Staging: IIO: lis3l02dq ring buffer and data ready trigger support

Example of relatively common case of device sampling
based on internal clock and providing a data ready
signal to indicate that new data is available to be
read out.

Generic trigger approach used to allow other devices
to be sampled 'at the same time' as this the accelerometer.
This is very useful in various motion estimation algorithms.
Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/accel/Makefile

@@ -4,6 +4,7 @@
 obj-$(CONFIG_KXSD9)	+= kxsd9.o
 
 lis3l02dq-y		:= lis3l02dq_core.o
+lis3l02dq-$(CONFIG_IIO_RING_BUFFER) += lis3l02dq_ring.o
 obj-$(CONFIG_LIS3L02DQ)	+= lis3l02dq.o
 
 sca3000-y		:= sca3000_core.o sca3000_ring.o

drivers/staging/iio/accel/lis3l02dq.h

@@ -183,6 +183,26 @@ int lis3l02dq_spi_write_reg_8(struct device *dev,
 #define LIS3L02DQ_SCAN_ACC_Y 1
 #define LIS3L02DQ_SCAN_ACC_Z 2
 
+
+#ifdef CONFIG_IIO_RING_BUFFER
+/* At the moment triggers are only used for ring buffer
+ * filling. This may change!
+ */
+void lis3l02dq_remove_trigger(struct iio_dev *indio_dev);
+int lis3l02dq_probe_trigger(struct iio_dev *indio_dev);
+
+ssize_t lis3l02dq_read_accel_from_ring(struct device *dev,
+				       struct device_attribute *attr,
+				       char *buf);
+
+
+int lis3l02dq_configure_ring(struct iio_dev *indio_dev);
+void lis3l02dq_unconfigure_ring(struct iio_dev *indio_dev);
+
+int lis3l02dq_initialize_ring(struct iio_ring_buffer *ring);
+void lis3l02dq_uninitialize_ring(struct iio_ring_buffer *ring);
+#else /* CONFIG_IIO_RING_BUFFER */
+
 static inline void lis3l02dq_remove_trigger(struct iio_dev *indio_dev) {};
 static inline int lis3l02dq_probe_trigger(struct iio_dev *indio_dev)
 {
@@ -208,5 +228,5 @@ static inline int lis3l02dq_initialize_ring(struct iio_ring_buffer *ring)
 	return 0;
 };
 static inline void lis3l02dq_uninitialize_ring(struct iio_ring_buffer *ring) {};
-
+#endif /* CONFIG_IIO_RING_BUFFER */
 #endif /* SPI_LIS3L02DQ_H_ */

drivers/staging/iio/accel/lis3l02dq_ring.c

+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/gpio.h>
+#include <linux/workqueue.h>
+#include <linux/mutex.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/spi/spi.h>
+#include <linux/sysfs.h>
+#include <linux/list.h>
+
+#include "../iio.h"
+#include "../sysfs.h"
+#include "../ring_sw.h"
+#include "accel.h"
+#include "../trigger.h"
+#include "lis3l02dq.h"
+
+/**
+ * combine_8_to_16() utility function to munge to u8s into u16
+ **/
+static inline u16 combine_8_to_16(u8 lower, u8 upper)
+{
+	u16 _lower = lower;
+	u16 _upper = upper;
+	return _lower | (_upper << 8);
+}
+
+/**
+ * lis3l02dq_scan_el_set_state() set whether a scan contains a given channel
+ * @scan_el:	associtate iio scan element attribute
+ * @indio_dev:	the device structure
+ * @bool:	desired state
+ *
+ * mlock already held when this is called.
