[PATCH 36/36] staging: iio: resolver: new driver for AD2S1210 devices

[Mike Frysinger <vapier@gentoo.org>]

From: Graf Yang <graf.yang@analog.com>

Signed-off-by: Graf Yang <graf.yang@analog.com>
Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
---
 drivers/staging/iio/resolver/Kconfig    |   35 ++
 drivers/staging/iio/resolver/Makefile   |    1 +
 drivers/staging/iio/resolver/ad2s1210.c |  872 +++++++++++++++++++++++++++++++
 3 files changed, 908 insertions(+), 0 deletions(-)
 create mode 100644 drivers/staging/iio/resolver/ad2s1210.c

diff --git a/drivers/staging/iio/resolver/Kconfig b/drivers/staging/iio/resolver/Kconfig
index 32df73a..a4a3634 100644
--- a/drivers/staging/iio/resolver/Kconfig
+++ b/drivers/staging/iio/resolver/Kconfig
@@ -17,3 +17,38 @@ config AD2S120X
 	  Say yes here to build support for Analog Devices spi resolver
 	  to digital converters, ad2s1200 and ad2s1205, provides direct access
 	  via sysfs.
+
+config AD2S1210
+	tristate "Analog Devices ad2s1210 driver"
+	depends on SPI
+	help
+	  Say yes here to build support for Analog Devices spi resolver
+	  to digital converters, ad2s1210, provides direct access via sysfs.
+
+choice
+	prompt "Resolution Control"
+	depends on AD2S1210
+	default AD2S1210_GPIO_NONE
+	help
+	  In normal mode, the resolution of the digital output is selected
+	  using the RES0 and RES1 input pins. In configuration mode, the
+	  resolution is selected by setting the RES0 and RES1 bits in the
+	  control regsiter. When switching between normal mode and configuration
+	  mode, there are some schemes to keep them matchs.
+
+config AD2S1210_GPIO_INPUT
+	bool "read resolution from gpio pins"
+	help
+	  GPIO pins are sampling RES0 and RES1 pins, read the resolution
+	  settings from the GPIO pins.
+
+config AD2S1210_GPIO_OUTPUT
+	bool "set gpio pins to set resolution"
+	help
+	  RES0 and RES1 pins are controlled by GPIOs, setting GPIO pins to
+	  set the resolution.
+
+config AD2S1210_GPIO_NONE
+	bool "take the responsibility by user"
+
+endchoice
diff --git a/drivers/staging/iio/resolver/Makefile b/drivers/staging/iio/resolver/Makefile
index b2b3cc1..0b84a89 100644
--- a/drivers/staging/iio/resolver/Makefile
+++ b/drivers/staging/iio/resolver/Makefile
@@ -4,3 +4,4 @@
 
 obj-$(CONFIG_AD2S90) += ad2s90.o
 obj-$(CONFIG_AD2S120X) += ad2s120x.o
+obj-$(CONFIG_AD2S1210) += ad2s1210.o
diff --git a/drivers/staging/iio/resolver/ad2s1210.c b/drivers/staging/iio/resolver/ad2s1210.c
new file mode 100644
index 0000000..34fb21a
--- /dev/null
+++ b/drivers/staging/iio/resolver/ad2s1210.c
@@ -0,0 +1,872 @@
+/*
+ * ad2s1210.c support for the ADI Resolver to Digital Converters: AD2S1210
+ *
+ * Copyright (c) 2010-2010 Analog Devices Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+#include <linux/types.h>
+#include <linux/mutex.h>
+#include <linux/device.h>
+#include <linux/spi/spi.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+#include <linux/delay.h>
+#include <linux/gpio.h>
+
+#include "../iio.h"
+#include "../sysfs.h"
+
+#define DRV_NAME "ad2s1210"
+
+#define DEF_CONTROL		0x7E
+
+#define MSB_IS_HIGH		0x80
