[PATCH v4 1/2] iio: light: add driver for MAX44009

[PATCH v4 1/2] iio: light: add driver for MAX44009

[Robert Eshleman]

The MAX44009 is a low-power ambient light sensor from Maxim
Integrated. It differs from the MAX44000 in that it doesn't have
proximity sensing and that it requires far less current (1 micro-amp
vs 5 micro-amps). The register mapping and feature set between the
two are different enough to require a new driver for the MAX44009.

Developed and tested with a BeagleBone Black and UDOO Neo (i.MX6SX)

Supported features:

* Reading lux (processed value)

* Rising and falling illuminance threshold
  events

* Configuring integration time

https://datasheets.maximintegrated.com/en/ds/MAX44009.pdf

Signed-off-by: Robert Eshleman <bobbyeshleman@gmail.com>
---
Changes to v4:
- Reformat subject line
- Clean up whitespace

Changes to v3:
- Remove unnecessary mask when setting integration time
- Return IRQ_NONE in IRQ handler when interrupt not from this device
- Fix incorrect register usage when reading lux low byte
- Clean up style

Changes to v2:
- Remove unnecessary mutex locking
- Remove unnecessary triggered buffer support
- Remove unnecessary wrapper functions for smbus reads and writes
- Remove scale avail support
- Use constant scale to provide processed values instead of raw
- Remove IRQ_NONE return for non-shared IRQ
- Clean up style

 drivers/iio/light/Kconfig    |  10 +
 drivers/iio/light/Makefile   |   1 +
 drivers/iio/light/max44009.c | 555 +++++++++++++++++++++++++++++++++++
 3 files changed, 566 insertions(+)
 create mode 100644 drivers/iio/light/max44009.c

diff --git a/drivers/iio/light/Kconfig b/drivers/iio/light/Kconfig
index 36f458433480..5190eacfeb0a 100644
--- a/drivers/iio/light/Kconfig
+++ b/drivers/iio/light/Kconfig
@@ -299,6 +299,16 @@ config MAX44000
 	 To compile this driver as a module, choose M here:
 	 the module will be called max44000.
 
