mode
> +   echo 655 > /sys/bus/iio/devices/iio:deviceX/out_voltage0_raw
> +
> +   # Set channel 1 (current mode)
> +   # Output is updated immediately in transparent mode
> +   echo 1024 > /sys/bus/iio/devices/iio:deviceX/out_current1_raw
> +
> +Controlling channel power modes:
> +
> +.. code-block:: bash
> +
> +   # Enable channel 0 (power up)
> +   echo 0 > /sys/bus/iio/devices/iio:deviceX/out_voltage0_powerdown
> +
> +   # Disable channel 1 (power down)
> +   echo 1 > /sys/bus/iio/devices/iio:deviceX/out_current1_powerdown
> +
> +   # Check current power state (0=powered up, 1=powered down)
> +   cat /sys/bus/iio/devices/iio:deviceX/out_voltage0_powerdown
> +
> +Reading channel values and scale factors:
> +
> +.. code-block:: bash
> +
> +   # Read raw DAC value
> +   cat /sys/bus/iio/devices/iio:deviceX/out_voltage0_raw
> +
> +   # Read scale factor (volts per LSB)
> +   cat /sys/bus/iio/devices/iio:deviceX/out_voltage0_scale
> +
> +Check available channels:
> +
> +.. code-block:: bash
> +
> +   ls /sys/bus/iio/devices/iio:deviceX/out_*_raw
> +
> +Scale Calculations
> +==================
> +
> +The driver provides accurate scale factors based on the hardware configuration:

This information doesn't need to be provided explicitly.  Anyone who
wonders in detail about it can check the driver. For most users the fact
it obeys the standard ABI rules is eough.

> +
> +**Voltage Mode:**
> +
> +- Scale = (5 × 2.5V) / 4096 = 0.003051757 V per LSB
> +- Range: 0V to 12.5V over 12-bit (0-4095)
> +- Formula: Output = Raw_Value × Scale
> +
> +**Current Mode:**
> +
> +- Scale = (2.5V / (2 × 50Ω)) / 4096 = 0.000006103515625 A per LSB
> +- Range: 0A to 0.025A over 12-bit (0-4095)
> +- Formula: Output = Raw_Value × Scale
> +
> +Driver Architecture
> +===================
> +
> +The driver implements:
> +
> +* **CRC8 Error Checking**: Always-enabled CRC8 for SPI data integrity
> +* **Channel Configuration**: Supports per-channel mode and power configuration
> +
> +Channel configuration (voltage/current mode) is set via the ``adi,type``
> +device tree property and cannot be changed dynamically The driver requires
> +proper device tree configuration with mandatory ``adi,type`` property for each
> +channel.
> diff --git a/MAINTAINERS b/MAINTAINERS
> index e1addbd21562..6561455732c9 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1599,6 +1599,7 @@ L:	linux-iio@vger.kernel.org
>  S:	Supported
>  W:	https://ez.analog.com/linux-software-drivers
>  F:	Documentation/devicetree/bindings/iio/dac/adi,max22007.yaml
> +F:	Documentation/iio/max22007.rst
>  
>  ANALOG DEVICES INC ADA4250 DRIVER
>  M:	Antoniu Miclaus <antoniu.miclaus@analog.com>
> 

Re: [PATCH 3/3] iio: dac: Add MAX22007 DAC driver support

[Jonathan Cameron]

On Fri, 19 Dec 2025 16:31:17 +0100
Janani Sunil <janani.sunil@analog.com> wrote:

> Add support for the MAX22007 4 channel DAC
> that drives a voltage or current output on each channel.
wrap to 75 chars rather than 50-60ish
> 
> Signed-off-by: Janani Sunil <janani.sunil@analog.com>
Hi Janani

A few minor things inline.  Also add turning on any required
power supplies.  See how other drivers do it with a single call
in in probe. If your board is using always on supplies it will just
work as a stub regulator will be provided by the regulator core.


Thanks,

Jonathan

> diff --git a/drivers/iio/dac/max22007.c b/drivers/iio/dac/max22007.c
> new file mode 100644
> index 000000000000..0d57fee27367
> --- /dev/null
> +++ b/drivers/iio/dac/max22007.c
> @@ -0,0 +1,487 @@

> +
> +#define MAX22007_NUM_CHANNELS				4
> +#define MAX22007_REV_ID_REG				0x00
> +#define MAX22007_STAT_INTR_REG				0x01
> +#define MAX22007_INTERRUPT_EN_REG			0x02
> +#define MAX22007_CONFIG_REG				0x03
> +#define MAX22007_CONTROL_REG				0x04
> +#define MAX22007_CHANNEL_MODE_REG			0x05
> +#define MAX22007_SOFT_RESET_REG				0x06
> +#define MAX22007_DAC_CHANNEL_REG(ch)			(0x07 + (ch))
> +#define MAX22007_GPIO_CTRL_REG				0x0B
> +#define MAX22007_GPIO_DATA_REG				0x0C
> +#define MAX22007_GPI_EDGE_INT_CTRL_REG			0x0D
> +#define MAX22007_GPI_INT_STATUS_REG			0x0E
> +
> +/* Channel mask definitions */
> +#define     MAX22007_CH_MODE_CH_MASK(channel)		BIT(12 + (channel))
maybe use x or ch rather than channel to shorten the defines a little.