+#define MSB_IS_LOW		0x7F
+#define PHASE_LOCK_RANGE_44	0x20
+#define ENABLE_HYSTERESIS	0x10
+#define SET_ENRES1		0x08
+#define SET_ENRES0		0x04
+#define SET_RES1		0x02
+#define SET_RES0		0x01
+
+#define SET_ENRESOLUTION	(SET_ENRES1 | SET_ENRES0)
+#define SET_RESOLUTION		(SET_RES1 | SET_RES0)
+
+#define REG_POSITION		0x80
+#define REG_VELOCITY		0x82
+#define REG_LOS_THRD		0x88
+#define REG_DOS_OVR_THRD	0x89
+#define REG_DOS_MIS_THRD	0x8A
+#define REG_DOS_RST_MAX_THRD	0x8B
+#define REG_DOS_RST_MIN_THRD	0x8C
+#define REG_LOT_HIGH_THRD	0x8D
+#define REG_LOT_LOW_THRD	0x8E
+#define REG_EXCIT_FREQ		0x91
+#define REG_CONTROL		0x92
+#define REG_SOFT_RESET		0xF0
+#define REG_FAULT		0xFF
+
+/* pin SAMPLE, A0, A1, RES0, RES1, is controlled by driver */
+#define AD2S1210_SAA		3
+#if defined(CONFIG_AD2S1210_GPIO_INPUT) || defined(CONFIG_AD2S1210_GPIO_OUTPUT)
+# define AD2S1210_RES		2
+#else
+# define AD2S1210_RES		0
+#endif
+#define AD2S1210_PN		(AD2S1210_SAA + AD2S1210_RES)
+
+#define AD2S1210_MIN_CLKIN	6144000
+#define AD2S1210_MAX_CLKIN	10240000
+#define AD2S1210_MIN_EXCIT	2000
+#define AD2S1210_MAX_EXCIT	20000
+#define AD2S1210_MIN_FCW	0x4
+#define AD2S1210_MAX_FCW	0x50
+
+/* default input clock on serial interface */
+#define AD2S1210_DEF_CLKIN	8192000
+/* clock period in nano second */
+#define AD2S1210_DEF_TCK	(1000000000/AD2S1210_DEF_CLKIN)
+#define AD2S1210_DEF_EXCIT	10000
+
+enum ad2s1210_mode {
+	MOD_POS = 0,
+	MOD_VEL,
+	MOD_RESERVED,
+	MOD_CONFIG,
+};
+
+enum ad2s1210_res {
+	RES_10 = 10,
+	RES_12 = 12,
+	RES_14 = 14,
+	RES_16 = 16,
+};
+
+static unsigned int resolution_value[] = {
+		RES_10, RES_12, RES_14, RES_16};
+
+struct ad2s1210_state {
+	struct mutex lock;
+	struct iio_dev *idev;
+	struct spi_device *sdev;
+	struct spi_transfer xfer;
+	unsigned int hysteresis;
+	unsigned int old_data;
+	enum ad2s1210_mode mode;
+	enum ad2s1210_res resolution;
+	unsigned int fclkin;
+	unsigned int fexcit;
+	unsigned short sample;
+	unsigned short a0;
+	unsigned short a1;
+	unsigned short res0;
+	unsigned short res1;
+	u8 rx[3];
+	u8 tx[3];
+};
+
+static inline void start_sample(struct ad2s1210_state *st)
+{
+	gpio_set_value(st->sample, 0);
+}
+
+static inline void stop_sample(struct ad2s1210_state *st)
+{
+	gpio_set_value(st->sample, 1);
+}
+
+static inline void set_mode(enum ad2s1210_mode mode, struct ad2s1210_state *st)
+{
+	switch (mode) {
+	case MOD_POS:
+		gpio_set_value(st->a0, 0);
+		gpio_set_value(st->a1, 0);
+		break;
+	case MOD_VEL:
+		gpio_set_value(st->a0, 0);
+		gpio_set_value(st->a1, 1);
+		break;
+	case MOD_CONFIG:
+		gpio_set_value(st->a0, 1);
+		gpio_set_value(st->a1, 1);
+		break;
+	default:
+		/* set to reserved mode */
+		gpio_set_value(st->a0, 1);
+		gpio_set_value(st->a1, 0);
+	}
+	st->mode = mode;
+}
+
+/* write 1 bytes (address or data) to the chip */
+static int config_write(struct ad2s1210_state *st,
+					unsigned char data)
+{
+	struct spi_message msg;
+	int ret = 0;
+
+	st->xfer.len = 1;
+	set_mode(MOD_CONFIG, st);
+
+	spi_message_init(&msg);
+	spi_message_add_tail(&st->xfer, &msg);
+	st->tx[0] = data;
+	ret = spi_sync(st->sdev, &msg);
