Staging: IIO: VTI sca3000 series accelerometer driver (spi)

Example of how a device with a hardware ring buffer is
handled within IIO.

Changes since V2:
* Moved to new registration functions giving much cleaner
  interface.
Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/accel/Kconfig

@@ -17,3 +17,11 @@ config LIS3L02DQ
 	  Say yes here to build SPI support for the ST microelectronics
 	  accelerometer. The driver supplies direct access via sysfs files
 	  and an event interface via a character device.
+
+config SCA3000
+       depends on IIO_RING_BUFFER
+       depends on SPI
+       tristate "VTI SCA3000 series accelerometers"
+       help
+         Say yes here to build support for the VTI SCA3000 series of SPI
+	 accelerometers. These devices use a hardware ring buffer.
\ No newline at end of file

drivers/staging/iio/accel/Makefile

@@ -5,3 +5,6 @@ obj-$(CONFIG_KXSD9)	+= kxsd9.o
 
 lis3l02dq-y		:= lis3l02dq_core.o
 obj-$(CONFIG_LIS3L02DQ)	+= lis3l02dq.o
+
+sca3000-y		:= sca3000_core.o sca3000_ring.o
+obj-$(CONFIG_SCA3000)	+= sca3000.o
\ No newline at end of file

drivers/staging/iio/accel/sca3000.h

+/*
+ * sca3000.c -- support VTI sca3000 series accelerometers
+ *              via SPI
+ *
+ * Copyright (c) 2007 Jonathan Cameron <jic23@cam.ac.uk>
+ *
+ * Partly based upon tle62x0.c
+ *
+ * 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.
+ *
+ * Initial mode is direct measurement.
+ *
+ * Untested things
+ *
+ * Temperature reading (the e05 I'm testing with doesn't have a sensor)
+ *
+ * Free fall detection mode - supported but untested as I'm not droping my
+ * dubious wire rig far enough to test it.
+ *
+ * Unsupported as yet
+ *
+ * Time stamping of data from ring. Various ideas on how to do this but none
+ * are remotely simple. Suggestions welcome.
+ *
+ * Individual enabling disabling of channels going into ring buffer
+ *
+ * Overflow handling (this is signaled for all but 8 bit ring buffer mode.)
+ *
+ * Motion detector using AND combinations of signals.
+ *
+ * Note: Be very careful about not touching an register bytes marked
+ * as reserved on the data sheet. They really mean it as changing convents of
+ * some will cause the device to lock up.
+ *
+ * Known issues - on rare occasions the interrupts lock up. Not sure why as yet.
+ * Can probably alleviate this by reading the interrupt register on start, but
+ * that is really just brushing the problem under the carpet.
+ */
+#define SCA3000_WRITE_REG(a) (((a) << 2) | 0x02)
+#define SCA3000_READ_REG(a) ((a) << 2)
+
+#define SCA3000_REG_ADDR_REVID			0x00
+#define SCA3000_REVID_MAJOR_MASK		0xf0
+#define SCA3000_REVID_MINOR_MASK		0x0f
+
+#define SCA3000_REG_ADDR_STATUS			0x02
+#define SCA3000_LOCKED				0x20
+#define SCA3000_EEPROM_CS_ERROR			0x02
+#define SCA3000_SPI_FRAME_ERROR			0x01
+
+/* All reads done using register decrement so no need to directly access LSBs */
+#define SCA3000_REG_ADDR_X_MSB			0x05
+#define SCA3000_REG_ADDR_Y_MSB			0x07
+#define SCA3000_REG_ADDR_Z_MSB			0x09
+
+#define SCA3000_REG_ADDR_RING_OUT		0x0f
+
+/* Temp read untested - the e05 doesn't have the sensor */
+#define SCA3000_REG_ADDR_TEMP_MSB		0x13
+
+#define SCA3000_REG_ADDR_MODE			0x14
+#define SCA3000_MODE_PROT_MASK			0x28
+
+#define SCA3000_RING_BUF_ENABLE			0x80
+#define SCA3000_RING_BUF_8BIT			0x40
+/* Free fall detection triggers an interrupt if the acceleration
+ * is below a threshold for equivalent of 25cm drop
+ */
+#define SCA3000_FREE_FALL_DETECT		0x10
+#define SCA3000_MEAS_MODE_NORMAL		0x00
+#define SCA3000_MEAS_MODE_OP_1			0x01
