Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1999 insertions, 0 deletions

diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
new file mode 100644
index 000000000..7e7ee307a
--- /dev/null
+++ b/drivers/iio/industrialio-buffer.c
@@ -0,0 +1,1999 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* The industrial I/O core
+ *
+ * Copyright (c) 2008 Jonathan Cameron
+ *
+ * Handling of buffer allocation / resizing.
+ *
+ * Things to look at here.
+ * - Better memory allocation techniques?
+ * - Alternative access techniques?
+ */
+#include <linux/anon_inodes.h>
+#include <linux/kernel.h>
+#include <linux/export.h>
+#include <linux/device.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/cdev.h>
+#include <linux/slab.h>
+#include <linux/poll.h>
+#include <linux/sched/signal.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/iio-opaque.h>
+#include "iio_core.h"
+#include "iio_core_trigger.h"
+#include <linux/iio/sysfs.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/buffer_impl.h>
+
+static const char * const iio_endian_prefix[] = {
+	[IIO_BE] = "be",
+	[IIO_LE] = "le",
+};
+
+static bool iio_buffer_is_active(struct iio_buffer *buf)
+{
+	return !list_empty(&buf->buffer_list);
+}
+
+static size_t iio_buffer_data_available(struct iio_buffer *buf)
+{
+	return buf->access->data_available(buf);
+}
+
+static int iio_buffer_flush_hwfifo(struct iio_dev *indio_dev,
+				   struct iio_buffer *buf, size_t required)
+{
+	if (!indio_dev->info->hwfifo_flush_to_buffer)
+		return -ENODEV;
+
+	return indio_dev->info->hwfifo_flush_to_buffer(indio_dev, required);
+}
+
+static bool iio_buffer_ready(struct iio_dev *indio_dev, struct iio_buffer *buf,
+			     size_t to_wait, int to_flush)
+{
+	size_t avail;
+	int flushed = 0;
+
+	/* wakeup if the device was unregistered */
+	if (!indio_dev->info)
+		return true;
+
+	/* drain the buffer if it was disabled */
+	if (!iio_buffer_is_active(buf)) {
+		to_wait = min_t(size_t, to_wait, 1);
+		to_flush = 0;
+	}
+
+	avail = iio_buffer_data_available(buf);
+
+	if (avail >= to_wait) {
+		/* force a flush for non-blocking reads */
+		if (!to_wait && avail < to_flush)
+			iio_buffer_flush_hwfifo(indio_dev, buf,
+						to_flush - avail);
+		return true;
+	}
+
+	if (to_flush)
+		flushed = iio_buffer_flush_hwfifo(indio_dev, buf,
+						  to_wait - avail);
+	if (flushed <= 0)
+		return false;
+
+	if (avail + flushed >= to_wait)
+		return true;
+
+	return false;
+}
+
+/**
+ * iio_buffer_read() - chrdev read for buffer access
+ * @filp:	File structure pointer for the char device
+ * @buf:	Destination buffer for iio buffer read
+ * @n:		First n bytes to read
+ * @f_ps:	Long offset provided by the user as a seek position
+ *
+ * This function relies on all buffer implementations having an
+ * iio_buffer as their first element.
+ *
+ * Return: negative values corresponding to error codes or ret != 0
+ *	   for ending the reading activity
+ **/
+static ssize_t iio_buffer_read(struct file *filp, char __user *buf,
+			       size_t n, loff_t *f_ps)
+{
+	struct iio_dev_buffer_pair *ib = filp->private_data;
+	struct iio_buffer *rb = ib->buffer;
+	struct iio_dev *indio_dev = ib->indio_dev;
+	DEFINE_WAIT_FUNC(wait, woken_wake_function);
+	size_t datum_size;
+	size_t to_wait;
+	int ret = 0;
+
+	if (!indio_dev->info)
+		return -ENODEV;
+
+	if (!rb || !rb->access->read)
+		return -EINVAL;
+
+	if (rb->direction != IIO_BUFFER_DIRECTION_IN)
+		return -EPERM;
+
+	datum_size = rb->bytes_per_datum;
+
+	/*
+	 * If datum_size is 0 there will never be anything to read from the
+	 * buffer, so signal end of file now.
+	 */
+	if (!datum_size)
+		return 0;
+
+	if (filp->f_flags & O_NONBLOCK)
+		to_wait = 0;
+	else
+		to_wait = min_t(size_t, n / datum_size, rb->watermark);
+
+	add_wait_queue(&rb->pollq, &wait);
+	do {
+		if (!indio_dev->info) {
+			ret = -ENODEV;
+			break;
+		}
+
+		if (!iio_buffer_ready(indio_dev, rb, to_wait, n / datum_size)) {
+			if (signal_pending(current)) {
+				ret = -ERESTARTSYS;
+				break;
+			}
+
+			wait_woken(&wait, TASK_INTERRUPTIBLE,
+				   MAX_SCHEDULE_TIMEOUT);
+			continue;
+		}
+
+		ret = rb->access->read(rb, n, buf);
+		if (ret == 0 && (filp->f_flags & O_NONBLOCK))
+			ret = -EAGAIN;
+	} while (ret == 0);
+	remove_wait_queue(&rb->pollq, &wait);
+
+	return ret;
+}
+
+static size_t iio_buffer_space_available(struct iio_buffer *buf)
+{
+	if (buf->access->space_available)
+		return buf->access->space_available(buf);
+
+	return SIZE_MAX;
+}
+
+static ssize_t iio_buffer_write(struct file *filp, const char __user *buf,
+				size_t n, loff_t *f_ps)
+{
+	struct iio_dev_buffer_pair *ib = filp->private_data;
+	struct iio_buffer *rb = ib->buffer;
+	struct iio_dev *indio_dev = ib->indio_dev;
+	DEFINE_WAIT_FUNC(wait, woken_wake_function);
+	int ret = 0;
+	size_t written;
+
+	if (!indio_dev->info)
+		return -ENODEV;
+
+	if (!rb || !rb->access->write)
+		return -EINVAL;
+
+	if (rb->direction != IIO_BUFFER_DIRECTION_OUT)
+		return -EPERM;
+
+	written = 0;
+	add_wait_queue(&rb->pollq, &wait);
+	do {
+		if (indio_dev->info == NULL)
+			return -ENODEV;
+
+		if (!iio_buffer_space_available(rb)) {
+			if (signal_pending(current)) {
+				ret = -ERESTARTSYS;
+				break;
+			}
+
+			if (filp->f_flags & O_NONBLOCK) {
+				if (!written)
+					ret = -EAGAIN;
+				break;
+			}
+
+			wait_woken(&wait, TASK_INTERRUPTIBLE,
+					MAX_SCHEDULE_TIMEOUT);
+			continue;
+		}
+
+		ret = rb->access->write(rb, n - written, buf + written);
+		if (ret < 0)
+			break;
+
+		written += ret;
+
+	} while (written != n);
+	remove_wait_queue(&rb->pollq, &wait);
+
+	return ret < 0 ? ret : written;
+}
+
+/**
+ * iio_buffer_poll() - poll the buffer to find out if it has data
+ * @filp:	File structure pointer for device access
+ * @wait:	Poll table structure pointer for which the driver adds
+ *		a wait queue
+ *
+ * Return: (EPOLLIN | EPOLLRDNORM) if data is available for reading
+ *	   or 0 for other cases
+ */
+static __poll_t iio_buffer_poll(struct file *filp,
+				struct poll_table_struct *wait)
+{
+	struct iio_dev_buffer_pair *ib = filp->private_data;
+	struct iio_buffer *rb = ib->buffer;
+	struct iio_dev *indio_dev = ib->indio_dev;
+
+	if (!indio_dev->info || rb == NULL)
+		return 0;
+
+	poll_wait(filp, &rb->pollq, wait);
+
+	switch (rb->direction) {
+	case IIO_BUFFER_DIRECTION_IN:
+		if (iio_buffer_ready(indio_dev, rb, rb->watermark, 0))
+			return EPOLLIN | EPOLLRDNORM;
+		break;
+	case IIO_BUFFER_DIRECTION_OUT:
+		if (iio_buffer_space_available(rb))
+			return EPOLLOUT | EPOLLWRNORM;
+		break;
+	}
+
+	return 0;
+}
+
+ssize_t iio_buffer_read_wrapper(struct file *filp, char __user *buf,
+				size_t n, loff_t *f_ps)
+{
+	struct iio_dev_buffer_pair *ib = filp->private_data;
+	struct iio_buffer *rb = ib->buffer;
+
+	/* check if buffer was opened through new API */
+	if (test_bit(IIO_BUSY_BIT_POS, &rb->flags))
+		return -EBUSY;
+
+	return iio_buffer_read(filp, buf, n, f_ps);
+}
+
+ssize_t iio_buffer_write_wrapper(struct file *filp, const char __user *buf,
+				 size_t n, loff_t *f_ps)
+{
+	struct iio_dev_buffer_pair *ib = filp->private_data;
+	struct iio_buffer *rb = ib->buffer;
+
+	/* check if buffer was opened through new API */
+	if (test_bit(IIO_BUSY_BIT_POS, &rb->flags))
+		return -EBUSY;
+
+	return iio_buffer_write(filp, buf, n, f_ps);
+}
+
+__poll_t iio_buffer_poll_wrapper(struct file *filp,
+				 struct poll_table_struct *wait)
+{
+	struct iio_dev_buffer_pair *ib = filp->private_data;
+	struct iio_buffer *rb = ib->buffer;
+
+	/* check if buffer was opened through new API */
+	if (test_bit(IIO_BUSY_BIT_POS, &rb->flags))
+		return 0;
+
+	return iio_buffer_poll(filp, wait);
+}
+
+/**
+ * iio_buffer_wakeup_poll - Wakes up the buffer waitqueue
+ * @indio_dev: The IIO device
+ *
+ * Wakes up the event waitqueue used for poll(). Should usually
+ * be called when the device is unregistered.