+	if (ret)
+		return ret;
+	st->old_data = 1;
+	return ret;
+}
+
+/* read value from one of the registers */
+static int config_read(struct ad2s1210_state *st,
+				unsigned char address,
+					unsigned char *data)
+{
+	struct spi_message msg;
+	int ret = 0;
+
+	st->xfer.len = 2;
+	set_mode(MOD_CONFIG, st);
+
+	spi_message_init(&msg);
+	spi_message_add_tail(&st->xfer, &msg);
+	st->tx[0] = address | MSB_IS_HIGH;
+	st->tx[1] = REG_FAULT;
+	ret = spi_sync(st->sdev, &msg);
+	if (ret)
+		return ret;
+	*data = st->rx[1];
+	st->old_data = 1;
+	return ret;
+}
+
+static inline void update_frequency_control_word(struct ad2s1210_state *st)
+{
+	unsigned char fcw;
+	fcw = (unsigned char)(st->fexcit * (1 << 15) / st->fclkin);
+	if (fcw >= AD2S1210_MIN_FCW && fcw <= AD2S1210_MAX_FCW) {
+		config_write(st, REG_EXCIT_FREQ);
+		config_write(st, fcw);
+	} else
+		pr_err("ad2s1210: FCW out of range\n");
+}
+
+#if defined(CONFIG_AD2S1210_GPIO_INPUT)
+static inline unsigned char read_resolution_pin(struct ad2s1210_state *st)
+{
+	unsigned int data;
+	data = (gpio_get_value(st->res0) << 1)  |
+			gpio_get_value(st->res1);
+	return resolution_value[data];
+}
+#elif defined(CONFIG_AD2S1210_GPIO_OUTPUT)
+static inline void set_resolution_pin(struct ad2s1210_state *st)
+{
+	switch (st->resolution) {
+	case RES_10:
+		gpio_set_value(st->res0, 0);
+		gpio_set_value(st->res1, 0);
+		break;
+	case RES_12:
+		gpio_set_value(st->res0, 0);
+		gpio_set_value(st->res1, 1);
+		break;
+	case RES_14:
+		gpio_set_value(st->res0, 1);
+		gpio_set_value(st->res1, 0);
+		break;
+	case RES_16:
+		gpio_set_value(st->res0, 1);
+		gpio_set_value(st->res1, 1);
+		break;
+	}
+}
+#endif
+
+static inline void soft_reset(struct ad2s1210_state *st)
+{
+	config_write(st, REG_SOFT_RESET);
+	config_write(st, 0x0);
+}
+
+
+/* return the OLD DATA since last spi bus write */
+static ssize_t ad2s1210_show_raw(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct iio_dev *idev = dev_get_drvdata(dev);
+	struct ad2s1210_state *st = idev->dev_data;
+	int ret;
+
+	mutex_lock(&st->lock);
+	if (st->old_data) {
+		ret = sprintf(buf, "0x%x\n", st->rx[0]);
+		st->old_data = 0;
+	} else
+		ret = 0;
+	mutex_unlock(&st->lock);
+	return ret;
+}
+
+static ssize_t ad2s1210_store_raw(struct device *dev,
+		struct device_attribute *attr,
+		const char *buf, size_t len)
+{
+	struct iio_dev *idev = dev_get_drvdata(dev);
+	struct ad2s1210_state *st = idev->dev_data;
+	unsigned long udata;
+	unsigned char data;
+	int ret;
+
+	ret = strict_strtoul(buf, 16, &udata);
+	if (ret)
+		return -EINVAL;
+	data = udata & 0xff;
+	mutex_lock(&st->lock);
+	config_write(st, data);
+	mutex_unlock(&st->lock);
+	return 1;
+}
+
+static ssize_t ad2s1210_store_softreset(struct device *dev,
+			struct device_attribute *attr,
+			const char *buf, size_t len)
+{
+	struct iio_dev *idev = dev_get_drvdata(dev);
+	struct ad2s1210_state *st = idev->dev_data;
+	mutex_lock(&st->lock);
+	soft_reset(st);
+	mutex_unlock(&st->lock);
+	return len;
+}
+
+static ssize_t ad2s1210_show_fclkin(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct iio_dev *idev = dev_get_drvdata(dev);