+config MAX44009
+	tristate "MAX44009 Ambient Light Sensor"
+	depends on I2C
+	help
+	 Say Y here if you want to build support for Maxim Integrated's
+	 MAX44009 ambient light sensor device.
+
+	 To compile this driver as a module, choose M here:
+	 the module will be called max44009.
+
 config OPT3001
 	tristate "Texas Instruments OPT3001 Light Sensor"
 	depends on I2C
diff --git a/drivers/iio/light/Makefile b/drivers/iio/light/Makefile
index 286bf3975372..e40794fbb435 100644
--- a/drivers/iio/light/Makefile
+++ b/drivers/iio/light/Makefile
@@ -28,6 +28,7 @@ obj-$(CONFIG_SENSORS_LM3533)	+= lm3533-als.o
 obj-$(CONFIG_LTR501)		+= ltr501.o
 obj-$(CONFIG_LV0104CS)		+= lv0104cs.o
 obj-$(CONFIG_MAX44000)		+= max44000.o
+obj-$(CONFIG_MAX44009)		+= max44009.o
 obj-$(CONFIG_OPT3001)		+= opt3001.o
 obj-$(CONFIG_PA12203001)	+= pa12203001.o
 obj-$(CONFIG_RPR0521)		+= rpr0521.o
diff --git a/drivers/iio/light/max44009.c b/drivers/iio/light/max44009.c
new file mode 100644
index 000000000000..00ba15499638
--- /dev/null
+++ b/drivers/iio/light/max44009.c
@@ -0,0 +1,555 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * max44009.c - Support for MAX44009 Ambient Light Sensor
+ *
+ * Copyright (c) 2019 Robert Eshleman <bobbyeshleman@gmail.com>
+ *
+ * Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX44009.pdf
+ *
+ * TODO: Support continuous mode and configuring from manual mode to
+ *	 automatic mode.
+ *
+ * Default I2C address: 0x4a
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/bits.h>
+#include <linux/i2c.h>
+#include <linux/iio/events.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/util_macros.h>
+
+#define MAX44009_DRV_NAME "max44009"
+
+/* Registers in datasheet order */
+#define MAX44009_REG_INT_STATUS 0x0
+#define MAX44009_REG_INT_EN 0x1
+#define MAX44009_REG_CFG 0x2
+#define MAX44009_REG_LUX_HI 0x3
+#define MAX44009_REG_LUX_LO 0x4
+#define MAX44009_REG_UPPER_THR 0x5
+#define MAX44009_REG_LOWER_THR 0x6
+#define MAX44009_REG_THR_TIMER 0x7
+
+#define MAX44009_CFG_TIM_MASK GENMASK(2, 0)
+#define MAX44009_CFG_MAN_MODE_MASK BIT(6)
+
+/* The maximum rising threshold for the max44009 */
+#define MAX44009_MAXIMUM_THRESHOLD 7520256
+
+#define MAX44009_THRESH_EXP_MASK (0xf << 4)
+#define MAX44009_THRESH_EXP_RSHIFT 4
+#define MAX44009_THRESH_MANT_LSHIFT 4
+#define MAX44009_THRESH_MANT_MASK 0xf
+
+#define MAX44009_UPPER_THR_MINIMUM 15
+
+/* The max44009 always scales raw readings by 0.045 and is non-configurable */
+#define MAX44009_SCALE_NUMERATOR 45
+#define MAX44009_SCALE_DENOMINATOR 1000
+
+/* The fixed-point fractional multiplier for de-scaling threshold values */
+#define MAX44009_FRACT_MULT 1000000
+
+static const u32 max44009_int_time_ns_array[] = {
+	800000000,
+	400000000,
+	200000000,
+	100000000,
+	50000000, /* Manual mode only */
+	25000000, /* Manual mode only */
+	12500000, /* Manual mode only */
+	6250000,  /* Manual mode only */
+};
+
+static const char max44009_int_time_str[] =
+	"0.8 "
+	"0.4 "
+	"0.2 "
+	"0.1 "
+	"0.05 "
+	"0.025 "
+	"0.0125 "
+	"0.00625";
+
+struct max44009_data {
+	struct i2c_client *client;
+	struct mutex lock;
+};
+
+static const struct iio_event_spec max44009_event_spec[] = {
+	{
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_RISING,
+		.mask_separate = BIT(IIO_EV_INFO_VALUE) |
+				 BIT(IIO_EV_INFO_ENABLE),
+	},
+	{
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_FALLING,
+		.mask_separate = BIT(IIO_EV_INFO_VALUE) |
+				 BIT(IIO_EV_INFO_ENABLE),
+	},
+};
+
+static const struct iio_chan_spec max44009_channels[] = {
+	{
+		.type = IIO_LIGHT,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |
+				      BIT(IIO_CHAN_INFO_INT_TIME),
+		.event_spec = max44009_event_spec,
+		.num_event_specs = ARRAY_SIZE(max44009_event_spec),
+	},
+};
+
+static int max44009_read_int_time(struct max44009_data *data)
+{
+
+	int ret = i2c_smbus_read_byte_data(data->client, MAX44009_REG_CFG);
+
+	if (ret < 0)
+		return ret;
+
+	return max44009_int_time_ns_array[ret & MAX44009_CFG_TIM_MASK];
+}
+
+static int max44009_write_int_time(struct max44009_data *data,
+				   int val, int val2)
+{
+	struct i2c_client *client = data->client;
+	int ret, int_time, config;
+	s64 ns;
+
+	ns = val * NSEC_PER_SEC + val2;
+	int_time = find_closest_descending(
+			ns,
+			max44009_int_time_ns_array,
+			ARRAY_SIZE(max44009_int_time_ns_array));
+
+	ret = i2c_smbus_read_byte_data(client, MAX44009_REG_CFG);
+	if (ret < 0)
+		return ret;
+
+	config = ret;
+	config &= int_time;
+
+	/*
+	 * To set the integration time, the device must also be in manual
+	 * mode.
+	 */
+	config |= MAX44009_CFG_MAN_MODE_MASK;
+
+	return i2c_smbus_write_byte_data(client, MAX44009_REG_CFG, config);
+}
+
+static int max44009_write_raw(struct iio_dev *indio_dev,
+			      struct iio_chan_spec const *chan, int val,
+			      int val2, long mask)
+{
+	struct max44009_data *data = iio_priv(indio_dev);
+	int ret;
+
+	if (mask == IIO_CHAN_INFO_INT_TIME && chan->type == IIO_LIGHT) {
+		mutex_lock(&data->lock);
+		ret = max44009_write_int_time(data, val, val2);
+		mutex_unlock(&data->lock);
+		return ret;
+	}
+	return -EINVAL;
+}
+
+static int max44009_write_raw_get_fmt(struct iio_dev *indio_dev,
+				      struct iio_chan_spec const *chan,
+				      long mask)
+{
+	return IIO_VAL_INT_PLUS_NANO;
+}
+
+static int max44009_lux_raw(u8 hi, u8 lo)
+{
+	int mantissa;
+	int exponent;
+
+	/*
+	 * The mantissa consists of the low nibble of the Lux High Byte
+	 * and the low nibble of the Lux Low Byte.
+	 */
+	mantissa = ((hi & 0xf) << 4) | (lo & 0xf);
+
+	/* The exponent byte is just the upper nibble of the Lux High Byte */
+	exponent = (hi >> 4) & 0xf;
+
+	/*
+	 * The exponent value is base 2 to the power of the raw exponent byte.
+	 */
+	exponent = 1 << exponent;
+
+	return exponent * mantissa;
+}
+
+#define MAX44009_READ_LUX_XFER_LEN (4)
+
+static int max44009_read_lux_raw(struct max44009_data *data)
+{
+	int ret;
+	u8 hireg = MAX44009_REG_LUX_HI;
+	u8 loreg = MAX44009_REG_LUX_LO;
+	u8 lo = 0;
+	u8 hi = 0;
+
+	struct i2c_msg msgs[] = {
+		{
+			.addr = data->client->addr,
+			.flags = 0,
+			.len = sizeof(hireg),
+			.buf = &hireg,
+		},
+		{
+			.addr = data->client->addr,
+			.flags = I2C_M_RD,
+			.len = sizeof(hi),
+			.buf = &hi,
+		},
+		{
+			.addr = data->client->addr,
+			.flags = 0,
+			.len = sizeof(loreg),
+			.buf = &loreg,
+		},
+		{
+			.addr = data->client->addr,
+			.flags = I2C_M_RD,
+			.len = sizeof(lo),
+			.buf = &lo,
+		}
+	};
+
+	/*
+	 * Use i2c_transfer instead of smbus read because i2c_transfer
+	 * does NOT use a stop bit between address write and data read.
+	 * Using a stop bit causes disjoint upper/lower byte reads and
+	 * reduces accuracy.
+	 */
+	ret = i2c_transfer(data->client->adapter,
+			   msgs, MAX44009_READ_LUX_XFER_LEN);
+
+	if (ret != MAX44009_READ_LUX_XFER_LEN)
+		return -EIO;
+
+	return max44009_lux_raw(hi, lo);
+}
+
+static int max44009_read_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan, int *val,
+			     int *val2, long mask)
+{
+	struct max44009_data *data = iio_priv(indio_dev);
+	int lux_raw;
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_PROCESSED:
+		switch (chan->type) {
+		case IIO_LIGHT:
+			ret = max44009_read_lux_raw(data);
+			if (ret < 0)
+				return ret;
+			lux_raw = ret;
+
+			*val = lux_raw * MAX44009_SCALE_NUMERATOR;
+			*val2 = MAX44009_SCALE_DENOMINATOR;
+			return IIO_VAL_FRACTIONAL;
+		default:
+			return -EINVAL;
+		}
+	case IIO_CHAN_INFO_INT_TIME:
+		switch (chan->type) {
+		case IIO_LIGHT:
+			ret = max44009_read_int_time(data);
+			if (ret < 0)
+				return ret;
+
+			*val2 = ret;
+			*val = 0;
+			return IIO_VAL_INT_PLUS_NANO;
+		default:
+			return -EINVAL;
+		}
+	default:
+		return -EINVAL;
+	}
+}
+
+static IIO_CONST_ATTR(illuminance_integration_time_available,
+		      max44009_int_time_str);
+
+static struct attribute *max44009_attributes[] = {
+	&iio_const_attr_illuminance_integration_time_available.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group max44009_attribute_group = {
+	.attrs = max44009_attributes,
+};
+
+static int max44009_threshold_byte_from_fraction(int integral, int fractional)
+{
+	int mantissa, exp;
+
+	if ((integral <= 0 && fractional <= 0) ||
+	     integral > MAX44009_MAXIMUM_THRESHOLD ||
+	     (integral == MAX44009_MAXIMUM_THRESHOLD && fractional != 0))
+		return -EINVAL;
+
+	/* Reverse scaling of fixed-point integral */
+	mantissa = integral * MAX44009_SCALE_DENOMINATOR;
+	mantissa /= MAX44009_SCALE_NUMERATOR;
+
+	/* Reverse scaling of fixed-point fractional */
+	mantissa += fractional / MAX44009_FRACT_MULT *
+		    (MAX44009_SCALE_DENOMINATOR / MAX44009_SCALE_NUMERATOR);
+
+	for (exp = 0; mantissa > 0xff; exp++)
+		mantissa >>= 1;
+
+	mantissa >>= 4;
+	mantissa &= 0xf;
+	exp <<= 4;
+
+	return exp | mantissa;
+}
+
+static int max44009_get_thr_reg(enum iio_event_direction dir)
+{
+	switch (dir) {
+	case IIO_EV_DIR_RISING:
+		return MAX44009_REG_UPPER_THR;
+	case IIO_EV_DIR_FALLING:
+		return MAX44009_REG_LOWER_THR;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int max44009_write_event_value(struct iio_dev *indio_dev,
+				      const struct iio_chan_spec *chan,
+				      enum iio_event_type type,
+				      enum iio_event_direction dir,
+				      enum iio_event_info info,
+				      int val, int val2)
+{
+	struct max44009_data *data = iio_priv(indio_dev);
+	int reg, threshold;
+
+	if (info != IIO_EV_INFO_VALUE || chan->type != IIO_LIGHT)
+		return -EINVAL;
+
+	threshold = max44009_threshold_byte_from_fraction(val, val2);
+	if (threshold < 0)
+		return threshold;
+
+	reg = max44009_get_thr_reg(dir);
+	if (reg < 0)
+		return reg;
+
+	return i2c_smbus_write_byte_data(data->client, reg, threshold);
+}
+
+static int max44009_read_threshold(struct iio_dev *indio_dev,
+				   enum iio_event_direction dir)
+{
+	struct max44009_data *data = iio_priv(indio_dev);
+	int byte, reg;
+	int mantissa, exponent;
+
+	reg = max44009_get_thr_reg(dir);
+	if (reg < 0)
+		return reg;
+
+	byte = i2c_smbus_read_byte_data(data->client, reg);
+	if (byte < 0)
+		return byte;
+
+	mantissa = byte & MAX44009_THRESH_MANT_MASK;
+	mantissa <<= MAX44009_THRESH_MANT_LSHIFT;
+
+	/*
+	 * To get the upper threshold, always adds the minimum upper threshold
+	 * value to the shifted byte value (see datasheet).
+	 */
+	if (dir == IIO_EV_DIR_RISING)
+		mantissa += MAX44009_UPPER_THR_MINIMUM;
+
+	/*
+	 * Exponent is base 2 to the power of the threshold exponent byte
+	 * value
+	 */
+	exponent = byte & MAX44009_THRESH_EXP_MASK;
+	exponent >>= MAX44009_THRESH_EXP_RSHIFT;
+
+	return (1 << exponent) * mantissa;
+}
+
+static int max44009_read_event_value(struct iio_dev *indio_dev,
+				     const struct iio_chan_spec *chan,
+				     enum iio_event_type type,
+				     enum iio_event_direction dir,
+				     enum iio_event_info info,
+				     int *val, int *val2)
+{
+	int ret;
+	int threshold;
+
+	if (chan->type != IIO_LIGHT || type != IIO_EV_TYPE_THRESH)
+		return -EINVAL;
+
+	ret = max44009_read_threshold(indio_dev, dir);
+	if (ret < 0)
+		return ret;
+	threshold = ret;
+
+	*val = threshold * MAX44009_SCALE_NUMERATOR;
+	*val2 = MAX44009_SCALE_DENOMINATOR;
+
+	return IIO_VAL_FRACTIONAL;
+}
+
+static int max44009_write_event_config(struct iio_dev *indio_dev,
+				       const struct iio_chan_spec *chan,
+				       enum iio_event_type type,
+				       enum iio_event_direction dir,
+				       int state)
+{
+	struct max44009_data *data = iio_priv(indio_dev);
+	int ret;
+
+	if (chan->type != IIO_LIGHT || type != IIO_EV_TYPE_THRESH)
+		return -EINVAL;
+
+	ret = i2c_smbus_write_byte_data(data->client,
+					MAX44009_REG_INT_EN, state);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * Set device to trigger interrupt immediately upon exceeding
+	 * the threshold limit.
+	 */
+	return i2c_smbus_write_byte_data(data->client,
+					 MAX44009_REG_THR_TIMER, 0);
+}
+
+static int max44009_read_event_config(struct iio_dev *indio_dev,
+				      const struct iio_chan_spec *chan,
+				      enum iio_event_type type,
+				      enum iio_event_direction dir)
+{
+	struct max44009_data *data = iio_priv(indio_dev);
+
+	if (chan->type != IIO_LIGHT || type != IIO_EV_TYPE_THRESH)
+		return -EINVAL;
+
+	return i2c_smbus_read_byte_data(data->client, MAX44009_REG_INT_EN);
+}
+
+static const struct iio_info max44009_info = {
+	.read_raw = max44009_read_raw,
+	.write_raw = max44009_write_raw,
+	.write_raw_get_fmt = max44009_write_raw_get_fmt,
+	.read_event_value = max44009_read_event_value,
+	.read_event_config = max44009_read_event_config,
+	.write_event_value = max44009_write_event_value,
+	.write_event_config = max44009_write_event_config,
+	.attrs = &max44009_attribute_group,
+};
+
+static irqreturn_t max44009_threaded_irq_handler(int irq, void *p)
+{
+	struct iio_dev *indio_dev = p;
+	struct max44009_data *data = iio_priv(indio_dev);
+	int ret;
+
+	ret = i2c_smbus_read_byte_data(data->client, MAX44009_REG_INT_STATUS);
+	if (ret) {
+		iio_push_event(indio_dev,
+			       IIO_UNMOD_EVENT_CODE(IIO_LIGHT, 0,
+						    IIO_EV_TYPE_THRESH,
+						    IIO_EV_DIR_EITHER),
+			       iio_get_time_ns(indio_dev));
+
+		return IRQ_HANDLED;
+	}
+
+	return IRQ_NONE;
+}
+
+static int max44009_probe(struct i2c_client *client,
+			  const struct i2c_device_id *id)
+{
+	struct max44009_data *data;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+	i2c_set_clientdata(client, indio_dev);
+	data->client = client;
+	indio_dev->dev.parent = &client->dev;
+	indio_dev->info = &max44009_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->name = MAX44009_DRV_NAME;
+	indio_dev->channels = max44009_channels;
+	indio_dev->num_channels = ARRAY_SIZE(max44009_channels);
+	mutex_init(&data->lock);
+
+	/* Clear any stale interrupt bit */
+	ret = i2c_smbus_read_byte_data(client, MAX44009_REG_CFG);
+	if (ret < 0)
+		return ret;
+
+	if (client->irq > 0) {
+		ret = devm_request_threaded_irq(&client->dev, client->irq,
+						NULL,
+						max44009_threaded_irq_handler,
+						IRQF_TRIGGER_FALLING |
+						IRQF_ONESHOT | IRQF_SHARED,
+						"max44009_event",
+						indio_dev);
+		if (ret < 0)
+			return ret;
+	}
+
+	return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct i2c_device_id max44009_id[] = {
+	{ "max44009", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max44009_id);
+
+static struct i2c_driver max44009_driver = {
+	.driver = {
+		.name = MAX44009_DRV_NAME,
+	},
+	.probe = max44009_probe,
+	.id_table = max44009_id,
+};
+module_i2c_driver(max44009_driver);
+
+static const struct of_device_id max44009_of_match[] = {
+	{ .compatible = "maxim,max44009" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, max44009_of_match);
+
+MODULE_AUTHOR("Robert Eshleman <bobbyeshleman@gmail.com>");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("MAX44009 ambient light sensor driver");
-- 
2.20.1