+ */
+void iio_buffer_wakeup_poll(struct iio_dev *indio_dev)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+	struct iio_buffer *buffer;
+	unsigned int i;
+
+	for (i = 0; i < iio_dev_opaque->attached_buffers_cnt; i++) {
+		buffer = iio_dev_opaque->attached_buffers[i];
+		wake_up(&buffer->pollq);
+	}
+}
+
+int iio_pop_from_buffer(struct iio_buffer *buffer, void *data)
+{
+	if (!buffer || !buffer->access || !buffer->access->remove_from)
+		return -EINVAL;
+
+	return buffer->access->remove_from(buffer, data);
+}
+EXPORT_SYMBOL_GPL(iio_pop_from_buffer);
+
+void iio_buffer_init(struct iio_buffer *buffer)
+{
+	INIT_LIST_HEAD(&buffer->demux_list);
+	INIT_LIST_HEAD(&buffer->buffer_list);
+	init_waitqueue_head(&buffer->pollq);
+	kref_init(&buffer->ref);
+	if (!buffer->watermark)
+		buffer->watermark = 1;
+}
+EXPORT_SYMBOL(iio_buffer_init);
+
+void iio_device_detach_buffers(struct iio_dev *indio_dev)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+	struct iio_buffer *buffer;
+	unsigned int i;
+
+	for (i = 0; i < iio_dev_opaque->attached_buffers_cnt; i++) {
+		buffer = iio_dev_opaque->attached_buffers[i];
+		iio_buffer_put(buffer);
+	}
+
+	kfree(iio_dev_opaque->attached_buffers);
+}
+
+static ssize_t iio_show_scan_index(struct device *dev,
+				   struct device_attribute *attr,
+				   char *buf)
+{
+	return sysfs_emit(buf, "%u\n", to_iio_dev_attr(attr)->c->scan_index);
+}
+
+static ssize_t iio_show_fixed_type(struct device *dev,
+				   struct device_attribute *attr,
+				   char *buf)
+{
+	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
+	u8 type = this_attr->c->scan_type.endianness;
+
+	if (type == IIO_CPU) {
+#ifdef __LITTLE_ENDIAN
+		type = IIO_LE;
+#else
+		type = IIO_BE;
+#endif
+	}
+	if (this_attr->c->scan_type.repeat > 1)
+		return sysfs_emit(buf, "%s:%c%d/%dX%d>>%u\n",
+		       iio_endian_prefix[type],
+		       this_attr->c->scan_type.sign,
+		       this_attr->c->scan_type.realbits,
+		       this_attr->c->scan_type.storagebits,
+		       this_attr->c->scan_type.repeat,
+		       this_attr->c->scan_type.shift);
+	else
+		return sysfs_emit(buf, "%s:%c%d/%d>>%u\n",
+		       iio_endian_prefix[type],
+		       this_attr->c->scan_type.sign,
+		       this_attr->c->scan_type.realbits,
+		       this_attr->c->scan_type.storagebits,
+		       this_attr->c->scan_type.shift);
+}
+
+static ssize_t iio_scan_el_show(struct device *dev,
+				struct device_attribute *attr,
+				char *buf)
+{
+	int ret;
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
+
+	/* Ensure ret is 0 or 1. */
+	ret = !!test_bit(to_iio_dev_attr(attr)->address,
+		       buffer->scan_mask);
+
+	return sysfs_emit(buf, "%d\n", ret);
+}
+
+/* Note NULL used as error indicator as it doesn't make sense. */
+static const unsigned long *iio_scan_mask_match(const unsigned long *av_masks,
+					  unsigned int masklength,
+					  const unsigned long *mask,
+					  bool strict)
+{
+	if (bitmap_empty(mask, masklength))
+		return NULL;
+	while (*av_masks) {
+		if (strict) {
+			if (bitmap_equal(mask, av_masks, masklength))
+				return av_masks;
+		} else {
+			if (bitmap_subset(mask, av_masks, masklength))
+				return av_masks;
+		}
+		av_masks += BITS_TO_LONGS(masklength);
+	}
+	return NULL;
+}
+
+static bool iio_validate_scan_mask(struct iio_dev *indio_dev,
+	const unsigned long *mask)
+{
+	if (!indio_dev->setup_ops->validate_scan_mask)
+		return true;
+
+	return indio_dev->setup_ops->validate_scan_mask(indio_dev, mask);
+}
+
+/**
+ * iio_scan_mask_set() - set particular bit in the scan mask
+ * @indio_dev: the iio device
+ * @buffer: the buffer whose scan mask we are interested in
+ * @bit: the bit to be set.
+ *
+ * Note that at this point we have no way of knowing what other
+ * buffers might request, hence this code only verifies that the
+ * individual buffers request is plausible.
