/* 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/signal.h>

  #include <linux/iio/iio.h>

  #include "iio_core.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_first_n_outer() - 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

   **/

  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;

  	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_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;

  	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_first_n(rb, n, buf);
  		if (ret == 0 && (filp->f_flags & O_NONBLOCK))
  			ret = -EAGAIN;

  	} while (ret == 0);

  	remove_wait_queue(&rb->pollq, &wait);

  
  	return ret;

  }

  /**

   * 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: (POLLIN | POLLRDNORM) if data is available for reading
   *	   or 0 for other cases

   */

  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 || rb == NULL)

  		return 0;

  	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);

  	if (!buffer->watermark)
  		buffer->watermark = 1;

  }

  EXPORT_SYMBOL(iio_buffer_init);

  /**
   * iio_buffer_set_attrs - Set buffer specific attributes
   * @buffer: The buffer for which we are setting attributes
   * @attrs: Pointer to a null terminated list of pointers to attributes
   */
  void iio_buffer_set_attrs(struct iio_buffer *buffer,
  			 const struct attribute **attrs)
  {
  	buffer->attrs = attrs;
  }
  EXPORT_SYMBOL_GPL(iio_buffer_set_attrs);

  static ssize_t iio_show_scan_index(struct device *dev,

  				   struct device_attribute *attr,
  				   char *buf)

  {

  	return sprintf(buf, "%u
  ", 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
  ",
  		       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
  ",

  		       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
  ", 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;

  	trialmask = kmalloc_array(BITS_TO_LONGS(indio_dev->masklength),
  				  sizeof(*trialmask),
  				  GFP_KERNEL);

  	if (trialmask == NULL)
  		return -ENOMEM;
  	if (!indio_dev->masklength) {

  		WARN(1, "Trying to set scanmask prior to registering buffer
  ");

  		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, false);

  		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 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_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
  ", 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
  ", 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
  ", iio_buffer_is_active(indio_dev->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)
  {
  	return iio_storage_bytes_for_si(indio_dev,
  					indio_dev->scan_index_timestamp);
  }

  static int iio_compute_scan_bytes(struct iio_dev *indio_dev,
  				const unsigned long *mask, bool timestamp)

  {

  	unsigned bytes = 0;
  	int length, i;

  
  	/* 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;
  	}

  	if (timestamp) {

  		length = iio_storage_bytes_for_timestamp(indio_dev);

  		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);
  }

  static void iio_buffer_deactivate_all(struct iio_dev *indio_dev)
  {
  	struct iio_buffer *buffer, *_buffer;
  
  	list_for_each_entry_safe(buffer, _buffer,
  			&indio_dev->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)
  ",
  				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)
  		kfree(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)
  {
  	unsigned long *compound_mask;
  	const unsigned long *scan_mask;

  	bool strict_scanmask = false;

  	struct iio_buffer *buffer;
  	bool scan_timestamp;

  	unsigned int modes;

  
  	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(&indio_dev->buffer_list))
  			return 0;

  	modes = indio_dev->modes;
  
  	list_for_each_entry(buffer, &indio_dev->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(&indio_dev->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
  ");
  		return -EINVAL;
  	}
  
  	/* What scan mask do we actually have? */
  	compound_mask = kcalloc(BITS_TO_LONGS(indio_dev->masklength),
  				sizeof(long), GFP_KERNEL);
  	if (compound_mask == NULL)
  		return -ENOMEM;
  
  	scan_timestamp = false;
  
  	list_for_each_entry(buffer, &indio_dev->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);

  		kfree(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 from;
  	unsigned to;
  	unsigned 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 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);
  			length = iio_storage_bytes_for_si(indio_dev, in_ind);
  			/* Make sure we are aligned */
  			in_loc = roundup(in_loc, length) + length;
  		}
  		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;
  		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;
  }
  
  static 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;
  }

  static int iio_enable_buffers(struct iio_dev *indio_dev,
  	struct iio_device_config *config)

  {

  	struct iio_buffer *buffer;

  	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_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)
  ", 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)
  ",
  				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, &indio_dev->buffer_list, buffer_list) {
  		ret = iio_buffer_enable(buffer, indio_dev);
  		if (ret)
  			goto err_disable_buffers;
  	}

  	indio_dev->currentmode = config->mode;

  
  	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)
  ", ret);

  			goto err_disable_buffers;

  		}
  	}

  	return 0;

  err_disable_buffers:
  	list_for_each_entry_continue_reverse(buffer, &indio_dev->buffer_list,
  					     buffer_list)
  		iio_buffer_disable(buffer, indio_dev);

  err_run_postdisable:

  	indio_dev->currentmode = INDIO_DIRECT_MODE;

  	if (indio_dev->setup_ops->postdisable)
  		indio_dev->setup_ops->postdisable(indio_dev);

  err_undo_config:
  	indio_dev->active_scan_mask = NULL;

  	return ret;

  }
  
  static int iio_disable_buffers(struct iio_dev *indio_dev)
  {

  	struct iio_buffer *buffer;

  	int ret = 0;
  	int ret2;

  
  	/* Wind down existing buffers - iff there are any */
  	if (list_empty(&indio_dev->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;

  	}

  
  	list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list) {
  		ret2 = iio_buffer_disable(buffer, indio_dev);
  		if (ret2 && !ret)
  			ret = ret2;
  	}

  
  	indio_dev->currentmode = INDIO_DIRECT_MODE;
  
  	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;
  
  	return ret;

  }
  
  static int __iio_update_buffers(struct iio_dev *indio_dev,
  		       struct iio_buffer *insert_buffer,
  		       struct iio_buffer *remove_buffer)
  {

  	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(&indio_dev->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)
  {
  	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);

  void iio_disable_all_buffers(struct iio_dev *indio_dev)
  {

  	iio_disable_buffers(indio_dev);

  	iio_buffer_deactivate_all(indio_dev);

  }

  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);

  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
  ", 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;
  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 device_attribute dev_attr_watermark_ro = __ATTR(watermark,
  	S_IRUGO, iio_buffer_show_watermark, NULL);

  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;

  	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 (!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->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 *) * 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;

  			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);

  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;

  }

  /**
   * 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)

  {
  	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);

  /**
   * 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
   *
   * This function attaches a buffer to a IIO device. The buffer stays attached to
   * the device until the device is freed. The function should only be called at
   * most once per device.
   */
  void iio_device_attach_buffer(struct iio_dev *indio_dev,
  			      struct iio_buffer *buffer)
  {
  	indio_dev->buffer = iio_buffer_get(buffer);
  }
  EXPORT_SYMBOL_GPL(iio_device_attach_buffer);