+ **/
+static int lis3l02dq_scan_el_set_state(struct iio_scan_el *scan_el,
+				       struct iio_dev *indio_dev,
+				       bool state)
+{
+	u8 t, mask;
+	int ret;
+
+	ret = lis3l02dq_spi_read_reg_8(&indio_dev->dev,
+				       LIS3L02DQ_REG_CTRL_1_ADDR,
+				       &t);
+	if (ret)
+		goto error_ret;
+	switch (scan_el->label) {
+	case LIS3L02DQ_REG_OUT_X_L_ADDR:
+		mask = LIS3L02DQ_REG_CTRL_1_AXES_X_ENABLE;
+		break;
+	case LIS3L02DQ_REG_OUT_Y_L_ADDR:
+		mask = LIS3L02DQ_REG_CTRL_1_AXES_Y_ENABLE;
+		break;
+	case LIS3L02DQ_REG_OUT_Z_L_ADDR:
+		mask = LIS3L02DQ_REG_CTRL_1_AXES_Z_ENABLE;
+		break;
+	default:
+		ret = -EINVAL;
+		goto error_ret;
+	}
+
+	if (!(mask & t) == state) {
+		if (state)
+			t |= mask;
+		else
+			t &= ~mask;
+		ret = lis3l02dq_spi_write_reg_8(&indio_dev->dev,
+						LIS3L02DQ_REG_CTRL_1_ADDR,
+						&t);
+	}
+error_ret:
+	return ret;
+
+}
+static IIO_SCAN_EL_C(accel_x, LIS3L02DQ_SCAN_ACC_X, IIO_SIGNED(16),
+		     LIS3L02DQ_REG_OUT_X_L_ADDR,
+		     &lis3l02dq_scan_el_set_state);
+static IIO_SCAN_EL_C(accel_y, LIS3L02DQ_SCAN_ACC_Y, IIO_SIGNED(16),
+		     LIS3L02DQ_REG_OUT_Y_L_ADDR,
+		     &lis3l02dq_scan_el_set_state);
+static IIO_SCAN_EL_C(accel_z, LIS3L02DQ_SCAN_ACC_Z, IIO_SIGNED(16),
+		     LIS3L02DQ_REG_OUT_Z_L_ADDR,
+		     &lis3l02dq_scan_el_set_state);
+static IIO_SCAN_EL_TIMESTAMP;
+
+static struct attribute *lis3l02dq_scan_el_attrs[] = {
+	&iio_scan_el_accel_x.dev_attr.attr,
+	&iio_scan_el_accel_y.dev_attr.attr,
+	&iio_scan_el_accel_z.dev_attr.attr,
+	&iio_scan_el_timestamp.dev_attr.attr,
+	NULL,
+};
+
+static struct attribute_group lis3l02dq_scan_el_group = {
+	.attrs = lis3l02dq_scan_el_attrs,
+	.name = "scan_elements",
+};
+
+/**
+ * lis3l02dq_poll_func_th() top half interrupt handler called by trigger
+ * @private_data:	iio_dev
+ **/
+static void lis3l02dq_poll_func_th(struct iio_dev *indio_dev)
+{
+  struct lis3l02dq_state *st = iio_dev_get_devdata(indio_dev);
+	st->last_timestamp = indio_dev->trig->timestamp;
+	schedule_work(&st->work_trigger_to_ring);
+	/* Indicate that this interrupt is being handled */
+
+	/* Technically this is trigger related, but without this
+	 * handler running there is currently now way for the interrupt
+	 * to clear.
+	 */
+	st->inter = 1;
+}
+
+/**
+ * lis3l02dq_data_rdy_trig_poll() the event handler for the data rdy trig
+ **/
+static int lis3l02dq_data_rdy_trig_poll(struct iio_dev *dev_info,
+				       int index,
+				       s64 timestamp,
+				       int no_test)
+{
+	struct lis3l02dq_state *st = iio_dev_get_devdata(dev_info);
+	struct iio_trigger *trig = st->trig;
+
+	trig->timestamp = timestamp;
+	iio_trigger_poll(trig);
+
+	return IRQ_HANDLED;
+}
+
+/* This is an event as it is a response to a physical interrupt */
+IIO_EVENT_SH(data_rdy_trig, &lis3l02dq_data_rdy_trig_poll);
+
+/**
+ * lis3l02dq_read_accel_from_ring() individual acceleration read from ring
+ **/
+ssize_t lis3l02dq_read_accel_from_ring(struct device *dev,
+				       struct device_attribute *attr,
+				       char *buf)
+{
+	struct iio_scan_el *el = NULL;
+	int ret, len = 0, i = 0;
