// SPDX-License-Identifier: GPL-2.0-only
/* The industrial I/O core
 *
 * Copyright (c) 2008 Jonathan Cameron
 *
 * Handling of buffer allocation / resizing.
 *
 * Things to look at here.
 * - Better memory allocation techniques?
 * - Alternative access techniques?
 */
#include <linux/atomic.h>
#include <linux/anon_inodes.h>
#include <linux/cleanup.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/device.h>
#include <linux/dma-buf.h>
#include <linux/dma-fence.h>
#include <linux/dma-resv.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/poll.h>
#include <linux/sched/signal.h>

#include <linux/iio/iio.h>
#include <linux/iio/iio-opaque.h>
#include "iio_core.h"
#include "iio_core_trigger.h"
#include <linux/iio/sysfs.h>
#include <linux/iio/buffer.h>
#include <linux/iio/buffer_impl.h>

#define DMABUF_ENQUEUE_TIMEOUT_MS 5000

MODULE_IMPORT_NS("DMA_BUF");

struct iio_dmabuf_priv {
        struct list_head entry;
        struct kref ref;

        struct iio_buffer *buffer;
        struct iio_dma_buffer_block *block;

        u64 context;

        /* Spinlock used for locking the dma_fence */
        spinlock_t lock;

        struct dma_buf_attachment *attach;
        struct sg_table *sgt;
        enum dma_data_direction dir;
        atomic_t seqno;
};

struct iio_dma_fence {
        struct dma_fence base;
        struct iio_dmabuf_priv *priv;
        struct work_struct work;
};

static const char * const iio_endian_prefix[] = {
        [IIO_BE] = "be",
        [IIO_LE] = "le",
};

static bool iio_buffer_is_active(struct iio_buffer *buf)
{
        return !list_empty(&buf->buffer_list);
}

static size_t iio_buffer_data_available(struct iio_buffer *buf)
{
        return buf->access->data_available(buf);
}

static int iio_buffer_flush_hwfifo(struct iio_dev *indio_dev,
                                   struct iio_buffer *buf, size_t required)
{
        if (!indio_dev->info->hwfifo_flush_to_buffer)
                return -ENODEV;

        return indio_dev->info->hwfifo_flush_to_buffer(indio_dev, required);
}

static bool iio_buffer_ready(struct iio_dev *indio_dev, struct iio_buffer *buf,
                             size_t to_wait, int to_flush)
{
        size_t avail;
        int flushed = 0;

        /* wakeup if the device was unregistered */
        if (!indio_dev->info)
                return true;

        /* drain the buffer if it was disabled */
        if (!iio_buffer_is_active(buf)) {
                to_wait = min_t(size_t, to_wait, 1);
                to_flush = 0;
        }

        avail = iio_buffer_data_available(buf);

        if (avail >= to_wait) {
                /* force a flush for non-blocking reads */
                if (!to_wait && avail < to_flush)
                        iio_buffer_flush_hwfifo(indio_dev, buf,
                                                to_flush - avail);
                return true;
        }

        if (to_flush)
                flushed = iio_buffer_flush_hwfifo(indio_dev, buf,
                                                  to_wait - avail);
        if (flushed <= 0)
                return false;

        if (avail + flushed >= to_wait)
                return true;

        return false;
}

/**
 * iio_buffer_read() - chrdev read for buffer access
 * @filp:       File structure pointer for the char device
 * @buf:        Destination buffer for iio buffer read
 * @n:          First n bytes to read
 * @f_ps:       Long offset provided by the user as a seek position
 *
 * This function relies on all buffer implementations having an
 * iio_buffer as their first element.
 *
 * Return: negative values corresponding to error codes or ret != 0
 *         for ending the reading activity
 **/
static ssize_t iio_buffer_read(struct file *filp, char __user *buf,
                               size_t n, loff_t *f_ps)
{
        struct iio_dev_buffer_pair *ib = filp->private_data;
        struct iio_buffer *rb = ib->buffer;
        struct iio_dev *indio_dev = ib->indio_dev;
        DEFINE_WAIT_FUNC(wait, woken_wake_function);
        size_t datum_size;
        size_t to_wait;
        int ret = 0;

        if (!indio_dev->info)
                return -ENODEV;

        if (!rb || !rb->access->read)
                return -EINVAL;

        if (rb->direction != IIO_BUFFER_DIRECTION_IN)
                return -EPERM;

        datum_size = rb->bytes_per_datum;