+ */
+static int iio_scan_mask_set(struct iio_dev *indio_dev,
+		      struct iio_buffer *buffer, int bit)
+{
+	const unsigned long *mask;
+	unsigned long *trialmask;
+
+	if (!indio_dev->masklength) {
+		WARN(1, "Trying to set scanmask prior to registering buffer\n");
+		return -EINVAL;
+	}
+
+	trialmask = bitmap_alloc(indio_dev->masklength, GFP_KERNEL);
+	if (!trialmask)
+		return -ENOMEM;
+	bitmap_copy(trialmask, buffer->scan_mask, indio_dev->masklength);
+	set_bit(bit, trialmask);
+
+	if (!iio_validate_scan_mask(indio_dev, trialmask))
+		goto err_invalid_mask;
+
+	if (indio_dev->available_scan_masks) {
+		mask = iio_scan_mask_match(indio_dev->available_scan_masks,
+					   indio_dev->masklength,
+					   trialmask, false);
+		if (!mask)
+			goto err_invalid_mask;
+	}
+	bitmap_copy(buffer->scan_mask, trialmask, indio_dev->masklength);
+
+	bitmap_free(trialmask);
+
+	return 0;
+
+err_invalid_mask:
+	bitmap_free(trialmask);
+	return -EINVAL;
+}
+
+static int iio_scan_mask_clear(struct iio_buffer *buffer, int bit)
+{
+	clear_bit(bit, buffer->scan_mask);
+	return 0;
+}
+
+static int iio_scan_mask_query(struct iio_dev *indio_dev,
+			       struct iio_buffer *buffer, int bit)
+{
+	if (bit > indio_dev->masklength)
+		return -EINVAL;
+
+	if (!buffer->scan_mask)
+		return 0;
+
+	/* Ensure return value is 0 or 1. */
+	return !!test_bit(bit, buffer->scan_mask);
+};
+
+static ssize_t iio_scan_el_store(struct device *dev,
+				 struct device_attribute *attr,
+				 const char *buf,
+				 size_t len)
+{
+	int ret;
+	bool state;
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
+	struct iio_buffer *buffer = this_attr->buffer;
+
+	ret = kstrtobool(buf, &state);
+	if (ret < 0)
+		return ret;
+	mutex_lock(&indio_dev->mlock);
+	if (iio_buffer_is_active(buffer)) {
+		ret = -EBUSY;
+		goto error_ret;
+	}
+	ret = iio_scan_mask_query(indio_dev, buffer, this_attr->address);
+	if (ret < 0)
+		goto error_ret;
+	if (!state && ret) {
+		ret = iio_scan_mask_clear(buffer, this_attr->address);
+		if (ret)
+			goto error_ret;
+	} else if (state && !ret) {
+		ret = iio_scan_mask_set(indio_dev, buffer, this_attr->address);
+		if (ret)
+			goto error_ret;
+	}
+
+error_ret:
+	mutex_unlock(&indio_dev->mlock);
+
+	return ret < 0 ? ret : len;
+
+}
+
+static ssize_t iio_scan_el_ts_show(struct device *dev,
+				   struct device_attribute *attr,
+				   char *buf)
+{
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
+
+	return sysfs_emit(buf, "%d\n", buffer->scan_timestamp);
+}
+
+static ssize_t iio_scan_el_ts_store(struct device *dev,
+				    struct device_attribute *attr,
+				    const char *buf,
+				    size_t len)
+{
+	int ret;
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
+	bool state;
+
+	ret = kstrtobool(buf, &state);
+	if (ret < 0)
+		return ret;
+
+	mutex_lock(&indio_dev->mlock);
+	if (iio_buffer_is_active(buffer)) {
+		ret = -EBUSY;
+		goto error_ret;
+	}
+	buffer->scan_timestamp = state;
+error_ret:
+	mutex_unlock(&indio_dev->mlock);
+
+	return ret ? ret : len;
+}
+
+static int iio_buffer_add_channel_sysfs(struct iio_dev *indio_dev,
+					struct iio_buffer *buffer,
+					const struct iio_chan_spec *chan)
+{
+	int ret, attrcount = 0;
+
+	ret = __iio_add_chan_devattr("index",
+				     chan,
+				     &iio_show_scan_index,
+				     NULL,
+				     0,
+				     IIO_SEPARATE,
+				     &indio_dev->dev,
+				     buffer,
+				     &buffer->buffer_attr_list);
+	if (ret)
+		return ret;
+	attrcount++;
+	ret = __iio_add_chan_devattr("type",
+				     chan,
+				     &iio_show_fixed_type,
+				     NULL,
+				     0,
+				     0,
+				     &indio_dev->dev,
+				     buffer,
+				     &buffer->buffer_attr_list);
+	if (ret)
+		return ret;
+	attrcount++;
+	if (chan->type != IIO_TIMESTAMP)
+		ret = __iio_add_chan_devattr("en",
+					     chan,
+					     &iio_scan_el_show,
+					     &iio_scan_el_store,
+					     chan->scan_index,
+					     0,
+					     &indio_dev->dev,
+					     buffer,
+					     &buffer->buffer_attr_list);
+	else
+		ret = __iio_add_chan_devattr("en",
+					     chan,
+					     &iio_scan_el_ts_show,
+					     &iio_scan_el_ts_store,
+					     chan->scan_index,
+					     0,
+					     &indio_dev->dev,
+					     buffer,
+					     &buffer->buffer_attr_list);
+	if (ret)
+		return ret;
+	attrcount++;
+	ret = attrcount;
+	return ret;
+}
+
+static ssize_t length_show(struct device *dev, struct device_attribute *attr,
+			   char *buf)
+{
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
+
+	return sysfs_emit(buf, "%d\n", buffer->length);
+}
+
+static ssize_t length_store(struct device *dev, struct device_attribute *attr,
+			    const char *buf, size_t len)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
+	unsigned int val;
+	int ret;
+
+	ret = kstrtouint(buf, 10, &val);
+	if (ret)
+		return ret;
+
+	if (val == buffer->length)
+		return len;
+
+	mutex_lock(&indio_dev->mlock);
+	if (iio_buffer_is_active(buffer)) {
+		ret = -EBUSY;
+	} else {
+		buffer->access->set_length(buffer, val);
+		ret = 0;
+	}
+	if (ret)
+		goto out;
+	if (buffer->length && buffer->length < buffer->watermark)
+		buffer->watermark = buffer->length;
+out:
+	mutex_unlock(&indio_dev->mlock);
+
+	return ret ? ret : len;
+}
+
+static ssize_t enable_show(struct device *dev, struct device_attribute *attr,
+			   char *buf)
+{
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
+
+	return sysfs_emit(buf, "%d\n", iio_buffer_is_active(buffer));
+}
+
+static unsigned int iio_storage_bytes_for_si(struct iio_dev *indio_dev,
+					     unsigned int scan_index)
+{
+	const struct iio_chan_spec *ch;
+	unsigned int bytes;
+
+	ch = iio_find_channel_from_si(indio_dev, scan_index);
+	bytes = ch->scan_type.storagebits / 8;
+	if (ch->scan_type.repeat > 1)
+		bytes *= ch->scan_type.repeat;
+	return bytes;
+}
+
+static unsigned int iio_storage_bytes_for_timestamp(struct iio_dev *indio_dev)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+
+	return iio_storage_bytes_for_si(indio_dev,
+					iio_dev_opaque->scan_index_timestamp);
+}
+
+static int iio_compute_scan_bytes(struct iio_dev *indio_dev,
+				const unsigned long *mask, bool timestamp)
+{
+	unsigned int bytes = 0;
+	int length, i, largest = 0;
+
+	/* How much space will the demuxed element take? */
+	for_each_set_bit(i, mask,
+			 indio_dev->masklength) {
+		length = iio_storage_bytes_for_si(indio_dev, i);
+		bytes = ALIGN(bytes, length);
+		bytes += length;
+		largest = max(largest, length);
+	}
+
+	if (timestamp) {
+		length = iio_storage_bytes_for_timestamp(indio_dev);
+		bytes = ALIGN(bytes, length);
+		bytes += length;
+		largest = max(largest, length);
+	}
+
+	bytes = ALIGN(bytes, largest);
+	return bytes;
+}
+
+static void iio_buffer_activate(struct iio_dev *indio_dev,
+	struct iio_buffer *buffer)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+
+	iio_buffer_get(buffer);
+	list_add(&buffer->buffer_list, &iio_dev_opaque->buffer_list);
+}
+
+static void iio_buffer_deactivate(struct iio_buffer *buffer)
+{
+	list_del_init(&buffer->buffer_list);
+	wake_up_interruptible(&buffer->pollq);
+	iio_buffer_put(buffer);
+}
+
+static void iio_buffer_deactivate_all(struct iio_dev *indio_dev)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+	struct iio_buffer *buffer, *_buffer;
+
+	list_for_each_entry_safe(buffer, _buffer,
+			&iio_dev_opaque->buffer_list, buffer_list)
+		iio_buffer_deactivate(buffer);
+}
+
+static int iio_buffer_enable(struct iio_buffer *buffer,
+	struct iio_dev *indio_dev)
+{
+	if (!buffer->access->enable)
+		return 0;
+	return buffer->access->enable(buffer, indio_dev);
+}
+
+static int iio_buffer_disable(struct iio_buffer *buffer,
+	struct iio_dev *indio_dev)
+{
+	if (!buffer->access->disable)
+		return 0;
+	return buffer->access->disable(buffer, indio_dev);
+}
+
+static void iio_buffer_update_bytes_per_datum(struct iio_dev *indio_dev,
+	struct iio_buffer *buffer)
+{
+	unsigned int bytes;
+
+	if (!buffer->access->set_bytes_per_datum)
+		return;
+
+	bytes = iio_compute_scan_bytes(indio_dev, buffer->scan_mask,
+		buffer->scan_timestamp);
+
+	buffer->access->set_bytes_per_datum(buffer, bytes);
+}
+
+static int iio_buffer_request_update(struct iio_dev *indio_dev,
+	struct iio_buffer *buffer)
+{
+	int ret;
+
+	iio_buffer_update_bytes_per_datum(indio_dev, buffer);
+	if (buffer->access->request_update) {
+		ret = buffer->access->request_update(buffer);
+		if (ret) {
+			dev_dbg(&indio_dev->dev,
+			       "Buffer not started: buffer parameter update failed (%d)\n",
+				ret);
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
+static void iio_free_scan_mask(struct iio_dev *indio_dev,
+	const unsigned long *mask)
+{
+	/* If the mask is dynamically allocated free it, otherwise do nothing */
+	if (!indio_dev->available_scan_masks)
+		bitmap_free(mask);
+}
+
+struct iio_device_config {
+	unsigned int mode;
+	unsigned int watermark;
+	const unsigned long *scan_mask;
+	unsigned int scan_bytes;
+	bool scan_timestamp;
+};
+
+static int iio_verify_update(struct iio_dev *indio_dev,
+	struct iio_buffer *insert_buffer, struct iio_buffer *remove_buffer,
+	struct iio_device_config *config)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+	unsigned long *compound_mask;
+	const unsigned long *scan_mask;
+	bool strict_scanmask = false;
+	struct iio_buffer *buffer;
+	bool scan_timestamp;
+	unsigned int modes;
+
+	if (insert_buffer &&
+	    bitmap_empty(insert_buffer->scan_mask, indio_dev->masklength)) {
+		dev_dbg(&indio_dev->dev,
+			"At least one scan element must be enabled first\n");
+		return -EINVAL;
+	}
+
+	memset(config, 0, sizeof(*config));
+	config->watermark = ~0;
+
+	/*
+	 * If there is just one buffer and we are removing it there is nothing
+	 * to verify.
