[PATCH v4 0/2] iio: adc: Add support for Texas Instruments ADS112C04

[PATCH v4 0/2] iio: adc: Add support for Texas Instruments ADS112C04

[Kyle Hsieh]

This patch series introduces support for the Texas Instruments ADS112C04
Analog-to-Digital Converters.

The ADS112C04 (16-bit) is precision, low-power, delta-sigma ADCs with
an I2C interface. They feature a flexible input multiplexer supporting
single-ended and differential measurements, a programmable gain amplifier,
and an internal voltage reference.

Note: While this chip shares similarities with the ADS112C14 (currently 
being upstreamed by David Lechner), the register maps and feature sets 
are sufficiently different to warrant a separate driver. However, the
DT bindings and channel parsing logic have been aligned with the
ADS112C14 conventions.

This initial submission provides a minimal feature set (single-shot 
conversions and basic DRDY interrupt) covering current use cases.

Signed-off-by: Kyle Hsieh <kylehsieh1995@gmail.com>
---
Changes in v4:
- dt-bindings: iio: adc: ti,ads112c04:
  - Fixed excitation-current-nanoamp to use single-entry list syntax
    (items: - enum: [...]) instead of combining maxItems: 1 with a
    mapping-style items, which failed dt_binding_check.
  - Widened excitation-channels to maximum: 5 to account for IDAC1/
    IDAC2 also being routable to REFP0/REFN0, and documented the
    mapping, per David Lechner.
  - Reduced excitation-current-nanoamp to a single entry, since the
    two IDAC outputs share one current setting, per David Lechner.
  - Changed burn-out-current-nanoamp to use `const: 10000`, per David
    Lechner.
  - Renamed reference-sources' internal enum value to "internal"
    (dropped voltage suffix, since there is only one internal
    reference), per David Lechner.

- iio: adc: ti-ads112c04:
  - Fixed word-read byte ordering by switching to
    i2c_smbus_read_word_swapped(), addressing a big-endian data
    corruption issue flagged by Sashiko AI review.
  - Masked the DRDY interrupt in the hardirq handler
    (disable_irq_nosync()) and re-enabled it once the conversion data
    is read, to avoid an interrupt storm on level-triggered DRDY
    configurations, without hardcoding the trigger type.
  - Reworked reference-sources handling in parse_channels(): it is now
    validated against the actually-selected refp-supply instead of
    being unconditionally rejected, per David Lechner.
  - Simplified regulator handling in probe() using
    devm_regulator_get_enable_read_voltage(), dropping the now-unused
    vref_reg field, per David Lechner.
  - Corrected the commit message to no longer claim refn-supply
    support, since it remains explicitly unsupported in probe().
- Added a MAINTAINERS entry for the new binding and driver.
- Link to v3: https://lore.kernel.org/r/20260805-ti-ads112c04-driver-v3-0-49f436829e01@gmail.com

Changes in v3:
- dt-bindings: iio: adc: ti,ads112c04:
  - Resolved dt_binding_check errors by removing redundant $ref for
    standard unit suffixes and fixing YAML array syntax.
  - Added full hardware capability descriptions (excitation-channels,
    excitation-current-nanoamp, burn-out-current-nanoamp,
    reference-sources) as suggested by David Lechner.
  - Restricted the reg maximum to 11 and updated the regex to
    ^channel@[0-9a-b]$ to accurately reflect the 12 possible MUX
    combinations.

- iio: adc: ti-ads112c04:
  - Transitioned all I2C read/write wrappers to use SMBus APIs
    (i2c_smbus_read_byte_data, i2c_smbus_read_word_data, etc.) to
    gracefully handle I2C errors, NACKs, and Repeated Starts, addressing
    feedback from Joshua Crofts and Jonathan Cameron.
  - Added forward compatibility checks in probe() and parse_channels()
    using dev_err_probe() to return -EOPNOTSUPP for unimplemented DT
    properties.
  - Reverted devm_request_irq() flags to 0 to let the driver inherit the
    trigger type strictly from the DT, per Jonathan Cameron's advice.
  - Reduced the data wait timeout to 100ms, reflecting the chip's slowest
    data rate of 20 SPS.
  - Fixed #include alphabetical sorting, grouped <linux/iio/*> headers,
    and added missing headers.
  - Fixed variable declaration ordering (reverse xmas tree) and updated
    variable naming to vref_mV (SI unit exception).
  - Optimized GPIO reset logic using GPIOD_OUT_HIGH.
- Link to v2: https://lore.kernel.org/r/20260731-ti-ads112c04-driver-v2-0-aab0168c3c01@gmail.com