+	struct ad2s1210_state *st = idev->dev_data;
+	return sprintf(buf, "%d\n", st->fclkin);
+}
+
+static ssize_t ad2s1210_store_fclkin(struct device *dev,
+			struct device_attribute *attr,
+			const char *buf, size_t len)
+{
+	struct iio_dev *idev = dev_get_drvdata(dev);
+	struct ad2s1210_state *st = idev->dev_data;
+	unsigned long fclkin;
+	int ret;
+
+	ret = strict_strtoul(buf, 10, &fclkin);
+	if (!ret && fclkin >= AD2S1210_MIN_CLKIN &&
+				fclkin <= AD2S1210_MAX_CLKIN) {
+		mutex_lock(&st->lock);
+		st->fclkin = fclkin;
+	} else {
+		pr_err("ad2s1210: fclkin out of range\n");
+		return -EINVAL;
+	}
+	update_frequency_control_word(st);
+	soft_reset(st);
+	mutex_unlock(&st->lock);
+	return len;
+}
+
+static ssize_t ad2s1210_show_fexcit(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct iio_dev *idev = dev_get_drvdata(dev);
+	struct ad2s1210_state *st = idev->dev_data;
+	return sprintf(buf, "%d\n", st->fexcit);
+}
+
+static ssize_t ad2s1210_store_fexcit(struct device *dev,
+			struct device_attribute *attr,
+			const char *buf, size_t len)
+{
+	struct iio_dev *idev = dev_get_drvdata(dev);
+	struct ad2s1210_state *st = idev->dev_data;
+	unsigned long fexcit;
+	int ret;
+
+	ret = strict_strtoul(buf, 10, &fexcit);
+	if (!ret && fexcit >= AD2S1210_MIN_EXCIT &&
+				fexcit <= AD2S1210_MAX_EXCIT) {
+		mutex_lock(&st->lock);
+		st->fexcit = fexcit;
+	} else {
+		pr_err("ad2s1210: excitation frequency out of range\n");
+		return -EINVAL;
+	}
+	update_frequency_control_word(st);
+	soft_reset(st);
+	mutex_unlock(&st->lock);
+	return len;
+}
+
+static ssize_t ad2s1210_show_control(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct iio_dev *idev = dev_get_drvdata(dev);
+	struct ad2s1210_state *st = idev->dev_data;
+	unsigned char data;
+	mutex_lock(&st->lock);
+	config_read(st, REG_CONTROL, &data);
+	mutex_unlock(&st->lock);
+	return sprintf(buf, "0x%x\n", data);
+}
+
+static ssize_t ad2s1210_store_control(struct device *dev,
+			struct device_attribute *attr,
+			const char *buf, size_t len)
+{
+	struct iio_dev *idev = dev_get_drvdata(dev);
+	struct ad2s1210_state *st = idev->dev_data;
+	unsigned long udata;
+	unsigned char data;
+	int ret;
+
+	ret = strict_strtoul(buf, 16, &udata);
+	if (ret) {
+		ret = -EINVAL;
+		goto error_ret;
+	}
+	mutex_lock(&st->lock);
+	config_write(st, REG_CONTROL);
+	data = udata & MSB_IS_LOW;
+	config_write(st, data);
+	config_read(st, REG_CONTROL, &data);
+	if (data & MSB_IS_HIGH) {
+		ret = -EIO;
+		pr_err("ad2s1210: write control register fail\n");
+		goto error_ret;
+	}
+	st->resolution = resolution_value[data & SET_RESOLUTION];
+#if defined(CONFIG_AD2S1210_GPIO_INPUT)
+	data = read_resolution_pin(st);
+	if (data != st->resolution)
+		pr_warning("ad2s1210: resolution settings not match\n");
+#elif defined(CONFIG_AD2S1210_GPIO_OUTPUT)
+	set_resolution_pin(st);
+#endif
+	ret = len;
+	if (data & ENABLE_HYSTERESIS)
+		st->hysteresis = 1;
+	else
+		st->hysteresis = 0;
+error_ret:
+	mutex_unlock(&st->lock);
+	return ret;
+}
+