+	 */
+	if (remove_buffer && !insert_buffer &&
+	    list_is_singular(&iio_dev_opaque->buffer_list))
+		return 0;
+
+	modes = indio_dev->modes;
+
+	list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list) {
+		if (buffer == remove_buffer)
+			continue;
+		modes &= buffer->access->modes;
+		config->watermark = min(config->watermark, buffer->watermark);
+	}
+
+	if (insert_buffer) {
+		modes &= insert_buffer->access->modes;
+		config->watermark = min(config->watermark,
+			insert_buffer->watermark);
+	}
+
+	/* Definitely possible for devices to support both of these. */
+	if ((modes & INDIO_BUFFER_TRIGGERED) && indio_dev->trig) {
+		config->mode = INDIO_BUFFER_TRIGGERED;
+	} else if (modes & INDIO_BUFFER_HARDWARE) {
+		/*
+		 * Keep things simple for now and only allow a single buffer to
+		 * be connected in hardware mode.
+		 */
+		if (insert_buffer && !list_empty(&iio_dev_opaque->buffer_list))
+			return -EINVAL;
+		config->mode = INDIO_BUFFER_HARDWARE;
+		strict_scanmask = true;
+	} else if (modes & INDIO_BUFFER_SOFTWARE) {
+		config->mode = INDIO_BUFFER_SOFTWARE;
+	} else {
+		/* Can only occur on first buffer */
+		if (indio_dev->modes & INDIO_BUFFER_TRIGGERED)
+			dev_dbg(&indio_dev->dev, "Buffer not started: no trigger\n");
+		return -EINVAL;
+	}
+
+	/* What scan mask do we actually have? */
+	compound_mask = bitmap_zalloc(indio_dev->masklength, GFP_KERNEL);
+	if (compound_mask == NULL)
+		return -ENOMEM;
+
+	scan_timestamp = false;
+
+	list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list) {
+		if (buffer == remove_buffer)
+			continue;
+		bitmap_or(compound_mask, compound_mask, buffer->scan_mask,
+			  indio_dev->masklength);
+		scan_timestamp |= buffer->scan_timestamp;
+	}
+
+	if (insert_buffer) {
+		bitmap_or(compound_mask, compound_mask,
+			  insert_buffer->scan_mask, indio_dev->masklength);
+		scan_timestamp |= insert_buffer->scan_timestamp;
+	}
+
+	if (indio_dev->available_scan_masks) {
+		scan_mask = iio_scan_mask_match(indio_dev->available_scan_masks,
+				    indio_dev->masklength,
+				    compound_mask,
+				    strict_scanmask);
+		bitmap_free(compound_mask);
+		if (scan_mask == NULL)
+			return -EINVAL;
+	} else {
+		scan_mask = compound_mask;
+	}
+
+	config->scan_bytes = iio_compute_scan_bytes(indio_dev,
+				    scan_mask, scan_timestamp);
+	config->scan_mask = scan_mask;
+	config->scan_timestamp = scan_timestamp;
+
+	return 0;
+}
+
+/**
+ * struct iio_demux_table - table describing demux memcpy ops
+ * @from:	index to copy from
+ * @to:		index to copy to
+ * @length:	how many bytes to copy
+ * @l:		list head used for management
+ */
+struct iio_demux_table {
+	unsigned int from;
+	unsigned int to;
+	unsigned int length;
+	struct list_head l;
+};
+
+static void iio_buffer_demux_free(struct iio_buffer *buffer)
+{
+	struct iio_demux_table *p, *q;
+
+	list_for_each_entry_safe(p, q, &buffer->demux_list, l) {
+		list_del(&p->l);
+		kfree(p);
+	}
+}
+
+static int iio_buffer_add_demux(struct iio_buffer *buffer,
+	struct iio_demux_table **p, unsigned int in_loc, unsigned int out_loc,
+	unsigned int length)
+{
+
+	if (*p && (*p)->from + (*p)->length == in_loc &&
+		(*p)->to + (*p)->length == out_loc) {
+		(*p)->length += length;
+	} else {
+		*p = kmalloc(sizeof(**p), GFP_KERNEL);
+		if (*p == NULL)
+			return -ENOMEM;
+		(*p)->from = in_loc;
+		(*p)->to = out_loc;
+		(*p)->length = length;
+		list_add_tail(&(*p)->l, &buffer->demux_list);
+	}
+
+	return 0;
+}
+
+static int iio_buffer_update_demux(struct iio_dev *indio_dev,
+				   struct iio_buffer *buffer)
+{
+	int ret, in_ind = -1, out_ind, length;
+	unsigned int in_loc = 0, out_loc = 0;
+	struct iio_demux_table *p = NULL;
+
+	/* Clear out any old demux */
+	iio_buffer_demux_free(buffer);
+	kfree(buffer->demux_bounce);
+	buffer->demux_bounce = NULL;
+
+	/* First work out which scan mode we will actually have */
+	if (bitmap_equal(indio_dev->active_scan_mask,
+			 buffer->scan_mask,
+			 indio_dev->masklength))
+		return 0;
+
+	/* Now we have the two masks, work from least sig and build up sizes */
+	for_each_set_bit(out_ind,
+			 buffer->scan_mask,
+			 indio_dev->masklength) {
+		in_ind = find_next_bit(indio_dev->active_scan_mask,
+				       indio_dev->masklength,
+				       in_ind + 1);
+		while (in_ind != out_ind) {
+			length = iio_storage_bytes_for_si(indio_dev, in_ind);
+			/* Make sure we are aligned */
+			in_loc = roundup(in_loc, length) + length;
+			in_ind = find_next_bit(indio_dev->active_scan_mask,
+					       indio_dev->masklength,
+					       in_ind + 1);
+		}
+		length = iio_storage_bytes_for_si(indio_dev, in_ind);
+		out_loc = roundup(out_loc, length);
+		in_loc = roundup(in_loc, length);
+		ret = iio_buffer_add_demux(buffer, &p, in_loc, out_loc, length);
+		if (ret)
+			goto error_clear_mux_table;
+		out_loc += length;
+		in_loc += length;
+	}
+	/* Relies on scan_timestamp being last */
+	if (buffer->scan_timestamp) {
+		length = iio_storage_bytes_for_timestamp(indio_dev);
+		out_loc = roundup(out_loc, length);
+		in_loc = roundup(in_loc, length);
+		ret = iio_buffer_add_demux(buffer, &p, in_loc, out_loc, length);
+		if (ret)
+			goto error_clear_mux_table;
+		out_loc += length;
+	}
+	buffer->demux_bounce = kzalloc(out_loc, GFP_KERNEL);
+	if (buffer->demux_bounce == NULL) {
+		ret = -ENOMEM;
+		goto error_clear_mux_table;
+	}
+	return 0;
+
+error_clear_mux_table:
+	iio_buffer_demux_free(buffer);
+
+	return ret;
+}
+