+	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
+	struct iio_dev *dev_info = dev_get_drvdata(dev);
+	s16 *data;
+
+	while (dev_info->scan_el_attrs->attrs[i]) {
+		el = to_iio_scan_el((struct device_attribute *)
+				    (dev_info->scan_el_attrs->attrs[i]));
+		/* label is in fact the address */
+		if (el->label == this_attr->address)
+			break;
+		i++;
+	}
+	if (!dev_info->scan_el_attrs->attrs[i]) {
+		ret = -EINVAL;
+		goto error_ret;
+	}
+	/* If this element is in the scan mask */
+	ret = iio_scan_mask_query(dev_info, el->number);
+	if (ret < 0)
+		goto error_ret;
+	if (ret) {
+		data = kmalloc(dev_info->ring->access.get_bpd(dev_info->ring),
+			       GFP_KERNEL);
+		if (data == NULL)
+			return -ENOMEM;
+		ret = dev_info->ring->access.read_last(dev_info->ring,
+						      (u8 *)data);
+		if (ret)
+			goto error_free_data;
+	} else {
+		ret = -EINVAL;
+		goto error_ret;
+	}
+	len = iio_scan_mask_count_to_right(dev_info, el->number);
+	if (len < 0) {
+		ret = len;
+		goto error_free_data;
+	}
+	len = sprintf(buf, "ring %d\n", data[len]);
+error_free_data:
+	kfree(data);
+error_ret:
+	return ret ? ret : len;
+
+}
+
+static const u8 read_all_tx_array[] =
+{
+	LIS3L02DQ_READ_REG(LIS3L02DQ_REG_OUT_X_L_ADDR), 0,
+	LIS3L02DQ_READ_REG(LIS3L02DQ_REG_OUT_X_H_ADDR), 0,
+	LIS3L02DQ_READ_REG(LIS3L02DQ_REG_OUT_Y_L_ADDR), 0,
+	LIS3L02DQ_READ_REG(LIS3L02DQ_REG_OUT_Y_H_ADDR), 0,
+	LIS3L02DQ_READ_REG(LIS3L02DQ_REG_OUT_Z_L_ADDR), 0,
+	LIS3L02DQ_READ_REG(LIS3L02DQ_REG_OUT_Z_H_ADDR), 0,
+};
+
+/**
+ * lis3l02dq_read_all() Reads all channels currently selected
+ * @st:		device specific state
+ * @rx_array:	(dma capable) recieve array, must be at least
+ *		4*number of channels
+ **/
+int lis3l02dq_read_all(struct lis3l02dq_state *st, u8 *rx_array)
+{
+	struct spi_transfer *xfers;
+	struct spi_message msg;
+	int ret, i, j = 0;
+
+	xfers = kzalloc((st->indio_dev->scan_count) * 2
+			* sizeof(*xfers), GFP_KERNEL);
+	if (!xfers)
+		return -ENOMEM;
+
+	mutex_lock(&st->buf_lock);
+
+	for (i = 0; i < ARRAY_SIZE(read_all_tx_array)/4; i++) {
+		if (st->indio_dev->scan_mask & (1 << i)) {
+			/* lower byte */
+			xfers[j].tx_buf = st->tx + 2*j;
+			st->tx[2*j] = read_all_tx_array[i*4];
+			st->tx[2*j + 1] = 0;
+			if (rx_array)
+				xfers[j].rx_buf = rx_array + j*2;
+			xfers[j].bits_per_word = 8;
+			xfers[j].len = 2;
+			xfers[j].cs_change = 1;
+			j++;
+
+			/* upper byte */
+			xfers[j].tx_buf = st->tx + 2*j;
+			st->tx[2*j] = read_all_tx_array[i*4 + 2];
+			st->tx[2*j + 1] = 0;
+			if (rx_array)
+				xfers[j].rx_buf = rx_array + j*2;
+			xfers[j].bits_per_word = 8;
+			xfers[j].len = 2;
+			xfers[j].cs_change = 1;
+			j++;
+		}
+	}
+	/* After these are transmitted, the rx_buff should have
+	 * values in alternate bytes
+	 */
+	spi_message_init(&msg);
+	for (j = 0; j < st->indio_dev->scan_count * 2; j++)
+		spi_message_add_tail(&xfers[j], &msg);
+
+	ret = spi_sync(st->us, &msg);
+	mutex_unlock(&st->buf_lock);
+	kfree(xfers);
+
+	return ret;
+}
+
+
+/* Whilst this makes a lot of calls to iio_sw_ring functions - it is to device
+ * specific to be rolled into the core.
