Date:   Tue, 27 Jun 2017 14:53:49 -1000
From:   Jack Andersen <jackoalan@...il.com>
To:     linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Jack Andersen <jackoalan@...il.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>
Subject: [PATCH v3] iio: adc: Add support for DLN2 ADC

This patch adds support for Diolan DLN2 ADC via IIO's ADC interface.
ADC is the fourth and final component of the DLN2 for the kernel.

Signed-off-by: Jack Andersen <jackoalan@...il.com>
---
Changes in v2:
- Address Peter's remarks; bringing consistency to C99 syntax, dev_dbg usage,
  and error handling.
- Remove probe/remove logging.
- Utilize stack-allocated buffer for pushing into IIO.
- Add timestamp channel to IIO spec.

Suggested-by: Peter Meerwald-Stadler <pmeerw@...erw.net>
---
Changes in v3:
- Remove lazy channel enabling; integrating with update_channel_mode instead.
- Implement memcpy demux table similar to subsystem core.
- Use iio_triggered_buffer_setup to create buffer.

Suggested-by: Jonathan Cameron <jic23@...nel.org>
---
 drivers/iio/adc/Kconfig    |   9 +
 drivers/iio/adc/Makefile   |   1 +
 drivers/iio/adc/dln2-adc.c | 733 +++++++++++++++++++++++++++++++++++++++++++++
 drivers/mfd/dln2.c         |  12 +
 tools/gpio/lsgpio.c        |   4 +-
 5 files changed, 757 insertions(+), 2 deletions(-)
 create mode 100644 drivers/iio/adc/dln2-adc.c

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 401f47b..78d7455 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -239,6 +239,15 @@ config DA9150_GPADC
 	  To compile this driver as a module, choose M here: the module will be
 	  called berlin2-adc.
 
+config DLN2_ADC
+	tristate "Diolan DLN-2 ADC driver support"
+	depends on MFD_DLN2
+	help
+	  Say yes here to build support for Diolan DLN-2 ADC.
+
+	  This driver can also be built as a module. If so, the module will be
+	  called adc_dln2.
+
 config ENVELOPE_DETECTOR
 	tristate "Envelope detector using a DAC and a comparator"
 	depends on OF
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 9339bec..378bc65 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -24,6 +24,7 @@ obj-$(CONFIG_BERLIN2_ADC) += berlin2-adc.o
 obj-$(CONFIG_CC10001_ADC) += cc10001_adc.o
 obj-$(CONFIG_CPCAP_ADC) += cpcap-adc.o
 obj-$(CONFIG_DA9150_GPADC) += da9150-gpadc.o
+obj-$(CONFIG_DLN2_ADC) += dln2-adc.o
 obj-$(CONFIG_ENVELOPE_DETECTOR) += envelope-detector.o
 obj-$(CONFIG_EXYNOS_ADC) += exynos_adc.o
 obj-$(CONFIG_FSL_MX25_ADC) += fsl-imx25-gcq.o
diff --git a/drivers/iio/adc/dln2-adc.c b/drivers/iio/adc/dln2-adc.c
new file mode 100644