+static int iio_update_demux(struct iio_dev *indio_dev)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+	struct iio_buffer *buffer;
+	int ret;
+
+	list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list) {
+		ret = iio_buffer_update_demux(indio_dev, buffer);
+		if (ret < 0)
+			goto error_clear_mux_table;
+	}
+	return 0;
+
+error_clear_mux_table:
+	list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list)
+		iio_buffer_demux_free(buffer);
+
+	return ret;
+}
+
+static int iio_enable_buffers(struct iio_dev *indio_dev,
+	struct iio_device_config *config)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+	struct iio_buffer *buffer, *tmp = NULL;
+	int ret;
+
+	indio_dev->active_scan_mask = config->scan_mask;
+	indio_dev->scan_timestamp = config->scan_timestamp;
+	indio_dev->scan_bytes = config->scan_bytes;
+	iio_dev_opaque->currentmode = config->mode;
+
+	iio_update_demux(indio_dev);
+
+	/* Wind up again */
+	if (indio_dev->setup_ops->preenable) {
+		ret = indio_dev->setup_ops->preenable(indio_dev);
+		if (ret) {
+			dev_dbg(&indio_dev->dev,
+			       "Buffer not started: buffer preenable failed (%d)\n", ret);
+			goto err_undo_config;
+		}
+	}
+
+	if (indio_dev->info->update_scan_mode) {
+		ret = indio_dev->info
+			->update_scan_mode(indio_dev,
+					   indio_dev->active_scan_mask);
+		if (ret < 0) {
+			dev_dbg(&indio_dev->dev,
+				"Buffer not started: update scan mode failed (%d)\n",
+				ret);
+			goto err_run_postdisable;
+		}
+	}
+
+	if (indio_dev->info->hwfifo_set_watermark)
+		indio_dev->info->hwfifo_set_watermark(indio_dev,
+			config->watermark);
+
+	list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list) {
+		ret = iio_buffer_enable(buffer, indio_dev);
+		if (ret) {
+			tmp = buffer;
+			goto err_disable_buffers;
+		}
+	}
+
+	if (iio_dev_opaque->currentmode == INDIO_BUFFER_TRIGGERED) {
+		ret = iio_trigger_attach_poll_func(indio_dev->trig,
+						   indio_dev->pollfunc);
+		if (ret)
+			goto err_disable_buffers;
+	}
+
+	if (indio_dev->setup_ops->postenable) {
+		ret = indio_dev->setup_ops->postenable(indio_dev);
+		if (ret) {
+			dev_dbg(&indio_dev->dev,
+			       "Buffer not started: postenable failed (%d)\n", ret);
+			goto err_detach_pollfunc;
+		}
+	}
+
+	return 0;
+
+err_detach_pollfunc:
+	if (iio_dev_opaque->currentmode == INDIO_BUFFER_TRIGGERED) {
+		iio_trigger_detach_poll_func(indio_dev->trig,
+					     indio_dev->pollfunc);
+	}
+err_disable_buffers:
+	buffer = list_prepare_entry(tmp, &iio_dev_opaque->buffer_list, buffer_list);
+	list_for_each_entry_continue_reverse(buffer, &iio_dev_opaque->buffer_list,
+					     buffer_list)
+		iio_buffer_disable(buffer, indio_dev);
+err_run_postdisable:
+	if (indio_dev->setup_ops->postdisable)
+		indio_dev->setup_ops->postdisable(indio_dev);
+err_undo_config:
+	iio_dev_opaque->currentmode = INDIO_DIRECT_MODE;
+	indio_dev->active_scan_mask = NULL;
+
+	return ret;
+}
+
+static int iio_disable_buffers(struct iio_dev *indio_dev)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+	struct iio_buffer *buffer;
+	int ret = 0;
+	int ret2;
+
+	/* Wind down existing buffers - iff there are any */
+	if (list_empty(&iio_dev_opaque->buffer_list))
+		return 0;
+
+	/*
+	 * If things go wrong at some step in disable we still need to continue
+	 * to perform the other steps, otherwise we leave the device in a
+	 * inconsistent state. We return the error code for the first error we
+	 * encountered.
+	 */
+
+	if (indio_dev->setup_ops->predisable) {
+		ret2 = indio_dev->setup_ops->predisable(indio_dev);
+		if (ret2 && !ret)
+			ret = ret2;
+	}
+
+	if (iio_dev_opaque->currentmode == INDIO_BUFFER_TRIGGERED) {
+		iio_trigger_detach_poll_func(indio_dev->trig,
+					     indio_dev->pollfunc);
+	}
+
+	list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list) {
+		ret2 = iio_buffer_disable(buffer, indio_dev);
+		if (ret2 && !ret)
+			ret = ret2;
+	}
+
+	if (indio_dev->setup_ops->postdisable) {
+		ret2 = indio_dev->setup_ops->postdisable(indio_dev);
+		if (ret2 && !ret)
+			ret = ret2;
+	}
+
+	iio_free_scan_mask(indio_dev, indio_dev->active_scan_mask);
+	indio_dev->active_scan_mask = NULL;
+	iio_dev_opaque->currentmode = INDIO_DIRECT_MODE;
+
+	return ret;
+}
+
+static int __iio_update_buffers(struct iio_dev *indio_dev,
+		       struct iio_buffer *insert_buffer,
+		       struct iio_buffer *remove_buffer)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+	struct iio_device_config new_config;
+	int ret;
+
+	ret = iio_verify_update(indio_dev, insert_buffer, remove_buffer,
+		&new_config);
+	if (ret)
+		return ret;
+
+	if (insert_buffer) {
+		ret = iio_buffer_request_update(indio_dev, insert_buffer);
+		if (ret)
+			goto err_free_config;
+	}
+
+	ret = iio_disable_buffers(indio_dev);
+	if (ret)
+		goto err_deactivate_all;
+
+	if (remove_buffer)
+		iio_buffer_deactivate(remove_buffer);
+	if (insert_buffer)
+		iio_buffer_activate(indio_dev, insert_buffer);
+
+	/* If no buffers in list, we are done */
+	if (list_empty(&iio_dev_opaque->buffer_list))
+		return 0;
+
+	ret = iio_enable_buffers(indio_dev, &new_config);
+	if (ret)
+		goto err_deactivate_all;
+
+	return 0;
+
+err_deactivate_all:
+	/*
+	 * We've already verified that the config is valid earlier. If things go
+	 * wrong in either enable or disable the most likely reason is an IO
+	 * error from the device. In this case there is no good recovery
+	 * strategy. Just make sure to disable everything and leave the device
+	 * in a sane state.  With a bit of luck the device might come back to
+	 * life again later and userspace can try again.
