/* 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/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_dev *indio_dev,
                                 struct iio_buffer *buf)
{
        struct list_head *p;

        list_for_each(p, &indio_dev->buffer_list)
                if (p == &buf->buffer_list)
                        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;

        if (!rb || !rb->access->read_first_n)
                return -EINVAL;
        return rb->access->read_first_n(rb, n, buf);
}

/**
 * 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;

        poll_wait(filp, &rb->pollq, wait);
        if (rb->stufftoread)
                return POLLIN | POLLRDNORM;
        /* need a way of knowing if there may be enough data... */
        return 0;
}

void iio_buffer_init(struct iio_buffer *buffer)
{
        INIT_LIST_HEAD(&buffer->demux_list);
        init_waitqueue_head(&buffer->pollq);
}
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
        }
        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);

        ret = test_bit(to_iio_dev_attr(attr)->address,
                       indio_dev->buffer->scan_mask);

        return sprintf(buf, "%d\n", ret);
}

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, 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, 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,
                                     0,
                                     &indio_dev->dev,
                                     &buffer->scan_el_dev_attr_list);
        if (ret)
                goto error_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)
                goto error_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);
        attrcount++;
        ret = attrcount;
error_ret:
        return ret;
}

static void iio_buffer_remove_and_free_scan_dev_attr(struct iio_dev *indio_dev,
                                                     struct iio_dev_attr *p)
{
        kfree(p->dev_attr.attr.name);
        kfree(p);
}

static void __iio_buffer_attr_cleanup(struct iio_dev *indio_dev)
{
        struct iio_dev_attr *p, *n;
        struct iio_buffer *buffer = indio_dev->buffer;

        list_for_each_entry_safe(p, n,
                                 &buffer->scan_el_dev_attr_list, l)
                iio_buffer_remove_and_free_scan_dev_attr(indio_dev, p);
}

static const char * const iio_scan_elements_group_name = "scan_elements";

int iio_buffer_register(struct iio_dev *indio_dev,
                        const struct iio_chan_spec *channels,
                        int num_channels)
{
        struct iio_dev_attr *p;
        struct attribute **attr;
        struct iio_buffer *buffer = indio_dev->buffer;
        int ret, i, attrn, attrcount, attrcount_orig = 0;

        if (buffer->attrs)
                indio_dev->groups[indio_dev->groupcounter++] = buffer->attrs;

        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);
        if (channels) {
                /* new magic */
                for (i = 0; i < 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_buffer_attr_cleanup(indio_dev);

        return ret;
}
EXPORT_SYMBOL(iio_buffer_register);

void iio_buffer_unregister(struct iio_dev *indio_dev)
{
        kfree(indio_dev->buffer->scan_mask);
        kfree(indio_dev->buffer->scan_el_group.attrs);
        __iio_buffer_attr_cleanup(indio_dev);
}
EXPORT_SYMBOL(iio_buffer_unregister);

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;

        if (buffer->access->get_length)
                return sprintf(buf, "%d\n",
                               buffer->access->get_length(buffer));

        return 0;
}
EXPORT_SYMBOL(iio_buffer_read_length);

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 (buffer->access->get_length)
                if (val == buffer->access->get_length(buffer))
                        return len;

        mutex_lock(&indio_dev->mlock);
        if (iio_buffer_is_active(indio_dev, indio_dev->buffer)) {
                ret = -EBUSY;
        } else {
                if (buffer->access->set_length)
                        buffer->access->set_length(buffer, val);
                ret = 0;
        }
        mutex_unlock(&indio_dev->mlock);

        return ret ? ret : len;
}
EXPORT_SYMBOL(iio_buffer_write_length);

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,
                                            indio_dev->buffer));
}
EXPORT_SYMBOL(iio_buffer_show_enable);

/* 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 int iio_compute_scan_bytes(struct iio_dev *indio_dev, const 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);
                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);
                length = ch->scan_type.storagebits / 8;
                bytes = ALIGN(bytes, length);
                bytes += length;
        }
        return bytes;
}