[PATCH v4 2/2] dt-bindings: iio: light: Add max44009

[Robert Eshleman]

Adds device tree bindings for the max44009 light sensor.

Signed-off-by: Robert Eshleman <bobbyeshleman@gmail.com>
---
Changes to v4:
- Use correct subject style
- Change node name to be 'light-sensor' 

Changes to v3:
- None

Changes to v2:
- Clean up style

 .../bindings/iio/light/max44009.txt           | 25 +++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/light/max44009.txt

diff --git a/Documentation/devicetree/bindings/iio/light/max44009.txt b/Documentation/devicetree/bindings/iio/light/max44009.txt
new file mode 100644
index 000000000000..557297c86fba
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/light/max44009.txt
@@ -0,0 +1,25 @@
+* MAX44009 Ambient Light Sensor
+
+Required properties:
+
+- compatible: should be "maxim,max44009"
+- reg: the I2C address of the device (default is <0x4a>)
+
+Optional properties:
+
+- interrupts: interrupt mapping for GPIO IRQ. Should be configured with
+  IRQ_TYPE_EDGE_FALLING.
+
+Refer to interrupt-controller/interrupts.txt for generic interrupt client
+node bindings.
+
+Example:
+
+max44009: light-sensor@4a {
+	compatible = "maxim,max44009";
+	reg = <0x4a>;
+
+	interrupt-parent = <&gpio1>;
+	interrupts = <17 IRQ_TYPE_EDGE_FALLING>;
+};
+
-- 
2.20.1

[PATCH v4 2/2] dt-bindings: iio: light: Add max44009

[Robert Eshleman]

Adds device tree bindings for the max44009 light sensor.

Signed-off-by: Robert Eshleman <bobbyeshleman@gmail.com>
---
Changes to v4:
- Add subsystem to subject line
- Change node name to be 'light-sensor' 
- Clean up style

Changes to v3:
- None

Changes to v2:
- Clean up style

 .../bindings/iio/light/max44009.txt           | 25 +++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/light/max44009.txt

diff --git a/Documentation/devicetree/bindings/iio/light/max44009.txt b/Documentation/devicetree/bindings/iio/light/max44009.txt
new file mode 100644
index 000000000000..557297c86fba
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/light/max44009.txt
@@ -0,0 +1,25 @@
+* MAX44009 Ambient Light Sensor
+
+Required properties:
+
+- compatible: should be "maxim,max44009"
+- reg: the I2C address of the device (default is <0x4a>)
+
+Optional properties:
+
+- interrupts: interrupt mapping for GPIO IRQ. Should be configured with
+  IRQ_TYPE_EDGE_FALLING.
+
+Refer to interrupt-controller/interrupts.txt for generic interrupt client
+node bindings.
+
+Example:
+
+max44009: light-sensor@4a {
+	compatible = "maxim,max44009";
+	reg = <0x4a>;
+
+	interrupt-parent = <&gpio1>;
+	interrupts = <17 IRQ_TYPE_EDGE_FALLING>;
+};
+
-- 
2.20.1

Re: [PATCH v4 1/2] iio: light: add driver for MAX44009

[Jonathan Cameron]

On Thu, 31 Jan 2019 07:29:01 -0800
Robert Eshleman <bobbyeshleman@gmail.com> wrote:

> The MAX44009 is a low-power ambient light sensor from Maxim
> Integrated. It differs from the MAX44000 in that it doesn't have
> proximity sensing and that it requires far less current (1 micro-amp
> vs 5 micro-amps). The register mapping and feature set between the
> two are different enough to require a new driver for the MAX44009.
> 
> Developed and tested with a BeagleBone Black and UDOO Neo (i.MX6SX)
> 
> Supported features:
> 
> * Reading lux (processed value)
> 
> * Rising and falling illuminance threshold
>   events
> 
> * Configuring integration time
> 
> https://datasheets.maximintegrated.com/en/ds/MAX44009.pdf
> 
> Signed-off-by: Robert Eshleman <bobbyeshleman@gmail.com>
Applied to the togreg branch of iio.git and pushed out as testing
for the autobuilders to play with it.