+	 */
+	iio_buffer_deactivate_all(indio_dev);
+
+err_free_config:
+	iio_free_scan_mask(indio_dev, new_config.scan_mask);
+	return ret;
+}
+
+int iio_update_buffers(struct iio_dev *indio_dev,
+		       struct iio_buffer *insert_buffer,
+		       struct iio_buffer *remove_buffer)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+	int ret;
+
+	if (insert_buffer == remove_buffer)
+		return 0;
+
+	if (insert_buffer &&
+	    (insert_buffer->direction == IIO_BUFFER_DIRECTION_OUT))
+		return -EINVAL;
+
+	mutex_lock(&iio_dev_opaque->info_exist_lock);
+	mutex_lock(&indio_dev->mlock);
+
+	if (insert_buffer && iio_buffer_is_active(insert_buffer))
+		insert_buffer = NULL;
+
+	if (remove_buffer && !iio_buffer_is_active(remove_buffer))
+		remove_buffer = NULL;
+
+	if (!insert_buffer && !remove_buffer) {
+		ret = 0;
+		goto out_unlock;
+	}
+
+	if (indio_dev->info == NULL) {
+		ret = -ENODEV;
+		goto out_unlock;
+	}
+
+	ret = __iio_update_buffers(indio_dev, insert_buffer, remove_buffer);
+
+out_unlock:
+	mutex_unlock(&indio_dev->mlock);
+	mutex_unlock(&iio_dev_opaque->info_exist_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(iio_update_buffers);
+
+void iio_disable_all_buffers(struct iio_dev *indio_dev)
+{
+	iio_disable_buffers(indio_dev);
+	iio_buffer_deactivate_all(indio_dev);
+}
+
+static ssize_t enable_store(struct device *dev, struct device_attribute *attr,
+			    const char *buf, size_t len)
+{
+	int ret;
+	bool requested_state;
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
+	bool inlist;
+
+	ret = kstrtobool(buf, &requested_state);
+	if (ret < 0)
+		return ret;
+
+	mutex_lock(&indio_dev->mlock);
+
+	/* Find out if it is in the list */
+	inlist = iio_buffer_is_active(buffer);
+	/* Already in desired state */
+	if (inlist == requested_state)
+		goto done;
+
+	if (requested_state)
+		ret = __iio_update_buffers(indio_dev, buffer, NULL);
+	else
+		ret = __iio_update_buffers(indio_dev, NULL, buffer);
+
+done:
+	mutex_unlock(&indio_dev->mlock);
+	return (ret < 0) ? ret : len;
+}
+
+static ssize_t watermark_show(struct device *dev, struct device_attribute *attr,
+			      char *buf)
+{
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
+
+	return sysfs_emit(buf, "%u\n", buffer->watermark);
+}
+
+static ssize_t watermark_store(struct device *dev,
+			       struct device_attribute *attr,
+			       const char *buf, size_t len)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
+	unsigned int val;
+	int ret;
+
+	ret = kstrtouint(buf, 10, &val);
+	if (ret)
+		return ret;
+	if (!val)
+		return -EINVAL;
+
+	mutex_lock(&indio_dev->mlock);
+
+	if (val > buffer->length) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (iio_buffer_is_active(buffer)) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	buffer->watermark = val;
+out:
+	mutex_unlock(&indio_dev->mlock);
+
+	return ret ? ret : len;
+}
+
+static ssize_t data_available_show(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
+
+	return sysfs_emit(buf, "%zu\n", iio_buffer_data_available(buffer));
+}
+
+static ssize_t direction_show(struct device *dev,
+			      struct device_attribute *attr,
+			      char *buf)
+{
+	struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
+
+	switch (buffer->direction) {
+	case IIO_BUFFER_DIRECTION_IN:
+		return sysfs_emit(buf, "in\n");
+	case IIO_BUFFER_DIRECTION_OUT:
+		return sysfs_emit(buf, "out\n");
+	default:
+		return -EINVAL;
+	}
+}
+
+static DEVICE_ATTR_RW(length);
+static struct device_attribute dev_attr_length_ro = __ATTR_RO(length);
+static DEVICE_ATTR_RW(enable);
+static DEVICE_ATTR_RW(watermark);
+static struct device_attribute dev_attr_watermark_ro = __ATTR_RO(watermark);
+static DEVICE_ATTR_RO(data_available);
+static DEVICE_ATTR_RO(direction);
+
+/*
+ * When adding new attributes here, put the at the end, at least until
+ * the code that handles the length/length_ro & watermark/watermark_ro
+ * assignments gets cleaned up. Otherwise these can create some weird
+ * duplicate attributes errors under some setups.
+ */
+static struct attribute *iio_buffer_attrs[] = {
+	&dev_attr_length.attr,
+	&dev_attr_enable.attr,
+	&dev_attr_watermark.attr,
+	&dev_attr_data_available.attr,
+	&dev_attr_direction.attr,
+};
+
+#define to_dev_attr(_attr) container_of(_attr, struct device_attribute, attr)
+
+static struct attribute *iio_buffer_wrap_attr(struct iio_buffer *buffer,
+					      struct attribute *attr)
+{
+	struct device_attribute *dattr = to_dev_attr(attr);
+	struct iio_dev_attr *iio_attr;
+
+	iio_attr = kzalloc(sizeof(*iio_attr), GFP_KERNEL);
+	if (!iio_attr)
+		return NULL;
+
+	iio_attr->buffer = buffer;
+	memcpy(&iio_attr->dev_attr, dattr, sizeof(iio_attr->dev_attr));
+	iio_attr->dev_attr.attr.name = kstrdup_const(attr->name, GFP_KERNEL);
+	if (!iio_attr->dev_attr.attr.name) {
+		kfree(iio_attr);
+		return NULL;
+	}
+
+	sysfs_attr_init(&iio_attr->dev_attr.attr);
+
+	list_add(&iio_attr->l, &buffer->buffer_attr_list);
+
+	return &iio_attr->dev_attr.attr;
+}
+
+static int iio_buffer_register_legacy_sysfs_groups(struct iio_dev *indio_dev,
+						   struct attribute **buffer_attrs,
+						   int buffer_attrcount,
+						   int scan_el_attrcount)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+	struct attribute_group *group;
+	struct attribute **attrs;
+	int ret;
+
+	attrs = kcalloc(buffer_attrcount + 1, sizeof(*attrs), GFP_KERNEL);
+	if (!attrs)
+		return -ENOMEM;
+
+	memcpy(attrs, buffer_attrs, buffer_attrcount * sizeof(*attrs));
+
+	group = &iio_dev_opaque->legacy_buffer_group;
+	group->attrs = attrs;
+	group->name = "buffer";
+
+	ret = iio_device_register_sysfs_group(indio_dev, group);
+	if (ret)
+		goto error_free_buffer_attrs;
+
+	attrs = kcalloc(scan_el_attrcount + 1, sizeof(*attrs), GFP_KERNEL);
+	if (!attrs) {
+		ret = -ENOMEM;
+		goto error_free_buffer_attrs;
+	}
+
+	memcpy(attrs, &buffer_attrs[buffer_attrcount],
+	       scan_el_attrcount * sizeof(*attrs));
+
+	group = &iio_dev_opaque->legacy_scan_el_group;
+	group->attrs = attrs;
+	group->name = "scan_elements";
+
+	ret = iio_device_register_sysfs_group(indio_dev, group);
+	if (ret)
+		goto error_free_scan_el_attrs;
+
+	return 0;
+
+error_free_scan_el_attrs:
+	kfree(iio_dev_opaque->legacy_scan_el_group.attrs);
+error_free_buffer_attrs:
+	kfree(iio_dev_opaque->legacy_buffer_group.attrs);
+
+	return ret;
+}
+
+static void iio_buffer_unregister_legacy_sysfs_groups(struct iio_dev *indio_dev)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+
+	kfree(iio_dev_opaque->legacy_buffer_group.attrs);
+	kfree(iio_dev_opaque->legacy_scan_el_group.attrs);
+}
+
+static int iio_buffer_chrdev_release(struct inode *inode, struct file *filep)
+{
+	struct iio_dev_buffer_pair *ib = filep->private_data;
+	struct iio_dev *indio_dev = ib->indio_dev;
+	struct iio_buffer *buffer = ib->buffer;
+
+	wake_up(&buffer->pollq);
+
+	kfree(ib);
+	clear_bit(IIO_BUSY_BIT_POS, &buffer->flags);
+	iio_device_put(indio_dev);
+
+	return 0;
+}
+
+static const struct file_operations iio_buffer_chrdev_fileops = {
+	.owner = THIS_MODULE,
+	.llseek = noop_llseek,
+	.read = iio_buffer_read,
+	.write = iio_buffer_write,
+	.poll = iio_buffer_poll,
+	.release = iio_buffer_chrdev_release,
+};
+
+static long iio_device_buffer_getfd(struct iio_dev *indio_dev, unsigned long arg)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+	int __user *ival = (int __user *)arg;
+	struct iio_dev_buffer_pair *ib;
+	struct iio_buffer *buffer;
+	int fd, idx, ret;
+
+	if (copy_from_user(&idx, ival, sizeof(idx)))
+		return -EFAULT;
+
+	if (idx >= iio_dev_opaque->attached_buffers_cnt)
+		return -ENODEV;
+
+	iio_device_get(indio_dev);
+
+	buffer = iio_dev_opaque->attached_buffers[idx];
+
+	if (test_and_set_bit(IIO_BUSY_BIT_POS, &buffer->flags)) {
+		ret = -EBUSY;
+		goto error_iio_dev_put;
+	}
+
+	ib = kzalloc(sizeof(*ib), GFP_KERNEL);
+	if (!ib) {
+		ret = -ENOMEM;
+		goto error_clear_busy_bit;
+	}
+
+	ib->indio_dev = indio_dev;
+	ib->buffer = buffer;
+
+	fd = anon_inode_getfd("iio:buffer", &iio_buffer_chrdev_fileops,
+			      ib, O_RDWR | O_CLOEXEC);
+	if (fd < 0) {
+		ret = fd;
+		goto error_free_ib;
+	}
+
+	if (copy_to_user(ival, &fd, sizeof(fd))) {
+		/*
+		 * "Leak" the fd, as there's not much we can do about this
+		 * anyway. 'fd' might have been closed already, as
+		 * anon_inode_getfd() called fd_install() on it, which made
+		 * it reachable by userland.