index 0000000..07569d5
--- /dev/null
+++ b/drivers/iio/adc/dln2-adc.c
@@ -0,0 +1,733 @@
+/*
+ * Driver for the Diolan DLN-2 USB-ADC adapter
+ *
+ * Copyright (c) 2017 Jack Andersen
+ *
+ * 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, version 2.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/platform_device.h>
+#include <linux/mfd/dln2.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/iio/trigger.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/kfifo_buf.h>
+
+#define DLN2_ADC_MOD_NAME "dln2-adc"
+
+#define DLN2_ADC_ID             0x06
+
+#define DLN2_ADC_GET_CHANNEL_COUNT	DLN2_CMD(0x01, DLN2_ADC_ID)
+#define DLN2_ADC_ENABLE			DLN2_CMD(0x02, DLN2_ADC_ID)
+#define DLN2_ADC_DISABLE		DLN2_CMD(0x03, DLN2_ADC_ID)
+#define DLN2_ADC_CHANNEL_ENABLE		DLN2_CMD(0x05, DLN2_ADC_ID)
+#define DLN2_ADC_CHANNEL_DISABLE	DLN2_CMD(0x06, DLN2_ADC_ID)
+#define DLN2_ADC_SET_RESOLUTION		DLN2_CMD(0x08, DLN2_ADC_ID)
+#define DLN2_ADC_CHANNEL_GET_VAL	DLN2_CMD(0x0A, DLN2_ADC_ID)
+#define DLN2_ADC_CHANNEL_GET_ALL_VAL	DLN2_CMD(0x0B, DLN2_ADC_ID)
+#define DLN2_ADC_CHANNEL_SET_CFG	DLN2_CMD(0x0C, DLN2_ADC_ID)
+#define DLN2_ADC_CHANNEL_GET_CFG	DLN2_CMD(0x0D, DLN2_ADC_ID)
+#define DLN2_ADC_CONDITION_MET_EV	DLN2_CMD(0x10, DLN2_ADC_ID)
+
+#define DLN2_ADC_EVENT_NONE		0
+#define DLN2_ADC_EVENT_BELOW		1
+#define DLN2_ADC_EVENT_LEVEL_ABOVE	2
+#define DLN2_ADC_EVENT_OUTSIDE		3
+#define DLN2_ADC_EVENT_INSIDE		4
+#define DLN2_ADC_EVENT_ALWAYS		5
+
+#define DLN2_ADC_MAX_CHANNELS 8
+#define DLN2_ADC_DATA_BITS 10
+
+/*
+ * Plays similar role to iio_demux_table in subsystem core; except allocated
+ * in a fixed 8-element array.
+ */
+struct dln2_adc_demux_table {
+	unsigned int from;
+	unsigned int to;
+	unsigned int length;
+};
+
+struct dln2_adc {
+	struct platform_device *pdev;
+	struct iio_chan_spec iio_channels[DLN2_ADC_MAX_CHANNELS + 1];
+	int port, trigger_chan;
+	struct iio_trigger *trig;
+	struct mutex mutex;
+	/* Cached sample period in milliseconds */
+	unsigned int sample_period;
+	/* Demux table */
+	unsigned int demux_count;
+	struct dln2_adc_demux_table demux[DLN2_ADC_MAX_CHANNELS];
+	/* Precomputed timestamp padding offset and length */
+	unsigned int ts_pad_offset, ts_pad_length;
+};
+
+struct dln2_adc_port_chan {
+	u8 port;
+	u8 chan;
+};
+
+struct dln2_adc_get_all_vals {
+	__le16 channel_mask;
+	__le16 values[DLN2_ADC_MAX_CHANNELS];
+};
+
+static void dln2_adc_add_demux(struct dln2_adc *dln2,
+	unsigned int in_loc, unsigned int out_loc,
+	unsigned int length)
+{
+	struct dln2_adc_demux_table *p = dln2->demux_count ?