        /*
         * If datum_size is 0 there will never be anything to read from the
         * buffer, so signal end of file now.
         */
        if (!datum_size)
                return 0;

        if (filp->f_flags & O_NONBLOCK)
                to_wait = 0;
        else
                to_wait = min_t(size_t, n / datum_size, rb->watermark);

        add_wait_queue(&rb->pollq, &wait);
        do {
                if (!indio_dev->info) {
                        ret = -ENODEV;
                        break;
                }

                if (!iio_buffer_ready(indio_dev, rb, to_wait, n / datum_size)) {
                        if (signal_pending(current)) {
                                ret = -ERESTARTSYS;
                                break;
                        }

                        wait_woken(&wait, TASK_INTERRUPTIBLE,
                                   MAX_SCHEDULE_TIMEOUT);
                        continue;
                }

                ret = rb->access->read(rb, n, buf);
                if (ret == 0 && (filp->f_flags & O_NONBLOCK))
                        ret = -EAGAIN;
        } while (ret == 0);
        remove_wait_queue(&rb->pollq, &wait);

        return ret;
}

static size_t iio_buffer_space_available(struct iio_buffer *buf)
{
        if (buf->access->space_available)
                return buf->access->space_available(buf);

        return SIZE_MAX;
}

static ssize_t iio_buffer_write(struct file *filp, const char __user *buf,
                                size_t n, loff_t *f_ps)
{
        struct iio_dev_buffer_pair *ib = filp->private_data;
        struct iio_buffer *rb = ib->buffer;
        struct iio_dev *indio_dev = ib->indio_dev;
        DEFINE_WAIT_FUNC(wait, woken_wake_function);
        int ret = 0;
        size_t written;

        if (!indio_dev->info)
                return -ENODEV;

        if (!rb || !rb->access->write)
                return -EINVAL;

        if (rb->direction != IIO_BUFFER_DIRECTION_OUT)
                return -EPERM;

        written = 0;
        add_wait_queue(&rb->pollq, &wait);
        do {
                if (!indio_dev->info) {
                        ret = -ENODEV;
                        break;
                }

                if (!iio_buffer_space_available(rb)) {
                        if (signal_pending(current)) {
                                ret = -ERESTARTSYS;
                                break;
                        }

                        if (filp->f_flags & O_NONBLOCK) {
                                if (!written)
                                        ret = -EAGAIN;
                                break;
                        }

                        wait_woken(&wait, TASK_INTERRUPTIBLE,
                                   MAX_SCHEDULE_TIMEOUT);
                        continue;
                }

                ret = rb->access->write(rb, n - written, buf + written);
                if (ret < 0)
                        break;

                written += ret;

        } while (written != n);
        remove_wait_queue(&rb->pollq, &wait);

        return ret < 0 ? ret : written;
}

/**
 * iio_buffer_poll() - poll the buffer to find out if it has data
 * @filp:       File structure pointer for device access
 * @wait:       Poll table structure pointer for which the driver adds
 *              a wait queue
 *
 * Return: (EPOLLIN | EPOLLRDNORM) if data is available for reading
 *         or 0 for other cases
 */
static __poll_t iio_buffer_poll(struct file *filp,
                                struct poll_table_struct *wait)
{
        struct iio_dev_buffer_pair *ib = filp->private_data;
        struct iio_buffer *rb = ib->buffer;
        struct iio_dev *indio_dev = ib->indio_dev;

        if (!indio_dev->info || !rb)
                return 0;

        poll_wait(filp, &rb->pollq, wait);