Thanks,

Jonathan

> ---
> Changes to v4:
> - Reformat subject line
> - Clean up whitespace
> 
> Changes to v3:
> - Remove unnecessary mask when setting integration time
> - Return IRQ_NONE in IRQ handler when interrupt not from this device
> - Fix incorrect register usage when reading lux low byte
> - Clean up style
> 
> Changes to v2:
> - Remove unnecessary mutex locking
> - Remove unnecessary triggered buffer support
> - Remove unnecessary wrapper functions for smbus reads and writes
> - Remove scale avail support
> - Use constant scale to provide processed values instead of raw
> - Remove IRQ_NONE return for non-shared IRQ
> - Clean up style
> 
>  drivers/iio/light/Kconfig    |  10 +
>  drivers/iio/light/Makefile   |   1 +
>  drivers/iio/light/max44009.c | 555 +++++++++++++++++++++++++++++++++++
>  3 files changed, 566 insertions(+)
>  create mode 100644 drivers/iio/light/max44009.c
> 
> diff --git a/drivers/iio/light/Kconfig b/drivers/iio/light/Kconfig
> index 36f458433480..5190eacfeb0a 100644
> --- a/drivers/iio/light/Kconfig
> +++ b/drivers/iio/light/Kconfig
> @@ -299,6 +299,16 @@ config MAX44000
>  	 To compile this driver as a module, choose M here:
>  	 the module will be called max44000.
>  
> +config MAX44009
> +	tristate "MAX44009 Ambient Light Sensor"
> +	depends on I2C
> +	help
> +	 Say Y here if you want to build support for Maxim Integrated's
> +	 MAX44009 ambient light sensor device.
> +
> +	 To compile this driver as a module, choose M here:
> +	 the module will be called max44009.
> +
>  config OPT3001
>  	tristate "Texas Instruments OPT3001 Light Sensor"
>  	depends on I2C
> diff --git a/drivers/iio/light/Makefile b/drivers/iio/light/Makefile
> index 286bf3975372..e40794fbb435 100644
> --- a/drivers/iio/light/Makefile
> +++ b/drivers/iio/light/Makefile
> @@ -28,6 +28,7 @@ obj-$(CONFIG_SENSORS_LM3533)	+= lm3533-als.o
>  obj-$(CONFIG_LTR501)		+= ltr501.o
>  obj-$(CONFIG_LV0104CS)		+= lv0104cs.o
>  obj-$(CONFIG_MAX44000)		+= max44000.o
> +obj-$(CONFIG_MAX44009)		+= max44009.o
>  obj-$(CONFIG_OPT3001)		+= opt3001.o
>  obj-$(CONFIG_PA12203001)	+= pa12203001.o
>  obj-$(CONFIG_RPR0521)		+= rpr0521.o
> diff --git a/drivers/iio/light/max44009.c b/drivers/iio/light/max44009.c
> new file mode 100644
> index 000000000000..00ba15499638
> --- /dev/null
> +++ b/drivers/iio/light/max44009.c
> @@ -0,0 +1,555 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * max44009.c - Support for MAX44009 Ambient Light Sensor
> + *
> + * Copyright (c) 2019 Robert Eshleman <bobbyeshleman@gmail.com>
> + *
> + * Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX44009.pdf
> + *
> + * TODO: Support continuous mode and configuring from manual mode to
> + *	 automatic mode.
> + *
> + * Default I2C address: 0x4a
> + */
> +
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/bits.h>
> +#include <linux/i2c.h>
> +#include <linux/iio/events.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/interrupt.h>
> +#include <linux/module.h>
> +#include <linux/util_macros.h>
> +
> +#define MAX44009_DRV_NAME "max44009"
> +
> +/* Registers in datasheet order */
> +#define MAX44009_REG_INT_STATUS 0x0
> +#define MAX44009_REG_INT_EN 0x1
> +#define MAX44009_REG_CFG 0x2
> +#define MAX44009_REG_LUX_HI 0x3
> +#define MAX44009_REG_LUX_LO 0x4
> +#define MAX44009_REG_UPPER_THR 0x5
> +#define MAX44009_REG_LOWER_THR 0x6
> +#define MAX44009_REG_THR_TIMER 0x7
> +
> +#define MAX44009_CFG_TIM_MASK GENMASK(2, 0)
> +#define MAX44009_CFG_MAN_MODE_MASK BIT(6)
> +
> +/* The maximum rising threshold for the max44009 */
> +#define MAX44009_MAXIMUM_THRESHOLD 7520256
> +
> +#define MAX44009_THRESH_EXP_MASK (0xf << 4)
> +#define MAX44009_THRESH_EXP_RSHIFT 4
> +#define MAX44009_THRESH_MANT_LSHIFT 4
> +#define MAX44009_THRESH_MANT_MASK 0xf
> +
> +#define MAX44009_UPPER_THR_MINIMUM 15
> +
> +/* The max44009 always scales raw readings by 0.045 and is non-configurable */
> +#define MAX44009_SCALE_NUMERATOR 45
> +#define MAX44009_SCALE_DENOMINATOR 1000
> +
> +/* The fixed-point fractional multiplier for de-scaling threshold values */
> +#define MAX44009_FRACT_MULT 1000000
> +
> +static const u32 max44009_int_time_ns_array[] = {
> +	800000000,
> +	400000000,
> +	200000000,
> +	100000000,
> +	50000000, /* Manual mode only */
> +	25000000, /* Manual mode only */
> +	12500000, /* Manual mode only */
> +	6250000,  /* Manual mode only */
> +};
> +
> +static const char max44009_int_time_str[] =
> +	"0.8 "
> +	"0.4 "
> +	"0.2 "
> +	"0.1 "
> +	"0.05 "
> +	"0.025 "
> +	"0.0125 "
> +	"0.00625";
> +
> +struct max44009_data {
> +	struct i2c_client *client;
> +	struct mutex lock;
> +};
> +
> +static const struct iio_event_spec max44009_event_spec[] = {
> +	{
> +		.type = IIO_EV_TYPE_THRESH,
> +		.dir = IIO_EV_DIR_RISING,
> +		.mask_separate = BIT(IIO_EV_INFO_VALUE) |
> +				 BIT(IIO_EV_INFO_ENABLE),
> +	},
> +	{
> +		.type = IIO_EV_TYPE_THRESH,
> +		.dir = IIO_EV_DIR_FALLING,
> +		.mask_separate = BIT(IIO_EV_INFO_VALUE) |
> +				 BIT(IIO_EV_INFO_ENABLE),
> +	},
> +};
> +
> +static const struct iio_chan_spec max44009_channels[] = {
> +	{
> +		.type = IIO_LIGHT,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |
> +				      BIT(IIO_CHAN_INFO_INT_TIME),
> +		.event_spec = max44009_event_spec,
> +		.num_event_specs = ARRAY_SIZE(max44009_event_spec),
> +	},
> +};
> +
> +static int max44009_read_int_time(struct max44009_data *data)
> +{
> +
> +	int ret = i2c_smbus_read_byte_data(data->client, MAX44009_REG_CFG);
> +
> +	if (ret < 0)
> +		return ret;
> +
> +	return max44009_int_time_ns_array[ret & MAX44009_CFG_TIM_MASK];
> +}
> +
> +static int max44009_write_int_time(struct max44009_data *data,
> +				   int val, int val2)
> +{
> +	struct i2c_client *client = data->client;
> +	int ret, int_time, config;
> +	s64 ns;