+		&dln2->demux[dln2->demux_count - 1] : NULL;
+	if (p && p->from + p->length == in_loc &&
+		p->to + p->length == out_loc) {
+		p->length += length;
+	} else if (dln2->demux_count < DLN2_ADC_MAX_CHANNELS) {
+		p = &dln2->demux[dln2->demux_count++];
+		p->from = in_loc;
+		p->to = out_loc;
+		p->length = length;
+	}
+}
+
+static void dln2_adc_update_demux(struct dln2_adc *dln2)
+{
+	int in_ind = -1, out_ind;
+	unsigned int in_loc = 0, out_loc = 0;
+	struct iio_dev *indio_dev = platform_get_drvdata(dln2->pdev);
+
+	/* Clear out any old demux */
+	dln2->demux_count = 0;
+
+	/* Optimize all 8-channels case */
+	if (indio_dev->masklength &&
+	    (*indio_dev->active_scan_mask & 0xff) == 0xff) {
+		dln2_adc_add_demux(dln2, 0, 0, 16);
+		dln2->ts_pad_offset = 0;
+		dln2->ts_pad_length = 0;
+		return;
+	}
+
+	/* Build demux table from fixed 8-channels to active_scan_mask */
+	for_each_set_bit(out_ind,
+			 indio_dev->active_scan_mask,
+			 indio_dev->masklength) {
+		/* Handle timestamp separately */
+		if (out_ind == DLN2_ADC_MAX_CHANNELS)
+			break;
+		for (++in_ind; in_ind != out_ind; ++in_ind)
+			in_loc += 2;
+		dln2_adc_add_demux(dln2, in_loc, out_loc, 2);
+		out_loc += 2;
+		in_loc += 2;
+	}
+
+	if (indio_dev->scan_timestamp) {
+		size_t ts_offset = indio_dev->scan_bytes / sizeof(int64_t) - 1;
+
+		dln2->ts_pad_offset = out_loc;
+		dln2->ts_pad_length = ts_offset * sizeof(int64_t) - out_loc;
+	} else {
+		dln2->ts_pad_offset = 0;
+		dln2->ts_pad_length = 0;
+	}
+}
+
+static int dln2_adc_get_chan_count(struct dln2_adc *dln2)
+{
+	int ret;
+	u8 port = dln2->port;
+	u8 count;
+	int olen = sizeof(count);
+
+	ret = dln2_transfer(dln2->pdev, DLN2_ADC_GET_CHANNEL_COUNT,
+			    &port, sizeof(port), &count, &olen);
+	if (ret < 0) {
+		dev_dbg(&dln2->pdev->dev, "Problem in %s\n", __func__);
+		return ret;
+	}
+	if (olen < sizeof(count))
+		return -EPROTO;
+
+	return count;
+}
+
+static int dln2_adc_set_port_resolution(struct dln2_adc *dln2)
+{
+	int ret;
+	struct dln2_adc_port_chan port_chan = {
+		.port = dln2->port,
+		.chan = DLN2_ADC_DATA_BITS,
+	};
+
+	ret = dln2_transfer_tx(dln2->pdev, DLN2_ADC_SET_RESOLUTION,
+			       &port_chan, sizeof(port_chan));
+	if (ret < 0) {
+		dev_dbg(&dln2->pdev->dev, "Problem in %s\n", __func__);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int dln2_adc_set_chan_enabled(struct dln2_adc *dln2,
+				     int channel, bool enable)
+{
+	int ret;
+	struct dln2_adc_port_chan port_chan = {
+		.port = dln2->port,
+		.chan = channel,
+	};
+
+	u16 cmd = enable ? DLN2_ADC_CHANNEL_ENABLE : DLN2_ADC_CHANNEL_DISABLE;
+
+	ret = dln2_transfer_tx(dln2->pdev, cmd, &port_chan, sizeof(port_chan));
+	if (ret < 0) {
+		dev_dbg(&dln2->pdev->dev, "Problem in %s\n", __func__);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int dln2_adc_set_port_enabled(struct dln2_adc *dln2, bool enable,
+				     u16 *conflict_out)
+{
+	int ret;
+	u8 port = dln2->port;
+	__le16 conflict;
