[PATCH v6 0/2] iio: potentiostat: add LMP91000 support

[PATCH v6 0/2] iio: potentiostat: add LMP91000 support

[Matt Ranostay]

Changes from v1:
 * Rename ti-adc1x1s.c driver to ti-adc161s626.c
 * Switch from iio_channel_read() to using the industrialio-buffer-cb
   interface
 * Process data in ADC trigger handler for buffer callbacks
 * Set the mux trigger to the ADC referenced by io-channels by default

Changes from v2:
 * Fix configuration index shifting values
 * Switch from wait_for_completion_interruptible to wait_for_completion_timeout

Changes from v3:
 * Fix order of probe function error rollback

Changes from v4:
 * Report back scale + offset from adc
 * Switch temperature channel from IIO_VOLTAGE to IIO_TEMP with processing
 * Add iio_read_channel_offset helper

Changes from v5:
 * making IIO_CHAN_INFO_SCALE consumer access have less duplicate code
 * fixed race condition with trigger getting registered before immutable trigger
   being set to the ADC consumer

Matt Ranostay (2):
  iio: inkern: add iio_read_channel_offset helper
  iio: potentiostat: add LMP91000 support

 .../bindings/iio/potentiostat/lmp91000.txt         |  30 ++
 drivers/iio/Kconfig                                |   1 +
 drivers/iio/Makefile                               |   1 +
 drivers/iio/inkern.c                               |  39 +-
 drivers/iio/potentiostat/Kconfig                   |  22 +
 drivers/iio/potentiostat/Makefile                  |   6 +
 drivers/iio/potentiostat/lmp91000.c                | 445 +++++++++++++++++++++
 include/linux/iio/consumer.h                       |  13 +
 8 files changed, 544 insertions(+), 13 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/iio/potentiostat/lmp91000.txt
 create mode 100644 drivers/iio/potentiostat/Kconfig
 create mode 100644 drivers/iio/potentiostat/Makefile
 create mode 100644 drivers/iio/potentiostat/lmp91000.c

-- 
2.7.4

[PATCH v6 1/2] iio: inkern: add iio_read_channel_offset helper

[Matt Ranostay]

Allow access to underlying channel IIO_CHAN_INFO_OFFSET from a consumer.

Signed-off-by: Matt Ranostay <matt@ranostay.consulting>
---
 drivers/iio/inkern.c         | 39 ++++++++++++++++++++++++++-------------
 include/linux/iio/consumer.h | 13 +++++++++++++
 2 files changed, 39 insertions(+), 13 deletions(-)

diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
index c4757e6367e7..29df11572858 100644
--- a/drivers/iio/inkern.c
+++ b/drivers/iio/inkern.c
@@ -658,6 +658,31 @@ int iio_convert_raw_to_processed(struct iio_channel *chan, int raw,
 }
 EXPORT_SYMBOL_GPL(iio_convert_raw_to_processed);
 
+static int iio_read_channel_attribute(struct iio_channel *chan,
+				      int *val, int *val2,
+				      enum iio_chan_info_enum attribute)
+{
+	int ret;
+
+	mutex_lock(&chan->indio_dev->info_exist_lock);
+	if (chan->indio_dev->info == NULL) {
+		ret = -ENODEV;
+		goto err_unlock;
+	}
+
+	ret = iio_channel_read(chan, val, val2, attribute);
+err_unlock:
+	mutex_unlock(&chan->indio_dev->info_exist_lock);
+
+	return ret;
+}
+
+int iio_read_channel_offset(struct iio_channel *chan, int *val, int *val2)
+{
+	return iio_read_channel_attribute(chan, val, val2, IIO_CHAN_INFO_OFFSET);
+}
+EXPORT_SYMBOL_GPL(iio_read_channel_offset);
+
 int iio_read_channel_processed(struct iio_channel *chan, int *val)
 {
 	int ret;
@@ -687,19 +712,7 @@ EXPORT_SYMBOL_GPL(iio_read_channel_processed);
 
 int iio_read_channel_scale(struct iio_channel *chan, int *val, int *val2)
 {
-	int ret;
-
-	mutex_lock(&chan->indio_dev->info_exist_lock);
-	if (chan->indio_dev->info == NULL) {
-		ret = -ENODEV;
-		goto err_unlock;
-	}
-
-	ret = iio_channel_read(chan, val, val2, IIO_CHAN_INFO_SCALE);
-err_unlock:
-	mutex_unlock(&chan->indio_dev->info_exist_lock);
-
-	return ret;
+	return iio_read_channel_attribute(chan, val, val2, IIO_CHAN_INFO_SCALE);
 }
 EXPORT_SYMBOL_GPL(iio_read_channel_scale);
 
diff --git a/include/linux/iio/consumer.h b/include/linux/iio/consumer.h
index 9edccfba1ffb..638157234357 100644
--- a/include/linux/iio/consumer.h
+++ b/include/linux/iio/consumer.h
@@ -236,6 +236,19 @@ int iio_get_channel_type(struct iio_channel *channel,
 			 enum iio_chan_type *type);
 
 /**
+ * iio_read_channel_offset() - read the offset value for a channel
+ * @chan:		The channel being queried.
+ * @val:		First part of value read back.
+ * @val2:		Second part of value read back.
+ *
+ * Note returns a description of what is in val and val2, such
+ * as IIO_VAL_INT_PLUS_MICRO telling us we have a value of val
+ * + val2/1e6
+ */
+int iio_read_channel_offset(struct iio_channel *chan, int *val,
+			   int *val2);
+
+/**
  * iio_read_channel_scale() - read the scale value for a channel
  * @chan:		The channel being queried.
  * @val:		First part of value read back.
-- 
2.7.4

[PATCH v6 2/2] iio: potentiostat: add LMP91000 support

[Matt Ranostay]

Add support for the LMP91000 potentiostat which is used for chemical
sensing applications.