Changes in v2:
- Replaced `vref-supply` with `refp-supply` and `refn-supply` to accurately reflect hardware.
- Refactored the driver to dynamically parse channel configurations and routing from DT child nodes.
- Modernized the driver using kernel macros.
- Handled endianness elegantly.
- Added hardware reset fallback logic.
- Inherited IRQ trigger type from device tree instead of hardcoding.
- Fixed a bug where the MUX software cache could desync from hardware if the I2C write failed.
- Added strict return value checking for all I2C writes during probe.
- Updated the `i2c_device_id` array to use C99 named initializers.
- Link to v1: https://lore.kernel.org/r/20260728-ti-ads112c04-driver-v1-0-475efe4e2b78@gmail.com

---
Kyle Hsieh (2):
      dt-bindings: iio: adc: ti,ads112c04: Add binding for ADS112C04
      iio: adc: ti-ads112c04: Add support for TI ADS112C04

 .../devicetree/bindings/iio/adc/ti,ads112c04.yaml  | 148 +++++++
 MAINTAINERS                                        |   7 +
 drivers/iio/adc/Kconfig                            |  10 +
 drivers/iio/adc/Makefile                           |   1 +
 drivers/iio/adc/ti-ads112c04.c                     | 425 +++++++++++++++++++++
 5 files changed, 591 insertions(+)
---
base-commit: 350d1fb9204b13c5f95e511e98b8bcb47574d425
change-id: 20260724-ti-ads112c04-driver-be7e89047834

Best regards,
-- 
Kyle Hsieh <kylehsieh1995@gmail.com>

[PATCH v4 1/2] dt-bindings: iio: adc: ti,ads112c04: Add binding for ADS112C04

[Kyle Hsieh]

Add device tree binding documentation for Texas Instruments ADS112C04
I2C Analog-to-Digital Converters.

These devices provide 4-channel, 16-bit delta-sigma ADCs with an I2C
interface, programmable gain amplifier (PGA), and data-ready (DRDY)
interrupt output.

The binding uses child nodes to dynamically define the connected
single-ended or differential channels.

Excitation current, burn-out current, and reference source properties
are also included to fully describe the chip's hardware capabilities,
aligned with the ti,ads112c14 binding conventions.

Signed-off-by: Kyle Hsieh <kylehsieh1995@gmail.com>
---
 .../devicetree/bindings/iio/adc/ti,ads112c04.yaml  | 148 +++++++++++++++++++++
 MAINTAINERS                                        |   6 +
 2 files changed, 154 insertions(+)

diff --git a/Documentation/devicetree/bindings/iio/adc/ti,ads112c04.yaml b/Documentation/devicetree/bindings/iio/adc/ti,ads112c04.yaml
new file mode 100644
index 000000000000..68a0df21cedd
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/ti,ads112c04.yaml
@@ -0,0 +1,148 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/ti,ads112c04.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Texas Instruments ADS112C04 ADC
+
+maintainers:
+  - Kyle Hsieh <kylehsieh1995@gmail.com>
+
+description:
+  The ADS112C04 (16-bit) are precision analog-to-digital converters (ADCs)
+  with an I2C interface. They feature a flexible input multiplexer, a
+  low-noise programmable gain amplifier (PGA), two programmable excitation
+  current sources, a voltage reference, and a precision temperature sensor.
+
+properties:
+  compatible:
+    enum:
+      - ti,ads112c04
+
+  reg:
+    maxItems: 1
+    description: I2C address of the device.
+
+  interrupts:
+    maxItems: 1
+    description: Data ready (DRDY) interrupt output.
+
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 0
+
+  reset-gpios:
+    maxItems: 1
+    description: GPIO connected to the RESET pin. Active low.
+
+  avdd-supply: true
+  dvdd-supply: true
+
+  refp-supply: true
+  refn-supply: true
+
+  ti,refp-refn-resistor-ohms:
+    description: Resistance of the external resistor between REFP and REFN.
+
+patternProperties:
+  "^channel@[0-9a-b]$":
+    $ref: adc.yaml
+    unevaluatedProperties: false
+    properties:
+      reg:
+        items:
+          - maximum: 11
+
+      single-channel:
+        maximum: 3
+
+      diff-channels:
+        items:
+          maximum: 3
+
+      excitation-channels:
+        maxItems: 2
+        items:
+          maximum: 5
+        description:
+          Additionally to AIN0-AIN3, IDAC1/IDAC2 can also be routed to
+          REFP0 (4) and REFN0 (5).
+
+      excitation-current-nanoamp:
+        items:
+          - enum: [10000, 50000, 100000, 250000, 500000, 1000000, 1500000]
+
+      burn-out-current-nanoamp:
+        items:
+          - const: 10000
+
+      reference-sources:
+        items:
+          - enum: [internal, external, avdd]
+            default: internal
+
+    dependencies:
+      excitation-channels: [ excitation-current-nanoamp ]
+      excitation-current-nanoamp: [ excitation-channels ]
+
+    oneOf:
+      - required: [ single-channel ]
+      - required: [ diff-channels ]
+
+required:
+  - compatible
+  - reg
+  - avdd-supply
+  - dvdd-supply
+
+dependencies:
+  refn-supply: [ refp-supply ]
+
+oneOf:
+  - required:
+      - refp-supply
+  - required:
+      - ti,refp-refn-resistor-ohms
+  - properties:
+      refp-supply: false
+      refn-supply: false
+      ti,refp-refn-resistor-ohms: false
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    #include <dt-bindings/gpio/gpio.h>
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        adc@40 {
+            compatible = "ti,ads112c04";
+            reg = <0x40>;
+            interrupt-parent = <&gpio>;
+            interrupts = <12 IRQ_TYPE_EDGE_FALLING>;
+
+            reset-gpios = <&gpio 13 GPIO_ACTIVE_LOW>;
+            avdd-supply = <&vdd_3v3_reg>;
+            dvdd-supply = <&vdd_3v3_reg>;
+            refp-supply = <&vref_reg>;
+
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            channel@0 {
+                reg = <0>;
+                diff-channels = <0>, <1>;
+            };
+
+            channel@1 {
+                reg = <1>;
+                single-channel = <2>;
+            };
+        };
+    };
diff --git a/MAINTAINERS b/MAINTAINERS
index 04fa5322d9f7..417d74b6d6cc 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -26987,6 +26987,12 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/iio/adc/ti,ads1119.yaml
 F:	drivers/iio/adc/ti-ads1119.c
 