+		 *
+		 * Instead of allowing a malicious user to play tricks with
+		 * us, rely on the process exit path to do any necessary
+		 * cleanup, as in releasing the file, if still needed.
+		 */
+		return -EFAULT;
+	}
+
+	return 0;
+
+error_free_ib:
+	kfree(ib);
+error_clear_busy_bit:
+	clear_bit(IIO_BUSY_BIT_POS, &buffer->flags);
+error_iio_dev_put:
+	iio_device_put(indio_dev);
+	return ret;
+}
+
+static long iio_device_buffer_ioctl(struct iio_dev *indio_dev, struct file *filp,
+				    unsigned int cmd, unsigned long arg)
+{
+	switch (cmd) {
+	case IIO_BUFFER_GET_FD_IOCTL:
+		return iio_device_buffer_getfd(indio_dev, arg);
+	default:
+		return IIO_IOCTL_UNHANDLED;
+	}
+}
+
+static int __iio_buffer_alloc_sysfs_and_mask(struct iio_buffer *buffer,
+					     struct iio_dev *indio_dev,
+					     int index)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+	struct iio_dev_attr *p;
+	struct attribute **attr;
+	int ret, i, attrn, scan_el_attrcount, buffer_attrcount;
+	const struct iio_chan_spec *channels;
+
+	buffer_attrcount = 0;
+	if (buffer->attrs) {
+		while (buffer->attrs[buffer_attrcount] != NULL)
+			buffer_attrcount++;
+	}
+
+	scan_el_attrcount = 0;
+	INIT_LIST_HEAD(&buffer->buffer_attr_list);
+	channels = indio_dev->channels;
+	if (channels) {
+		/* new magic */
+		for (i = 0; i < indio_dev->num_channels; i++) {
+			if (channels[i].scan_index < 0)
+				continue;
+
+			/* Verify that sample bits fit into storage */
+			if (channels[i].scan_type.storagebits <
+			    channels[i].scan_type.realbits +
+			    channels[i].scan_type.shift) {
+				dev_err(&indio_dev->dev,
+					"Channel %d storagebits (%d) < shifted realbits (%d + %d)\n",
+					i, channels[i].scan_type.storagebits,
+					channels[i].scan_type.realbits,
+					channels[i].scan_type.shift);
+				ret = -EINVAL;
+				goto error_cleanup_dynamic;
+			}
+
+			ret = iio_buffer_add_channel_sysfs(indio_dev, buffer,
+							 &channels[i]);
+			if (ret < 0)
+				goto error_cleanup_dynamic;
+			scan_el_attrcount += ret;
+			if (channels[i].type == IIO_TIMESTAMP)
+				iio_dev_opaque->scan_index_timestamp =
+					channels[i].scan_index;
+		}
+		if (indio_dev->masklength && buffer->scan_mask == NULL) {
+			buffer->scan_mask = bitmap_zalloc(indio_dev->masklength,
+							  GFP_KERNEL);
+			if (buffer->scan_mask == NULL) {
+				ret = -ENOMEM;
+				goto error_cleanup_dynamic;
+			}
+		}
+	}
+
+	attrn = buffer_attrcount + scan_el_attrcount + ARRAY_SIZE(iio_buffer_attrs);
+	attr = kcalloc(attrn + 1, sizeof(*attr), GFP_KERNEL);
+	if (!attr) {
+		ret = -ENOMEM;
+		goto error_free_scan_mask;
+	}
+
+	memcpy(attr, iio_buffer_attrs, sizeof(iio_buffer_attrs));
+	if (!buffer->access->set_length)
+		attr[0] = &dev_attr_length_ro.attr;
+
+	if (buffer->access->flags & INDIO_BUFFER_FLAG_FIXED_WATERMARK)
+		attr[2] = &dev_attr_watermark_ro.attr;
+
+	if (buffer->attrs)
+		memcpy(&attr[ARRAY_SIZE(iio_buffer_attrs)], buffer->attrs,
+		       sizeof(struct attribute *) * buffer_attrcount);
+
+	buffer_attrcount += ARRAY_SIZE(iio_buffer_attrs);
+	buffer->buffer_group.attrs = attr;
+
+	for (i = 0; i < buffer_attrcount; i++) {
+		struct attribute *wrapped;
+
+		wrapped = iio_buffer_wrap_attr(buffer, attr[i]);
+		if (!wrapped) {
+			ret = -ENOMEM;
+			goto error_free_buffer_attrs;
+		}
+		attr[i] = wrapped;
+	}
+
+	attrn = 0;
+	list_for_each_entry(p, &buffer->buffer_attr_list, l)
+		attr[attrn++] = &p->dev_attr.attr;
+
+	buffer->buffer_group.name = kasprintf(GFP_KERNEL, "buffer%d", index);
+	if (!buffer->buffer_group.name) {
+		ret = -ENOMEM;
+		goto error_free_buffer_attrs;
+	}
+
+	ret = iio_device_register_sysfs_group(indio_dev, &buffer->buffer_group);
+	if (ret)
+		goto error_free_buffer_attr_group_name;
+
+	/* we only need to register the legacy groups for the first buffer */
+	if (index > 0)
+		return 0;
+
+	ret = iio_buffer_register_legacy_sysfs_groups(indio_dev, attr,
+						      buffer_attrcount,
+						      scan_el_attrcount);
+	if (ret)
+		goto error_free_buffer_attr_group_name;
+
+	return 0;
+
+error_free_buffer_attr_group_name:
+	kfree(buffer->buffer_group.name);
+error_free_buffer_attrs:
+	kfree(buffer->buffer_group.attrs);
+error_free_scan_mask:
+	bitmap_free(buffer->scan_mask);
+error_cleanup_dynamic:
+	iio_free_chan_devattr_list(&buffer->buffer_attr_list);
+
+	return ret;
+}
+
+static void __iio_buffer_free_sysfs_and_mask(struct iio_buffer *buffer,
+					     struct iio_dev *indio_dev,
+					     int index)
+{
+	if (index == 0)
+		iio_buffer_unregister_legacy_sysfs_groups(indio_dev);
+	bitmap_free(buffer->scan_mask);
+	kfree(buffer->buffer_group.name);
+	kfree(buffer->buffer_group.attrs);
+	iio_free_chan_devattr_list(&buffer->buffer_attr_list);
+}
+
+int iio_buffers_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+	const struct iio_chan_spec *channels;
+	struct iio_buffer *buffer;
+	int ret, i, idx;
+	size_t sz;
+
+	channels = indio_dev->channels;
+	if (channels) {
+		int ml = indio_dev->masklength;
+
+		for (i = 0; i < indio_dev->num_channels; i++)
+			ml = max(ml, channels[i].scan_index + 1);
+		indio_dev->masklength = ml;
+	}
+
+	if (!iio_dev_opaque->attached_buffers_cnt)
+		return 0;
+
+	for (idx = 0; idx < iio_dev_opaque->attached_buffers_cnt; idx++) {
+		buffer = iio_dev_opaque->attached_buffers[idx];
+		ret = __iio_buffer_alloc_sysfs_and_mask(buffer, indio_dev, idx);
+		if (ret)
+			goto error_unwind_sysfs_and_mask;
+	}
+
+	sz = sizeof(*(iio_dev_opaque->buffer_ioctl_handler));
+	iio_dev_opaque->buffer_ioctl_handler = kzalloc(sz, GFP_KERNEL);
+	if (!iio_dev_opaque->buffer_ioctl_handler) {
+		ret = -ENOMEM;
+		goto error_unwind_sysfs_and_mask;
+	}
+
+	iio_dev_opaque->buffer_ioctl_handler->ioctl = iio_device_buffer_ioctl;
+	iio_device_ioctl_handler_register(indio_dev,
+					  iio_dev_opaque->buffer_ioctl_handler);
+
+	return 0;
+
+error_unwind_sysfs_and_mask:
+	while (idx--) {
+		buffer = iio_dev_opaque->attached_buffers[idx];
+		__iio_buffer_free_sysfs_and_mask(buffer, indio_dev, idx);
+	}
+	return ret;
+}
+
+void iio_buffers_free_sysfs_and_mask(struct iio_dev *indio_dev)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+	struct iio_buffer *buffer;
+	int i;
+
+	if (!iio_dev_opaque->attached_buffers_cnt)
+		return;
+
+	iio_device_ioctl_handler_unregister(iio_dev_opaque->buffer_ioctl_handler);
+	kfree(iio_dev_opaque->buffer_ioctl_handler);
+
+	for (i = iio_dev_opaque->attached_buffers_cnt - 1; i >= 0; i--) {
+		buffer = iio_dev_opaque->attached_buffers[i];
+		__iio_buffer_free_sysfs_and_mask(buffer, indio_dev, i);
+	}
+}
+
+/**
+ * iio_validate_scan_mask_onehot() - Validates that exactly one channel is selected
+ * @indio_dev: the iio device
+ * @mask: scan mask to be checked
+ *
+ * Return true if exactly one bit is set in the scan mask, false otherwise. It
+ * can be used for devices where only one channel can be active for sampling at
+ * a time.