+#define SCA3000_MEAS_MODE_OP_2			0x02
+
+/* In motion detection mode the accelerations are band pass filtered
+ * (aprox 1 - 25Hz) and then a programmable theshold used to trigger
+ * and interrupt.
+ */
+#define SCA3000_MEAS_MODE_MOT_DET		0x03
+
+#define SCA3000_REG_ADDR_BUF_COUNT		0x15
+
+#define SCA3000_REG_ADDR_INT_STATUS		0x16
+
+#define SCA3000_INT_STATUS_THREE_QUARTERS	0x80
+#define SCA3000_INT_STATUS_HALF			0x40
+
+#define SCA3000_INT_STATUS_FREE_FALL		0x08
+#define SCA3000_INT_STATUS_Y_TRIGGER		0x04
+#define SCA3000_INT_STATUS_X_TRIGGER		0x02
+#define SCA3000_INT_STATUS_Z_TRIGGER		0x01
+
+/* Used to allow accesss to multiplexed registers */
+#define SCA3000_REG_ADDR_CTRL_SEL		0x18
+/* Only available for SCA3000-D03 and SCA3000-D01 */
+#define SCA3000_REG_CTRL_SEL_I2C_DISABLE	0x01
+#define SCA3000_REG_CTRL_SEL_MD_CTRL		0x02
+#define SCA3000_REG_CTRL_SEL_MD_Y_TH		0x03
+#define SCA3000_REG_CTRL_SEL_MD_X_TH		0x04
+#define SCA3000_REG_CTRL_SEL_MD_Z_TH		0x05
+/* BE VERY CAREFUL WITH THIS, IF 3 BITS ARE NOT SET the device
+   will not function */
+#define SCA3000_REG_CTRL_SEL_OUT_CTRL		0x0B
+#define SCA3000_OUT_CTRL_PROT_MASK		0xE0
+#define SCA3000_OUT_CTRL_BUF_X_EN		0x10
+#define SCA3000_OUT_CTRL_BUF_Y_EN		0x08
+#define SCA3000_OUT_CTRL_BUF_Z_EN		0x04
+#define SCA3000_OUT_CTRL_BUF_DIV_4		0x02
+#define SCA3000_OUT_CTRL_BUF_DIV_2		0x01
+
+/* Control which motion detector interrupts are on.
+ * For now only OR combinations are supported.x
+ */
+#define SCA3000_MD_CTRL_PROT_MASK		0xC0
+#define SCA3000_MD_CTRL_OR_Y			0x01
+#define SCA3000_MD_CTRL_OR_X			0x02
+#define SCA3000_MD_CTRL_OR_Z			0x04
+/* Currently unsupported */
+#define SCA3000_MD_CTRL_AND_Y			0x08
+#define SCA3000_MD_CTRL_AND_X			0x10
+#define SAC3000_MD_CTRL_AND_Z			0x20
+
+/* Some control registers of complex access methods requiring this register to
+ * be used to remove a lock.
+ */
+#define SCA3000_REG_ADDR_UNLOCK			0x1e
+
+#define SCA3000_REG_ADDR_INT_MASK		0x21
+#define SCA3000_INT_MASK_PROT_MASK		0x1C
+
+#define SCA3000_INT_MASK_RING_THREE_QUARTER	0x80
+#define SCA3000_INT_MASK_RING_HALF		0x40
+
+#define SCA3000_INT_MASK_ALL_INTS		0x02
+#define SCA3000_INT_MASK_ACTIVE_HIGH		0x01
+#define SCA3000_INT_MASK_ACTIVE_LOW		0x00
+
+/* Values of mulipexed registers (write to ctrl_data after select) */
+#define SCA3000_REG_ADDR_CTRL_DATA		0x22
+
+/* Measurment modes available on some sca3000 series chips. Code assumes others
+ * may become available in the future.
+ *
+ * Bypass - Bypass the low-pass filter in the signal channel so as to increase
+ *          signal bandwidth.
+ *
+ * Narrow - Narrow low-pass filtering of the signal channel and half output
+ *          data rate by decimation.
+ *
+ * Wide - Widen low-pass filtering of signal channel to increase bandwidth
+ */
+#define SCA3000_OP_MODE_BYPASS			0x01
+#define SCA3000_OP_MODE_NARROW			0x02
+#define SCA3000_OP_MODE_WIDE			0x04
+#define SCA3000_MAX_TX 6
+#define SCA3000_MAX_RX 2
+
+/**
+ * struct sca3000_state - device instance state information
+ * @us: 	 		the associated spi device
+ * @info: 	  		chip variant information
+ * @indio_dev: 	 		device information used by the IIO core
+ * @interrupt_handler_ws: 	event interrupt handler for all events
+ * @last_timestamp: 		the timestamp of the last event
+ * @mo_det_use_count: 		reference counter for the motion detection unit
+ * @lock: 		 	lock used to protect elements of sca3000_state
+ * 	 			and the underlying device state.
+ * @bpse: 		 	number of bits per scan element
+ * @tx: 		 	dma-able transmit buffer
+ * @rx: 		 	dma-able receive buffer