Signed-off-by: Matt Ranostay <matt@ranostay.consulting>
---
 .../bindings/iio/potentiostat/lmp91000.txt         |  30 ++
 drivers/iio/Kconfig                                |   1 +
 drivers/iio/Makefile                               |   1 +
 drivers/iio/potentiostat/Kconfig                   |  22 +
 drivers/iio/potentiostat/Makefile                  |   6 +
 drivers/iio/potentiostat/lmp91000.c                | 445 +++++++++++++++++++++
 6 files changed, 505 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/potentiostat/lmp91000.txt
 create mode 100644 drivers/iio/potentiostat/Kconfig
 create mode 100644 drivers/iio/potentiostat/Makefile
 create mode 100644 drivers/iio/potentiostat/lmp91000.c

diff --git a/Documentation/devicetree/bindings/iio/potentiostat/lmp91000.txt b/Documentation/devicetree/bindings/iio/potentiostat/lmp91000.txt
new file mode 100644
index 000000000000..b9b621e94cd7
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/potentiostat/lmp91000.txt
@@ -0,0 +1,30 @@
+* Texas Instruments LMP91000 potentiostat
+
+http://www.ti.com/lit/ds/symlink/lmp91000.pdf
+
+Required properties:
+
+  - compatible: should be "ti,lmp91000"
+  - reg: the I2C address of the device
+  - io-channels: the phandle of the iio provider
+
+  - ti,external-tia-resistor: if the property ti,tia-gain-ohm is not defined this
+    needs to be set to signal that an external resistor value is being used.
+
+Optional properties:
+
+  - ti,tia-gain-ohm: ohm value of the internal resistor for the transimpedance
+    amplifier. Must be 2750, 3500, 7000, 14000, 35000, 120000, or 350000 ohms.
+
+  - ti,rload-ohm: ohm value of the internal resistor load applied to the gas
+    sensor. Must be 10, 33, 50, or 100 (default) ohms.
+
+Example:
+
+lmp91000@48 {
+	compatible = "ti,lmp91000";
+	reg = <0x48>;
+	ti,tia-gain-ohm = <7500>;
+	ti,rload = <100>;
+	io-channels = <&adc>;
+};
diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
index 6743b18194fb..a31a8cf2c330 100644
--- a/drivers/iio/Kconfig
+++ b/drivers/iio/Kconfig
@@ -87,6 +87,7 @@ if IIO_TRIGGER
    source "drivers/iio/trigger/Kconfig"
 endif #IIO_TRIGGER
 source "drivers/iio/potentiometer/Kconfig"
+source "drivers/iio/potentiostat/Kconfig"
 source "drivers/iio/pressure/Kconfig"
 source "drivers/iio/proximity/Kconfig"
 source "drivers/iio/temperature/Kconfig"
diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
index 87e4c4369e2f..2b6e2762a886 100644
--- a/drivers/iio/Makefile
+++ b/drivers/iio/Makefile
@@ -29,6 +29,7 @@ obj-y += light/
 obj-y += magnetometer/
 obj-y += orientation/
 obj-y += potentiometer/
+obj-y += potentiostat/
 obj-y += pressure/
 obj-y += proximity/
 obj-y += temperature/
diff --git a/drivers/iio/potentiostat/Kconfig b/drivers/iio/potentiostat/Kconfig
new file mode 100644
index 000000000000..1e3baf2cc97d
--- /dev/null
+++ b/drivers/iio/potentiostat/Kconfig
@@ -0,0 +1,22 @@
+#
+# Potentiostat drivers
+#
+# When adding new entries keep the list in alphabetical order
+
+menu "Digital potentiostats"
+
+config LMP91000
+	tristate "Texas Instruments LMP91000 potentiostat driver"
+	depends on I2C
+	select REGMAP_I2C
+	select IIO_BUFFER
+	select IIO_BUFFER_CB
+	select IIO_TRIGGERED_BUFFER
+	help
+	  Say yes here to build support for the Texas Instruments
+	  LMP91000 digital potentiostat chip.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called lmp91000
+
+endmenu
diff --git a/drivers/iio/potentiostat/Makefile b/drivers/iio/potentiostat/Makefile
new file mode 100644
index 000000000000..64d315ef4449
--- /dev/null
+++ b/drivers/iio/potentiostat/Makefile
@@ -0,0 +1,6 @@
+#
+# Makefile for industrial I/O potentiostat drivers
+#
+
+# When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_LMP91000) += lmp91000.o
diff --git a/drivers/iio/potentiostat/lmp91000.c b/drivers/iio/potentiostat/lmp91000.c
new file mode 100644
index 000000000000..600e97d98f91
--- /dev/null
+++ b/drivers/iio/potentiostat/lmp91000.c
@@ -0,0 +1,445 @@
+/*
+ * lmp91000.c - Support for Texas Instruments digital potentiostats
+ *
+ * Copyright (C) 2016 Matt Ranostay <mranostay@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * TODO: bias voltage + polarity control, and multiple chip support
+ */
+
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/delay.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/consumer.h>
+#include <linux/iio/trigger.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+
+#define LMP91000_REG_LOCK		0x01
+#define LMP91000_REG_TIACN		0x10
+#define LMP91000_REG_TIACN_GAIN_SHIFT	2
+
+#define LMP91000_REG_REFCN		0x11
+#define LMP91000_REG_REFCN_EXT_REF	0x20
+#define LMP91000_REG_REFCN_50_ZERO	0x80
+
+#define LMP91000_REG_MODECN		0x12
+#define LMP91000_REG_MODECN_3LEAD	0x03
+#define LMP91000_REG_MODECN_TEMP	0x07
+
+#define LMP91000_DRV_NAME	"lmp91000"
+
+static const int lmp91000_tia_gain[] = { 0, 2750, 3500, 7000, 14000, 35000,
+					 120000, 350000 };
+
+static const int lmp91000_rload[] = { 10, 33, 50, 100 };
+
+#define LMP91000_TEMP_BASE	-40