        switch (rb->direction) {
        case IIO_BUFFER_DIRECTION_IN:
                if (iio_buffer_ready(indio_dev, rb, rb->watermark, 0))
                        return EPOLLIN | EPOLLRDNORM;
                break;
        case IIO_BUFFER_DIRECTION_OUT:
                if (iio_buffer_space_available(rb))
                        return EPOLLOUT | EPOLLWRNORM;
                break;
        }

        return 0;
}

ssize_t iio_buffer_read_wrapper(struct file *filp, char __user *buf,
                                size_t n, loff_t *f_ps)
{
        struct iio_dev_buffer_pair *ib = filp->private_data;
        struct iio_buffer *rb = ib->buffer;

        /* check if buffer was opened through new API */
        if (test_bit(IIO_BUSY_BIT_POS, &rb->flags))
                return -EBUSY;

        return iio_buffer_read(filp, buf, n, f_ps);
}

ssize_t iio_buffer_write_wrapper(struct file *filp, const char __user *buf,
                                 size_t n, loff_t *f_ps)
{
        struct iio_dev_buffer_pair *ib = filp->private_data;
        struct iio_buffer *rb = ib->buffer;

        /* check if buffer was opened through new API */
        if (test_bit(IIO_BUSY_BIT_POS, &rb->flags))
                return -EBUSY;

        return iio_buffer_write(filp, buf, n, f_ps);
}

__poll_t iio_buffer_poll_wrapper(struct file *filp,
                                 struct poll_table_struct *wait)
{
        struct iio_dev_buffer_pair *ib = filp->private_data;
        struct iio_buffer *rb = ib->buffer;

        /* check if buffer was opened through new API */
        if (test_bit(IIO_BUSY_BIT_POS, &rb->flags))
                return 0;

        return iio_buffer_poll(filp, wait);
}

/**
 * iio_buffer_wakeup_poll - Wakes up the buffer waitqueue
 * @indio_dev: The IIO device
 *
 * Wakes up the event waitqueue used for poll(). Should usually
 * be called when the device is unregistered.
 */
void iio_buffer_wakeup_poll(struct iio_dev *indio_dev)
{
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
        struct iio_buffer *buffer;
        unsigned int i;

        for (i = 0; i < iio_dev_opaque->attached_buffers_cnt; i++) {
                buffer = iio_dev_opaque->attached_buffers[i];
                wake_up(&buffer->pollq);
        }
}

int iio_pop_from_buffer(struct iio_buffer *buffer, void *data)
{
        if (!buffer || !buffer->access || !buffer->access->remove_from)
                return -EINVAL;

        return buffer->access->remove_from(buffer, data);
}
EXPORT_SYMBOL_GPL(iio_pop_from_buffer);

void iio_buffer_init(struct iio_buffer *buffer)
{
        INIT_LIST_HEAD(&buffer->demux_list);
        INIT_LIST_HEAD(&buffer->buffer_list);
        INIT_LIST_HEAD(&buffer->dmabufs);
        mutex_init(&buffer->dmabufs_mutex);
        init_waitqueue_head(&buffer->pollq);
        kref_init(&buffer->ref);
        if (!buffer->watermark)
                buffer->watermark = 1;
}
EXPORT_SYMBOL(iio_buffer_init);

void iio_device_detach_buffers(struct iio_dev *indio_dev)
{
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
        struct iio_buffer *buffer;
        unsigned int i;

        for (i = 0; i < iio_dev_opaque->attached_buffers_cnt; i++) {
                buffer = iio_dev_opaque->attached_buffers[i];
                iio_buffer_put(buffer);
        }

        kfree(iio_dev_opaque->attached_buffers);
}

static ssize_t iio_show_scan_index(struct device *dev,
                                   struct device_attribute *attr,
                                   char *buf)
{
        return sysfs_emit(buf, "%u\n", to_iio_dev_attr(attr)->c->scan_index);
}

static ssize_t iio_show_fixed_type(struct device *dev,
                                   struct device_attribute *attr,
                                   char *buf)
{
        struct iio_dev *indio_dev = dev_to_iio_dev(dev);
        struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
        const struct iio_scan_type *scan_type;
        u8 type;

