Initial import

1 files changed, 1262 insertions, 0 deletions

diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
new file mode 100644
index 000000000..df919f44d
--- /dev/null
+++ b/drivers/iio/industrialio-buffer.c
@@ -0,0 +1,1262 @@
+/* The industrial I/O core
+ *
+ * Copyright (c) 2008 Jonathan Cameron
+ *
+ * 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.
+ *
+ * Handling of buffer allocation / resizing.
+ *
+ *
+ * Things to look at here.
+ * - Better memory allocation techniques?
+ * - Alternative access techniques?
+ */
+#include <linux/kernel.h>
+#include <linux/export.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/cdev.h>
+#include <linux/slab.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
+
+#include <linux/iio/iio.h>
+#include "iio_core.h"
+#include <linux/iio/sysfs.h>
+#include <linux/iio/buffer.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);
+		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_first_n_outer() - chrdev read for buffer access
+ *
+ * This function relies on all buffer implementations having an
+ * iio_buffer as their first element.
+ **/
+ssize_t iio_buffer_read_first_n_outer(struct file *filp, char __user *buf,
+				      size_t n, loff_t *f_ps)
+{
+	struct iio_dev *indio_dev = filp->private_data;
+	struct iio_buffer *rb = indio_dev->buffer;
+	size_t datum_size;
+	size_t to_wait = 0;
+	size_t to_read;
+	int ret;
+
+	if (!indio_dev->info)
+		return -ENODEV;
+
+	if (!rb || !rb->access->read_first_n)
+		return -EINVAL;
+
+	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;
+
+	to_read = min_t(size_t, n / datum_size, rb->watermark);
+
+	if (!(filp->f_flags & O_NONBLOCK))
+		to_wait = to_read;
+
+	do {
+		ret = wait_event_interruptible(rb->pollq,
+			iio_buffer_ready(indio_dev, rb, to_wait, to_read));
+		if (ret)
+			return ret;
+
+		if (!indio_dev->info)
+			return -ENODEV;
+
+		ret = rb->access->read_first_n(rb, n, buf);
+		if (ret == 0 && (filp->f_flags & O_NONBLOCK))
+			ret = -EAGAIN;
+	 } while (ret == 0);
+
+	return ret;
+}
+
+/**
+ * iio_buffer_poll() - poll the buffer to find out if it has data
+ */
+unsigned int iio_buffer_poll(struct file *filp,
+			     struct poll_table_struct *wait)
+{
+	struct iio_dev *indio_dev = filp->private_data;
+	struct iio_buffer *rb = indio_dev->buffer;
+
+	if (!indio_dev->info)
+		return -ENODEV;
+
+	poll_wait(filp, &rb->pollq, wait);
+	if (iio_buffer_ready(indio_dev, rb, rb->watermark, 0))
+		return POLLIN | POLLRDNORM;
+	return 0;
+}
+
+/**
+ * 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)
+{
+	if (!indio_dev->buffer)
+		return;
+
+	wake_up(&indio_dev->buffer->pollq);
+}
+
+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);
+	buffer->watermark = 1;
+}
+EXPORT_SYMBOL(iio_buffer_init);
+
+static ssize_t iio_show_scan_index(struct device *dev,
+				   struct device_attribute *attr,
+				   char *buf)
+{
+	return sprintf(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 sprintf(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 sprintf(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_dev *indio_dev = dev_to_iio_dev(dev);
+
+	/* Ensure ret is 0 or 1. */
+	ret = !!test_bit(to_iio_dev_attr(attr)->address,
+		       indio_dev->buffer->scan_mask);
+
+	return sprintf(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)