+
+static const u16 lmp91000_temp_lut[] = {
+	1875, 1867, 1860, 1852, 1844, 1836, 1828, 1821, 1813, 1805,
+	1797, 1789, 1782, 1774, 1766, 1758, 1750, 1742, 1734, 1727,
+	1719, 1711, 1703, 1695, 1687, 1679, 1671, 1663, 1656, 1648,
+	1640, 1632, 1624, 1616, 1608, 1600, 1592, 1584, 1576, 1568,
+	1560, 1552, 1544, 1536, 1528, 1520, 1512, 1504, 1496, 1488,
+	1480, 1472, 1464, 1456, 1448, 1440, 1432, 1424, 1415, 1407,
+	1399, 1391, 1383, 1375, 1367, 1359, 1351, 1342, 1334, 1326,
+	1318, 1310, 1302, 1293, 1285, 1277, 1269, 1261, 1253, 1244,
+	1236, 1228, 1220, 1212, 1203, 1195, 1187, 1179, 1170, 1162,
+	1154, 1146, 1137, 1129, 1121, 1112, 1104, 1096, 1087, 1079,
+	1071, 1063, 1054, 1046, 1038, 1029, 1021, 1012, 1004,  996,
+	 987,  979,  971,  962,  954,  945,  937,  929,  920,  912,
+	 903,  895,  886,  878,  870,  861 };
+
+static const struct regmap_config lmp91000_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+struct lmp91000_data {
+	struct regmap *regmap;
+	struct device *dev;
+
+	struct iio_trigger *trig;
+	struct iio_cb_buffer *cb_buffer;
+	struct iio_channel *adc_chan;
+
+	struct completion completion;
+	u8 chan_select;
+
+	u32 buffer[4]; /* 64-bit data + 64-bit timestamp */
+};
+
+static const struct iio_chan_spec lmp91000_channels[] = {
+	{ /* chemical channel mV */
+		.type = IIO_VOLTAGE,
+		.channel = 0,
+		.address = LMP91000_REG_MODECN_3LEAD,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+				      BIT(IIO_CHAN_INFO_OFFSET) |
+				      BIT(IIO_CHAN_INFO_SCALE),
+		.scan_index = 0,
+		.scan_type = {
+			.sign = 's',
+			.realbits = 32,
+			.storagebits = 32,
+		},
+	},
+	IIO_CHAN_SOFT_TIMESTAMP(1),
+	{ /* temperature channel mV */
+		.type = IIO_TEMP,
+		.channel = 1,
+		.address = LMP91000_REG_MODECN_TEMP,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
+		.scan_index = -1,
+	},
+};
+
+static int lmp91000_read(struct lmp91000_data *data, int channel, int *val)
+{
+	int state, ret;
+
+	ret = regmap_read(data->regmap, LMP91000_REG_MODECN, &state);
+	if (ret)
+		return -EINVAL;
+
+	ret = regmap_write(data->regmap, LMP91000_REG_MODECN, channel);
+	if (ret)
+		return -EINVAL;
+
+	/* delay till first temperature reading is complete */
+	if ((state != channel) && (channel == LMP91000_REG_MODECN_TEMP))
+		usleep_range(3000, 4000);
+
+	data->chan_select = channel != LMP91000_REG_MODECN_3LEAD;
+
+	iio_trigger_poll_chained(data->trig);
+
+	ret = wait_for_completion_timeout(&data->completion, HZ);
+	reinit_completion(&data->completion);
+
+	if (!ret)
+		return -ETIMEDOUT;
+
+	*val = data->buffer[data->chan_select];
+
+	return 0;
+}
+
+static irqreturn_t lmp91000_buffer_handler(int irq, void *private)
+{
+	struct iio_poll_func *pf = private;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct lmp91000_data *data = iio_priv(indio_dev);
+	int ret, val;
+
+	memset(data->buffer, 0, sizeof(data->buffer));
+
+	ret = lmp91000_read(data, LMP91000_REG_MODECN_3LEAD, &val);
+	if (!ret) {
+		data->buffer[0] = val;
+		iio_push_to_buffers_with_timestamp(indio_dev, data->buffer,
+						   iio_get_time_ns(indio_dev));
+	}
+
+	iio_trigger_notify_done(indio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
+static int lmp91000_read_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int *val, int *val2, long mask)
+{
+	struct lmp91000_data *data = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+	case IIO_CHAN_INFO_PROCESSED: {
+		int ret = iio_channel_start_all_cb(data->cb_buffer);
+
+		if (ret)
+			return ret;
+
+		ret = lmp91000_read(data, chan->address, val);
+
+		iio_channel_stop_all_cb(data->cb_buffer);
+
+		if (ret)
+			return ret;
+
+		if (mask == IIO_CHAN_INFO_PROCESSED) {
+			int tmp, i;
+
+			ret = iio_convert_raw_to_processed(data->adc_chan,
+							   *val, &tmp, 1);
+			if (ret)
+				return ret;
+
+			for (i = 0; i < ARRAY_SIZE(lmp91000_temp_lut); i++)
+				if (lmp91000_temp_lut[i] < tmp)
+					break;
+
+			*val = (LMP91000_TEMP_BASE + i) * 1000;
+		}
+		return IIO_VAL_INT;
+	}
+	case IIO_CHAN_INFO_OFFSET:
+		return iio_read_channel_offset(data->adc_chan, val, val2);
+	case IIO_CHAN_INFO_SCALE:
+		return iio_read_channel_scale(data->adc_chan, val, val2);
+	}
+
+	return -EINVAL;
+}
+
+static const struct iio_info lmp91000_info = {
+	.driver_module = THIS_MODULE,
+	.read_raw = lmp91000_read_raw,
+};
+
+static int lmp91000_read_config(struct lmp91000_data *data)
+{
+	struct device *dev = data->dev;
+	struct device_node *np = dev->of_node;
+	unsigned int reg, val;
+	int i, ret;
+
+	ret = of_property_read_u32(np, "ti,tia-gain-ohm", &val);
+	if (ret) {
+		if (of_property_read_bool(np, "ti,external-tia-resistor"))
+			val = 0;
+		else {
+			dev_err(dev, "no ti,tia-gain-ohm defined");
+			return ret;
+		}
+	}
+
+	ret = -EINVAL;
+	for (i = 0; i < ARRAY_SIZE(lmp91000_tia_gain); i++) {
+		if (lmp91000_tia_gain[i] == val) {
+			reg = i << LMP91000_REG_TIACN_GAIN_SHIFT;
+			ret = 0;
+			break;
+		}
+	}
+
+	if (ret) {
+		dev_err(dev, "invalid ti,tia-gain-ohm %d\n", val);
+		return ret;
+	}
+