+TI ADS112C04 ADC DRIVER
+M:	Kyle Hsieh <kylehsieh1995@gmail.com>
+L:	linux-iio@vger.kernel.org
+S:	Maintained
+F:	Documentation/devicetree/bindings/iio/adc/ti,ads112c04.yaml
+
 TI ADS112C14 ADC DRIVER
 M:	David Lechner <dlechner@baylibre.com>
 L:	linux-iio@vger.kernel.org

-- 
2.34.1

[PATCH v4 2/2] iio: adc: ti-ads112c04: Add support for TI ADS112C04

[Kyle Hsieh]

Add IIO driver support for the Texas Instruments ADS112C04 (16-bit)
delta-sigma ADCs.

The driver implements:
- Single-shot conversions using the IIO raw read interface.
- Dynamic parsing of single-ended and differential channels from
  device tree child nodes.
- Hardware interrupt support via the DRDY pin, falling back to
  software polling if no IRQ is provided.
- Scale calculation based on the internal 2.048V reference.
- Reference voltage scaling via the regulator subsystem (refp-supply),
  falling back to the internal 2.048V reference if not specified.
  refn-supply is not yet supported.
- Hardware reset fallback using GPIO.

Signed-off-by: Kyle Hsieh <kylehsieh1995@gmail.com>
---
 MAINTAINERS                    |   1 +
 drivers/iio/adc/Kconfig        |  10 +
 drivers/iio/adc/Makefile       |   1 +
 drivers/iio/adc/ti-ads112c04.c | 425 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 437 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 417d74b6d6cc..f51fbda9d4b9 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -26992,6 +26992,7 @@ M:	Kyle Hsieh <kylehsieh1995@gmail.com>
 L:	linux-iio@vger.kernel.org
 S:	Maintained
 F:	Documentation/devicetree/bindings/iio/adc/ti,ads112c04.yaml
+F:	drivers/iio/adc/ti-ads112c04.c
 
 TI ADS112C14 ADC DRIVER
 M:	David Lechner <dlechner@baylibre.com>
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 990e7b3e7212..0ee50828f9e4 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -1817,6 +1817,16 @@ config TI_ADS1119
          This driver can also be built as a module. If so, the module will be
          called ti-ads1119.
 