> +#define     MAX22007_CH_PWR_CH_MASK(channel)		BIT(8 + (channel))
> +#define     MAX22007_DAC_LATCH_MODE_MASK(channel)	BIT(12 + (channel))
> +#define     MAX22007_LDAC_UPDATE_MASK(channel)		BIT(12 + (channel))
> +#define     MAX22007_SW_RST_MASK			BIT(8)
> +#define     MAX22007_SW_CLR_MASK			BIT(12)
> +#define     MAX22007_SOFT_RESET_BITS_MASK		(MAX22007_SW_RST_MASK | \
> +	    MAX22007_SW_CLR_MASK)

Align after (

> +#define     MAX22007_DAC_DATA_MASK			GENMASK(15, 4)
> +#define     MAX22007_DAC_MAX_RAW			GENMASK(11, 0)
> +#define     MAX22007_CRC8_POLYNOMIAL			0x8C
> +#define     MAX22007_CRC_EN_MASK			BIT(0)
> +#define     MAX22007_RW_MASK				BIT(0)
> +#define     MAX22007_CRC_OVERHEAD			1
> +
> +/* Field value preparation macros with masking */
> +#define     MAX22007_CH_PWR_VAL(channel, val)	(((val) & 0x1) << (8 + (channel)))
> +#define     MAX22007_CH_MODE_VAL(channel, val)	(((val) & 0x1) << (12 + (channel)))
> +#define     MAX22007_DAC_LATCH_MODE_VAL(channel, val)	(((val) & 0x1) << (12 + (channel)))
> +
> +static u8 max22007_crc8_table[256];
> +
> +enum max22007_channel_mode {
> +	MAX22007_VOLTAGE_MODE,
> +	MAX22007_CURRENT_MODE
Add trailing comma. Not obvious there will never be more if other devices are supported
by the driver.

I'd also give these explicit values given they are written to HW.
= 0, 
= 1,

> +};
> +
> +enum max22007_channel_power {
> +	MAX22007_CH_POWER_OFF,
> +	MAX22007_CH_POWER_ON,
This isn't bringing value over renaming the field mask define
to MAX22007_CH_PWRON_CH_MASK()
and using 0 / 1 as appropriate.

> +};
> +
> +struct max22007_state {
> +	struct spi_device *spi;
> +	struct regmap *regmap;
> +	struct iio_chan_spec *iio_chan;

I'd go with iio_chans just to make it clear there can be multiple.

> +	u8 tx_buf[4] __aligned(IIO_DMA_MINALIGN);
> +	u8 rx_buf[4];
> +};
> +
> +static int max22007_spi_read(void *context, const void *reg, size_t reg_size,
> +			     void *val, size_t val_size)
> +{
> +	struct max22007_state *st = context;
> +	u8 calculated_crc, received_crc;
> +	u8 crc_data[3];
> +	int ret;
> +	struct spi_transfer xfer = {
> +		.tx_buf = st->tx_buf,
> +		.rx_buf = st->rx_buf,
> +	};
> +
> +	xfer.len = reg_size + val_size + MAX22007_CRC_OVERHEAD;
> +
> +	memcpy(st->tx_buf, reg, reg_size);
> +
> +	ret = spi_sync_transfer(st->spi, &xfer, 1);
> +	if (ret) {
> +		dev_err(&st->spi->dev, "SPI transfer failed: %d\n", ret);
> +		return ret;
> +	}
> +
> +	crc_data[0] = st->tx_buf[0];
> +	crc_data[1] = st->rx_buf[1];
> +	crc_data[2] = st->rx_buf[2]

The use of only the first byte for tx and later for rx suggest this a
spi_write_then_read()

Using that should simplify your code a little particularly as it doesn't need
dma safe buffers (bounces anyway).

I'd be tempted to check reg_size == 1 then hard code that through this function.