> +
> +	ns = val * NSEC_PER_SEC + val2;
> +	int_time = find_closest_descending(
> +			ns,
> +			max44009_int_time_ns_array,
> +			ARRAY_SIZE(max44009_int_time_ns_array));
> +
> +	ret = i2c_smbus_read_byte_data(client, MAX44009_REG_CFG);
> +	if (ret < 0)
> +		return ret;
> +
> +	config = ret;
> +	config &= int_time;
> +
> +	/*
> +	 * To set the integration time, the device must also be in manual
> +	 * mode.
> +	 */
> +	config |= MAX44009_CFG_MAN_MODE_MASK;
> +
> +	return i2c_smbus_write_byte_data(client, MAX44009_REG_CFG, config);
> +}
> +
> +static int max44009_write_raw(struct iio_dev *indio_dev,
> +			      struct iio_chan_spec const *chan, int val,
> +			      int val2, long mask)
> +{
> +	struct max44009_data *data = iio_priv(indio_dev);
> +	int ret;
> +
> +	if (mask == IIO_CHAN_INFO_INT_TIME && chan->type == IIO_LIGHT) {
> +		mutex_lock(&data->lock);
> +		ret = max44009_write_int_time(data, val, val2);
> +		mutex_unlock(&data->lock);
> +		return ret;
> +	}
> +	return -EINVAL;
> +}
> +
> +static int max44009_write_raw_get_fmt(struct iio_dev *indio_dev,
> +				      struct iio_chan_spec const *chan,
> +				      long mask)
> +{
> +	return IIO_VAL_INT_PLUS_NANO;
> +}
> +
> +static int max44009_lux_raw(u8 hi, u8 lo)
> +{
> +	int mantissa;
> +	int exponent;
> +
> +	/*
> +	 * The mantissa consists of the low nibble of the Lux High Byte
> +	 * and the low nibble of the Lux Low Byte.
> +	 */
> +	mantissa = ((hi & 0xf) << 4) | (lo & 0xf);
> +
> +	/* The exponent byte is just the upper nibble of the Lux High Byte */
> +	exponent = (hi >> 4) & 0xf;
> +
> +	/*
> +	 * The exponent value is base 2 to the power of the raw exponent byte.
> +	 */
> +	exponent = 1 << exponent;
> +
> +	return exponent * mantissa;
> +}
> +
> +#define MAX44009_READ_LUX_XFER_LEN (4)
> +
> +static int max44009_read_lux_raw(struct max44009_data *data)
> +{
> +	int ret;
> +	u8 hireg = MAX44009_REG_LUX_HI;
> +	u8 loreg = MAX44009_REG_LUX_LO;
> +	u8 lo = 0;
> +	u8 hi = 0;
> +
> +	struct i2c_msg msgs[] = {
> +		{
> +			.addr = data->client->addr,
> +			.flags = 0,
> +			.len = sizeof(hireg),
> +			.buf = &hireg,
> +		},
> +		{
> +			.addr = data->client->addr,
> +			.flags = I2C_M_RD,
> +			.len = sizeof(hi),
> +			.buf = &hi,
> +		},
> +		{
> +			.addr = data->client->addr,
> +			.flags = 0,
> +			.len = sizeof(loreg),
> +			.buf = &loreg,
> +		},
> +		{
> +			.addr = data->client->addr,
> +			.flags = I2C_M_RD,
> +			.len = sizeof(lo),
> +			.buf = &lo,
> +		}
> +	};
> +
> +	/*
> +	 * Use i2c_transfer instead of smbus read because i2c_transfer
> +	 * does NOT use a stop bit between address write and data read.
> +	 * Using a stop bit causes disjoint upper/lower byte reads and
> +	 * reduces accuracy.
> +	 */
> +	ret = i2c_transfer(data->client->adapter,
> +			   msgs, MAX44009_READ_LUX_XFER_LEN);
> +
> +	if (ret != MAX44009_READ_LUX_XFER_LEN)
> +		return -EIO;
> +
> +	return max44009_lux_raw(hi, lo);
> +}
> +
> +static int max44009_read_raw(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan, int *val,
> +			     int *val2, long mask)
> +{
> +	struct max44009_data *data = iio_priv(indio_dev);
> +	int lux_raw;
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_PROCESSED:
> +		switch (chan->type) {
> +		case IIO_LIGHT:
> +			ret = max44009_read_lux_raw(data);
> +			if (ret < 0)
> +				return ret;
> +			lux_raw = ret;
> +
> +			*val = lux_raw * MAX44009_SCALE_NUMERATOR;
> +			*val2 = MAX44009_SCALE_DENOMINATOR;
> +			return IIO_VAL_FRACTIONAL;
> +		default:
> +			return -EINVAL;
> +		}
> +	case IIO_CHAN_INFO_INT_TIME:
> +		switch (chan->type) {
> +		case IIO_LIGHT:
> +			ret = max44009_read_int_time(data);
> +			if (ret < 0)
> +				return ret;
> +
> +			*val2 = ret;
> +			*val = 0;
> +			return IIO_VAL_INT_PLUS_NANO;
> +		default:
> +			return -EINVAL;
> +		}
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static IIO_CONST_ATTR(illuminance_integration_time_available,
> +		      max44009_int_time_str);
> +
> +static struct attribute *max44009_attributes[] = {
> +	&iio_const_attr_illuminance_integration_time_available.dev_attr.attr,
> +	NULL,
> +};
> +
> +static const struct attribute_group max44009_attribute_group = {
> +	.attrs = max44009_attributes,
> +};
> +
> +static int max44009_threshold_byte_from_fraction(int integral, int fractional)
> +{
> +	int mantissa, exp;
> +
> +	if ((integral <= 0 && fractional <= 0) ||
> +	     integral > MAX44009_MAXIMUM_THRESHOLD ||
> +	     (integral == MAX44009_MAXIMUM_THRESHOLD && fractional != 0))
> +		return -EINVAL;
> +
> +	/* Reverse scaling of fixed-point integral */
> +	mantissa = integral * MAX44009_SCALE_DENOMINATOR;
> +	mantissa /= MAX44009_SCALE_NUMERATOR;
> +
> +	/* Reverse scaling of fixed-point fractional */
> +	mantissa += fractional / MAX44009_FRACT_MULT *
> +		    (MAX44009_SCALE_DENOMINATOR / MAX44009_SCALE_NUMERATOR);
> +
> +	for (exp = 0; mantissa > 0xff; exp++)
> +		mantissa >>= 1;
> +
> +	mantissa >>= 4;
> +	mantissa &= 0xf;
> +	exp <<= 4;
> +
> +	return exp | mantissa;
> +}
> +
> +static int max44009_get_thr_reg(enum iio_event_direction dir)
> +{
> +	switch (dir) {
> +	case IIO_EV_DIR_RISING:
> +		return MAX44009_REG_UPPER_THR;
> +	case IIO_EV_DIR_FALLING:
> +		return MAX44009_REG_LOWER_THR;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int max44009_write_event_value(struct iio_dev *indio_dev,
> +				      const struct iio_chan_spec *chan,
> +				      enum iio_event_type type,
> +				      enum iio_event_direction dir,
> +				      enum iio_event_info info,
> +				      int val, int val2)
> +{
> +	struct max44009_data *data = iio_priv(indio_dev);
> +	int reg, threshold;
> +
> +	if (info != IIO_EV_INFO_VALUE || chan->type != IIO_LIGHT)
> +		return -EINVAL;
> +
> +	threshold = max44009_threshold_byte_from_fraction(val, val2);