+	ret = of_property_read_u32(np, "ti,rload-ohm", &val);
+	if (ret) {
+		val = 100;
+		dev_info(dev, "no ti,rload-ohm defined, default to %d\n", val);
+	}
+
+	ret = -EINVAL;
+	for (i = 0; i < ARRAY_SIZE(lmp91000_rload); i++) {
+		if (lmp91000_rload[i] == val) {
+			reg |= i;
+			ret = 0;
+			break;
+		}
+	}
+
+	if (ret) {
+		dev_err(dev, "invalid ti,rload-ohm %d\n", val);
+		return ret;
+	}
+
+	regmap_write(data->regmap, LMP91000_REG_LOCK, 0);
+	regmap_write(data->regmap, LMP91000_REG_TIACN, reg);
+	regmap_write(data->regmap, LMP91000_REG_REFCN, LMP91000_REG_REFCN_EXT_REF
+					| LMP91000_REG_REFCN_50_ZERO);
+	regmap_write(data->regmap, LMP91000_REG_LOCK, 1);
+
+	return 0;
+}
+
+static int lmp91000_buffer_cb(const void *val, void *private)
+{
+	struct iio_dev *indio_dev = private;
+	struct lmp91000_data *data = iio_priv(indio_dev);
+
+	data->buffer[data->chan_select] = *((int *)val);
+	complete_all(&data->completion);
+
+	return 0;
+}
+
+static const struct iio_trigger_ops lmp91000_trigger_ops = {
+	.owner = THIS_MODULE,
+};
+
+
+static int lmp91000_buffer_preenable(struct iio_dev *indio_dev)
+{
+	struct lmp91000_data *data = iio_priv(indio_dev);
+
+	return iio_channel_start_all_cb(data->cb_buffer);
+}
+
+static int lmp91000_buffer_predisable(struct iio_dev *indio_dev)
+{
+	struct lmp91000_data *data = iio_priv(indio_dev);
+
+	iio_channel_stop_all_cb(data->cb_buffer);
+
+	return 0;
+}
+
+static const struct iio_buffer_setup_ops lmp91000_buffer_setup_ops = {
+	.preenable = lmp91000_buffer_preenable,
+	.postenable = iio_triggered_buffer_postenable,
+	.predisable = lmp91000_buffer_predisable,
+};
+
+static int lmp91000_probe(struct i2c_client *client,
+			  const struct i2c_device_id *id)
+{
+	struct device *dev = &client->dev;
+	struct lmp91000_data *data;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	indio_dev->info = &lmp91000_info;
+	indio_dev->channels = lmp91000_channels;
+	indio_dev->num_channels = ARRAY_SIZE(lmp91000_channels);
+	indio_dev->name = LMP91000_DRV_NAME;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	i2c_set_clientdata(client, indio_dev);
+
+	data = iio_priv(indio_dev);
+	data->dev = dev;
+	data->regmap = devm_regmap_init_i2c(client, &lmp91000_regmap_config);
+	if (IS_ERR(data->regmap)) {
+		dev_err(dev, "regmap initialization failed.\n");
+		return PTR_ERR(data->regmap);
+	}
+
+	data->trig = devm_iio_trigger_alloc(data->dev, "%s-mux%d",
+					    indio_dev->name, indio_dev->id);
+	if (!data->trig) {
+		dev_err(dev, "cannot allocate iio trigger.\n");
+		return -ENOMEM;
+	}
+
+	data->trig->ops = &lmp91000_trigger_ops;
+	data->trig->dev.parent = dev;
+	init_completion(&data->completion);
+
+	ret = lmp91000_read_config(data);
+	if (ret)
+		return ret;
+
+	ret = iio_triggered_buffer_setup(indio_dev, NULL,
+					 &lmp91000_buffer_handler,
+					 &lmp91000_buffer_setup_ops);
+	if (ret)
+		return ret;
+
+	ret = iio_device_register(indio_dev);
+	if (ret)
+		goto error_unreg_buffer;
+
+	data->cb_buffer = iio_channel_get_all_cb(dev, &lmp91000_buffer_cb,
+						 indio_dev);
+
+	if (IS_ERR(data->cb_buffer)) {
+		if (PTR_ERR(data->cb_buffer) == -ENODEV)
+			ret = -EPROBE_DEFER;
+		else
+			ret = PTR_ERR(data->cb_buffer);
+
+		goto error_unreg_device;
+	}
+	data->adc_chan = iio_channel_cb_get_channels(data->cb_buffer);
+
+	ret = iio_trigger_set_immutable(iio_channel_cb_get_iio_dev(data->cb_buffer),
+					data->trig);
+	if (ret) {
+		dev_err(dev, "cannot set immutable trigger.\n");
+		goto error_unreg_cb_buffer;
+	}
+
+	ret = iio_trigger_register(data->trig);
+	if (ret) {
+		dev_err(dev, "cannot register iio trigger.\n");
+		goto error_unreg_cb_buffer;
+	}
+
+	return 0;
+
+error_unreg_cb_buffer:
+	iio_channel_release_all_cb(data->cb_buffer);
+
+error_unreg_device:
+	iio_device_unregister(indio_dev);
+
+error_unreg_buffer:
+	iio_triggered_buffer_cleanup(indio_dev);
+
+	return ret;
+}
+
+static int lmp91000_remove(struct i2c_client *client)
+{
+	struct iio_dev *indio_dev = i2c_get_clientdata(client);
+	struct lmp91000_data *data = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+
+	iio_channel_stop_all_cb(data->cb_buffer);
+	iio_channel_release_all_cb(data->cb_buffer);
+
+	iio_triggered_buffer_cleanup(indio_dev);
+	iio_trigger_unregister(data->trig);
+
+	return 0;
+}
+
+static const struct of_device_id lmp91000_of_match[] = {
+	{ .compatible = "ti,lmp91000", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, lmp91000_of_match);
+
+static const struct i2c_device_id lmp91000_id[] = {
+	{ "lmp91000", 0 },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, lmp91000_id);
+
+static struct i2c_driver lmp91000_driver = {
+	.driver = {
+		.name = LMP91000_DRV_NAME,
+		.of_match_table = of_match_ptr(lmp91000_of_match),
+	},
+	.probe = lmp91000_probe,
+	.remove = lmp91000_remove,
+	.id_table = lmp91000_id,
+};
+module_i2c_driver(lmp91000_driver);
+
+MODULE_AUTHOR("Matt Ranostay <mranostay@gmail.com>");
+MODULE_DESCRIPTION("LMP91000 digital potentiostat");
+MODULE_LICENSE("GPL");
-- 
2.7.4