+config TI_ADS112C04
+    tristate "Texas Instruments ADS112C04 ADC"
+    depends on I2C
+    help
+      If you say yes here you get support for Texas Instruments
+      ADS112C04 (16-bit) I2C analog to digital converters.
+
+      This driver can also be built as a module. If so, the module will be
+      called ti-ads112c04.
+
 config TI_ADS112C14
 	tristate "Texas Instruments ADS112C14/ADS122C14"
 	depends on I2C
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index dcec0abb03b7..d8acf2831fd2 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -155,6 +155,7 @@ obj-$(CONFIG_TI_ADS1015) += ti-ads1015.o
 obj-$(CONFIG_TI_ADS1018) += ti-ads1018.o
 obj-$(CONFIG_TI_ADS1100) += ti-ads1100.o
 obj-$(CONFIG_TI_ADS1119) += ti-ads1119.o
+obj-$(CONFIG_TI_ADS112C04) += ti-ads112c04.o
 obj-$(CONFIG_TI_ADS112C14) += ti-ads112c14.o
 obj-$(CONFIG_TI_ADS124S08) += ti-ads124s08.o
 obj-$(CONFIG_TI_ADS1298) += ti-ads1298.o
diff --git a/drivers/iio/adc/ti-ads112c04.c b/drivers/iio/adc/ti-ads112c04.c
new file mode 100644
index 000000000000..3a775da2ae23
--- /dev/null
+++ b/drivers/iio/adc/ti-ads112c04.c
@@ -0,0 +1,425 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Texas Instruments ADS112C04 16-bit I2C ADC driver
+ *
+ * Copyright (c) 2026 Kyle Hsieh <kylehsieh1995@gmail.com>
+ *
+ * Datasheet: https://www.ti.com/lit/ds/symlink/ads112c04.pdf
+ * Based on TI Reference Code and standard Linux IIO framework.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/iopoll.h>
+#include <linux/jiffies.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/property.h>
+#include <linux/regulator/consumer.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/units.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+#define ADS112C04_CMD_RESET         0x06
+#define ADS112C04_CMD_START_SYNC    0x08
+#define ADS112C04_CMD_POWERDOWN     0x02
+#define ADS112C04_CMD_RDATA         0x10
+#define ADS112C04_CMD_RREG(reg)     (0x20 | ((reg) << 2))
+#define ADS112C04_CMD_WREG(reg)     (0x40 | ((reg) << 2))
+
+#define ADS112C04_REG_CONFIG0       0x00
+#define ADS112C04_REG_CONFIG1       0x01
+#define ADS112C04_REG_CONFIG2       0x02
+#define ADS112C04_REG_CONFIG3       0x03
+
+#define ADS112C04_CONFIG0_MUX         GENMASK(7, 4)
+#define ADS112C04_CONFIG0_PGA_BYPASS  BIT(0)
+#define ADS112C04_CONFIG2_DRDY        BIT(7)
+
+struct ads112c04_state {
+	struct i2c_client *client;
+	/* Protects concurrent ADC reads and device configuration */
+	struct mutex lock;
+	struct completion completion;
+	int vref_mV;
+	u8 config0;
+	u8 config1;
+	bool has_refp;
+};
+
+static int ads112c04_write_cmd(struct i2c_client *client, u8 cmd)
+{
+	return i2c_smbus_write_byte(client, cmd);
+}
+
+static int ads112c04_read_reg(struct i2c_client *client, u8 reg, u8 *val)
+{
+	int ret;
+
+	ret = i2c_smbus_read_byte_data(client, ADS112C04_CMD_RREG(reg));
+	if (ret < 0)
+		return ret;
+
+	*val = ret;
+
+	return 0;
+}
+
+static int ads112c04_write_reg(struct i2c_client *client, u8 reg, u8 val)
+{
+	return i2c_smbus_write_byte_data(client, ADS112C04_CMD_WREG(reg), val);
+}
+
+static int ads112c04_wait_for_data(struct ads112c04_state *st)
+{
+	int ret, err;
+	u8 val;
+
+	if (st->client->irq > 0) {
+		/* Timeout is 100ms (slowest data rate is 20 SPS) */
+		ret = wait_for_completion_timeout(&st->completion,
+						  msecs_to_jiffies(100));
+		if (!ret)
+			return -ETIMEDOUT;
+
+		return 0;
+	}
+
+	err = read_poll_timeout(ads112c04_read_reg, ret,
+				(ret < 0 || (val & ADS112C04_CONFIG2_DRDY)),
+				1000, 100 * USEC_PER_MSEC, false,
+				st->client, ADS112C04_REG_CONFIG2, &val);
+
+	if (ret < 0)
+		return ret;
+
+	return err;
+}
+
+static int ads112c04_read_data(struct ads112c04_state *st, int *val)
+{
+	int ret;
+
+	ret = i2c_smbus_read_word_swapped(st->client, ADS112C04_CMD_RDATA);
+	if (ret < 0)
+		return ret;
+
+	*val = sign_extend32(ret, 15);
+
+	return 0;
+}
+
+static int ads112c04_get_adc_result(struct ads112c04_state *st,
+				    struct iio_chan_spec const *chan,
+				    int *val)
+{
+	u8 new_config0;