+	int olen = sizeof(conflict);
+
+	u16 cmd = enable ? DLN2_ADC_ENABLE : DLN2_ADC_DISABLE;
+
+	if (conflict_out)
+		*conflict_out = 0;
+
+	ret = dln2_transfer(dln2->pdev, cmd, &port, sizeof(port),
+			    &conflict, &olen);
+	if (ret < 0) {
+		dev_dbg(&dln2->pdev->dev, "Problem in %s(%d)\n",
+			__func__, (int)enable);
+		if (conflict_out && enable && olen >= sizeof(conflict))
+			*conflict_out = le16_to_cpu(conflict);
+		return ret;
+	}
+	if (enable && olen < sizeof(conflict))
+		return -EPROTO;
+
+	return 0;
+}
+
+static int dln2_adc_set_chan_period(struct dln2_adc *dln2,
+	unsigned int channel, unsigned int period)
+{
+	int ret;
+	struct {
+		struct dln2_adc_port_chan port_chan;
+		__u8 type;
+		__le16 period;
+		__le16 low;
+		__le16 high;
+	} __packed set_cfg = {
+		.port_chan.port = dln2->port,
+		.port_chan.chan = channel,
+		.type = period ? DLN2_ADC_EVENT_ALWAYS : DLN2_ADC_EVENT_NONE,
+		.period = cpu_to_le16(period)
+	};
+
+	ret = dln2_transfer_tx(dln2->pdev, DLN2_ADC_CHANNEL_SET_CFG,
+			       &set_cfg, sizeof(set_cfg));
+	if (ret < 0) {
+		dev_dbg(&dln2->pdev->dev, "Problem in %s\n", __func__);
+		return ret;
+	}
+	return 0;
+}
+
+static int dln2_adc_read(struct dln2_adc *dln2, unsigned int channel)
+{
+	int ret, i;
+	struct iio_dev *indio_dev = platform_get_drvdata(dln2->pdev);
+	u16 conflict;
+
+	if (iio_buffer_enabled(indio_dev)) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	ret = dln2_adc_set_chan_enabled(dln2, channel, true);
+	if (ret < 0)
+		goto out;
+
+	ret = dln2_adc_set_port_enabled(dln2, true, &conflict);
+	if (ret < 0) {
+		if (conflict) {
+			dev_err(&dln2->pdev->dev,
+				"ADC pins conflict with mask %04X\n",
+				(int)conflict);
+			ret = -EBUSY;
+		}
+		goto disable_chan;
+	}
+
+	struct dln2_adc_port_chan port_chan = {
+		.port = dln2->port,
+		.chan = channel,
+	};
+	__le16 value;
+	int olen = sizeof(value);
+
+	/*
+	 * Call GET_VAL twice due to initial zero-return immediately after
+	 * enabling channel.
+	 */
+	for (i = 0; i < 2; ++i) {
+		ret = dln2_transfer(dln2->pdev, DLN2_ADC_CHANNEL_GET_VAL,
+				    &port_chan, sizeof(port_chan),
+				    &value, &olen);
+		if (ret < 0) {
+			dev_dbg(&dln2->pdev->dev, "Problem in %s\n", __func__);
+			goto disable_port;
+		}
+		if (olen < sizeof(value)) {
+			ret = -EPROTO;
+			goto disable_port;
+		}
+	}
+
+	ret = le16_to_cpu(value);
+
+disable_port:
+	dln2_adc_set_port_enabled(dln2, false, NULL);
+disable_chan:
+	dln2_adc_set_chan_enabled(dln2, channel, false);
+out:
+	return ret;
+}
+
+static int dln2_adc_read_all(struct dln2_adc *dln2,
+			     struct dln2_adc_get_all_vals *get_all_vals)
+{
+	int ret;
+	__u8 port = dln2->port;
+	int olen = sizeof(*get_all_vals);
+
+	ret = dln2_transfer(dln2->pdev, DLN2_ADC_CHANNEL_GET_ALL_VAL,
+			    &port, sizeof(port), get_all_vals, &olen);
+	if (ret < 0) {
+		dev_dbg(&dln2->pdev->dev, "Problem in %s\n", __func__);
+		return ret;
+	}
+	if (olen < sizeof(*get_all_vals))