Re: [PATCH v6 1/2] iio: inkern: add iio_read_channel_offset helper

[Jonathan Cameron]

On 24/09/16 07:04, Matt Ranostay wrote:
> Allow access to underlying channel IIO_CHAN_INFO_OFFSET from a consumer.
> 
> Signed-off-by: Matt Ranostay <matt@ranostay.consulting>
Applied to the togreg branch of iio.git and pushed out as testing for
the autobuilders to play with it.

Thanks,

Jonathan
> ---
>  drivers/iio/inkern.c         | 39 ++++++++++++++++++++++++++-------------
>  include/linux/iio/consumer.h | 13 +++++++++++++
>  2 files changed, 39 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
> index c4757e6367e7..29df11572858 100644
> --- a/drivers/iio/inkern.c
> +++ b/drivers/iio/inkern.c
> @@ -658,6 +658,31 @@ int iio_convert_raw_to_processed(struct iio_channel *chan, int raw,
>  }
>  EXPORT_SYMBOL_GPL(iio_convert_raw_to_processed);
>  
> +static int iio_read_channel_attribute(struct iio_channel *chan,
> +				      int *val, int *val2,
> +				      enum iio_chan_info_enum attribute)
> +{
> +	int ret;
> +
> +	mutex_lock(&chan->indio_dev->info_exist_lock);
> +	if (chan->indio_dev->info == NULL) {
> +		ret = -ENODEV;
> +		goto err_unlock;
> +	}
> +
> +	ret = iio_channel_read(chan, val, val2, attribute);
> +err_unlock:
> +	mutex_unlock(&chan->indio_dev->info_exist_lock);
> +
> +	return ret;
> +}
> +
> +int iio_read_channel_offset(struct iio_channel *chan, int *val, int *val2)
> +{
> +	return iio_read_channel_attribute(chan, val, val2, IIO_CHAN_INFO_OFFSET);
> +}
> +EXPORT_SYMBOL_GPL(iio_read_channel_offset);
> +
>  int iio_read_channel_processed(struct iio_channel *chan, int *val)
>  {
>  	int ret;
> @@ -687,19 +712,7 @@ EXPORT_SYMBOL_GPL(iio_read_channel_processed);
>  
>  int iio_read_channel_scale(struct iio_channel *chan, int *val, int *val2)
>  {
> -	int ret;
> -
> -	mutex_lock(&chan->indio_dev->info_exist_lock);
> -	if (chan->indio_dev->info == NULL) {
> -		ret = -ENODEV;
> -		goto err_unlock;
> -	}
> -
> -	ret = iio_channel_read(chan, val, val2, IIO_CHAN_INFO_SCALE);
> -err_unlock:
> -	mutex_unlock(&chan->indio_dev->info_exist_lock);
> -
> -	return ret;
> +	return iio_read_channel_attribute(chan, val, val2, IIO_CHAN_INFO_SCALE);
>  }
>  EXPORT_SYMBOL_GPL(iio_read_channel_scale);
>  
> diff --git a/include/linux/iio/consumer.h b/include/linux/iio/consumer.h
> index 9edccfba1ffb..638157234357 100644
> --- a/include/linux/iio/consumer.h
> +++ b/include/linux/iio/consumer.h
> @@ -236,6 +236,19 @@ int iio_get_channel_type(struct iio_channel *channel,
>  			 enum iio_chan_type *type);
>  
>  /**
> + * iio_read_channel_offset() - read the offset value for a channel
> + * @chan:		The channel being queried.
> + * @val:		First part of value read back.
> + * @val2:		Second part of value read back.
> + *
> + * Note returns a description of what is in val and val2, such
> + * as IIO_VAL_INT_PLUS_MICRO telling us we have a value of val
> + * + val2/1e6
> + */
> +int iio_read_channel_offset(struct iio_channel *chan, int *val,
> +			   int *val2);
> +
> +/**
>   * iio_read_channel_scale() - read the scale value for a channel
>   * @chan:		The channel being queried.
>   * @val:		First part of value read back.
> 

Re: [PATCH v6 2/2] iio: potentiostat: add LMP91000 support

[Jonathan Cameron]

On 24/09/16 07:04, Matt Ranostay wrote:
> Add support for the LMP91000 potentiostat which is used for chemical
> sensing applications.
> 
> Signed-off-by: Matt Ranostay <matt@ranostay.consulting>
Hi Matt,

Still the second race condition I raised for probe in V5.
The iio_register_device is the point at which userspace
interfaces for reading channels etc get exposed.
Everything needs to be ready before you call that...
At the moment the callback buffer and the trigger
we are using to drive the ADC are not ready at that point.