+static ssize_t ad2s1210_show_resolution(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct iio_dev *idev = dev_get_drvdata(dev);
+	struct ad2s1210_state *st = idev->dev_data;
+	return sprintf(buf, "%d\n", st->resolution);
+}
+
+static ssize_t ad2s1210_store_resolution(struct device *dev,
+			struct device_attribute *attr,
+			const char *buf, size_t len)
+{
+	struct iio_dev *idev = dev_get_drvdata(dev);
+	struct ad2s1210_state *st = idev->dev_data;
+	unsigned char data;
+	unsigned long udata;
+	int ret;
+
+	ret = strict_strtoul(buf, 10, &udata);
+	if (ret || udata < RES_10 || udata > RES_16) {
+		pr_err("ad2s1210: resolution out of range\n");
+		return -EINVAL;
+	}
+	mutex_lock(&st->lock);
+	config_read(st, REG_CONTROL, &data);
+	data &= ~SET_RESOLUTION;
+	data |= (udata - RES_10) >> 1;
+	config_write(st, REG_CONTROL);
+	config_write(st, data & MSB_IS_LOW);
+	config_read(st, REG_CONTROL, &data);
+	if (data & MSB_IS_HIGH) {
+		ret = -EIO;
+		pr_err("ad2s1210: setting resolution fail\n");
+		goto error_ret;
+	}
+	st->resolution = resolution_value[data & SET_RESOLUTION];
+#if defined(CONFIG_AD2S1210_GPIO_INPUT)
+	data = read_resolution_pin(st);
+	if (data != st->resolution)
+		pr_warning("ad2s1210: resolution settings not match\n");
+#elif defined(CONFIG_AD2S1210_GPIO_OUTPUT)
+	set_resolution_pin(st);
+#endif
+	ret = len;
+error_ret:
+	mutex_unlock(&st->lock);
+	return ret;
+}
+/* read the fault register since last sample */
+static ssize_t ad2s1210_show_fault(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	int ret = 0;
+	ssize_t len = 0;
+	unsigned char data;
+	struct iio_dev *idev = dev_get_drvdata(dev);
+	struct ad2s1210_state *st = idev->dev_data;
+
+	mutex_lock(&st->lock);
+	ret = config_read(st, REG_FAULT, &data);
+
+	if (ret)
+		goto error_ret;
+	len = sprintf(buf, "0x%x\n", data);
+error_ret:
+	mutex_unlock(&st->lock);
+	return ret ? ret : len;
+}
+
+static ssize_t ad2s1210_clear_fault(struct device *dev,
+			struct device_attribute *attr,
+			const char *buf, size_t len)
+{
+	struct iio_dev *idev = dev_get_drvdata(dev);
+	struct ad2s1210_state *st = idev->dev_data;
+	unsigned char data;
+
+	mutex_lock(&st->lock);
+	start_sample(st);
+	/* delay (2 * tck + 20) nano seconds */
+	udelay(1);
+	stop_sample(st);
+	config_read(st, REG_FAULT, &data);
+	start_sample(st);
+	stop_sample(st);
+	mutex_unlock(&st->lock);
+
+	return 0;
+}
+
+static ssize_t ad2s1210_show_reg(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct iio_dev *idev = dev_get_drvdata(dev);
+	struct ad2s1210_state *st = idev->dev_data;
+	unsigned char data;
+	struct iio_dev_attr *iattr = to_iio_dev_attr(attr);
+
+	mutex_lock(&st->lock);
+	config_read(st, iattr->address, &data);
+	mutex_unlock(&st->lock);
+	return sprintf(buf, "%d\n", data);
+}
+
+static ssize_t ad2s1210_store_reg(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	struct iio_dev *idev = dev_get_drvdata(dev);
+	struct ad2s1210_state *st = idev->dev_data;
+	unsigned long data;
+	int ret;
+	struct iio_dev_attr *iattr = to_iio_dev_attr(attr);
+
+	ret = strict_strtoul(buf, 10, &data);
+	if (ret)
+		return -EINVAL;
+	mutex_lock(&st->lock);
+	config_write(st, iattr->address);