+{
+	if (bitmap_empty(mask, masklength))
+		return NULL;
+	while (*av_masks) {
+		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;
+
+	trialmask = kmalloc(sizeof(*trialmask)*
+			    BITS_TO_LONGS(indio_dev->masklength),
+			    GFP_KERNEL);
+
+	if (trialmask == NULL)
+		return -ENOMEM;
+	if (!indio_dev->masklength) {
+		WARN_ON("Trying to set scanmask prior to registering buffer\n");
+		goto err_invalid_mask;
+	}
+	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);
+		if (!mask)
+			goto err_invalid_mask;
+	}
+	bitmap_copy(buffer->scan_mask, trialmask, indio_dev->masklength);
+
+	kfree(trialmask);
+
+	return 0;
+
+err_invalid_mask:
+	kfree(trialmask);
+	return -EINVAL;
+}
+
+static int iio_scan_mask_clear(struct iio_buffer *buffer, int bit)
+{
+	clear_bit(bit, buffer->scan_mask);
+	return 0;
+}
+
+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_buffer *buffer = indio_dev->buffer;
+	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
+
+	ret = strtobool(buf, &state);
+	if (ret < 0)
+		return ret;
+	mutex_lock(&indio_dev->mlock);
+	if (iio_buffer_is_active(indio_dev->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_dev *indio_dev = dev_to_iio_dev(dev);
+	return sprintf(buf, "%d\n", indio_dev->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);
+	bool state;
+
+	ret = strtobool(buf, &state);
+	if (ret < 0)
+		return ret;
+
+	mutex_lock(&indio_dev->mlock);
+	if (iio_buffer_is_active(indio_dev->buffer)) {
+		ret = -EBUSY;
+		goto error_ret;
+	}
+	indio_dev->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,
+					const struct iio_chan_spec *chan)
+{
+	int ret, attrcount = 0;
+	struct iio_buffer *buffer = indio_dev->buffer;
+
+	ret = __iio_add_chan_devattr("index",
+				     chan,
+				     &iio_show_scan_index,
+				     NULL,
+				     0,
+				     IIO_SEPARATE,
+				     &indio_dev->dev,
+				     &buffer->scan_el_dev_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->scan_el_dev_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->scan_el_dev_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->scan_el_dev_attr_list);
+	if (ret)
+		return ret;
+	attrcount++;
+	ret = attrcount;
+	return ret;
+}
+
+static ssize_t iio_buffer_read_length(struct device *dev,
+				      struct device_attribute *attr,
+				      char *buf)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct iio_buffer *buffer = indio_dev->buffer;
+
+	return sprintf(buf, "%d\n", buffer->length);
+}
+
+static ssize_t iio_buffer_write_length(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 = indio_dev->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(indio_dev->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 iio_buffer_show_enable(struct device *dev,
+				      struct device_attribute *attr,
+				      char *buf)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	return sprintf(buf, "%d\n", iio_buffer_is_active(indio_dev->buffer));
+}
+
+static int iio_compute_scan_bytes(struct iio_dev *indio_dev,
+				const unsigned long *mask, bool timestamp)
+{
+	const struct iio_chan_spec *ch;
+	unsigned bytes = 0;
+	int length, i;
+
+	/* How much space will the demuxed element take? */
+	for_each_set_bit(i, mask,
+			 indio_dev->masklength) {
+		ch = iio_find_channel_from_si(indio_dev, i);
+		if (ch->scan_type.repeat > 1)