> +	if (threshold < 0)
> +		return threshold;
> +
> +	reg = max44009_get_thr_reg(dir);
> +	if (reg < 0)
> +		return reg;
> +
> +	return i2c_smbus_write_byte_data(data->client, reg, threshold);
> +}
> +
> +static int max44009_read_threshold(struct iio_dev *indio_dev,
> +				   enum iio_event_direction dir)
> +{
> +	struct max44009_data *data = iio_priv(indio_dev);
> +	int byte, reg;
> +	int mantissa, exponent;
> +
> +	reg = max44009_get_thr_reg(dir);
> +	if (reg < 0)
> +		return reg;
> +
> +	byte = i2c_smbus_read_byte_data(data->client, reg);
> +	if (byte < 0)
> +		return byte;
> +
> +	mantissa = byte & MAX44009_THRESH_MANT_MASK;
> +	mantissa <<= MAX44009_THRESH_MANT_LSHIFT;
> +
> +	/*
> +	 * To get the upper threshold, always adds the minimum upper threshold
> +	 * value to the shifted byte value (see datasheet).
> +	 */
> +	if (dir == IIO_EV_DIR_RISING)
> +		mantissa += MAX44009_UPPER_THR_MINIMUM;
> +
> +	/*
> +	 * Exponent is base 2 to the power of the threshold exponent byte
> +	 * value
> +	 */
> +	exponent = byte & MAX44009_THRESH_EXP_MASK;
> +	exponent >>= MAX44009_THRESH_EXP_RSHIFT;
> +
> +	return (1 << exponent) * mantissa;
> +}
> +
> +static int max44009_read_event_value(struct iio_dev *indio_dev,
> +				     const struct iio_chan_spec *chan,
> +				     enum iio_event_type type,
> +				     enum iio_event_direction dir,
> +				     enum iio_event_info info,
> +				     int *val, int *val2)
> +{
> +	int ret;
> +	int threshold;
> +
> +	if (chan->type != IIO_LIGHT || type != IIO_EV_TYPE_THRESH)
> +		return -EINVAL;
> +
> +	ret = max44009_read_threshold(indio_dev, dir);
> +	if (ret < 0)
> +		return ret;
> +	threshold = ret;
> +
> +	*val = threshold * MAX44009_SCALE_NUMERATOR;
> +	*val2 = MAX44009_SCALE_DENOMINATOR;
> +
> +	return IIO_VAL_FRACTIONAL;
> +}
> +
> +static int max44009_write_event_config(struct iio_dev *indio_dev,
> +				       const struct iio_chan_spec *chan,
> +				       enum iio_event_type type,
> +				       enum iio_event_direction dir,
> +				       int state)
> +{
> +	struct max44009_data *data = iio_priv(indio_dev);
> +	int ret;
> +
> +	if (chan->type != IIO_LIGHT || type != IIO_EV_TYPE_THRESH)
> +		return -EINVAL;
> +
> +	ret = i2c_smbus_write_byte_data(data->client,
> +					MAX44009_REG_INT_EN, state);
> +	if (ret < 0)
> +		return ret;
> +
> +	/*
> +	 * Set device to trigger interrupt immediately upon exceeding
> +	 * the threshold limit.
> +	 */
> +	return i2c_smbus_write_byte_data(data->client,
> +					 MAX44009_REG_THR_TIMER, 0);
> +}
> +
> +static int max44009_read_event_config(struct iio_dev *indio_dev,
> +				      const struct iio_chan_spec *chan,
> +				      enum iio_event_type type,
> +				      enum iio_event_direction dir)
> +{
> +	struct max44009_data *data = iio_priv(indio_dev);
> +
> +	if (chan->type != IIO_LIGHT || type != IIO_EV_TYPE_THRESH)
> +		return -EINVAL;
> +
> +	return i2c_smbus_read_byte_data(data->client, MAX44009_REG_INT_EN);
> +}
> +
> +static const struct iio_info max44009_info = {
> +	.read_raw = max44009_read_raw,
> +	.write_raw = max44009_write_raw,
> +	.write_raw_get_fmt = max44009_write_raw_get_fmt,
> +	.read_event_value = max44009_read_event_value,
> +	.read_event_config = max44009_read_event_config,
> +	.write_event_value = max44009_write_event_value,
> +	.write_event_config = max44009_write_event_config,
> +	.attrs = &max44009_attribute_group,
> +};
> +
> +static irqreturn_t max44009_threaded_irq_handler(int irq, void *p)
> +{
> +	struct iio_dev *indio_dev = p;
> +	struct max44009_data *data = iio_priv(indio_dev);
> +	int ret;
> +
> +	ret = i2c_smbus_read_byte_data(data->client, MAX44009_REG_INT_STATUS);
> +	if (ret) {
> +		iio_push_event(indio_dev,
> +			       IIO_UNMOD_EVENT_CODE(IIO_LIGHT, 0,
> +						    IIO_EV_TYPE_THRESH,
> +						    IIO_EV_DIR_EITHER),
> +			       iio_get_time_ns(indio_dev));
> +
> +		return IRQ_HANDLED;
> +	}
> +
> +	return IRQ_NONE;
> +}
> +
> +static int max44009_probe(struct i2c_client *client,
> +			  const struct i2c_device_id *id)
> +{
> +	struct max44009_data *data;
> +	struct iio_dev *indio_dev;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	data = iio_priv(indio_dev);
> +	i2c_set_clientdata(client, indio_dev);
> +	data->client = client;
> +	indio_dev->dev.parent = &client->dev;
> +	indio_dev->info = &max44009_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->name = MAX44009_DRV_NAME;
> +	indio_dev->channels = max44009_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(max44009_channels);
> +	mutex_init(&data->lock);
> +
> +	/* Clear any stale interrupt bit */
> +	ret = i2c_smbus_read_byte_data(client, MAX44009_REG_CFG);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (client->irq > 0) {
> +		ret = devm_request_threaded_irq(&client->dev, client->irq,
> +						NULL,
> +						max44009_threaded_irq_handler,
> +						IRQF_TRIGGER_FALLING |
> +						IRQF_ONESHOT | IRQF_SHARED,
> +						"max44009_event",
> +						indio_dev);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	return devm_iio_device_register(&client->dev, indio_dev);
> +}
> +
> +static const struct i2c_device_id max44009_id[] = {
> +	{ "max44009", 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, max44009_id);
> +
> +static struct i2c_driver max44009_driver = {
> +	.driver = {
> +		.name = MAX44009_DRV_NAME,
> +	},
> +	.probe = max44009_probe,
> +	.id_table = max44009_id,
> +};
> +module_i2c_driver(max44009_driver);
> +
> +static const struct of_device_id max44009_of_match[] = {
> +	{ .compatible = "maxim,max44009" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, max44009_of_match);
> +
> +MODULE_AUTHOR("Robert Eshleman <bobbyeshleman@gmail.com>");
> +MODULE_LICENSE("GPL v2");
> +MODULE_DESCRIPTION("MAX44009 ambient light sensor driver");