Jonathan
> ---
>  .../bindings/iio/potentiostat/lmp91000.txt         |  30 ++
>  drivers/iio/Kconfig                                |   1 +
>  drivers/iio/Makefile                               |   1 +
>  drivers/iio/potentiostat/Kconfig                   |  22 +
>  drivers/iio/potentiostat/Makefile                  |   6 +
>  drivers/iio/potentiostat/lmp91000.c                | 445 +++++++++++++++++++++
>  6 files changed, 505 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/potentiostat/lmp91000.txt
>  create mode 100644 drivers/iio/potentiostat/Kconfig
>  create mode 100644 drivers/iio/potentiostat/Makefile
>  create mode 100644 drivers/iio/potentiostat/lmp91000.c
> 
> diff --git a/Documentation/devicetree/bindings/iio/potentiostat/lmp91000.txt b/Documentation/devicetree/bindings/iio/potentiostat/lmp91000.txt
> new file mode 100644
> index 000000000000..b9b621e94cd7
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/potentiostat/lmp91000.txt
> @@ -0,0 +1,30 @@
> +* Texas Instruments LMP91000 potentiostat
> +
> +http://www.ti.com/lit/ds/symlink/lmp91000.pdf
> +
> +Required properties:
> +
> +  - compatible: should be "ti,lmp91000"
> +  - reg: the I2C address of the device
> +  - io-channels: the phandle of the iio provider
> +
> +  - ti,external-tia-resistor: if the property ti,tia-gain-ohm is not defined this
> +    needs to be set to signal that an external resistor value is being used.
> +
> +Optional properties:
> +
> +  - ti,tia-gain-ohm: ohm value of the internal resistor for the transimpedance
> +    amplifier. Must be 2750, 3500, 7000, 14000, 35000, 120000, or 350000 ohms.
> +
> +  - ti,rload-ohm: ohm value of the internal resistor load applied to the gas
> +    sensor. Must be 10, 33, 50, or 100 (default) ohms.
> +
> +Example:
> +
> +lmp91000@48 {
> +	compatible = "ti,lmp91000";
> +	reg = <0x48>;
> +	ti,tia-gain-ohm = <7500>;
> +	ti,rload = <100>;
> +	io-channels = <&adc>;
> +};
> diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
> index 6743b18194fb..a31a8cf2c330 100644
> --- a/drivers/iio/Kconfig
> +++ b/drivers/iio/Kconfig
> @@ -87,6 +87,7 @@ if IIO_TRIGGER
>     source "drivers/iio/trigger/Kconfig"
>  endif #IIO_TRIGGER
>  source "drivers/iio/potentiometer/Kconfig"
> +source "drivers/iio/potentiostat/Kconfig"
>  source "drivers/iio/pressure/Kconfig"
>  source "drivers/iio/proximity/Kconfig"
>  source "drivers/iio/temperature/Kconfig"
> diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
> index 87e4c4369e2f..2b6e2762a886 100644
> --- a/drivers/iio/Makefile
> +++ b/drivers/iio/Makefile
> @@ -29,6 +29,7 @@ obj-y += light/
>  obj-y += magnetometer/
>  obj-y += orientation/
>  obj-y += potentiometer/
> +obj-y += potentiostat/
>  obj-y += pressure/
>  obj-y += proximity/
>  obj-y += temperature/
> diff --git a/drivers/iio/potentiostat/Kconfig b/drivers/iio/potentiostat/Kconfig
> new file mode 100644
> index 000000000000..1e3baf2cc97d
> --- /dev/null
> +++ b/drivers/iio/potentiostat/Kconfig
> @@ -0,0 +1,22 @@
> +#
> +# Potentiostat drivers
> +#
> +# When adding new entries keep the list in alphabetical order
> +
> +menu "Digital potentiostats"
> +
> +config LMP91000
> +	tristate "Texas Instruments LMP91000 potentiostat driver"
> +	depends on I2C
> +	select REGMAP_I2C
> +	select IIO_BUFFER
> +	select IIO_BUFFER_CB
> +	select IIO_TRIGGERED_BUFFER
> +	help
> +	  Say yes here to build support for the Texas Instruments
> +	  LMP91000 digital potentiostat chip.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called lmp91000
> +
> +endmenu
> diff --git a/drivers/iio/potentiostat/Makefile b/drivers/iio/potentiostat/Makefile
> new file mode 100644
> index 000000000000..64d315ef4449
> --- /dev/null
> +++ b/drivers/iio/potentiostat/Makefile
> @@ -0,0 +1,6 @@
> +#
> +# Makefile for industrial I/O potentiostat drivers
> +#
> +
> +# When adding new entries keep the list in alphabetical order
> +obj-$(CONFIG_LMP91000) += lmp91000.o
> diff --git a/drivers/iio/potentiostat/lmp91000.c b/drivers/iio/potentiostat/lmp91000.c
> new file mode 100644
> index 000000000000..600e97d98f91
> --- /dev/null
> +++ b/drivers/iio/potentiostat/lmp91000.c
> @@ -0,0 +1,445 @@
> +/*
> + * lmp91000.c - Support for Texas Instruments digital potentiostats
> + *
> + * Copyright (C) 2016 Matt Ranostay <mranostay@gmail.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * TODO: bias voltage + polarity control, and multiple chip support
> + */
> +
> +#include <linux/module.h>
> +#include <linux/i2c.h>
> +#include <linux/delay.h>
> +#include <linux/of.h>
> +#include <linux/regmap.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/buffer.h>
> +#include <linux/iio/consumer.h>
> +#include <linux/iio/trigger.h>
> +#include <linux/iio/trigger_consumer.h>
> +#include <linux/iio/triggered_buffer.h>
> +
> +#define LMP91000_REG_LOCK		0x01
> +#define LMP91000_REG_TIACN		0x10
> +#define LMP91000_REG_TIACN_GAIN_SHIFT	2
> +
> +#define LMP91000_REG_REFCN		0x11
> +#define LMP91000_REG_REFCN_EXT_REF	0x20
> +#define LMP91000_REG_REFCN_50_ZERO	0x80
> +
> +#define LMP91000_REG_MODECN		0x12
> +#define LMP91000_REG_MODECN_3LEAD	0x03
> +#define LMP91000_REG_MODECN_TEMP	0x07
> +
> +#define LMP91000_DRV_NAME	"lmp91000"
> +
> +static const int lmp91000_tia_gain[] = { 0, 2750, 3500, 7000, 14000, 35000,
> +					 120000, 350000 };
> +
> +static const int lmp91000_rload[] = { 10, 33, 50, 100 };
> +
> +#define LMP91000_TEMP_BASE	-40
> +
> +static const u16 lmp91000_temp_lut[] = {
> +	1875, 1867, 1860, 1852, 1844, 1836, 1828, 1821, 1813, 1805,
> +	1797, 1789, 1782, 1774, 1766, 1758, 1750, 1742, 1734, 1727,
> +	1719, 1711, 1703, 1695, 1687, 1679, 1671, 1663, 1656, 1648,
> +	1640, 1632, 1624, 1616, 1608, 1600, 1592, 1584, 1576, 1568,
> +	1560, 1552, 1544, 1536, 1528, 1520, 1512, 1504, 1496, 1488,
> +	1480, 1472, 1464, 1456, 1448, 1440, 1432, 1424, 1415, 1407,
> +	1399, 1391, 1383, 1375, 1367, 1359, 1351, 1342, 1334, 1326,
> +	1318, 1310, 1302, 1293, 1285, 1277, 1269, 1261, 1253, 1244,
> +	1236, 1228, 1220, 1212, 1203, 1195, 1187, 1179, 1170, 1162,
> +	1154, 1146, 1137, 1129, 1121, 1112, 1104, 1096, 1087, 1079,
> +	1071, 1063, 1054, 1046, 1038, 1029, 1021, 1012, 1004,  996,
> +	 987,  979,  971,  962,  954,  945,  937,  929,  920,  912,
> +	 903,  895,  886,  878,  870,  861 };
> +
> +static const struct regmap_config lmp91000_regmap_config = {
> +	.reg_bits = 8,
> +	.val_bits = 8,
> +};
> +
> +struct lmp91000_data {
> +	struct regmap *regmap;
> +	struct device *dev;
> +
> +	struct iio_trigger *trig;
> +	struct iio_cb_buffer *cb_buffer;
> +	struct iio_channel *adc_chan;
> +
> +	struct completion completion;
> +	u8 chan_select;
> +
> +	u32 buffer[4]; /* 64-bit data + 64-bit timestamp */
> +};
> +
> +static const struct iio_chan_spec lmp91000_channels[] = {
> +	{ /* chemical channel mV */
> +		.type = IIO_VOLTAGE,
> +		.channel = 0,
> +		.address = LMP91000_REG_MODECN_3LEAD,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
> +				      BIT(IIO_CHAN_INFO_OFFSET) |
> +				      BIT(IIO_CHAN_INFO_SCALE),
> +		.scan_index = 0,
> +		.scan_type = {
> +			.sign = 's',
> +			.realbits = 32,
> +			.storagebits = 32,
> +		},
> +	},