+	config_write(st, data & MSB_IS_LOW);
+	mutex_unlock(&st->lock);
+	return len;
+}
+
+static ssize_t ad2s1210_show_pos(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct spi_message msg;
+	int ret = 0;
+	ssize_t len = 0;
+	u16 pos;
+	struct iio_dev *idev = dev_get_drvdata(dev);
+	struct ad2s1210_state *st = idev->dev_data;
+
+	st->xfer.len = 2;
+	mutex_lock(&st->lock);
+	start_sample(st);
+	/* delay (6 * tck + 20) nano seconds */
+	udelay(1);
+
+	set_mode(MOD_POS, st);
+
+	spi_message_init(&msg);
+	spi_message_add_tail(&st->xfer, &msg);
+	ret = spi_sync(st->sdev, &msg);
+	if (ret)
+		goto error_ret;
+	pos = ((((u16)(st->rx[0])) << 8) | (st->rx[1]));
+	if (st->hysteresis)
+		pos >>= 16 - st->resolution;
+	len = sprintf(buf, "%d\n", pos);
+error_ret:
+	stop_sample(st);
+	/* delay (2 * tck + 20) nano seconds */
+	udelay(1);
+	mutex_unlock(&st->lock);
+
+	return ret ? ret : len;
+}
+
+static ssize_t ad2s1210_show_vel(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct spi_message msg;
+	unsigned short negative;
+	int ret = 0;
+	ssize_t len = 0;
+	s16 vel;
+	struct iio_dev *idev = dev_get_drvdata(dev);
+	struct ad2s1210_state *st = idev->dev_data;
+
+	st->xfer.len = 2;
+	mutex_lock(&st->lock);
+	start_sample(st);
+	/* delay (6 * tck + 20) nano seconds */
+	udelay(1);
+
+	set_mode(MOD_VEL, st);
+
+	spi_message_init(&msg);
+	spi_message_add_tail(&st->xfer, &msg);
+	ret = spi_sync(st->sdev, &msg);
+	if (ret)
+		goto error_ret;
+	negative = st->rx[0] & 0x80;
+	vel = ((((s16)(st->rx[0])) << 8) | (st->rx[1]));
+	vel >>= 16 - st->resolution;
+	if (negative) {
+		negative = (0xffff >> st->resolution) << st->resolution;
+		vel |= negative;
+	}
+	len = sprintf(buf, "%d\n", vel);
+error_ret:
+	stop_sample(st);
+	/* delay (2 * tck + 20) nano seconds */
+	udelay(1);
+	mutex_unlock(&st->lock);
+
+	return ret ? ret : len;
+}
+
+static ssize_t ad2s1210_show_pos_vel(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct spi_message msg;
+	unsigned short negative;
+	int ret = 0;
+	ssize_t len = 0;
+	u16 pos;
+	s16 vel;
+	struct iio_dev *idev = dev_get_drvdata(dev);
+	struct ad2s1210_state *st = idev->dev_data;
+
+	st->xfer.len = 2;
+	mutex_lock(&st->lock);
+	start_sample(st);
+	/* delay (6 * tck + 20) nano seconds */
+	udelay(1);
+
+	set_mode(MOD_POS, st);
+
+	spi_message_init(&msg);
+	spi_message_add_tail(&st->xfer, &msg);
+	ret = spi_sync(st->sdev, &msg);
+	if (ret)
+		goto error_ret;
+	pos = ((((u16)(st->rx[0])) << 8) | (st->rx[1]));
+	if (st->hysteresis)
+		pos >>= 16 - st->resolution;
+	len = sprintf(buf, "%d ", pos);
+
+	st->xfer.len = 2;
+	set_mode(MOD_VEL, st);
+	spi_message_init(&msg);
+	spi_message_add_tail(&st->xfer, &msg);
+	ret = spi_sync(st->sdev, &msg);
+	if (ret)
+		goto error_ret;
+	negative = st->rx[0] & 0x80;
+	vel = ((((s16)(st->rx[0])) << 8) | (st->rx[1]));
+	vel >>= 16 - st->resolution;
+	if (negative) {
+		negative = (0xffff >> st->resolution) << st->resolution;
+		vel |= negative;
+	}
+	len += sprintf(buf + len, "%d\n", vel);
+error_ret:
+	stop_sample(st);
+	/* delay (2 * tck + 20) nano seconds */
+	udelay(1);