+ **/
+struct sca3000_state {
+	struct spi_device		*us;
+	const struct sca3000_chip_info	*info;
+	struct iio_dev			*indio_dev;
+	struct work_struct		interrupt_handler_ws;
+	s64				last_timestamp;
+	int				mo_det_use_count;
+	struct mutex			lock;
+	int				bpse;
+	u8				*tx;
+	/* not used during a ring buffer read */
+	u8				*rx;
+};
+
+/**
+ * struct sca3000_chip_info - model dependant parameters
+ * @name: 			model identification
+ * @temp_output:		some devices have temperature sensors.
+ * @measurement_mode_freq:	normal mode sampling frequency
+ * @option_mode_1:		first optional mode. Not all models have one
+ * @option_mode_1_freq:		option mode 1 sampling frequency
+ * @option_mode_2:		second optional mode. Not all chips have one
+ * @option_mode_2_freq:		option mode 2 sampling frequency
+ *
+ * This structure is used to hold information about the functionality of a given
+ * sca3000 variant.
+ **/
+struct sca3000_chip_info {
+	const char		*name;
+	bool			temp_output;
+	int			measurement_mode_freq;
+	int			option_mode_1;
+	int			option_mode_1_freq;
+	int			option_mode_2;
+	int			option_mode_2_freq;
+};
+
+/**
+ * sca3000_read_data() read a series of values from the device
+ * @dev:		device
+ * @reg_address_high:	start address (decremented read)
+ * @rx:			pointer where recieved data is placed. Callee
+ *			responsible for freeing this.
+ * @len:		number of bytes to read
+ *
+ * The main lock must be held.
+ **/
+int sca3000_read_data(struct sca3000_state *st,
+		      u8 reg_address_high,
+		      u8 **rx_p,
+		      int len);
+
+/**
+ * sca3000_write_reg() write a single register
+ * @address:	address of register on chip
+ * @val:	value to be written to register
+ *
+ * The main lock must be held.
+ **/
+int sca3000_write_reg(struct sca3000_state *st, u8 address, u8 val);
+
+/* Conversion function for use with the ring buffer when in 11bit mode */
+static inline int sca3000_11bit_convert(uint8_t msb, uint8_t lsb)
+{
+	int16_t val;
+
+	val = ((lsb >> 3) & 0x1C) | (msb << 5);
+	val |= (val & (1 << 12)) ? 0xE000 : 0;
+
+	return val;
+};
+
+static inline int sca3000_13bit_convert(uint8_t msb, uint8_t lsb)
+{
+	s16 val;
+
+	val = ((lsb >> 3) & 0x1F) | (msb << 5);
+	/* sign fill */
+	val |= (val & (1 << 12)) ? 0xE000 : 0;
+
+	return val;
+};
+
+
+#ifdef CONFIG_IIO_RING_BUFFER
+/**
+ * sca3000_register_ring_funcs() setup the ring state change functions
+ **/
+void sca3000_register_ring_funcs(struct iio_dev *indio_dev);
+
+/**
+ * sca3000_configure_ring() - allocate and configure ring buffer
+ * @indio_dev: iio-core device whose ring is to be configured
+ *
+ * The hardware ring buffer needs far fewer ring buffer functions than
+ * a software one as a lot of things are handled automatically.
+ * This function also tells the iio core that our device supports a
+ * hardware ring buffer mode.
+ **/
+int sca3000_configure_ring(struct iio_dev *indio_dev);
+
+/**
+ * sca3000_unconfigure_ring() - deallocate the ring buffer
+ * @indio_dev: iio-core device whose ring we are freeing
+ **/
+void sca3000_unconfigure_ring(struct iio_dev *indio_dev);
+
+/**
+ * sca3000_ring_int_process() handles ring related event pushing and escalation
+ * @val:	the event code
+ **/
+void sca3000_ring_int_process(u8 val, struct iio_ring_buffer *ring);
+
+#else
+static inline void sca3000_register_ring_funcs(struct iio_dev *indio_dev) {};
+
+static inline
+int sca3000_register_ring_access_and_init(struct iio_dev *indio_dev)
+{
+	return 0;
+};
+
+static inline void sca3000_ring_int_process(u8 val, void *ring) {};
+
+#endif
+