+		return -EPROTO;
+
+	return 0;
+}
+
+static int dln2_adc_read_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int *val,
+			     int *val2,
+			     long mask)
+{
+	int ret;
+	unsigned int microhertz;
+	struct dln2_adc *dln2 = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		mutex_lock(&dln2->mutex);
+		ret = dln2_adc_read(dln2, chan->channel);
+		mutex_unlock(&dln2->mutex);
+
+		if (ret < 0)
+			return ret;
+
+		*val = ret;
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_SCALE:
+		/*
+		 * Voltage reference is fixed at 3.3v
+		 *  3.3 / (1 << 10) * 1000000000
+		 */
+		*val = 0;
+		*val2 = 3222656;
+		return IIO_VAL_INT_PLUS_NANO;
+
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		if (dln2->sample_period) {
+			microhertz = 1000000000 / dln2->sample_period;
+			*val = microhertz / 1000000;
+			*val2 = microhertz % 1000000;
+		} else {
+			*val = 0;
+			*val2 = 0;
+		}
+
+		return IIO_VAL_INT_PLUS_MICRO;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static int dln2_adc_write_raw(struct iio_dev *indio_dev,
+			      struct iio_chan_spec const *chan,
+			      int val,
+			      int val2,
+			      long mask)
+{
+	int ret;
+	unsigned int microhertz;
+	struct dln2_adc *dln2 = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		microhertz = 1000000 * val + val2;
+
+		mutex_lock(&dln2->mutex);
+
+		dln2->sample_period =
+			microhertz ? 1000000000 / microhertz : UINT_MAX;
+		if (dln2->sample_period > 65535) {
+			dln2->sample_period = 65535;
+			dev_warn(&dln2->pdev->dev,
+				 "clamping period to 65535ms\n");
+		}
+
+		/*
+		 * The first requested channel is arbitrated as a shared
+		 * trigger source, so only one event is registered with the
+		 * DLN. The event handler will then read all enabled channel
+		 * values using DLN2_ADC_CHANNEL_GET_ALL_VAL to maintain
+		 * synchronization between ADC readings.
+		 */
+		if (dln2->trigger_chan != -1)
+			ret = dln2_adc_set_chan_period(dln2,
+				dln2->trigger_chan, dln2->sample_period);
+		else
+			ret = 0;
+
+		mutex_unlock(&dln2->mutex);
+
+		return ret;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static int dln2_update_scan_mode(struct iio_dev *indio_dev,
+				 const unsigned long *scan_mask)
+{
+	struct dln2_adc *dln2 = iio_priv(indio_dev);
+	int chan_count = indio_dev->num_channels - 1;
+	int ret, i, j;
+
+	mutex_lock(&dln2->mutex);
+
+	for (i = 0; i < chan_count; ++i) {
+		ret = dln2_adc_set_chan_enabled(dln2, i,
+						test_bit(i, scan_mask));
+		if (ret < 0) {
+			for (j = 0; j < i; ++j)
+				dln2_adc_set_chan_enabled(dln2, j, false);
+			mutex_unlock(&dln2->mutex);
+			dev_err(&dln2->pdev->dev,
+				"Unable to enable ADC channel %d\n", i);
+			return -EBUSY;
+		}
+	}
+
+	dln2_adc_update_demux(dln2);
+
+	mutex_unlock(&dln2->mutex);
+
+	return 0;
+}
+
+#define DLN2_ADC_CHAN(idx) {					\
+	.type = IIO_VOLTAGE,					\
+	.channel = idx,						\
+	.indexed = 1,						\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