+	int ret;
+
+	new_config0 = st->config0;
+	FIELD_MODIFY(ADS112C04_CONFIG0_MUX, &new_config0, chan->address);
+
+	if (st->config0 != new_config0) {
+		ret = ads112c04_write_reg(st->client, ADS112C04_REG_CONFIG0, new_config0);
+		if (ret < 0)
+			return ret;
+		st->config0 = new_config0;
+	}
+
+	reinit_completion(&st->completion);
+
+	ret = ads112c04_write_cmd(st->client, ADS112C04_CMD_START_SYNC);
+	if (ret < 0)
+		return ret;
+
+	ret = ads112c04_wait_for_data(st);
+	if (ret < 0)
+		return ret;
+
+	ret = ads112c04_read_data(st, val);
+	if (st->client->irq > 0)
+		enable_irq(st->client->irq);
+
+	return ret;
+}
+
+static int ads112c04_read_raw(struct iio_dev *indio_dev,
+			      struct iio_chan_spec const *chan,
+			      int *val, int *val2, long mask)
+{
+	struct ads112c04_state *st = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		mutex_lock(&st->lock);
+		ret = ads112c04_get_adc_result(st, chan, val);
+		mutex_unlock(&st->lock);
+
+		if (ret < 0)
+			return ret;
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_SCALE:
+		*val = st->vref_mV;
+		*val2 = 15;
+		return IIO_VAL_FRACTIONAL_LOG2;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static irqreturn_t ads112c04_irq_handler(int irq, void *private)
+{
+	struct iio_dev *indio_dev = private;
+	struct ads112c04_state *st = iio_priv(indio_dev);
+
+	disable_irq_nosync(irq);
+	complete(&st->completion);
+
+	return IRQ_HANDLED;
+}
+
+static const struct iio_info ads112c04_info = {
+	.read_raw = ads112c04_read_raw,
+};
+
+static int ads112c04_parse_channels(struct iio_dev *indio_dev)
+{
+	struct device *dev = indio_dev->dev.parent;
+	struct ads112c04_state *st = iio_priv(indio_dev);
+	struct iio_chan_spec *channels;
+	u32 num_channels, pair[2];
+	int ret, i = 0;
+
+	num_channels = device_get_named_child_node_count(dev, "channel");
+	if (!num_channels)
+		return dev_err_probe(dev, -EINVAL, "no channel subnodes found\n");
+
+	if (num_channels > 12)
+		return dev_err_probe(dev, -EINVAL,
+				     "num of channel nodes exceeds 12\n");
+
+	channels = devm_kcalloc(dev, num_channels, sizeof(*channels), GFP_KERNEL);
+	if (!channels)
+		return -ENOMEM;
+
+	device_for_each_named_child_node_scoped(dev, child, "channel") {
+		struct iio_chan_spec *spec = &channels[i];
+
+		if (fwnode_property_present(child, "excitation-channels"))
+			return dev_err_probe(dev, -EOPNOTSUPP,
+					     "excitation-channels is not supported yet\n");
+
+		if (fwnode_property_present(child, "reference-sources")) {
+			const char *ref;
+
+			ret = fwnode_property_read_string(child, "reference-sources", &ref);
+			if (ret)
+				return dev_err_probe(dev, ret,
+						     "failed to read reference-sources\n");
+
+			if ((!strcmp(ref, "external") && !st->has_refp) ||
+			    (!strcmp(ref, "internal") && st->has_refp))
+				return dev_err_probe(dev, -EINVAL,
+						     "reference-sources does not match refp-supply\n");
+		}
+
+		spec->type = IIO_VOLTAGE;
+		spec->indexed = 1;
+		spec->info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE);
+
+		if (fwnode_property_present(child, "single-channel")) {
+			ret = fwnode_property_read_u32(child, "single-channel", &pair[0]);
+			if (ret)
+				return dev_err_probe(dev, ret,
+						     "failed to read single-channel property\n");
+
+			if (pair[0] > 3)
+				return dev_err_probe(dev, -EINVAL,
+						     "single-channel must be 0-3\n");
+
+			spec->channel = pair[0];
+			spec->address = 0x08 + pair[0];
+		} else if (fwnode_property_present(child, "diff-channels")) {
+			ret = fwnode_property_read_u32_array(child, "diff-channels", pair, 2);
+			if (ret)
+				return dev_err_probe(dev, ret,
+						     "failed to read diff-channels property\n");
+
+			if (pair[0] > 3 || pair[1] > 3)
+				return dev_err_probe(dev, -EINVAL,
+						     "diff-channels must be 0-3\n");
+
+			spec->channel = pair[0];
+			spec->channel2 = pair[1];
+			spec->differential = 1;
+
+			if (pair[0] == 0 && pair[1] == 1)
+				spec->address = 0x00;
+			else if (pair[0] == 0 && pair[1] == 2)
+				spec->address = 0x01;