        scan_type = iio_get_current_scan_type(indio_dev, this_attr->c);
        if (IS_ERR(scan_type))
                return PTR_ERR(scan_type);

        type = scan_type->endianness;

        if (type == IIO_CPU) {
#ifdef __LITTLE_ENDIAN
                type = IIO_LE;
#else
                type = IIO_BE;
#endif
        }
        if (scan_type->repeat > 1)
                return sysfs_emit(buf, "%s:%c%d/%dX%d>>%u\n",
                       iio_endian_prefix[type],
                       scan_type->sign,
                       scan_type->realbits,
                       scan_type->storagebits,
                       scan_type->repeat,
                       scan_type->shift);
        else
                return sysfs_emit(buf, "%s:%c%d/%d>>%u\n",
                       iio_endian_prefix[type],
                       scan_type->sign,
                       scan_type->realbits,
                       scan_type->storagebits,
                       scan_type->shift);
}

static ssize_t iio_scan_el_show(struct device *dev,
                                struct device_attribute *attr,
                                char *buf)
{
        int ret;
        struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;

        /* Ensure ret is 0 or 1. */
        ret = !!test_bit(to_iio_dev_attr(attr)->address,
                       buffer->scan_mask);

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

/* Note NULL used as error indicator as it doesn't make sense. */
static const unsigned long *iio_scan_mask_match(const unsigned long *av_masks,
                                                unsigned int masklength,
                                                const unsigned long *mask,
                                                bool strict)
{
        if (bitmap_empty(mask, masklength))
                return NULL;
        /*
         * The condition here do not handle multi-long masks correctly.
         * It only checks the first long to be zero, and will use such mask
         * as a terminator even if there was bits set after the first long.
         *
         * Correct check would require using:
         * while (!bitmap_empty(av_masks, masklength))
         * instead. This is potentially hazardous because the
         * avaliable_scan_masks is a zero terminated array of longs - and
         * using the proper bitmap_empty() check for multi-long wide masks
         * would require the array to be terminated with multiple zero longs -
         * which is not such an usual pattern.
         *
         * As writing of this no multi-long wide masks were found in-tree, so
         * the simple while (*av_masks) check is working.
         */
        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)
{
        unsigned int masklength = iio_get_masklength(indio_dev);
        const unsigned long *mask;
        unsigned long *trialmask;

        if (!masklength) {
                WARN(1, "Trying to set scanmask prior to registering buffer\n");
                return -EINVAL;
        }

        trialmask = bitmap_alloc(masklength, GFP_KERNEL);
        if (!trialmask)
                return -ENOMEM;
        bitmap_copy(trialmask, buffer->scan_mask, 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,
                                           masklength, trialmask, false);
                if (!mask)
                        goto err_invalid_mask;
        }
        bitmap_copy(buffer->scan_mask, trialmask, masklength);

        bitmap_free(trialmask);

        return 0;

err_invalid_mask:
        bitmap_free(trialmask);
        return -EINVAL;
}

static int iio_scan_mask_clear(struct iio_buffer *buffer, int bit)
{
        clear_bit(bit, buffer->scan_mask);
        return 0;
}

static int iio_scan_mask_query(struct iio_dev *indio_dev,
                               struct iio_buffer *buffer, int bit)
{
        if (bit > iio_get_masklength(indio_dev))
                return -EINVAL;

        if (!buffer->scan_mask)
                return 0;