> +
> +	calculated_crc = crc8(max22007_crc8_table, crc_data, 3, 0x00);
> +	received_crc = st->rx_buf[3];
> +
> +	if (calculated_crc != received_crc) {
> +		dev_err(&st->spi->dev, "CRC mismatch on read register %02x:\n", *(u8 *)reg);
> +		return -EIO;
> +	}
> +
> +	/* Ignore the dummy byte 0 */
> +	memcpy(val, &st->rx_buf[1], val_size);
> +
> +	return 0;
> +}
> +
> +static int max22007_spi_write(void *context, const void *data, size_t count)
> +{
> +	struct max22007_state *st = context;
> +	struct spi_transfer xfer = {
> +		.tx_buf = st->tx_buf,
> +		.rx_buf = st->rx_buf,
> +	};
> +
> +	memset(st->tx_buf, 0, sizeof(st->tx_buf));
> +
> +	xfer.len = count + MAX22007_CRC_OVERHEAD;
> +
> +	memcpy(st->tx_buf, data, count);
> +	st->tx_buf[count] = crc8(max22007_crc8_table, st->tx_buf,
> +				 sizeof(st->tx_buf) - 1, 0x00);
> +
> +	return spi_sync_transfer(st->spi, &xfer, 1);
> +}

> +static int max22007_write_channel_data(struct max22007_state *state, unsigned int channel,
> +				       unsigned int data)
> +{
> +	unsigned int reg_val;
> +
> +	if (data > MAX22007_DAC_MAX_RAW)
> +		return -EINVAL;
> +
> +	reg_val = FIELD_PREP(MAX22007_DAC_DATA_MASK, data);
> +
> +	return regmap_write(state->regmap, MAX22007_DAC_CHANNEL_REG(channel), reg_val);
> +}
> +
> +static int max22007_read_channel_data(struct max22007_state *state, unsigned int channel,

Where it doesn't hurt readability my preference is still to stay nearer to 80 chars.

> +				      int *data)
> +{
> +	int ret;
> +	unsigned int reg_val;
> +
> +	ret = regmap_read(state->regmap, MAX22007_DAC_CHANNEL_REG(channel), &reg_val);
> +	if (ret)
> +		return ret;
> +
> +	*data = FIELD_GET(MAX22007_DAC_DATA_MASK, reg_val);
> +
> +	return 0;
> +}
> +
> +static int max22007_read_raw(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan,
> +			     int *val, int *val2, long mask)
> +{
> +	struct max22007_state *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		ret = max22007_read_channel_data(st, chan->channel, val);
> +		if (ret)
> +			return ret;
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		if (chan->type == IIO_VOLTAGE) {
> +			*val = 5 * 2500;  /* 5 * Vref(2.5V) in mV */
> +			*val2 = 12;  /* 12-bit DAC resolution (2^12) */

Given resolution is the same either way, drop that out of the if / else
		if (chan->type == IIO_VOLTAGE)
			*val = ...
		else
			*val = ...
		val2 = 12; /* 12-bit DAC resolution */

The 2^12 is a bit confusing so I'd drop that bit.

> +		} else {
> +			*val = 25;  /* Vref / (2 * Rsense) = 2500mV / 100 */
> +			*val2 = 12;  /* 12-bit DAC resolution (2^12) */
> +		}
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +	default:
> +		return -EINVAL;
> +	}
> +}


> +static const struct iio_chan_spec_ext_info max22007_ext_info[] = {
> +	{
> +		.name = "powerdown",
> +		.read = max22007_read_dac_powerdown,
> +		.write = max22007_write_dac_powerdown,
> +		.shared = IIO_SEPARATE,
> +	},
> +	{ },
No trailing comma for a 'terminating' entry like this. We don't want
to make it easy to add stuff after.
> +};
> +
> +static const struct iio_chan_spec max22007_channel_template = {
> +	.output = 1,
> +	.indexed = 1,
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
> +	.ext_info = max22007_ext_info,
> +};
> +
> +static int max22007_parse_channel_cfg(struct max22007_state *st, u8 *num_channels)
> +{
> +	struct device *dev = &st->spi->dev;
> +	struct iio_chan_spec *iio_chan;
> +	int ret, num_chan = 0, i = 0;
Please don't mix declarations that assign with those that don't. It makes
it to easy to miss which ones are in which category.
	int num_chan = 0, i = 0;
	int ret;

> +	u32 reg;
> +
> +	num_chan = device_get_child_node_count(dev);
> +	if (!num_chan)
> +		return dev_err_probe(dev, -ENODEV, "no channels configured\n");
> +
> +	st->iio_chan = devm_kcalloc(dev, num_chan, sizeof(*st->iio_chan), GFP_KERNEL);
> +	if (!st->iio_chan)
> +		return -ENOMEM;
> +
> +	device_for_each_child_node_scoped(dev, child) {
> +		const char *channel_type_str;
> +		enum max22007_channel_mode mode;
> +
> +		ret = fwnode_property_read_u32(child, "reg", &reg);
> +		if (ret)
> +			return dev_err_probe(dev, ret,
> +					     "failed to read reg property of %pfwP\n", child);
> +
> +		if (reg >= MAX22007_NUM_CHANNELS)
> +			return dev_err_probe(dev, -EINVAL,
> +					     "reg out of range in %pfwP\n", child);
> +
> +		iio_chan = &st->iio_chan[i];
> +
> +		*iio_chan = max22007_channel_template;
The template is only used here so I'd be tempted to just do
		*iio_chan = (struct iio_chan_spec) {
			.output = 1,
			.indexed = 1,
			.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
					      BIT(IIO_CHAN_INFO_SCALE),
			.ext_info = max22007_ext_info,
			.channel = reg,
		};
inline here.
Or after other changes suggested below you can do