+ */
+static void lis3l02dq_trigger_bh_to_ring(struct work_struct *work_s)
+{
+	struct lis3l02dq_state *st
+		= container_of(work_s, struct lis3l02dq_state,
+			       work_trigger_to_ring);
+
+	u8 *rx_array;
+	int i = 0;
+	u16 *data;
+	size_t datasize = st->indio_dev
+		->ring->access.get_bpd(st->indio_dev->ring);
+
+	data = kmalloc(datasize , GFP_KERNEL);
+	if (data == NULL) {
+		dev_err(&st->us->dev, "memory alloc failed in ring bh");
+		return;
+	}
+	/* Due to interleaved nature of transmission this buffer must be
+	 * twice the number of bytes, or 4 times the number of channels
+	 */
+	rx_array = kmalloc(4 * (st->indio_dev->scan_count), GFP_KERNEL);
+	if (rx_array == NULL) {
+		dev_err(&st->us->dev, "memory alloc failed in ring bh");
+		return;
+	}
+
+	/* whilst trigger specific, if this read does nto occur the data
+	   ready interrupt will not be cleared.  Need to add a mechanism
+	   to provide a dummy read function if this is not triggering on
+	   the data ready function but something else is.
+	*/
+	st->inter = 0;
+
+	if (st->indio_dev->scan_count)
+		if (lis3l02dq_read_all(st, rx_array) >= 0)
+			for (; i < st->indio_dev->scan_count; i++)
+				data[i] = combine_8_to_16(rx_array[i*4+1],
+							  rx_array[i*4+3]);
+	/* Guaranteed to be aligned with 8 byte boundary */
+	if (st->indio_dev->scan_timestamp)
+		*((s64 *)(data + ((i + 3)/4)*4)) = st->last_timestamp;
+
+	st->indio_dev->ring->access.store_to(st->indio_dev->ring,
+					    (u8 *)data,
+					    st->last_timestamp);
+
+	iio_trigger_notify_done(st->indio_dev->trig);
+	kfree(rx_array);
+	kfree(data);
+
+	return;
+}
+/* in these circumstances is it better to go with unaligned packing and
+ * deal with the cost?*/
+static int lis3l02dq_data_rdy_ring_preenable(struct iio_dev *indio_dev)
+{
+	size_t size;
+	/* Check if there are any scan elements enabled, if not fail*/
+	if (!(indio_dev->scan_count || indio_dev->scan_timestamp))
+		return -EINVAL;
+
+	if (indio_dev->ring->access.set_bpd) {
+		if (indio_dev->scan_timestamp)
+			if (indio_dev->scan_count) /* Timestamp and data */
+				size = 2*sizeof(s64);
+			else /* Timestamp only  */
+				size = sizeof(s64);
+		else /* Data only */
+			size = indio_dev->scan_count*sizeof(s16);
+		indio_dev->ring->access.set_bpd(indio_dev->ring, size);
+	}
+
+	return 0;
+}
+
+static int lis3l02dq_data_rdy_ring_postenable(struct iio_dev *indio_dev)
+{
+	return indio_dev->trig
+		? iio_trigger_attach_poll_func(indio_dev->trig,
+					       indio_dev->pollfunc)
+		: 0;
+}
+
+static int lis3l02dq_data_rdy_ring_predisable(struct iio_dev *indio_dev)
+{
+	return indio_dev->trig
+		? iio_trigger_dettach_poll_func(indio_dev->trig,
+						indio_dev->pollfunc)
+		: 0;
+}
+
+
+/* Caller responsible for locking as necessary. */
+static int __lis3l02dq_write_data_ready_config(struct device *dev,
+					       struct
+					       iio_event_handler_list *list,
+					       bool state)
+{
+	int ret;
+	u8 valold;
+	bool currentlyset;
+	struct iio_dev *indio_dev = dev_get_drvdata(dev);