        /* Ensure return value is 0 or 1. */
        return !!test_bit(bit, buffer->scan_mask);
};

static ssize_t iio_scan_el_store(struct device *dev,
                                 struct device_attribute *attr,
                                 const char *buf,
                                 size_t len)
{
        int ret;
        bool state;
        struct iio_dev *indio_dev = dev_to_iio_dev(dev);
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
        struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
        struct iio_buffer *buffer = this_attr->buffer;

        ret = kstrtobool(buf, &state);
        if (ret < 0)
                return ret;

        guard(mutex)(&iio_dev_opaque->mlock);
        if (iio_buffer_is_active(buffer))
                return -EBUSY;

        ret = iio_scan_mask_query(indio_dev, buffer, this_attr->address);
        if (ret < 0)
                return ret;

        if (state && ret)
                return len;

        if (state)
                ret = iio_scan_mask_set(indio_dev, buffer, this_attr->address);
        else
                ret = iio_scan_mask_clear(buffer, this_attr->address);
        if (ret)
                return ret;

        return len;
}

static ssize_t iio_scan_el_ts_show(struct device *dev,
                                   struct device_attribute *attr,
                                   char *buf)
{
        struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;

        return sysfs_emit(buf, "%d\n", buffer->scan_timestamp);
}

static ssize_t iio_scan_el_ts_store(struct device *dev,
                                    struct device_attribute *attr,
                                    const char *buf,
                                    size_t len)
{
        int ret;
        struct iio_dev *indio_dev = dev_to_iio_dev(dev);
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
        struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
        bool state;

        ret = kstrtobool(buf, &state);
        if (ret < 0)
                return ret;

        guard(mutex)(&iio_dev_opaque->mlock);
        if (iio_buffer_is_active(buffer))
                return -EBUSY;

        buffer->scan_timestamp = state;

        return len;
}

static int iio_buffer_add_channel_sysfs(struct iio_dev *indio_dev,
                                        struct iio_buffer *buffer,
                                        const struct iio_chan_spec *chan)
{
        int ret, attrcount = 0;

        ret = __iio_add_chan_devattr("index",
                                     chan,
                                     &iio_show_scan_index,
                                     NULL,
                                     0,
                                     IIO_SEPARATE,
                                     &indio_dev->dev,
                                     buffer,
                                     &buffer->buffer_attr_list);
        if (ret)
                return ret;
        attrcount++;
        ret = __iio_add_chan_devattr("type",
                                     chan,
                                     &iio_show_fixed_type,
                                     NULL,
                                     0,
                                     IIO_SEPARATE,
                                     &indio_dev->dev,
                                     buffer,
                                     &buffer->buffer_attr_list);
        if (ret)
                return ret;
        attrcount++;
        if (chan->type != IIO_TIMESTAMP)
                ret = __iio_add_chan_devattr("en",
                                             chan,
                                             &iio_scan_el_show,
                                             &iio_scan_el_store,
                                             chan->scan_index,
                                             IIO_SEPARATE,
                                             &indio_dev->dev,
                                             buffer,
                                             &buffer->buffer_attr_list);
        else
                ret = __iio_add_chan_devattr("en",
                                             chan,
                                             &iio_scan_el_ts_show,
                                             &iio_scan_el_ts_store,
                                             chan->scan_index,
                                             IIO_SEPARATE,
                                             &indio_dev->dev,
                                             buffer,
                                             &buffer->buffer_attr_list);
        if (ret)
                return ret;
        attrcount++;
        ret = attrcount;
        return ret;
}

static ssize_t length_show(struct device *dev, struct device_attribute *attr,
                           char *buf)
{
        struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;

        return sysfs_emit(buf, "%d\n", buffer->length);
}

static ssize_t length_store(struct device *dev, struct device_attribute *attr,
                            const char *buf, size_t len)
{
        struct iio_dev *indio_dev = dev_to_iio_dev(dev);
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
        struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
        unsigned int val;
        int ret;

        ret = kstrtouint(buf, 10, &val);
        if (ret)
                return ret;

        if (val == buffer->length)
                return len;

        guard(mutex)(&iio_dev_opaque->mlock);
        if (iio_buffer_is_active(buffer))
                return -EBUSY;

        buffer->access->set_length(buffer, val);

        if (buffer->length && buffer->length < buffer->watermark)
                buffer->watermark = buffer->length;

        return len;
}

static ssize_t enable_show(struct device *dev, struct device_attribute *attr,
                           char *buf)
{
        struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;