+			else if (pair[0] == 0 && pair[1] == 3)
+				spec->address = 0x02;
+			else if (pair[0] == 1 && pair[1] == 0)
+				spec->address = 0x03;
+			else if (pair[0] == 1 && pair[1] == 2)
+				spec->address = 0x04;
+			else if (pair[0] == 1 && pair[1] == 3)
+				spec->address = 0x05;
+			else if (pair[0] == 2 && pair[1] == 3)
+				spec->address = 0x06;
+			else if (pair[0] == 3 && pair[1] == 2)
+				spec->address = 0x07;
+			else
+				return dev_err_probe(dev, -EINVAL,
+						     "invalid diff-channels combination\n");
+		} else {
+			return dev_err_probe(dev, -EINVAL,
+					     "channel node must have single-channel or diff-channels\n");
+		}
+
+		i++;
+	}
+
+	indio_dev->channels = channels;
+	indio_dev->num_channels = i;
+
+	return 0;
+}
+
+#define ADS112C04_VREF_INTERNAL_MV	2048
+
+static int ads112c04_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct iio_dev *indio_dev;
+	struct ads112c04_state *st;
+	struct gpio_desc *reset_gpio;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	st = iio_priv(indio_dev);
+	st->client = client;
+
+	ret = devm_mutex_init(dev, &st->lock);
+	if (ret)
+		return ret;
+
+	init_completion(&st->completion);
+
+	indio_dev->name = "ads112c04";
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &ads112c04_info;
+
+	/* Forward compatibility checks for unimplemented DT properties */
+	if (device_property_present(dev, "refn-supply") ||
+	    device_property_present(dev, "ti,refp-refn-resistor-ohms"))
+		return dev_err_probe(dev, -EOPNOTSUPP,
+				     "refn-supply and external resistors are not supported yet\n");
+
+	st->has_refp = device_property_present(dev, "refp-supply");
+
+	ret = ads112c04_parse_channels(indio_dev);
+	if (ret)
+		return ret;
+
+	ret = devm_regulator_get_enable(dev, "avdd");
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to get avdd regulator\n");
+
+	ret = devm_regulator_get_enable(dev, "dvdd");
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to get dvdd regulator\n");
+
+	if (device_property_present(dev, "refp-supply")) {
+		ret = devm_regulator_get_enable_read_voltage(dev, "refp");
+		if (ret < 0)
+			return dev_err_probe(dev, ret,
+					     "failed to get refp voltage\n");
+
+		st->vref_mV = ret / (MICRO / MILLI);
+		st->config1 = 0x02;
+	} else {
+		st->vref_mV = ADS112C04_VREF_INTERNAL_MV;
+		st->config1 = 0x00;
+	}
+
+	/* Power-On Reset (POR) delay */
+	fsleep(50 * USEC_PER_MSEC);
+
+	/* Requesting OUT_HIGH asserts the active-low reset pin immediately */
+	reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(reset_gpio))
+		return PTR_ERR(reset_gpio);
+
+	if (reset_gpio) {
+		fsleep(1000);
+		gpiod_set_value_cansleep(reset_gpio, 0);
+	} else {
+		ret = ads112c04_write_cmd(client, ADS112C04_CMD_RESET);
+		if (ret < 0)
+			return ret;
+	}
+
+	fsleep(1000);
+
+	/* Bypass PGA for now to allow full-scale single-ended measurements */
+	st->config0 = ADS112C04_CONFIG0_PGA_BYPASS;
+	ret = ads112c04_write_reg(client, ADS112C04_REG_CONFIG0, st->config0);
+	if (ret)
+		return ret;
+
+	ret = ads112c04_write_reg(client, ADS112C04_REG_CONFIG1, st->config1);
+	if (ret)
+		return ret;
+
+	if (client->irq > 0) {
+		ret = devm_request_irq(dev, client->irq,
+				       ads112c04_irq_handler,
+				       0,
+				       indio_dev->name, indio_dev);
+		if (ret)
+			return ret;
+	}
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct i2c_device_id ads112c04_id[] = {
+	{ .name = "ads112c04" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ads112c04_id);
+
+static const struct of_device_id ads112c04_of_match[] = {
+	{ .compatible = "ti,ads112c04" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ads112c04_of_match);
+
+static struct i2c_driver ads112c04_driver = {
+	.driver = {
+		.name = "ads112c04",
+		.of_match_table = ads112c04_of_match,
+	},
+	.probe = ads112c04_probe,
+	.id_table = ads112c04_id,
+};
+module_i2c_driver(ads112c04_driver);
+
+MODULE_AUTHOR("Kyle Hsieh <kylehsieh1995@gmail.com>");
+MODULE_DESCRIPTION("Texas Instruments ADS112C04 ADC driver");
+MODULE_LICENSE("GPL");