+	mutex_unlock(&st->lock);
+
+	return ret ? ret : len;
+}
+
+static IIO_CONST_ATTR(description,
+	"Variable Resolution, 10-Bit to 16Bit R/D\n\
+Converter with Reference Oscillator");
+static IIO_DEVICE_ATTR(raw_io, S_IRUGO | S_IWUGO,
+		ad2s1210_show_raw, ad2s1210_store_raw, 0);
+static IIO_DEVICE_ATTR(reset, S_IWUGO,
+		NULL, ad2s1210_store_softreset, 0);
+static IIO_DEVICE_ATTR(fclkin, S_IRUGO | S_IWUGO,
+		ad2s1210_show_fclkin, ad2s1210_store_fclkin, 0);
+static IIO_DEVICE_ATTR(fexcit, S_IRUGO | S_IWUGO,
+		ad2s1210_show_fexcit,	ad2s1210_store_fexcit, 0);
+static IIO_DEVICE_ATTR(control, S_IRUGO | S_IWUGO,
+		ad2s1210_show_control, ad2s1210_store_control, 0);
+static IIO_DEVICE_ATTR(bits, S_IRUGO | S_IWUGO,
+		ad2s1210_show_resolution, ad2s1210_store_resolution, 0);
+static IIO_DEVICE_ATTR(fault, S_IRUGO | S_IWUGO,
+		ad2s1210_show_fault, ad2s1210_clear_fault, 0);
+static IIO_DEVICE_ATTR(pos, S_IRUGO,
+		ad2s1210_show_pos, NULL, 0);
+static IIO_DEVICE_ATTR(vel, S_IRUGO,
+		ad2s1210_show_vel, NULL, 0);
+static IIO_DEVICE_ATTR(pos_vel, S_IRUGO,
+		ad2s1210_show_pos_vel, NULL, 0);
+static IIO_DEVICE_ATTR(los_thrd, S_IRUGO | S_IWUGO,
+		ad2s1210_show_reg, ad2s1210_store_reg, REG_LOS_THRD);
+static IIO_DEVICE_ATTR(dos_ovr_thrd, S_IRUGO | S_IWUGO,
+		ad2s1210_show_reg, ad2s1210_store_reg, REG_DOS_OVR_THRD);
+static IIO_DEVICE_ATTR(dos_mis_thrd, S_IRUGO | S_IWUGO,
+		ad2s1210_show_reg, ad2s1210_store_reg, REG_DOS_MIS_THRD);
+static IIO_DEVICE_ATTR(dos_rst_max_thrd, S_IRUGO | S_IWUGO,
+		ad2s1210_show_reg, ad2s1210_store_reg, REG_DOS_RST_MAX_THRD);
+static IIO_DEVICE_ATTR(dos_rst_min_thrd, S_IRUGO | S_IWUGO,
+		ad2s1210_show_reg, ad2s1210_store_reg, REG_DOS_RST_MIN_THRD);
+static IIO_DEVICE_ATTR(lot_high_thrd, S_IRUGO | S_IWUGO,
+		ad2s1210_show_reg, ad2s1210_store_reg, REG_LOT_HIGH_THRD);
+static IIO_DEVICE_ATTR(lot_low_thrd, S_IRUGO | S_IWUGO,
+		ad2s1210_show_reg, ad2s1210_store_reg, REG_LOT_LOW_THRD);
+
+static struct attribute *ad2s1210_attributes[] = {
+	&iio_const_attr_description.dev_attr.attr,
+	&iio_dev_attr_raw_io.dev_attr.attr,
+	&iio_dev_attr_reset.dev_attr.attr,
+	&iio_dev_attr_fclkin.dev_attr.attr,
+	&iio_dev_attr_fexcit.dev_attr.attr,
+	&iio_dev_attr_control.dev_attr.attr,
+	&iio_dev_attr_bits.dev_attr.attr,
+	&iio_dev_attr_fault.dev_attr.attr,
+	&iio_dev_attr_pos.dev_attr.attr,
+	&iio_dev_attr_vel.dev_attr.attr,
+	&iio_dev_attr_pos_vel.dev_attr.attr,
+	&iio_dev_attr_los_thrd.dev_attr.attr,
+	&iio_dev_attr_dos_ovr_thrd.dev_attr.attr,
+	&iio_dev_attr_dos_mis_thrd.dev_attr.attr,
+	&iio_dev_attr_dos_rst_max_thrd.dev_attr.attr,
+	&iio_dev_attr_dos_rst_min_thrd.dev_attr.attr,
+	&iio_dev_attr_lot_high_thrd.dev_attr.attr,
+	&iio_dev_attr_lot_low_thrd.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group ad2s1210_attribute_group = {
+	.name = DRV_NAME,
+	.attrs = ad2s1210_attributes,
+};
+
+static int __devinit ad2s1210_initial(struct ad2s1210_state *st)
+{
+	unsigned char data;
+	int ret;
+
+	mutex_lock(&st->lock);
+#if defined(CONFIG_AD2S1210_GPIO_INPUT)
+	st->resolution = read_resolution_pin(st);
+#elif defined(CONFIG_AD2S1210_GPIO_OUTPUT)