+ */
+bool iio_validate_scan_mask_onehot(struct iio_dev *indio_dev,
+	const unsigned long *mask)
+{
+	return bitmap_weight(mask, indio_dev->masklength) == 1;
+}
+EXPORT_SYMBOL_GPL(iio_validate_scan_mask_onehot);
+
+static const void *iio_demux(struct iio_buffer *buffer,
+				 const void *datain)
+{
+	struct iio_demux_table *t;
+
+	if (list_empty(&buffer->demux_list))
+		return datain;
+	list_for_each_entry(t, &buffer->demux_list, l)
+		memcpy(buffer->demux_bounce + t->to,
+		       datain + t->from, t->length);
+
+	return buffer->demux_bounce;
+}
+
+static int iio_push_to_buffer(struct iio_buffer *buffer, const void *data)
+{
+	const void *dataout = iio_demux(buffer, data);
+	int ret;
+
+	ret = buffer->access->store_to(buffer, dataout);
+	if (ret)
+		return ret;
+
+	/*
+	 * We can't just test for watermark to decide if we wake the poll queue
+	 * because read may request less samples than the watermark.
+	 */
+	wake_up_interruptible_poll(&buffer->pollq, EPOLLIN | EPOLLRDNORM);
+	return 0;
+}
+
+/**
+ * iio_push_to_buffers() - push to a registered buffer.
+ * @indio_dev:		iio_dev structure for device.
+ * @data:		Full scan.
+ */
+int iio_push_to_buffers(struct iio_dev *indio_dev, const void *data)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+	int ret;
+	struct iio_buffer *buf;
+
+	list_for_each_entry(buf, &iio_dev_opaque->buffer_list, buffer_list) {
+		ret = iio_push_to_buffer(buf, data);
+		if (ret < 0)
+			return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(iio_push_to_buffers);
+
+/**
+ * iio_push_to_buffers_with_ts_unaligned() - push to registered buffer,
+ *    no alignment or space requirements.
+ * @indio_dev:		iio_dev structure for device.
+ * @data:		channel data excluding the timestamp.
+ * @data_sz:		size of data.
+ * @timestamp:		timestamp for the sample data.
+ *
+ * This special variant of iio_push_to_buffers_with_timestamp() does
+ * not require space for the timestamp, or 8 byte alignment of data.
+ * It does however require an allocation on first call and additional
+ * copies on all calls, so should be avoided if possible.
+ */
+int iio_push_to_buffers_with_ts_unaligned(struct iio_dev *indio_dev,
+					  const void *data,
+					  size_t data_sz,
+					  int64_t timestamp)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+
+	/*
+	 * Conservative estimate - we can always safely copy the minimum
+	 * of either the data provided or the length of the destination buffer.
+	 * This relaxed limit allows the calling drivers to be lax about
+	 * tracking the size of the data they are pushing, at the cost of
+	 * unnecessary copying of padding.
+	 */
+	data_sz = min_t(size_t, indio_dev->scan_bytes, data_sz);
+	if (iio_dev_opaque->bounce_buffer_size !=  indio_dev->scan_bytes) {
+		void *bb;
+
+		bb = devm_krealloc(&indio_dev->dev,
+				   iio_dev_opaque->bounce_buffer,
+				   indio_dev->scan_bytes, GFP_KERNEL);
+		if (!bb)
+			return -ENOMEM;
+		iio_dev_opaque->bounce_buffer = bb;
+		iio_dev_opaque->bounce_buffer_size = indio_dev->scan_bytes;
+	}
+	memcpy(iio_dev_opaque->bounce_buffer, data, data_sz);
+	return iio_push_to_buffers_with_timestamp(indio_dev,
+						  iio_dev_opaque->bounce_buffer,
+						  timestamp);
+}
+EXPORT_SYMBOL_GPL(iio_push_to_buffers_with_ts_unaligned);
+
+/**
+ * iio_buffer_release() - Free a buffer's resources
+ * @ref: Pointer to the kref embedded in the iio_buffer struct
+ *
+ * This function is called when the last reference to the buffer has been
+ * dropped. It will typically free all resources allocated by the buffer. Do not
+ * call this function manually, always use iio_buffer_put() when done using a
+ * buffer.
+ */
+static void iio_buffer_release(struct kref *ref)
+{
+	struct iio_buffer *buffer = container_of(ref, struct iio_buffer, ref);
+
+	buffer->access->release(buffer);
+}
+
+/**
+ * iio_buffer_get() - Grab a reference to the buffer
+ * @buffer: The buffer to grab a reference for, may be NULL
+ *
+ * Returns the pointer to the buffer that was passed into the function.
+ */
+struct iio_buffer *iio_buffer_get(struct iio_buffer *buffer)
+{
+	if (buffer)
+		kref_get(&buffer->ref);
+
+	return buffer;
+}
+EXPORT_SYMBOL_GPL(iio_buffer_get);
+
+/**
+ * iio_buffer_put() - Release the reference to the buffer
+ * @buffer: The buffer to release the reference for, may be NULL
+ */
+void iio_buffer_put(struct iio_buffer *buffer)
+{
+	if (buffer)
+		kref_put(&buffer->ref, iio_buffer_release);
+}
+EXPORT_SYMBOL_GPL(iio_buffer_put);
+
+/**
+ * iio_device_attach_buffer - Attach a buffer to a IIO device
+ * @indio_dev: The device the buffer should be attached to
+ * @buffer: The buffer to attach to the device
+ *
+ * Return 0 if successful, negative if error.
+ *
+ * This function attaches a buffer to a IIO device. The buffer stays attached to
+ * the device until the device is freed. For legacy reasons, the first attached
+ * buffer will also be assigned to 'indio_dev->buffer'.
+ * The array allocated here, will be free'd via the iio_device_detach_buffers()
+ * call which is handled by the iio_device_free().
+ */
+int iio_device_attach_buffer(struct iio_dev *indio_dev,
+			     struct iio_buffer *buffer)
+{
+	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
+	struct iio_buffer **new, **old = iio_dev_opaque->attached_buffers;
+	unsigned int cnt = iio_dev_opaque->attached_buffers_cnt;
+
+	cnt++;
+
+	new = krealloc(old, sizeof(*new) * cnt, GFP_KERNEL);
+	if (!new)
+		return -ENOMEM;
+	iio_dev_opaque->attached_buffers = new;
+
+	buffer = iio_buffer_get(buffer);
+
+	/* first buffer is legacy; attach it to the IIO device directly */
+	if (!indio_dev->buffer)
+		indio_dev->buffer = buffer;
+
+	iio_dev_opaque->attached_buffers[cnt - 1] = buffer;
+	iio_dev_opaque->attached_buffers_cnt = cnt;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(iio_device_attach_buffer);