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)
                                goto error_ret;
                }
                indio_dev->currentmode = INDIO_DIRECT_MODE;
                if (indio_dev->setup_ops->postdisable) {
                        ret = indio_dev->setup_ops->postdisable(indio_dev);
                        if (ret)
                                goto error_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)
                list_del(&remove_buffer->buffer_list);
        if (insert_buffer)
                list_add(&insert_buffer->buffer_list, &indio_dev->buffer_list);

        /* 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.
                         */
                        list_del(&insert_buffer->buffer_list);
                        indio_dev->active_scan_mask = old_mask;
                        success = -EINVAL;
                }
        } 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)
                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) {
                if (!indio_dev->trig) {
                        printk(KERN_INFO "Buffer not started: no trigger\n");
                        ret = -EINVAL;
                        /* Can only occur on first buffer */
                        goto error_run_postdisable;
                }
                indio_dev->currentmode = INDIO_BUFFER_TRIGGERED;
        } else if (indio_dev->modes & INDIO_BUFFER_HARDWARE) {
                indio_dev->currentmode = INDIO_BUFFER_HARDWARE;
        } else { /* should never be reached */
                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)
                list_del(&insert_buffer->buffer_list);
        indio_dev->active_scan_mask = old_mask;
        kfree(compound_mask);
error_ret:

        return ret;
}
EXPORT_SYMBOL_GPL(iio_update_buffers);

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);
        struct iio_buffer *pbuf = indio_dev->buffer;
        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, pbuf);
        /* 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;
}
EXPORT_SYMBOL(iio_buffer_store_enable);

int iio_sw_buffer_preenable(struct iio_dev *indio_dev)
{
        struct iio_buffer *buffer;
        unsigned bytes;
        dev_dbg(&indio_dev->dev, "%s\n", __func__);

        list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list)
                if (buffer->access->set_bytes_per_datum) {
                        bytes = iio_compute_scan_bytes(indio_dev,
                                                       buffer->scan_mask,
                                                       buffer->scan_timestamp);

                        buffer->access->set_bytes_per_datum(buffer, bytes);
                }
        return 0;
}
EXPORT_SYMBOL(iio_sw_buffer_preenable);

/**
 * 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 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
 * @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.
 */
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;
}
EXPORT_SYMBOL_GPL(iio_scan_mask_set);

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;

        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 unsigned char *iio_demux(struct iio_buffer *buffer,
                                 unsigned char *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, unsigned char *data)
{
        unsigned char *dataout = iio_demux(buffer, data);

        return buffer->access->store_to(buffer, dataout);
}

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, unsigned char *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_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;

        /* 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,
                         indio_dev->active_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);
                        length = ch->scan_type.storagebits/8;
                        /* Make sure we are aligned */
                        in_loc += length;
                        if (in_loc % length)
                                in_loc += length - in_loc % length;
                }
                p = kmalloc(sizeof(*p), GFP_KERNEL);
                if (p == NULL) {
                        ret = -ENOMEM;
                        goto error_clear_mux_table;
                }
                ch = iio_find_channel_from_si(indio_dev, in_ind);
                length = ch->scan_type.storagebits/8;
                if (out_loc % length)
                        out_loc += length - out_loc % length;
                if (in_loc % length)
                        in_loc += length - in_loc % length;
                p->from = in_loc;
                p->to = out_loc;
                p->length = length;
                list_add_tail(&p->l, &buffer->demux_list);
                out_loc += length;
                in_loc += length;
        }
        /* Relies on scan_timestamp being last */
        if (buffer->scan_timestamp) {
                p = kmalloc(sizeof(*p), GFP_KERNEL);
                if (p == NULL) {
                        ret = -ENOMEM;
                        goto error_clear_mux_table;
                }
                ch = iio_find_channel_from_si(indio_dev,
                        indio_dev->scan_index_timestamp);
                length = ch->scan_type.storagebits/8;
                if (out_loc % length)
                        out_loc += length - out_loc % length;
                if (in_loc % length)
                        in_loc += length - in_loc % length;
                p->from = in_loc;
                p->to = out_loc;
                p->length = length;
                list_add_tail(&p->l, &buffer->demux_list);
                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);