-- 
2.34.1

Re: [PATCH v4 2/2] iio: adc: ti-ads112c04: Add support for TI ADS112C04

[Andy Shevchenko]

On Tue, Aug 11, 2026 at 10:48:38AM +0800, Kyle Hsieh wrote:
> Add IIO driver support for the Texas Instruments ADS112C04 (16-bit)
> delta-sigma ADCs.
> 
> The driver implements:
> - Single-shot conversions using the IIO raw read interface.
> - Dynamic parsing of single-ended and differential channels from
>   device tree child nodes.
> - Hardware interrupt support via the DRDY pin, falling back to
>   software polling if no IRQ is provided.
> - Scale calculation based on the internal 2.048V reference.
> - Reference voltage scaling via the regulator subsystem (refp-supply),
>   falling back to the internal 2.048V reference if not specified.
>   refn-supply is not yet supported.
> - Hardware reset fallback using GPIO.

...

> +#include <linux/bitfield.h>
> +#include <linux/bitops.h>
> +#include <linux/delay.h>
> +#include <linux/err.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/i2c.h>
> +#include <linux/interrupt.h>
> +#include <linux/iopoll.h>
> +#include <linux/jiffies.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/property.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/string.h>
> +#include <linux/types.h>
> +#include <linux/units.h>

...

> +static int ads112c04_wait_for_data(struct ads112c04_state *st)
> +{
> +	int ret, err;
> +	u8 val;
> +
> +	if (st->client->irq > 0) {
> +		/* Timeout is 100ms (slowest data rate is 20 SPS) */
> +		ret = wait_for_completion_timeout(&st->completion,
> +						  msecs_to_jiffies(100));
> +		if (!ret)

In this case semantics of ret differs, that's why it's better to write as

		if (!wait_for_completion_timeout(&st->completion, msecs_to_jiffies(100)))

// and I would even dare to put on a single line.

> +			return -ETIMEDOUT;
> +
> +		return 0;
> +	}
> +
> +	err = read_poll_timeout(ads112c04_read_reg, ret,
> +				(ret < 0 || (val & ADS112C04_CONFIG2_DRDY)),
> +				1000, 100 * USEC_PER_MSEC, false,
> +				st->client, ADS112C04_REG_CONFIG2, &val);
> +
> +	if (ret < 0)
> +		return ret;
> +
> +	return err;

In this piece I would swap err and ret, so the ret is outer one and err is
the inner one. This will be consistent with other code pieces.

> +}

...

> +static int ads112c04_get_adc_result(struct ads112c04_state *st,
> +				    struct iio_chan_spec const *chan,
> +				    int *val)
> +{
> +	u8 new_config0;
> +	int ret;
> +
> +	new_config0 = st->config0;
> +	FIELD_MODIFY(ADS112C04_CONFIG0_MUX, &new_config0, chan->address);
> +
> +	if (st->config0 != new_config0) {
> +		ret = ads112c04_write_reg(st->client, ADS112C04_REG_CONFIG0, new_config0);
> +		if (ret < 0)
> +			return ret;
> +		st->config0 = new_config0;
> +	}
> +
> +	reinit_completion(&st->completion);
> +
> +	ret = ads112c04_write_cmd(st->client, ADS112C04_CMD_START_SYNC);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = ads112c04_wait_for_data(st);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = ads112c04_read_data(st, val);

> +	if (st->client->irq > 0)
> +		enable_irq(st->client->irq);

Why is it fine to leave IRQ enabled even in the error case?

> +	return ret;
> +}

...

> +static int ads112c04_read_raw(struct iio_dev *indio_dev,
> +			      struct iio_chan_spec const *chan,
> +			      int *val, int *val2, long mask)
> +{
> +	struct ads112c04_state *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		mutex_lock(&st->lock);
> +		ret = ads112c04_get_adc_result(st, chan, val);
> +		mutex_unlock(&st->lock);
> +
> +		if (ret < 0)
> +			return ret;

If IRQ is left enabled and we call it here, we end up with the unbalanced
depth counting.

> +		return IIO_VAL_INT;
> +
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = st->vref_mV;
> +		*val2 = 15;
> +		return IIO_VAL_FRACTIONAL_LOG2;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +}

...

> +static irqreturn_t ads112c04_irq_handler(int irq, void *private)
> +{
> +	struct iio_dev *indio_dev = private;
> +	struct ads112c04_state *st = iio_priv(indio_dev);

> +	disable_irq_nosync(irq);

This is unconditionally called. Where is the guarantee that it becomes enabled
once again?

> +	complete(&st->completion);

> +	return IRQ_HANDLED;
> +}

...

> +static int ads112c04_parse_channels(struct iio_dev *indio_dev)
> +{
> +	struct device *dev = indio_dev->dev.parent;
> +	struct ads112c04_state *st = iio_priv(indio_dev);
> +	struct iio_chan_spec *channels;
> +	u32 num_channels, pair[2];

> +	int ret, i = 0;

Why is 'i' signed? And it's better to decouple definition and assignment, so
the assignment will happen closer to when it's really needed.

...