+			length = ch->scan_type.storagebits / 8 *
+				ch->scan_type.repeat;
+		else
+			length = ch->scan_type.storagebits / 8;
+		bytes = ALIGN(bytes, length);
+		bytes += length;
+	}
+	if (timestamp) {
+		ch = iio_find_channel_from_si(indio_dev,
+					      indio_dev->scan_index_timestamp);
+		if (ch->scan_type.repeat > 1)
+			length = ch->scan_type.storagebits / 8 *
+				ch->scan_type.repeat;
+		else
+			length = ch->scan_type.storagebits / 8;
+		bytes = ALIGN(bytes, length);
+		bytes += length;
+	}
+	return bytes;
+}
+
+static void iio_buffer_activate(struct iio_dev *indio_dev,
+	struct iio_buffer *buffer)
+{
+	iio_buffer_get(buffer);
+	list_add(&buffer->buffer_list, &indio_dev->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);
+}
+
+void iio_disable_all_buffers(struct iio_dev *indio_dev)
+{
+	struct iio_buffer *buffer, *_buffer;
+
+	if (list_empty(&indio_dev->buffer_list))
+		return;
+
+	if (indio_dev->setup_ops->predisable)
+		indio_dev->setup_ops->predisable(indio_dev);
+
+	list_for_each_entry_safe(buffer, _buffer,
+			&indio_dev->buffer_list, buffer_list)
+		iio_buffer_deactivate(buffer);
+
+	indio_dev->currentmode = INDIO_DIRECT_MODE;
+	if (indio_dev->setup_ops->postdisable)
+		indio_dev->setup_ops->postdisable(indio_dev);
+
+	if (indio_dev->available_scan_masks == NULL)
+		kfree(indio_dev->active_scan_mask);
+}
+
+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_update_buffers(struct iio_dev *indio_dev,
+		       struct iio_buffer *insert_buffer,
+		       struct iio_buffer *remove_buffer)
+{
+	int ret;
+	int success = 0;
+	struct iio_buffer *buffer;
+	unsigned long *compound_mask;
+	const unsigned long *old_mask;
+
+	/* Wind down existing buffers - iff there are any */
+	if (!list_empty(&indio_dev->buffer_list)) {
+		if (indio_dev->setup_ops->predisable) {
+			ret = indio_dev->setup_ops->predisable(indio_dev);
+			if (ret)
+				return ret;
+		}
+		indio_dev->currentmode = INDIO_DIRECT_MODE;
+		if (indio_dev->setup_ops->postdisable) {
+			ret = indio_dev->setup_ops->postdisable(indio_dev);
+			if (ret)
+				return ret;
+		}
+	}
+	/* Keep a copy of current setup to allow roll back */
+	old_mask = indio_dev->active_scan_mask;
+	if (!indio_dev->available_scan_masks)
+		indio_dev->active_scan_mask = NULL;
+
+	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(&indio_dev->buffer_list)) {
+		indio_dev->currentmode = INDIO_DIRECT_MODE;
+		if (indio_dev->available_scan_masks == NULL)
+			kfree(old_mask);
+		return 0;
+	}
+
+	/* What scan mask do we actually have? */
+	compound_mask = kcalloc(BITS_TO_LONGS(indio_dev->masklength),
+				sizeof(long), GFP_KERNEL);
+	if (compound_mask == NULL) {
+		if (indio_dev->available_scan_masks == NULL)
+			kfree(old_mask);
+		return -ENOMEM;
+	}
+	indio_dev->scan_timestamp = 0;
+
+	list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list) {
+		bitmap_or(compound_mask, compound_mask, buffer->scan_mask,
+			  indio_dev->masklength);
+		indio_dev->scan_timestamp |= buffer->scan_timestamp;
+	}
+	if (indio_dev->available_scan_masks) {
+		indio_dev->active_scan_mask =
+			iio_scan_mask_match(indio_dev->available_scan_masks,
+					    indio_dev->masklength,
+					    compound_mask);
+		if (indio_dev->active_scan_mask == NULL) {
+			/*
+			 * Roll back.
+			 * Note can only occur when adding a buffer.