		st->iio_chan[i++] = (struct iio_chan_spec) {
			.output = 1,
			.indexed = 1,
			.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
					      BIT(IIO_CHAN_INFO_SCALE),
			.ext_info = max22007_ext_info,
			.channel = reg,
			.type = chan_type,
		}

> +		iio_chan->channel = reg;
> +
> +		ret = fwnode_property_read_string(child, "adi,type", &channel_type_str);
> +		if (ret)
> +			return dev_err_probe(dev, ret,
> +					     "missing adi,type property for %pfwP\n", child);
> +
> +		if (strcmp(channel_type_str, "current") == 0) {
> +			mode = MAX22007_CURRENT_MODE;
> +			iio_chan->type = IIO_CURRENT;
> +		} else if (strcmp(channel_type_str, "voltage") == 0) {
> +			mode = MAX22007_VOLTAGE_MODE;
> +			iio_chan->type = IIO_VOLTAGE;
> +		} else {
> +			return dev_err_probe(dev, -EINVAL,
> +					     "invalid adi,type '%s' for %pfwP\n",
> +					     channel_type_str, child);
> +		}

If you do this to set a local type variable before the *iio_chan =
suggestion above, can assign it when filling in the rest of the chan_spec

> +
> +		ret = regmap_update_bits(st->regmap, MAX22007_CHANNEL_MODE_REG,
> +					 MAX22007_CH_MODE_CH_MASK(reg),
> +					 MAX22007_CH_MODE_VAL(reg, mode));
> +		if (ret)
> +			return ret;
> +
> +		/* Set DAC to transparent mode (immediate update) */
> +		ret = regmap_update_bits(st->regmap, MAX22007_CONFIG_REG,
> +					 MAX22007_DAC_LATCH_MODE_MASK(reg),
> +					 MAX22007_DAC_LATCH_MODE_VAL(reg, 1));
> +		if (ret)
> +			return ret;
> +
> +		i++;
With other changes suggested above, i will only be used in one place I think
so you can do the ++ inline at that point. See above for details.

		
> +	}
> +
> +	*num_channels = num_chan;
> +
> +	return 0;
> +}
> +
> +static int max22007_probe(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev;
> +	struct max22007_state *state;
> +	struct gpio_desc *reset_gpio;
> +	u8 num_channels;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*state));
Use a local
	struct device *dev = &spi->dev;
to shorten all the places you have &spi->dev currently in this function.

> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	state = iio_priv(indio_dev);
> +	state->spi = spi;
> +
> +	crc8_populate_lsb(max22007_crc8_table, MAX22007_CRC8_POLYNOMIAL);
> +
> +	state->regmap = devm_regmap_init(&spi->dev, &max22007_regmap_bus, state,
> +					 &max22007_regmap_config);
> +	if (IS_ERR(state->regmap))
> +		return dev_err_probe(&spi->dev, PTR_ERR(state->regmap),
> +				     "Failed to initialize regmap\n");
> +
> +	reset_gpio = devm_gpiod_get_optional(&spi->dev, "reset", GPIOD_OUT_LOW);

What sets the gpio high? I'd expect a transition from what is requested here
to what is set in the set_value() below.

> +	if (IS_ERR(reset_gpio))
> +		return dev_err_probe(&spi->dev, PTR_ERR(reset_gpio),
> +				     "Failed to get reset GPIO\n");
> +
> +	if (reset_gpio) {
> +		gpiod_set_value_cansleep(reset_gpio, 0);
> +	} else {
> +		ret = regmap_write(state->regmap, MAX22007_SOFT_RESET_REG,
> +				   MAX22007_SOFT_RESET_BITS_MASK);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	ret = regmap_update_bits(state->regmap, MAX22007_CONFIG_REG,
> +				 MAX22007_CRC_EN_MASK,
> +				 MAX22007_CRC_EN_MASK);

regmap_set_bits() saves repeating the mask.

> +	if (ret)
> +		return ret;
> +
> +	ret = max22007_parse_channel_cfg(state, &num_channels);
> +	if (ret)
> +		return ret;
> +
> +	indio_dev->info = &max22007_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = state->iio_chan;
> +	indio_dev->num_channels = num_channels;
> +	indio_dev->name = "max22007";
> +
> +	return devm_iio_device_register(&spi->dev, indio_dev);
> +}