+	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SCALE) |	\
+				   BIT(IIO_CHAN_INFO_SAMP_FREQ),\
+	.scan_index = idx,					\
+	.scan_type = {						\
+		.sign = 'u',					\
+		.realbits = DLN2_ADC_DATA_BITS,			\
+		.storagebits = 16,				\
+		.endianness = IIO_LE,				\
+	}							\
+}
+
+static const struct iio_info dln2_adc_info = {
+	.read_raw = dln2_adc_read_raw,
+	.write_raw = dln2_adc_write_raw,
+	.update_scan_mode = dln2_update_scan_mode,
+	.driver_module = THIS_MODULE,
+};
+
+static irqreturn_t dln2_adc_trigger_h(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct {
+		__le16 values[DLN2_ADC_MAX_CHANNELS];
+		int64_t timestamp_space;
+	} data;
+	struct dln2_adc_get_all_vals dev_data;
+	struct dln2_adc *dln2 = iio_priv(indio_dev);
+	const struct dln2_adc_demux_table *t;
+	int ret, i;
+
+	mutex_lock(&dln2->mutex);
+	ret = dln2_adc_read_all(dln2, &dev_data);
+	mutex_unlock(&dln2->mutex);
+	if (ret < 0)
+		goto done;
+
+	/* Demux operation */
+	for (i = 0; i < dln2->demux_count; ++i) {
+		t = &dln2->demux[i];
+		memcpy((void *)data.values + t->to,
+		       (void *)dev_data.values + t->from, t->length);
+	}
+
+	/* Zero padding space between values and timestamp */
+	if (dln2->ts_pad_length)
+		memset((void *)data.values + dln2->ts_pad_offset,
+		       0, dln2->ts_pad_length);
+
+	iio_push_to_buffers_with_timestamp(indio_dev, &data,
+					   iio_get_time_ns(indio_dev));
+
+done:
+	iio_trigger_notify_done(indio_dev->trig);
+	return IRQ_HANDLED;
+}
+
+static int dln2_adc_triggered_buffer_postenable(struct iio_dev *indio_dev)
+{
+	int ret;
+	struct dln2_adc *dln2 = iio_priv(indio_dev);
+	u16 conflict;
+
+	mutex_lock(&dln2->mutex);
+
+	/* Enable ADC */
+	ret = dln2_adc_set_port_enabled(dln2, true, &conflict);
+	if (ret < 0) {
+		mutex_unlock(&dln2->mutex);
+		dev_dbg(&dln2->pdev->dev, "Problem in %s\n", __func__);
+		if (conflict) {
+			dev_err(&dln2->pdev->dev,
+				"ADC pins conflict with mask %04X\n",
+				(int)conflict);
+			ret = -EBUSY;
+		}
+		return ret;
+	}
+
+	/* Assign trigger channel based on first enabled channel */
+	unsigned int trigger_chan =
+		find_first_bit(indio_dev->active_scan_mask,
+			       indio_dev->masklength);
+	if (trigger_chan < DLN2_ADC_MAX_CHANNELS) {
+		dln2->trigger_chan = trigger_chan;
+		ret = dln2_adc_set_chan_period(dln2, dln2->trigger_chan,
+					       dln2->sample_period);
+		mutex_unlock(&dln2->mutex);
+		if (ret < 0) {
+			dev_dbg(&dln2->pdev->dev, "Problem in %s\n", __func__);
+			return ret;
+		}
+	} else {
+		dln2->trigger_chan = -1;
+		mutex_unlock(&dln2->mutex);
+	}
+
+	return iio_triggered_buffer_postenable(indio_dev);
+}
+
+static int dln2_adc_triggered_buffer_predisable(struct iio_dev *indio_dev)
+{
+	int ret;
+	struct dln2_adc *dln2 = iio_priv(indio_dev);
+
+	mutex_lock(&dln2->mutex);
+
+	/* Disable trigger channel */
+	if (dln2->trigger_chan != -1) {
+		dln2_adc_set_chan_period(dln2, dln2->trigger_chan, 0);