+			 */
+			iio_buffer_deactivate(insert_buffer);
+			if (old_mask) {
+				indio_dev->active_scan_mask = old_mask;
+				success = -EINVAL;
+			}
+			else {
+				kfree(compound_mask);
+				ret = -EINVAL;
+				return ret;
+			}
+		}
+	} else {
+		indio_dev->active_scan_mask = compound_mask;
+	}
+
+	iio_update_demux(indio_dev);
+
+	/* Wind up again */
+	if (indio_dev->setup_ops->preenable) {
+		ret = indio_dev->setup_ops->preenable(indio_dev);
+		if (ret) {
+			printk(KERN_ERR
+			       "Buffer not started: buffer preenable failed (%d)\n", ret);
+			goto error_remove_inserted;
+		}
+	}
+	indio_dev->scan_bytes =
+		iio_compute_scan_bytes(indio_dev,
+				       indio_dev->active_scan_mask,
+				       indio_dev->scan_timestamp);
+	list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list) {
+		iio_buffer_update_bytes_per_datum(indio_dev, buffer);
+		if (buffer->access->request_update) {
+			ret = buffer->access->request_update(buffer);
+			if (ret) {
+				printk(KERN_INFO
+				       "Buffer not started: buffer parameter update failed (%d)\n", ret);
+				goto error_run_postdisable;
+			}
+		}
+	}
+	if (indio_dev->info->update_scan_mode) {
+		ret = indio_dev->info
+			->update_scan_mode(indio_dev,
+					   indio_dev->active_scan_mask);
+		if (ret < 0) {
+			printk(KERN_INFO "Buffer not started: update scan mode failed (%d)\n", ret);
+			goto error_run_postdisable;
+		}
+	}
+	/* Definitely possible for devices to support both of these. */
+	if ((indio_dev->modes & INDIO_BUFFER_TRIGGERED) && indio_dev->trig) {
+		indio_dev->currentmode = INDIO_BUFFER_TRIGGERED;
+	} else if (indio_dev->modes & INDIO_BUFFER_HARDWARE) {
+		indio_dev->currentmode = INDIO_BUFFER_HARDWARE;
+	} else if (indio_dev->modes & INDIO_BUFFER_SOFTWARE) {
+		indio_dev->currentmode = INDIO_BUFFER_SOFTWARE;
+	} else { /* Should never be reached */
+		/* Can only occur on first buffer */
+		if (indio_dev->modes & INDIO_BUFFER_TRIGGERED)
+			pr_info("Buffer not started: no trigger\n");
+		ret = -EINVAL;
+		goto error_run_postdisable;
+	}
+
+	if (indio_dev->setup_ops->postenable) {
+		ret = indio_dev->setup_ops->postenable(indio_dev);
+		if (ret) {
+			printk(KERN_INFO
+			       "Buffer not started: postenable failed (%d)\n", ret);
+			indio_dev->currentmode = INDIO_DIRECT_MODE;
+			if (indio_dev->setup_ops->postdisable)
+				indio_dev->setup_ops->postdisable(indio_dev);
+			goto error_disable_all_buffers;
+		}
+	}
+
+	if (indio_dev->available_scan_masks)
+		kfree(compound_mask);
+	else
+		kfree(old_mask);
+
+	return success;
+
+error_disable_all_buffers:
+	indio_dev->currentmode = INDIO_DIRECT_MODE;
+error_run_postdisable:
+	if (indio_dev->setup_ops->postdisable)
+		indio_dev->setup_ops->postdisable(indio_dev);
+error_remove_inserted:
+	if (insert_buffer)
+		iio_buffer_deactivate(insert_buffer);
+	indio_dev->active_scan_mask = old_mask;
+	kfree(compound_mask);
+	return ret;
+}
+
+int iio_update_buffers(struct iio_dev *indio_dev,
+		       struct iio_buffer *insert_buffer,
+		       struct iio_buffer *remove_buffer)
+{
+	int ret;
+
+	if (insert_buffer == remove_buffer)
+		return 0;
+
+	mutex_lock(&indio_dev->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(&indio_dev->info_exist_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(iio_update_buffers);
+
+static ssize_t iio_buffer_store_enable(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);
+	bool inlist;
+
+	ret = strtobool(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(indio_dev->buffer);
+	/* Already in desired state */
+	if (inlist == requested_state)
+		goto done;
+
+	if (requested_state)