Re: [PATCH v4 2/2] dt-bindings: iio: light: Add max44009

[Jonathan Cameron]

On Thu, 31 Jan 2019 07:49:16 -0800
Robert Eshleman <bobbyeshleman@gmail.com> wrote:

> Adds device tree bindings for the max44009 light sensor.
> 
> Signed-off-by: Robert Eshleman <bobbyeshleman@gmail.com>

Still time for Rob to comment if he want's to, but I think
with few tweaks as below this matches what he asked for.

Applied to the togreg branch of iio.git and pushed out as testing for the
autobuilders to play with it.

Thanks,

Jonathan

> ---
> Changes to v4:
> - Add subsystem to subject line
> - Change node name to be 'light-sensor' 
> - Clean up style
> 
> Changes to v3:
> - None
> 
> Changes to v2:
> - Clean up style
> 
>  .../bindings/iio/light/max44009.txt           | 25 +++++++++++++++++++
>  1 file changed, 25 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/light/max44009.txt
> 
> diff --git a/Documentation/devicetree/bindings/iio/light/max44009.txt b/Documentation/devicetree/bindings/iio/light/max44009.txt
> new file mode 100644
> index 000000000000..557297c86fba
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/light/max44009.txt
> @@ -0,0 +1,25 @@
> +* MAX44009 Ambient Light Sensor
> +
> +Required properties:
> +
> +- compatible: should be "maxim,max44009"
> +- reg: the I2C address of the device (default is <0x4a>)
> +
> +Optional properties:
> +
> +- interrupts: interrupt mapping for GPIO IRQ. Should be configured with
> +  IRQ_TYPE_EDGE_FALLING.
> +
> +Refer to interrupt-controller/interrupts.txt for generic interrupt client
> +node bindings.
> +
> +Example:
> +
> +max44009: light-sensor@4a {
The label is only useful if something is going to cross reference it.
Can't see that happening so dropped it. Above now reads.

light-sensor@4a {


> +	compatible = "maxim,max44009";
> +	reg = <0x4a>;
> +
> +	interrupt-parent = <&gpio1>;
> +	interrupts = <17 IRQ_TYPE_EDGE_FALLING>;
> +};
> +
Cleaned up extra entirely blank line at end of file.