> +	IIO_CHAN_SOFT_TIMESTAMP(1),
> +	{ /* temperature channel mV */
> +		.type = IIO_TEMP,
> +		.channel = 1,
> +		.address = LMP91000_REG_MODECN_TEMP,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
> +		.scan_index = -1,
> +	},
> +};
> +
> +static int lmp91000_read(struct lmp91000_data *data, int channel, int *val)
> +{
> +	int state, ret;
> +
> +	ret = regmap_read(data->regmap, LMP91000_REG_MODECN, &state);
> +	if (ret)
> +		return -EINVAL;
> +
> +	ret = regmap_write(data->regmap, LMP91000_REG_MODECN, channel);
> +	if (ret)
> +		return -EINVAL;
> +
> +	/* delay till first temperature reading is complete */
> +	if ((state != channel) && (channel == LMP91000_REG_MODECN_TEMP))
> +		usleep_range(3000, 4000);
> +
> +	data->chan_select = channel != LMP91000_REG_MODECN_3LEAD;
> +
> +	iio_trigger_poll_chained(data->trig);
> +
> +	ret = wait_for_completion_timeout(&data->completion, HZ);
> +	reinit_completion(&data->completion);
> +
> +	if (!ret)
> +		return -ETIMEDOUT;
> +
> +	*val = data->buffer[data->chan_select];
> +
> +	return 0;
> +}
> +
> +static irqreturn_t lmp91000_buffer_handler(int irq, void *private)
> +{
> +	struct iio_poll_func *pf = private;
> +	struct iio_dev *indio_dev = pf->indio_dev;
> +	struct lmp91000_data *data = iio_priv(indio_dev);
> +	int ret, val;
> +
> +	memset(data->buffer, 0, sizeof(data->buffer));
> +
> +	ret = lmp91000_read(data, LMP91000_REG_MODECN_3LEAD, &val);
> +	if (!ret) {
> +		data->buffer[0] = val;
> +		iio_push_to_buffers_with_timestamp(indio_dev, data->buffer,
> +						   iio_get_time_ns(indio_dev));
> +	}
> +
> +	iio_trigger_notify_done(indio_dev->trig);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int lmp91000_read_raw(struct iio_dev *indio_dev,
> +			     struct iio_chan_spec const *chan,
> +			     int *val, int *val2, long mask)
> +{
> +	struct lmp91000_data *data = iio_priv(indio_dev);
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +	case IIO_CHAN_INFO_PROCESSED: {
> +		int ret = iio_channel_start_all_cb(data->cb_buffer);
> +
> +		if (ret)
> +			return ret;
> +
> +		ret = lmp91000_read(data, chan->address, val);
> +
> +		iio_channel_stop_all_cb(data->cb_buffer);
> +
> +		if (ret)
> +			return ret;
> +
> +		if (mask == IIO_CHAN_INFO_PROCESSED) {
> +			int tmp, i;
> +
> +			ret = iio_convert_raw_to_processed(data->adc_chan,
> +							   *val, &tmp, 1);
> +			if (ret)
> +				return ret;
> +
> +			for (i = 0; i < ARRAY_SIZE(lmp91000_temp_lut); i++)
> +				if (lmp91000_temp_lut[i] < tmp)
> +					break;
> +
> +			*val = (LMP91000_TEMP_BASE + i) * 1000;
> +		}
> +		return IIO_VAL_INT;
> +	}
> +	case IIO_CHAN_INFO_OFFSET:
> +		return iio_read_channel_offset(data->adc_chan, val, val2);
> +	case IIO_CHAN_INFO_SCALE:
> +		return iio_read_channel_scale(data->adc_chan, val, val2);
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static const struct iio_info lmp91000_info = {
> +	.driver_module = THIS_MODULE,
> +	.read_raw = lmp91000_read_raw,
> +};
> +
> +static int lmp91000_read_config(struct lmp91000_data *data)
> +{
> +	struct device *dev = data->dev;
> +	struct device_node *np = dev->of_node;
> +	unsigned int reg, val;
> +	int i, ret;
> +
> +	ret = of_property_read_u32(np, "ti,tia-gain-ohm", &val);
> +	if (ret) {
> +		if (of_property_read_bool(np, "ti,external-tia-resistor"))
> +			val = 0;
> +		else {
> +			dev_err(dev, "no ti,tia-gain-ohm defined");
> +			return ret;
> +		}
> +	}
> +
> +	ret = -EINVAL;
> +	for (i = 0; i < ARRAY_SIZE(lmp91000_tia_gain); i++) {
> +		if (lmp91000_tia_gain[i] == val) {
> +			reg = i << LMP91000_REG_TIACN_GAIN_SHIFT;
> +			ret = 0;
> +			break;
> +		}
> +	}
> +
> +	if (ret) {
> +		dev_err(dev, "invalid ti,tia-gain-ohm %d\n", val);
> +		return ret;
> +	}
> +
> +	ret = of_property_read_u32(np, "ti,rload-ohm", &val);
> +	if (ret) {
> +		val = 100;
> +		dev_info(dev, "no ti,rload-ohm defined, default to %d\n", val);
> +	}
> +
> +	ret = -EINVAL;
> +	for (i = 0; i < ARRAY_SIZE(lmp91000_rload); i++) {
> +		if (lmp91000_rload[i] == val) {
> +			reg |= i;
> +			ret = 0;
> +			break;
> +		}
> +	}
> +
> +	if (ret) {
> +		dev_err(dev, "invalid ti,rload-ohm %d\n", val);
> +		return ret;
> +	}
> +
> +	regmap_write(data->regmap, LMP91000_REG_LOCK, 0);
> +	regmap_write(data->regmap, LMP91000_REG_TIACN, reg);
> +	regmap_write(data->regmap, LMP91000_REG_REFCN, LMP91000_REG_REFCN_EXT_REF
> +					| LMP91000_REG_REFCN_50_ZERO);
> +	regmap_write(data->regmap, LMP91000_REG_LOCK, 1);
> +
> +	return 0;
> +}
> +
> +static int lmp91000_buffer_cb(const void *val, void *private)
> +{
> +	struct iio_dev *indio_dev = private;
> +	struct lmp91000_data *data = iio_priv(indio_dev);
> +
> +	data->buffer[data->chan_select] = *((int *)val);
> +	complete_all(&data->completion);
> +
> +	return 0;
> +}
> +
> +static const struct iio_trigger_ops lmp91000_trigger_ops = {
> +	.owner = THIS_MODULE,
> +};
> +
> +
> +static int lmp91000_buffer_preenable(struct iio_dev *indio_dev)
> +{
> +	struct lmp91000_data *data = iio_priv(indio_dev);
> +
> +	return iio_channel_start_all_cb(data->cb_buffer);
> +}
> +
> +static int lmp91000_buffer_predisable(struct iio_dev *indio_dev)
> +{
> +	struct lmp91000_data *data = iio_priv(indio_dev);
> +
> +	iio_channel_stop_all_cb(data->cb_buffer);
> +
> +	return 0;
> +}
> +
> +static const struct iio_buffer_setup_ops lmp91000_buffer_setup_ops = {
> +	.preenable = lmp91000_buffer_preenable,
> +	.postenable = iio_triggered_buffer_postenable,
> +	.predisable = lmp91000_buffer_predisable,
> +};
> +
> +static int lmp91000_probe(struct i2c_client *client,
> +			  const struct i2c_device_id *id)
> +{
> +	struct device *dev = &client->dev;
> +	struct lmp91000_data *data;
> +	struct iio_dev *indio_dev;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	indio_dev->info = &lmp91000_info;
> +	indio_dev->channels = lmp91000_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(lmp91000_channels);
> +	indio_dev->name = LMP91000_DRV_NAME;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	i2c_set_clientdata(client, indio_dev);
> +
> +	data = iio_priv(indio_dev);
> +	data->dev = dev;
> +	data->regmap = devm_regmap_init_i2c(client, &lmp91000_regmap_config);
> +	if (IS_ERR(data->regmap)) {
> +		dev_err(dev, "regmap initialization failed.\n");
> +		return PTR_ERR(data->regmap);
> +	}
> +
> +	data->trig = devm_iio_trigger_alloc(data->dev, "%s-mux%d",
> +					    indio_dev->name, indio_dev->id);
> +	if (!data->trig) {
> +		dev_err(dev, "cannot allocate iio trigger.\n");
> +		return -ENOMEM;
> +	}
> +
> +	data->trig->ops = &lmp91000_trigger_ops;
> +	data->trig->dev.parent = dev;
> +	init_completion(&data->completion);
> +
> +	ret = lmp91000_read_config(data);
> +	if (ret)
> +		return ret;
> +
> +	ret = iio_triggered_buffer_setup(indio_dev, NULL,
> +					 &lmp91000_buffer_handler,
> +					 &lmp91000_buffer_setup_ops);
> +	if (ret)
> +		return ret;
> +
> +	ret = iio_device_register(indio_dev);
> +	if (ret)
> +		goto error_unreg_buffer;
This still leaves the second of the two races I pointed out in the
last review.  The moment this is called, the userspace interfaces
are exposed.  That means the buffer can get turned on - before we
are anywhere near ready for it.