+	set_resolution_pin(st);
+#endif
+
+	config_write(st, REG_CONTROL);
+	data = DEF_CONTROL & ~(SET_RESOLUTION);
+	data |= (st->resolution - RES_10) >> 1;
+	config_write(st, data);
+	ret = config_read(st, REG_CONTROL, &data);
+	if (ret)
+		goto error_ret;
+
+	if (data & MSB_IS_HIGH) {
+		ret = -EIO;
+		goto error_ret;
+	}
+
+	update_frequency_control_word(st);
+	soft_reset(st);
+error_ret:
+	mutex_unlock(&st->lock);
+	return ret;
+}
+
+static int __devinit ad2s1210_probe(struct spi_device *spi)
+{
+	struct ad2s1210_state *st;
+	int pn, ret = 0;
+	unsigned short *pins = spi->dev.platform_data;
+
+	for (pn = 0; pn < AD2S1210_PN; pn++) {
+		if (gpio_request(pins[pn], DRV_NAME)) {
+			pr_err("%s: request gpio pin %d failed\n",
+						DRV_NAME, pins[pn]);
+			goto error_ret;
+		}
+		if (pn < AD2S1210_SAA)
+			gpio_direction_output(pins[pn], 1);
+		else {
+#if defined(CONFIG_AD2S1210_GPIO_INPUT)
+			gpio_direction_input(pins[pn]);
+#elif defined(CONFIG_AD2S1210_GPIO_OUTPUT)
+			gpio_direction_output(pins[pn], 1);
+#endif
+		}
+	}
+
+	st = kzalloc(sizeof(*st), GFP_KERNEL);
+	if (st == NULL) {
+		ret = -ENOMEM;
+		goto error_ret;
+	}
+	spi_set_drvdata(spi, st);
+
+	mutex_init(&st->lock);
+	st->sdev = spi;
+	st->xfer.tx_buf = st->tx;
+	st->xfer.rx_buf = st->rx;
+	st->hysteresis = 1;
+	st->mode = MOD_CONFIG;
+	st->resolution = RES_12;
+	st->fclkin = AD2S1210_DEF_CLKIN;
+	st->fexcit = AD2S1210_DEF_EXCIT;
+	st->sample = pins[0];
+	st->a0 = pins[1];
+	st->a1 = pins[2];
+	st->res0 = pins[3];
+	st->res1 = pins[4];
+
+	st->idev = iio_allocate_device();
+	if (st->idev == NULL) {
+		ret = -ENOMEM;
+		goto error_free_st;
+	}
+	st->idev->dev.parent = &spi->dev;
+	st->idev->num_interrupt_lines = 0;
+	st->idev->event_attrs = NULL;
+
+	st->idev->attrs = &ad2s1210_attribute_group;
+	st->idev->dev_data = (void *)(st);
+	st->idev->driver_module = THIS_MODULE;
+	st->idev->modes = INDIO_DIRECT_MODE;
+
+	ret = iio_device_register(st->idev);
+	if (ret)
+		goto error_free_dev;
+
+	if (spi->max_speed_hz != AD2S1210_DEF_CLKIN)
+		st->fclkin = spi->max_speed_hz;
+	spi->mode = SPI_MODE_3;
+	spi_setup(spi);
+
+	ad2s1210_initial(st);
+	return 0;
+
+error_free_dev:
+	iio_free_device(st->idev);
+error_free_st:
+	kfree(st);
+error_ret:
+	for (--pn; pn >= 0; pn--)
+		gpio_free(pins[pn]);
+	return ret;
+}
+
+static int __devexit ad2s1210_remove(struct spi_device *spi)
+{
+	struct ad2s1210_state *st = spi_get_drvdata(spi);
+
+	iio_device_unregister(st->idev);
+	kfree(st);
+
+	return 0;
+}
+
+static struct spi_driver ad2s1210_driver = {
+	.driver = {
+		.name = DRV_NAME,
+		.owner = THIS_MODULE,
+	},
+	.probe = ad2s1210_probe,
+	.remove = __devexit_p(ad2s1210_remove),
+};
+
+static __init int ad2s1210_spi_init(void)
+{
+	return spi_register_driver(&ad2s1210_driver);
+}
+module_init(ad2s1210_spi_init);
+
+static __exit void ad2s1210_spi_exit(void)
+{
+	spi_unregister_driver(&ad2s1210_driver);
+}
+module_exit(ad2s1210_spi_exit);
+
+MODULE_AUTHOR("Graff Yang <graff.yang@gmail.com>");
+MODULE_DESCRIPTION("Analog Devices AD2S1210 Resolver to Digital SPI driver");
+MODULE_LICENSE("GPL v2");
-- 
1.7.3.2