drivers/staging/iio/accel/sca3000_ring.c

+/*
+ * sca3000_ring.c -- support VTI sca3000 series accelerometers via SPI
+ *
+ * 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.
+ *
+ * Copyright (c) 2009 Jonathan Cameron <jic23@cam.ac.uk>
+ *
+ */
+
+#include <linux/interrupt.h>
+#include <linux/gpio.h>
+#include <linux/fs.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/spi/spi.h>
+#include <linux/sysfs.h>
+
+#include "../iio.h"
+#include "../sysfs.h"
+#include "../ring_generic.h"
+#include "../ring_hw.h"
+#include "accel.h"
+#include "sca3000.h"
+
+/* RFC / future work
+ *
+ * The internal ring buffer doesn't actually change what it holds depending
+ * on which signals are enabled etc, merely whether you can read them.
+ * As such the scan mode selection is somewhat different than for a software
+ * ring buffer and changing it actually covers any data already in the buffer.
+ * Currently scan elements aren't configured so it doesn't matter.
+ */
+
+/**
+ * sca3000_rip_hw_rb() - main ring access function, pulls data from ring
+ * @r:			the ring
+ * @count:		number of samples to try and pull
+ * @data:		output the actual samples pulled from the hw ring
+ * @dead_offset:	cheating a bit here: Set to 1 so as to allow for the
+ *			leading byte used in bus comms.
+ *
+ * Currently does not provide timestamps.  As the hardware doesn't add them they
+ * can only be inferred aproximately from ring buffer events such as 50% full
+ * and knowledge of when buffer was last emptied.  This is left to userspace.
+ **/
+static int sca3000_rip_hw_rb(struct iio_ring_buffer *r,
+			     size_t count, u8 **data, int *dead_offset)
+{
+	struct iio_hw_ring_buffer *hw_ring = iio_to_hw_ring_buf(r);
+	struct iio_dev *indio_dev = hw_ring->private;
+	struct sca3000_state *st = indio_dev->dev_data;
+	u8 *rx;
+	int ret, num_available, num_read = 0;
+	int bytes_per_sample = 1;
+
+	if (st->bpse == 11)
+		bytes_per_sample = 2;
+
+	mutex_lock(&st->lock);
+	/* Check how much data is available:
+	 * RFC: Implement an ioctl to not bother checking whether there
+	 * is enough data in the ring?  Afterall, if we are responding
+	 * to an interrupt we have a minimum content guaranteed so it
+	 * seems slight silly to waste time checking it is there.
+	 */
+	ret = sca3000_read_data(st,
+				SCA3000_REG_ADDR_BUF_COUNT,
+				&rx, 1);
+	if (ret)
+		goto error_ret;
+	else
+		num_available = rx[1];
+	/* num_available is the total number of samples available
+	 * i.e. number of time points * number of channels.
+	 */
+	kfree(rx);
+	if (count > num_available * bytes_per_sample)
+		num_read = num_available*bytes_per_sample;
+	else
+		num_read = count - (count % (bytes_per_sample));
+
+	/* Avoid the read request byte */
+	*dead_offset = 1;
+	ret = sca3000_read_data(st,
+				SCA3000_REG_ADDR_RING_OUT,
+				data, num_read);
+error_ret:
+	mutex_unlock(&st->lock);
+
+	return ret ? ret : num_read;
+}
+
+/* This is only valid with all 3 elements enabled */
+static int sca3000_ring_get_length(struct iio_ring_buffer *r)
+{
+	return 64;
+}
+
+/* only valid if resolution is kept at 11bits */
+static int sca3000_ring_get_bpd(struct iio_ring_buffer *r)
+{
+	return 6;
+}
+static void sca3000_ring_release(struct device *dev)