+		ret = __iio_update_buffers(indio_dev,
+					 indio_dev->buffer, NULL);
+	else
+		ret = __iio_update_buffers(indio_dev,
+					 NULL, indio_dev->buffer);
+
+	if (ret < 0)
+		goto done;
+done:
+	mutex_unlock(&indio_dev->mlock);
+	return (ret < 0) ? ret : len;
+}
+
+static const char * const iio_scan_elements_group_name = "scan_elements";
+
+static ssize_t iio_buffer_show_watermark(struct device *dev,
+					 struct device_attribute *attr,
+					 char *buf)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct iio_buffer *buffer = indio_dev->buffer;
+
+	return sprintf(buf, "%u\n", buffer->watermark);
+}
+
+static ssize_t iio_buffer_store_watermark(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 = indio_dev->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(indio_dev->buffer)) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	buffer->watermark = val;
+
+	if (indio_dev->info->hwfifo_set_watermark)
+		indio_dev->info->hwfifo_set_watermark(indio_dev, val);
+out:
+	mutex_unlock(&indio_dev->mlock);
+
+	return ret ? ret : len;
+}
+
+static DEVICE_ATTR(length, S_IRUGO | S_IWUSR, iio_buffer_read_length,
+		   iio_buffer_write_length);
+static struct device_attribute dev_attr_length_ro = __ATTR(length,
+	S_IRUGO, iio_buffer_read_length, NULL);
+static DEVICE_ATTR(enable, S_IRUGO | S_IWUSR,
+		   iio_buffer_show_enable, iio_buffer_store_enable);
+static DEVICE_ATTR(watermark, S_IRUGO | S_IWUSR,
+		   iio_buffer_show_watermark, iio_buffer_store_watermark);
+
+static struct attribute *iio_buffer_attrs[] = {
+	&dev_attr_length.attr,
+	&dev_attr_enable.attr,
+	&dev_attr_watermark.attr,
+};
+
+int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
+{
+	struct iio_dev_attr *p;
+	struct attribute **attr;
+	struct iio_buffer *buffer = indio_dev->buffer;
+	int ret, i, attrn, attrcount, attrcount_orig = 0;
+	const struct iio_chan_spec *channels;
+
+	if (!buffer)
+		return 0;
+
+	attrcount = 0;
+	if (buffer->attrs) {
+		while (buffer->attrs[attrcount] != NULL)
+			attrcount++;
+	}
+
+	attr = kcalloc(attrcount + ARRAY_SIZE(iio_buffer_attrs) + 1,
+		       sizeof(struct attribute *), GFP_KERNEL);
+	if (!attr)
+		return -ENOMEM;
+
+	memcpy(attr, iio_buffer_attrs, sizeof(iio_buffer_attrs));
+	if (!buffer->access->set_length)
+		attr[0] = &dev_attr_length_ro.attr;
+
+	if (buffer->attrs)
+		memcpy(&attr[ARRAY_SIZE(iio_buffer_attrs)], buffer->attrs,
+		       sizeof(struct attribute *) * attrcount);
+
+	attr[attrcount + ARRAY_SIZE(iio_buffer_attrs)] = NULL;
+
+	buffer->buffer_group.name = "buffer";
+	buffer->buffer_group.attrs = attr;
+
+	indio_dev->groups[indio_dev->groupcounter++] = &buffer->buffer_group;
+
+	if (buffer->scan_el_attrs != NULL) {
+		attr = buffer->scan_el_attrs->attrs;
+		while (*attr++ != NULL)
+			attrcount_orig++;
+	}
+	attrcount = attrcount_orig;
+	INIT_LIST_HEAD(&buffer->scan_el_dev_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;
+
+			/* Establish necessary mask length */
+			if (channels[i].scan_index >
+			    (int)indio_dev->masklength - 1)
+				indio_dev->masklength
+					= channels[i].scan_index + 1;
+
+			ret = iio_buffer_add_channel_sysfs(indio_dev,
+							 &channels[i]);
+			if (ret < 0)
+				goto error_cleanup_dynamic;
+			attrcount += ret;
+			if (channels[i].type == IIO_TIMESTAMP)
+				indio_dev->scan_index_timestamp =
+					channels[i].scan_index;
+		}
+		if (indio_dev->masklength && buffer->scan_mask == NULL) {
+			buffer->scan_mask = kcalloc(BITS_TO_LONGS(indio_dev->masklength),
+						    sizeof(*buffer->scan_mask),
+						    GFP_KERNEL);
+			if (buffer->scan_mask == NULL) {
+				ret = -ENOMEM;