        return sysfs_emit(buf, "%d\n", iio_buffer_is_active(buffer));
}

static int iio_storage_bytes_for_si(struct iio_dev *indio_dev,
                                    unsigned int scan_index)
{
        const struct iio_chan_spec *ch;
        const struct iio_scan_type *scan_type;
        unsigned int bytes;

        ch = iio_find_channel_from_si(indio_dev, scan_index);
        scan_type = iio_get_current_scan_type(indio_dev, ch);
        if (IS_ERR(scan_type))
                return PTR_ERR(scan_type);

        bytes = scan_type->storagebits / 8;

        if (scan_type->repeat > 1)
                bytes *= scan_type->repeat;

        return bytes;
}

static int iio_storage_bytes_for_timestamp(struct iio_dev *indio_dev)
{
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);

        return iio_storage_bytes_for_si(indio_dev,
                                        iio_dev_opaque->scan_index_timestamp);
}

static int iio_compute_scan_bytes(struct iio_dev *indio_dev,
                                  const unsigned long *mask, bool timestamp)
{
        unsigned int bytes = 0;
        int length, i, largest = 0;

        /* How much space will the demuxed element take? */
        for_each_set_bit(i, mask, iio_get_masklength(indio_dev)) {
                length = iio_storage_bytes_for_si(indio_dev, i);
                if (length < 0)
                        return length;

                bytes = ALIGN(bytes, length);
                bytes += length;
                largest = max(largest, length);
        }

        if (timestamp) {
                length = iio_storage_bytes_for_timestamp(indio_dev);
                if (length < 0)
                        return length;

                bytes = ALIGN(bytes, length);
                bytes += length;
                largest = max(largest, length);
        }

        bytes = ALIGN(bytes, largest);
        return bytes;
}

static void iio_buffer_activate(struct iio_dev *indio_dev,
                                struct iio_buffer *buffer)
{
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);

        iio_buffer_get(buffer);
        list_add(&buffer->buffer_list, &iio_dev_opaque->buffer_list);
}

static void iio_buffer_deactivate(struct iio_buffer *buffer)
{
        list_del_init(&buffer->buffer_list);
        wake_up_interruptible(&buffer->pollq);
        iio_buffer_put(buffer);
}

static void iio_buffer_deactivate_all(struct iio_dev *indio_dev)
{
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
        struct iio_buffer *buffer, *_buffer;

        list_for_each_entry_safe(buffer, _buffer,
                                 &iio_dev_opaque->buffer_list, buffer_list)
                iio_buffer_deactivate(buffer);
}

static int iio_buffer_enable(struct iio_buffer *buffer,
                             struct iio_dev *indio_dev)
{
        if (!buffer->access->enable)
                return 0;
        return buffer->access->enable(buffer, indio_dev);
}

static int iio_buffer_disable(struct iio_buffer *buffer,
                              struct iio_dev *indio_dev)
{
        if (!buffer->access->disable)
                return 0;
        return buffer->access->disable(buffer, indio_dev);
}

static void iio_buffer_update_bytes_per_datum(struct iio_dev *indio_dev,
                                              struct iio_buffer *buffer)
{
        unsigned int bytes;

        if (!buffer->access->set_bytes_per_datum)
                return;

        bytes = iio_compute_scan_bytes(indio_dev, buffer->scan_mask,
                                       buffer->scan_timestamp);

        buffer->access->set_bytes_per_datum(buffer, bytes);
}

static int iio_buffer_request_update(struct iio_dev *indio_dev,
                                     struct iio_buffer *buffer)
{
        int ret;

        iio_buffer_update_bytes_per_datum(indio_dev, buffer);
        if (buffer->access->request_update) {
                ret = buffer->access->request_update(buffer);
                if (ret) {
                        dev_dbg(&indio_dev->dev,
                                "Buffer not started: buffer parameter update failed (%d)\n",
                                ret);
                        return ret;
                }
        }