+{
+	struct iio_ring_buffer *r = to_iio_ring_buffer(dev);
+	kfree(iio_to_hw_ring_buf(r));
+}
+
+static IIO_RING_ENABLE_ATTR;
+static IIO_RING_BPS_ATTR;
+static IIO_RING_LENGTH_ATTR;
+
+/**
+ * sca3000_show_ring_bpse() -sysfs function to query bits per sample from ring
+ * @dev: ring buffer device
+ * @attr: this device attribute
+ * @buf: buffer to write to
+ **/
+static ssize_t sca3000_show_ring_bpse(struct device *dev,
+				      struct device_attribute *attr,
+				      char *buf)
+{
+	int len = 0, ret;
+	u8 *rx;
+	struct iio_ring_buffer *r = dev_get_drvdata(dev);
+	struct sca3000_state *st = r->indio_dev->dev_data;
+
+	mutex_lock(&st->lock);
+	ret = sca3000_read_data(st, SCA3000_REG_ADDR_MODE, &rx, 1);
+	if (ret)
+		goto error_ret;
+	len = sprintf(buf, "%d\n", (rx[1] & SCA3000_RING_BUF_8BIT) ? 8 : 11);
+	kfree(rx);
+error_ret:
+	mutex_unlock(&st->lock);
+
+	return ret ? ret : len;
+}
+
+/**
+ * sca3000_store_ring_bpse() - bits per scan element
+ * @dev: ring buffer device
+ * @attr: attribute called from
+ * @buf: input from userspace
+ * @len: length of input
+ **/
+static ssize_t sca3000_store_ring_bpse(struct device *dev,
+				      struct device_attribute *attr,
+				      const char *buf,
+				      size_t len)
+{
+	struct iio_ring_buffer *r = dev_get_drvdata(dev);
+	struct sca3000_state *st = r->indio_dev->dev_data;
+	int ret;
+	u8 *rx;
+	long val;
+	ret = strict_strtol(buf, 10, &val);
+	if (ret)
+		return ret;
+
+	mutex_lock(&st->lock);
+
+	ret = sca3000_read_data(st, SCA3000_REG_ADDR_MODE, &rx, 1);
+	if (!ret)
+		switch (val) {
+		case 8:
+			ret = sca3000_write_reg(st, SCA3000_REG_ADDR_MODE,
+						rx[1] | SCA3000_RING_BUF_8BIT);
+			st->bpse = 8;
+			break;
+		case 11:
+			ret = sca3000_write_reg(st, SCA3000_REG_ADDR_MODE,
+						rx[1] & ~SCA3000_RING_BUF_8BIT);
+			st->bpse = 11;
+			break;
+		default:
+			ret = -EINVAL;
+			break;
+		}
+	mutex_unlock(&st->lock);
+
+	return ret ? ret : len;
+}
+
+static IIO_CONST_ATTR(bpse_available, "8 11");
+
+static IIO_DEV_ATTR_BPSE(S_IRUGO | S_IWUSR,
+			      sca3000_show_ring_bpse,
+			      sca3000_store_ring_bpse);
+
+/*
+ * Ring buffer attributes
+ * This device is a bit unusual in that the sampling frequency and bpse
+ * only apply to the ring buffer.  At all times full rate and accuracy
+ * is available via direct reading from registers.
+ */
+static struct attribute *iio_ring_attributes[] = {
+	&dev_attr_length.attr,
+	&dev_attr_bps.attr,
+	&dev_attr_ring_enable.attr,
+	&iio_dev_attr_bpse.dev_attr.attr,
+	&iio_const_attr_bpse_available.dev_attr.attr,
+	NULL,
+};
+
+static struct attribute_group sca3000_ring_attr = {
+	.attrs = iio_ring_attributes,
+};
+
+static struct attribute_group *sca3000_ring_attr_groups[] = {
+	&sca3000_ring_attr,
+	NULL
+};
+
+static struct device_type sca3000_ring_type = {
+	.release = sca3000_ring_release,
+	.groups = sca3000_ring_attr_groups,
+};
+
+static struct iio_ring_buffer *sca3000_rb_allocate(struct iio_dev *indio_dev)
+{
+	struct iio_ring_buffer *buf;
+	struct iio_hw_ring_buffer *ring;
+
+	ring = kzalloc(sizeof *ring, GFP_KERNEL);
+	if (!ring)
+		return 0;
+	ring->private = indio_dev;
+	buf = &ring->buf;
+	iio_ring_buffer_init(buf, indio_dev);