+		dln2->trigger_chan = -1;
+	}
+
+	/* Disable ADC */
+	ret = dln2_adc_set_port_enabled(dln2, false, NULL);
+
+	mutex_unlock(&dln2->mutex);
+	if (ret < 0) {
+		dev_dbg(&dln2->pdev->dev, "Problem in %s\n", __func__);
+		return ret;
+	}
+
+	return iio_triggered_buffer_predisable(indio_dev);
+}
+
+static const struct iio_buffer_setup_ops dln2_adc_buffer_setup_ops = {
+	.postenable = dln2_adc_triggered_buffer_postenable,
+	.predisable = dln2_adc_triggered_buffer_predisable,
+};
+
+static void dln2_adc_event(struct platform_device *pdev, u16 echo,
+			   const void *data, int len)
+{
+	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
+	struct dln2_adc *dln2 = iio_priv(indio_dev);
+
+	/* Called via URB completion handler */
+	iio_trigger_poll(dln2->trig);
+}
+
+static const struct iio_trigger_ops dln2_adc_trigger_ops = {
+	.owner = THIS_MODULE,
+};
+
+static int dln2_adc_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct dln2_adc *dln2;
+	struct dln2_platform_data *pdata = dev_get_platdata(&pdev->dev);
+	struct iio_dev *indio_dev;
+	int i, ret, chans;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*dln2));
+	if (!indio_dev) {
+		dev_err(dev, "failed allocating iio device\n");
+		return -ENOMEM;
+	}
+
+	dln2 = iio_priv(indio_dev);
+	dln2->pdev = pdev;
+	dln2->port = pdata->port;
+	dln2->trigger_chan = -1;
+	mutex_init(&dln2->mutex);
+	dln2->sample_period = 0;
+	dln2->demux_count = 0;
+
+	platform_set_drvdata(pdev, indio_dev);
+
+	ret = dln2_adc_set_port_resolution(dln2);
+	if (ret < 0) {
+		dev_err(dev, "failed to set ADC resolution to 10 bits\n");
+		goto dealloc_dev;
+	}
+
+	chans = dln2_adc_get_chan_count(dln2);
+	if (chans < 0) {
+		dev_err(dev, "failed to get channel count: %d\n", chans);
+		ret = chans;
+		goto dealloc_dev;
+	}
+	if (chans > DLN2_ADC_MAX_CHANNELS) {
+		chans = DLN2_ADC_MAX_CHANNELS;
+		dev_warn(dev, "clamping channels to %d\n",
+			 DLN2_ADC_MAX_CHANNELS);
+	}
+
+	for (i = 0; i < chans; ++i) {
+		struct iio_chan_spec chan_spec = DLN2_ADC_CHAN(i);
+		dln2->iio_channels[i] = chan_spec;
+	}
+	struct iio_chan_spec timestamp_spec = IIO_CHAN_SOFT_TIMESTAMP(i);
+	dln2->iio_channels[i] = timestamp_spec;
+
+	indio_dev->name = DLN2_ADC_MOD_NAME;
+	indio_dev->dev.parent = dev;
+	indio_dev->info = &dln2_adc_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = dln2->iio_channels;
+	indio_dev->num_channels = chans + 1;
+	indio_dev->setup_ops = &dln2_adc_buffer_setup_ops;
+
+	dln2->trig = devm_iio_trigger_alloc(dev, "%s-dev%d",
+					    indio_dev->name, indio_dev->id);
+	if (!dln2->trig) {
+		dev_err(dev, "failed to allocate trigger\n");
+		ret = -ENOMEM;
+		goto dealloc_dev;
+	}
+	dln2->trig->ops = &dln2_adc_trigger_ops;
+	iio_trigger_set_drvdata(dln2->trig, dln2);
+	iio_trigger_register(dln2->trig);
+	iio_trigger_set_immutable(indio_dev, dln2->trig);
+
+	ret = iio_triggered_buffer_setup(indio_dev, NULL, dln2_adc_trigger_h,
+					 &dln2_adc_buffer_setup_ops);
+	if (ret) {