        return 0;
}

static void iio_free_scan_mask(struct iio_dev *indio_dev,
                               const unsigned long *mask)
{
        /* If the mask is dynamically allocated free it, otherwise do nothing */
        if (!indio_dev->available_scan_masks)
                bitmap_free(mask);
}

struct iio_device_config {
        unsigned int mode;
        unsigned int watermark;
        const unsigned long *scan_mask;
        unsigned int scan_bytes;
        bool scan_timestamp;
};

static int iio_verify_update(struct iio_dev *indio_dev,
                             struct iio_buffer *insert_buffer,
                             struct iio_buffer *remove_buffer,
                             struct iio_device_config *config)
{
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
        unsigned int masklength = iio_get_masklength(indio_dev);
        unsigned long *compound_mask;
        const unsigned long *scan_mask;
        bool strict_scanmask = false;
        struct iio_buffer *buffer;
        bool scan_timestamp;
        unsigned int modes;

        if (insert_buffer &&
            bitmap_empty(insert_buffer->scan_mask, masklength)) {
                dev_dbg(&indio_dev->dev,
                        "At least one scan element must be enabled first\n");
                return -EINVAL;
        }

        memset(config, 0, sizeof(*config));
        config->watermark = ~0;

        /*
         * If there is just one buffer and we are removing it there is nothing
         * to verify.
         */
        if (remove_buffer && !insert_buffer &&
            list_is_singular(&iio_dev_opaque->buffer_list))
                return 0;

        modes = indio_dev->modes;

        list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list) {
                if (buffer == remove_buffer)
                        continue;
                modes &= buffer->access->modes;
                config->watermark = min(config->watermark, buffer->watermark);
        }

        if (insert_buffer) {
                modes &= insert_buffer->access->modes;
                config->watermark = min(config->watermark,
                                        insert_buffer->watermark);
        }

        /* Definitely possible for devices to support both of these. */
        if ((modes & INDIO_BUFFER_TRIGGERED) && indio_dev->trig) {
                config->mode = INDIO_BUFFER_TRIGGERED;
        } else if (modes & INDIO_BUFFER_HARDWARE) {
                /*
                 * Keep things simple for now and only allow a single buffer to
                 * be connected in hardware mode.
                 */
                if (insert_buffer && !list_empty(&iio_dev_opaque->buffer_list))
                        return -EINVAL;
                config->mode = INDIO_BUFFER_HARDWARE;
                strict_scanmask = true;
        } else if (modes & INDIO_BUFFER_SOFTWARE) {
                config->mode = INDIO_BUFFER_SOFTWARE;
        } else {
                /* Can only occur on first buffer */
                if (indio_dev->modes & INDIO_BUFFER_TRIGGERED)
                        dev_dbg(&indio_dev->dev, "Buffer not started: no trigger\n");
                return -EINVAL;
        }

        /* What scan mask do we actually have? */
        compound_mask = bitmap_zalloc(masklength, GFP_KERNEL);
        if (!compound_mask)
                return -ENOMEM;

        scan_timestamp = false;

        list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list) {
                if (buffer == remove_buffer)
                        continue;
                bitmap_or(compound_mask, compound_mask, buffer->scan_mask,
                          masklength);
                scan_timestamp |= buffer->scan_timestamp;
        }

        if (insert_buffer) {
                bitmap_or(compound_mask, compound_mask,
                          insert_buffer->scan_mask, masklength);
                scan_timestamp |= insert_buffer->scan_timestamp;
        }

        if (indio_dev->available_scan_masks) {
                scan_mask = iio_scan_mask_match(indio_dev->available_scan_masks,
                                                masklength, compound_mask,
                                                strict_scanmask);
                bitmap_free(compound_mask);
                if (!scan_mask)
                        return -EINVAL;
        } else {
                scan_mask = compound_mask;
        }

        config->scan_bytes = iio_compute_scan_bytes(indio_dev,
                                                    scan_mask, scan_timestamp);
        config->scan_mask = scan_mask;
        config->scan_timestamp = scan_timestamp;