As the trigger is controlled by this driver, there is much less of a
problem (I think) with having that interface exposed before the
rest of the driver.  Upshot is I think you need to have the
iio_device_register as the very last call in probe.
> +
> +	data->cb_buffer = iio_channel_get_all_cb(dev, &lmp91000_buffer_cb,
> +						 indio_dev);
> +
> +	if (IS_ERR(data->cb_buffer)) {
> +		if (PTR_ERR(data->cb_buffer) == -ENODEV)
> +			ret = -EPROBE_DEFER;
> +		else
> +			ret = PTR_ERR(data->cb_buffer);
> +
> +		goto error_unreg_device;
> +	}
> +	data->adc_chan = iio_channel_cb_get_channels(data->cb_buffer);
> +
> +	ret = iio_trigger_set_immutable(iio_channel_cb_get_iio_dev(data->cb_buffer),
> +					data->trig);
> +	if (ret) {
> +		dev_err(dev, "cannot set immutable trigger.\n");
> +		goto error_unreg_cb_buffer;
> +	}
> +
> +	ret = iio_trigger_register(data->trig);
> +	if (ret) {
> +		dev_err(dev, "cannot register iio trigger.\n");
> +		goto error_unreg_cb_buffer;
> +	}
> +
> +	return 0;
> +
> +error_unreg_cb_buffer:
> +	iio_channel_release_all_cb(data->cb_buffer);
> +
> +error_unreg_device:
> +	iio_device_unregister(indio_dev);
> +
> +error_unreg_buffer:
> +	iio_triggered_buffer_cleanup(indio_dev);
> +
> +	return ret;
> +}
> +
> +static int lmp91000_remove(struct i2c_client *client)
> +{
> +	struct iio_dev *indio_dev = i2c_get_clientdata(client);
> +	struct lmp91000_data *data = iio_priv(indio_dev);
> +
> +	iio_device_unregister(indio_dev);
Should be the reverse order of probe.  Though I've just
suggested reordering probe so that will actually end up with
pretty much this ordering...
> +
> +	iio_channel_stop_all_cb(data->cb_buffer);
> +	iio_channel_release_all_cb(data->cb_buffer);
> +
> +	iio_triggered_buffer_cleanup(indio_dev);
> +	iio_trigger_unregister(data->trig);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id lmp91000_of_match[] = {
> +	{ .compatible = "ti,lmp91000", },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, lmp91000_of_match);
> +
> +static const struct i2c_device_id lmp91000_id[] = {
> +	{ "lmp91000", 0 },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(i2c, lmp91000_id);
> +
> +static struct i2c_driver lmp91000_driver = {
> +	.driver = {
> +		.name = LMP91000_DRV_NAME,
> +		.of_match_table = of_match_ptr(lmp91000_of_match),
> +	},
> +	.probe = lmp91000_probe,
> +	.remove = lmp91000_remove,
> +	.id_table = lmp91000_id,
> +};
> +module_i2c_driver(lmp91000_driver);
> +
> +MODULE_AUTHOR("Matt Ranostay <mranostay@gmail.com>");
> +MODULE_DESCRIPTION("LMP91000 digital potentiostat");
> +MODULE_LICENSE("GPL");
>