+
+/* Get the current event mask register */
+	ret = lis3l02dq_spi_read_reg_8(dev,
+				       LIS3L02DQ_REG_CTRL_2_ADDR,
+				       &valold);
+	if (ret)
+		goto error_ret;
+/* Find out if data ready is already on */
+	currentlyset
+		= valold & LIS3L02DQ_REG_CTRL_2_ENABLE_DATA_READY_GENERATION;
+
+/* Disable requested */
+	if (!state && currentlyset) {
+
+		valold &= ~LIS3L02DQ_REG_CTRL_2_ENABLE_DATA_READY_GENERATION;
+		/* The double write is to overcome a hardware bug?*/
+		ret = lis3l02dq_spi_write_reg_8(dev,
+						LIS3L02DQ_REG_CTRL_2_ADDR,
+						&valold);
+		if (ret)
+			goto error_ret;
+		ret = lis3l02dq_spi_write_reg_8(dev,
+						LIS3L02DQ_REG_CTRL_2_ADDR,
+						&valold);
+		if (ret)
+			goto error_ret;
+
+		iio_remove_event_from_list(list,
+					   &indio_dev->interrupts[0]
+					   ->ev_list);
+
+/* Enable requested */
+	} else if (state && !currentlyset) {
+		/* if not set, enable requested */
+		valold |= LIS3L02DQ_REG_CTRL_2_ENABLE_DATA_READY_GENERATION;
+		iio_add_event_to_list(list, &indio_dev->interrupts[0]->ev_list);
+		ret = lis3l02dq_spi_write_reg_8(dev,
+						LIS3L02DQ_REG_CTRL_2_ADDR,
+						&valold);
+		if (ret)
+			goto error_ret;
+	}
+
+	return 0;
+error_ret:
+	return ret;
+}
+
+/**
+ * lis3l02dq_data_rdy_trigger_set_state() set datardy interrupt state
+ *
+ * If disabling the interrupt also does a final read to ensure it is clear.
+ * This is only important in some cases where the scan enable elements are
+ * switched before the ring is reenabled.
+ **/
+static int lis3l02dq_data_rdy_trigger_set_state(struct iio_trigger *trig,
+						bool state)
+{
+	struct lis3l02dq_state *st = trig->private_data;
+	int ret = 0;
+	u8 t;
+	__lis3l02dq_write_data_ready_config(&st->indio_dev->dev,
+					    &iio_event_data_rdy_trig,
+					    state);
+	if (state == false) {
+		/* possible quirk with handler currently worked around
+		   by ensuring the work queue is empty */
+		flush_scheduled_work();
+		/* Clear any outstanding ready events */
+		ret = lis3l02dq_read_all(st, NULL);
+	}
+	lis3l02dq_spi_read_reg_8(&st->indio_dev->dev,
+				 LIS3L02DQ_REG_WAKE_UP_SRC_ADDR,
+				 &t);
+	return ret;
+}
+DEVICE_ATTR(name, S_IRUGO, iio_trigger_read_name, NULL);
+
+static struct attribute *lis3l02dq_trigger_attrs[] = {
+	&dev_attr_name.attr,
+	NULL,
+};
+
+static const struct attribute_group lis3l02dq_trigger_attr_group = {
+	.attrs = lis3l02dq_trigger_attrs,
+};
+
+/**
+ * lis3l02dq_trig_try_reen() try renabling irq for data rdy trigger
+ * @trig:	the datardy trigger
+ *
+ * As the trigger may occur on any data element being updated it is
+ * really rather likely to occur during the read from the previous
+ * trigger event.  The only way to discover if this has occured on
+ * boards not supporting level interrupts is to take a look at the line.
+ * If it is indicating another interrupt and we don't seem to have a
+ * handler looking at it, then we need to notify the core that we need
+ * to tell the triggering core to try reading all these again.