+	buf->dev.type = &sca3000_ring_type;
+	device_initialize(&buf->dev);
+	buf->dev.parent = &indio_dev->dev;
+	dev_set_drvdata(&buf->dev, (void *)buf);
+
+	return buf;
+}
+
+static inline void sca3000_rb_free(struct iio_ring_buffer *r)
+{
+	if (r)
+		iio_put_ring_buffer(r);
+}
+
+int sca3000_configure_ring(struct iio_dev *indio_dev)
+{
+	indio_dev->ring = sca3000_rb_allocate(indio_dev);
+	if (indio_dev->ring == NULL)
+		return -ENOMEM;
+	indio_dev->modes |= INDIO_RING_HARDWARE_BUFFER;
+
+	indio_dev->ring->access.rip_lots = &sca3000_rip_hw_rb;
+	indio_dev->ring->access.get_length = &sca3000_ring_get_length;
+	indio_dev->ring->access.get_bpd = &sca3000_ring_get_bpd;
+
+	return 0;
+}
+
+void sca3000_unconfigure_ring(struct iio_dev *indio_dev)
+{
+	sca3000_rb_free(indio_dev->ring);
+}
+
+static inline
+int __sca3000_hw_ring_state_set(struct iio_dev *indio_dev, bool state)
+{
+	struct sca3000_state *st = indio_dev->dev_data;
+	int ret;
+	u8 *rx;
+
+	mutex_lock(&st->lock);
+	ret = sca3000_read_data(st, SCA3000_REG_ADDR_MODE, &rx, 1);
+	if (ret)
+		goto error_ret;
+	if (state) {
+		printk(KERN_INFO "supposedly enabling ring buffer\n");
+		ret = sca3000_write_reg(st,
+					SCA3000_REG_ADDR_MODE,
+					(rx[1] | SCA3000_RING_BUF_ENABLE));
+	} else
+		ret = sca3000_write_reg(st,
+					SCA3000_REG_ADDR_MODE,
+					(rx[1] & ~SCA3000_RING_BUF_ENABLE));
+	kfree(rx);
+error_ret:
+	mutex_unlock(&st->lock);
+
+	return ret;
+}
+/**
+ * sca3000_hw_ring_preenable() hw ring buffer preenable function
+ *
+ * Very simple enable function as the chip will allows normal reads
+ * during ring buffer operation so as long as it is indeed running
+ * before we notify the core, the precise ordering does not matter.
+ **/
+static int sca3000_hw_ring_preenable(struct iio_dev *indio_dev)
+{
+	return __sca3000_hw_ring_state_set(indio_dev, 1);
+}
+
+static int sca3000_hw_ring_postdisable(struct iio_dev *indio_dev)
+{
+	return __sca3000_hw_ring_state_set(indio_dev, 0);
+}
+
+void sca3000_register_ring_funcs(struct iio_dev *indio_dev)
+{
+	indio_dev->ring->preenable = &sca3000_hw_ring_preenable;
+	indio_dev->ring->postdisable = &sca3000_hw_ring_postdisable;
+}
+
+/**
+ * sca3000_ring_int_process() ring specific interrupt handling.
+ *
+ * This is only split from the main interrupt handler so as to
+ * reduce the amount of code if the ring buffer is not enabled.
+ **/
+void sca3000_ring_int_process(u8 val, struct iio_ring_buffer *ring)
+{
+	if (val & SCA3000_INT_STATUS_THREE_QUARTERS)
+		iio_push_or_escallate_ring_event(ring,
+						 IIO_EVENT_CODE_RING_75_FULL,
+						 0);
+	else if (val & SCA3000_INT_STATUS_HALF)
+		iio_push_ring_event(ring,
+				    IIO_EVENT_CODE_RING_50_FULL, 0);
+}

drivers/staging/iio/ring_hw.h

+/*
+ * ring_hw.h - common functionality for iio hardware ring buffers
+ *
+ * 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.
+ *
+ * Copyright (c) 2009 Jonathan Cameron <jic23@cam.ac.uk>
+ *
+ */
+
+/**
+ * struct iio_hw_ring_buffer- hardware ring buffer
+ * @buf:	generic ring buffer elements
+ * @private:	device specific data
+ */
+struct iio_hw_ring_buffer {
+	struct iio_ring_buffer buf;
+	void *private;
+};
+
+#define iio_to_hw_ring_buf(r) container_of(r, struct iio_hw_ring_buffer, buf)