+				goto error_cleanup_dynamic;
+			}
+		}
+	}
+
+	buffer->scan_el_group.name = iio_scan_elements_group_name;
+
+	buffer->scan_el_group.attrs = kcalloc(attrcount + 1,
+					      sizeof(buffer->scan_el_group.attrs[0]),
+					      GFP_KERNEL);
+	if (buffer->scan_el_group.attrs == NULL) {
+		ret = -ENOMEM;
+		goto error_free_scan_mask;
+	}
+	if (buffer->scan_el_attrs)
+		memcpy(buffer->scan_el_group.attrs, buffer->scan_el_attrs,
+		       sizeof(buffer->scan_el_group.attrs[0])*attrcount_orig);
+	attrn = attrcount_orig;
+
+	list_for_each_entry(p, &buffer->scan_el_dev_attr_list, l)
+		buffer->scan_el_group.attrs[attrn++] = &p->dev_attr.attr;
+	indio_dev->groups[indio_dev->groupcounter++] = &buffer->scan_el_group;
+
+	return 0;
+
+error_free_scan_mask:
+	kfree(buffer->scan_mask);
+error_cleanup_dynamic:
+	iio_free_chan_devattr_list(&buffer->scan_el_dev_attr_list);
+	kfree(indio_dev->buffer->buffer_group.attrs);
+
+	return ret;
+}
+
+void iio_buffer_free_sysfs_and_mask(struct iio_dev *indio_dev)
+{
+	if (!indio_dev->buffer)
+		return;
+
+	kfree(indio_dev->buffer->scan_mask);
+	kfree(indio_dev->buffer->buffer_group.attrs);
+	kfree(indio_dev->buffer->scan_el_group.attrs);
+	iio_free_chan_devattr_list(&indio_dev->buffer->scan_el_dev_attr_list);
+}
+
+/**
+ * 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);
+
+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);
+};
+EXPORT_SYMBOL_GPL(iio_scan_mask_query);
+
+/**
+ * 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 from;
+	unsigned to;
+	unsigned length;
+	struct list_head l;
+};
+
+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, POLLIN | POLLRDNORM);
+	return 0;
+}
+
+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);
+	}
+}
+
+
+int iio_push_to_buffers(struct iio_dev *indio_dev, const void *data)
+{
+	int ret;
+	struct iio_buffer *buf;
+
+	list_for_each_entry(buf, &indio_dev->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);
+
+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)
+{
+	const struct iio_chan_spec *ch;
+	int ret, in_ind = -1, out_ind, length;
+	unsigned 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) {
+			in_ind = find_next_bit(indio_dev->active_scan_mask,
+					       indio_dev->masklength,
+					       in_ind + 1);
+			ch = iio_find_channel_from_si(indio_dev, in_ind);
+			if (ch->scan_type.repeat > 1)
+				length = ch->scan_type.storagebits / 8 *
+					ch->scan_type.repeat;
+			else
+				length = ch->scan_type.storagebits / 8;
+			/* Make sure we are aligned */
+			in_loc = roundup(in_loc, length) + length;
+		}
+		ch = iio_find_channel_from_si(indio_dev, in_ind);
+		if (ch->scan_type.repeat > 1)
+			length = ch->scan_type.storagebits / 8 *
+				ch->scan_type.repeat;
+		else
+			length = ch->scan_type.storagebits / 8;
+		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) {
+		ch = iio_find_channel_from_si(indio_dev,
+			indio_dev->scan_index_timestamp);
+		if (ch->scan_type.repeat > 1)
+			length = ch->scan_type.storagebits / 8 *
+				ch->scan_type.repeat;
+		else
+			length = ch->scan_type.storagebits / 8;
+		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;
+	}
+	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;
+}
+
+int iio_update_demux(struct iio_dev *indio_dev)
+{
+	struct iio_buffer *buffer;
+	int ret;
+
+	list_for_each_entry(buffer, &indio_dev->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, &indio_dev->buffer_list, buffer_list)
+		iio_buffer_demux_free(buffer);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(iio_update_demux);
+
+/**
+ * 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);