+ **/
+static int lis3l02dq_trig_try_reen(struct iio_trigger *trig)
+{
+	struct lis3l02dq_state *st = trig->private_data;
+	enable_irq(st->us->irq);
+	/* If gpio still high (or high again) */
+	if (gpio_get_value(irq_to_gpio(st->us->irq)))
+		if (st->inter == 0) {
+			/* already interrupt handler dealing with it */
+			disable_irq_nosync(st->us->irq);
+			if (st->inter == 1) {
+				/* interrupt handler snuck in between test
+				 * and disable */
+				enable_irq(st->us->irq);
+				return 0;
+			}
+			return -EAGAIN;
+		}
+	/* irq reenabled so success! */
+	return 0;
+}
+
+int lis3l02dq_probe_trigger(struct iio_dev *indio_dev)
+{
+	int ret;
+	struct lis3l02dq_state *state = indio_dev->dev_data;
+
+	state->trig = iio_allocate_trigger();
+	state->trig->name = kmalloc(IIO_TRIGGER_NAME_LENGTH, GFP_KERNEL);
+	if (!state->trig->name) {
+		ret = -ENOMEM;
+		goto error_free_trig;
+	}
+	snprintf((char *)state->trig->name,
+		 IIO_TRIGGER_NAME_LENGTH,
+		 "lis3l02dq-dev%d", indio_dev->id);
+	state->trig->dev.parent = &state->us->dev;
+	state->trig->owner = THIS_MODULE;
+	state->trig->private_data = state;
+	state->trig->set_trigger_state = &lis3l02dq_data_rdy_trigger_set_state;
+	state->trig->try_reenable = &lis3l02dq_trig_try_reen;
+	state->trig->control_attrs = &lis3l02dq_trigger_attr_group;
+	ret = iio_trigger_register(state->trig);
+	if (ret)
+		goto error_free_trig_name;
+
+	return 0;
+
+error_free_trig_name:
+	kfree(state->trig->name);
+error_free_trig:
+	iio_free_trigger(state->trig);
+
+	return ret;
+}
+
+void lis3l02dq_remove_trigger(struct iio_dev *indio_dev)
+{
+	struct lis3l02dq_state *state = indio_dev->dev_data;
+
+	iio_trigger_unregister(state->trig);
+	kfree(state->trig->name);
+	iio_free_trigger(state->trig);
+}
+
+void lis3l02dq_unconfigure_ring(struct iio_dev *indio_dev)
+{
+	kfree(indio_dev->pollfunc);
+	iio_sw_rb_free(indio_dev->ring);
+}
+
+int lis3l02dq_configure_ring(struct iio_dev *indio_dev)
+{
+	int ret = 0;
+	struct lis3l02dq_state *st = indio_dev->dev_data;
+	struct iio_ring_buffer *ring;
+	INIT_WORK(&st->work_trigger_to_ring, lis3l02dq_trigger_bh_to_ring);
+	/* Set default scan mode */
+
+	iio_scan_mask_set(indio_dev, iio_scan_el_accel_x.number);
+	iio_scan_mask_set(indio_dev, iio_scan_el_accel_y.number);
+	iio_scan_mask_set(indio_dev, iio_scan_el_accel_z.number);
+	indio_dev->scan_timestamp = true;
+
+	indio_dev->scan_el_attrs = &lis3l02dq_scan_el_group;
+
+	ring = iio_sw_rb_allocate(indio_dev);
+	if (!ring) {
+		ret = -ENOMEM;
+		return ret;
+	}
+	indio_dev->ring = ring;
+	/* Effectively select the ring buffer implementation */
+	iio_ring_sw_register_funcs(&ring->access);
+	ring->preenable = &lis3l02dq_data_rdy_ring_preenable;
+	ring->postenable = &lis3l02dq_data_rdy_ring_postenable;
+	ring->predisable = &lis3l02dq_data_rdy_ring_predisable;
+	ring->owner = THIS_MODULE;
+
+	indio_dev->pollfunc = kzalloc(sizeof(*indio_dev->pollfunc), GFP_KERNEL);
+	if (indio_dev->pollfunc == NULL) {
+		ret = -ENOMEM;
+		goto error_iio_sw_rb_free;;
+	}
+	indio_dev->pollfunc->poll_func_main = &lis3l02dq_poll_func_th;
+	indio_dev->pollfunc->private_data = indio_dev;
+	indio_dev->modes |= INDIO_RING_TRIGGERED;
+	return 0;
+
+error_iio_sw_rb_free:
+	iio_sw_rb_free(indio_dev->ring);
+	return ret;
+}
+
+int lis3l02dq_initialize_ring(struct iio_ring_buffer *ring)
+{
+	return iio_ring_buffer_register(ring);
+}
+
+void lis3l02dq_uninitialize_ring(struct iio_ring_buffer *ring)
+{
+	iio_ring_buffer_unregister(ring);
+}
+
+
+int lis3l02dq_set_ring_length(struct iio_dev *indio_dev, int length)
+{
+	/* Set sensible defaults for the ring buffer */
+	if (indio_dev->ring->access.set_length)
+		return indio_dev->ring->access.set_length(indio_dev->ring, 500);
+	return 0;
+}
+
+