+		dev_err(dev, "failed to allocate triggered buffer: %d\n", ret);
+		goto dealloc_trigger;
+	}
+
+	ret = dln2_register_event_cb(pdev, DLN2_ADC_CONDITION_MET_EV,
+				     dln2_adc_event);
+	if (ret) {
+		dev_err(dev, "failed to register event cb: %d\n", ret);
+		goto dealloc_pollfunc;
+	}
+
+	ret = iio_device_register(indio_dev);
+	if (ret) {
+		dev_err(dev, "failed to register iio device: %d\n", ret);
+		goto dealloc_pollfunc;
+	}
+
+	return 0;
+
+dealloc_pollfunc:
+	iio_triggered_buffer_cleanup(indio_dev);
+dealloc_trigger:
+	iio_trigger_unregister(dln2->trig);
+dealloc_dev:
+
+	return ret;
+}
+
+static int dln2_adc_remove(struct platform_device *pdev)
+{
+	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
+	struct dln2_adc *dln2 = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+	dln2_unregister_event_cb(pdev, DLN2_ADC_CONDITION_MET_EV);
+	iio_trigger_unregister(dln2->trig);
+	iio_triggered_buffer_cleanup(indio_dev);
+
+	return 0;
+}
+
+static struct platform_driver dln2_adc_driver = {
+	.driver.name	= DLN2_ADC_MOD_NAME,
+	.probe		= dln2_adc_probe,
+	.remove		= dln2_adc_remove,
+};
+
+module_platform_driver(dln2_adc_driver);
+
+MODULE_AUTHOR("Jack Andersen <jackoalan@...il.com");
+MODULE_DESCRIPTION("Driver for the Diolan DLN2 ADC interface");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:dln2-adc");
diff --git a/drivers/mfd/dln2.c b/drivers/mfd/dln2.c
index 704e189..a22ab8c 100644
--- a/drivers/mfd/dln2.c
+++ b/drivers/mfd/dln2.c
@@ -53,6 +53,7 @@ enum dln2_handle {
 	DLN2_HANDLE_GPIO,
 	DLN2_HANDLE_I2C,
 	DLN2_HANDLE_SPI,
+	DLN2_HANDLE_ADC,
 	DLN2_HANDLES
 };
 
@@ -663,6 +664,12 @@ static int dln2_start_rx_urbs(struct dln2_dev *dln2, gfp_t gfp)
 	.port = 0,
 };
 
+/* Only one ADC port supported */
+static struct dln2_platform_data dln2_pdata_adc = {
+	.handle = DLN2_HANDLE_ADC,
+	.port = 0,
+};
+
 static const struct mfd_cell dln2_devs[] = {
 	{
 		.name = "dln2-gpio",
@@ -679,6 +686,11 @@ static int dln2_start_rx_urbs(struct dln2_dev *dln2, gfp_t gfp)
 		.platform_data = &dln2_pdata_spi,
 		.pdata_size = sizeof(struct dln2_platform_data),
 	},
+	{
+		.name = "dln2-adc",
+		.platform_data = &dln2_pdata_adc,
+		.pdata_size = sizeof(struct dln2_platform_data),
+	},
 };
 
 static void dln2_stop(struct dln2_dev *dln2)
diff --git a/tools/gpio/lsgpio.c b/tools/gpio/lsgpio.c
index eb3f56e..58ef924 100644
--- a/tools/gpio/lsgpio.c
+++ b/tools/gpio/lsgpio.c
@@ -77,7 +77,7 @@ int list_device(const char *device_name)
 	int ret;
 	int i;
 
-	ret = asprintf(&chrdev_name, "/dev/%s", device_name);
+	ret = asprintf(&chrdev_name, "/sys/class/gpio/%s", device_name);
 	if (ret < 0)
 		return -ENOMEM;
 
@@ -169,7 +169,7 @@ int main(int argc, char **argv)
 		DIR *dp;
 
 		/* List all GPIO devices one at a time */
-		dp = opendir("/dev");
+		dp = opendir("/sys/class/gpio");
 		if (!dp) {
 			ret = -errno;
 			goto error_out;
-- 
1.9.1

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