> +		if (fwnode_property_present(child, "reference-sources")) {
> +			const char *ref;
> +
> +			ret = fwnode_property_read_string(child, "reference-sources", &ref);
> +			if (ret)
> +				return dev_err_probe(dev, ret,
> +						     "failed to read reference-sources\n");
> +
> +			if ((!strcmp(ref, "external") && !st->has_refp) ||
> +			    (!strcmp(ref, "internal") && st->has_refp))
> +				return dev_err_probe(dev, -EINVAL,
> +						     "reference-sources does not match refp-supply\n");
> +		}

Reinvention of fwnode_property_match_property_string() ?

...

> +		if (fwnode_property_present(child, "single-channel")) {
> +			ret = fwnode_property_read_u32(child, "single-channel", &pair[0]);

I don't like the (partial) pair reuse here. It's semantically wrong. Just add
another temporary variable and let compiler to choose what to do with a stack
frame in such a case.

> +			if (ret)
> +				return dev_err_probe(dev, ret,
> +						     "failed to read single-channel property\n");
> +
> +			if (pair[0] > 3)
> +				return dev_err_probe(dev, -EINVAL,
> +						     "single-channel must be 0-3\n");
> +
> +			spec->channel = pair[0];
> +			spec->address = 0x08 + pair[0];
> +		} else if (fwnode_property_present(child, "diff-channels")) {
> +			ret = fwnode_property_read_u32_array(child, "diff-channels", pair, 2);

ARRAY_SIZE()

> +			if (ret)
> +				return dev_err_probe(dev, ret,
> +						     "failed to read diff-channels property\n");
> +
> +			if (pair[0] > 3 || pair[1] > 3)
> +				return dev_err_probe(dev, -EINVAL,
> +						     "diff-channels must be 0-3\n");
> +
> +			spec->channel = pair[0];
> +			spec->channel2 = pair[1];
> +			spec->differential = 1;

> +			if (pair[0] == 0 && pair[1] == 1)
> +				spec->address = 0x00;
> +			else if (pair[0] == 0 && pair[1] == 2)
> +				spec->address = 0x01;
> +			else if (pair[0] == 0 && pair[1] == 3)
> +				spec->address = 0x02;
> +			else if (pair[0] == 1 && pair[1] == 0)
> +				spec->address = 0x03;
> +			else if (pair[0] == 1 && pair[1] == 2)
> +				spec->address = 0x04;
> +			else if (pair[0] == 1 && pair[1] == 3)
> +				spec->address = 0x05;
> +			else if (pair[0] == 2 && pair[1] == 3)
> +				spec->address = 0x06;
> +			else if (pair[0] == 3 && pair[1] == 2)
> +				spec->address = 0x07;

I would do this as a 4x4 table

	-1, 0, 1, 2,
	3, -1, 4, 5,
	-1, -1, -1, 6,
	-1, -1, 7, -1,

With that done you can even supported the swapped cases

	-1, 0, 1, 2,
	3, -1, 4, 5,
	1, 4, -1, 6,
	2, 5, 7, -1,

(but I haven't studied the code if it's toughly relies on the pair[0]/pair[1]
 values to be in a strong order after the address being assigned).

> +			else
> +				return dev_err_probe(dev, -EINVAL,
> +						     "invalid diff-channels combination\n");

> +		} else {
> +			return dev_err_probe(dev, -EINVAL,
> +					     "channel node must have single-channel or diff-channels\n");
> +		}
> +
> +		i++;
> +	}
> +
> +	indio_dev->channels = channels;
> +	indio_dev->num_channels = i;
> +
> +	return 0;
> +}

...

> +#define ADS112C04_VREF_INTERNAL_MV	2048

_mV

...

> +	if (device_property_present(dev, "refp-supply")) {

A dup property check. if (st->has_refp) should suffice, no?

> +		ret = devm_regulator_get_enable_read_voltage(dev, "refp");
> +		if (ret < 0)
> +			return dev_err_probe(dev, ret,
> +					     "failed to get refp voltage\n");
> +
> +		st->vref_mV = ret / (MICRO / MILLI);
> +		st->config1 = 0x02;
> +	} else {
> +		st->vref_mV = ADS112C04_VREF_INTERNAL_MV;
> +		st->config1 = 0x00;
> +	}

...

> +	/* Requesting OUT_HIGH asserts the active-low reset pin immediately */
> +	reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
> +	if (IS_ERR(reset_gpio))
> +		return PTR_ERR(reset_gpio);

Why reset-gpio driver can't be used instead?

> +	if (reset_gpio) {
> +		fsleep(1000);

1 * USEC_PER_MSEC

> +		gpiod_set_value_cansleep(reset_gpio, 0);
> +	} else {
> +		ret = ads112c04_write_cmd(client, ADS112C04_CMD_RESET);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	fsleep(1000);

Ditto.

-- 
With Best Regards,
Andy Shevchenko