        return 0;
}

/**
 * struct iio_demux_table - table describing demux memcpy ops
 * @from:       index to copy from
 * @to:         index to copy to
 * @length:     how many bytes to copy
 * @l:          list head used for management
 */
struct iio_demux_table {
        unsigned int from;
        unsigned int to;
        unsigned int length;
        struct list_head l;
};

static void iio_buffer_demux_free(struct iio_buffer *buffer)
{
        struct iio_demux_table *p, *q;

        list_for_each_entry_safe(p, q, &buffer->demux_list, l) {
                list_del(&p->l);
                kfree(p);
        }
}

static int iio_buffer_add_demux(struct iio_buffer *buffer,
                                struct iio_demux_table **p, unsigned int in_loc,
                                unsigned int out_loc,
                                unsigned int length)
{
        if (*p && (*p)->from + (*p)->length == in_loc &&
            (*p)->to + (*p)->length == out_loc) {
                (*p)->length += length;
        } else {
                *p = kmalloc_obj(**p);
                if (!(*p))
                        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)
{
        unsigned int masklength = iio_get_masklength(indio_dev);
        int ret, in_ind = -1, out_ind, length;
        unsigned int in_loc = 0, out_loc = 0;
        struct iio_demux_table *p = NULL;

        /* Clear out any old demux */
        iio_buffer_demux_free(buffer);
        kfree(buffer->demux_bounce);
        buffer->demux_bounce = NULL;

        /* First work out which scan mode we will actually have */
        if (bitmap_equal(indio_dev->active_scan_mask,
                         buffer->scan_mask, 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, masklength) {
                in_ind = find_next_bit(indio_dev->active_scan_mask,
                                       masklength, in_ind + 1);
                while (in_ind != out_ind) {
                        ret = iio_storage_bytes_for_si(indio_dev, in_ind);
                        if (ret < 0)
                                goto error_clear_mux_table;

                        length = ret;
                        /* Make sure we are aligned */
                        in_loc = roundup(in_loc, length) + length;
                        in_ind = find_next_bit(indio_dev->active_scan_mask,
                                               masklength, in_ind + 1);
                }
                ret = iio_storage_bytes_for_si(indio_dev, in_ind);
                if (ret < 0)
                        goto error_clear_mux_table;

                length = ret;
                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) {
                ret = iio_storage_bytes_for_timestamp(indio_dev);
                if (ret < 0)
                        goto error_clear_mux_table;

                length = ret;
                out_loc = roundup(out_loc, length);
                in_loc = roundup(in_loc, length);
                ret = iio_buffer_add_demux(buffer, &p, in_loc, out_loc, length);
                if (ret)
                        goto error_clear_mux_table;
                out_loc += length;
        }
        buffer->demux_bounce = kzalloc(out_loc, GFP_KERNEL);
        if (!buffer->demux_bounce) {
                ret = -ENOMEM;
                goto error_clear_mux_table;
        }
        return 0;

error_clear_mux_table:
        iio_buffer_demux_free(buffer);

        return ret;
}

static int iio_update_demux(struct iio_dev *indio_dev)
{
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
        struct iio_buffer *buffer;
        int ret;

        list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list) {
                ret = iio_buffer_update_demux(indio_dev, buffer);
                if (ret < 0)
                        goto error_clear_mux_table;
        }
        return 0;

error_clear_mux_table:
        list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list)
                iio_buffer_demux_free(buffer);

        return ret;
}

static int iio_enable_buffers(struct iio_dev *indio_dev,
                              struct iio_device_config *config)
{
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
        struct iio_buffer *buffer, *tmp = NULL;
        int ret;

        indio_dev->active_scan_mask = config->scan_mask;
        ACCESS_PRIVATE(indio_dev, scan_timestamp) = config->scan_timestamp;
        indio_dev->scan_bytes = config->scan_bytes;
        iio_dev_opaque->currentmode = config->mode;

        iio_update_demux(indio_dev);

        /* Wind up again */
        if (indio_dev->setup_ops->preenable) {
                ret = indio_dev->setup_ops->preenable(indio_dev);
                if (ret) {
                        dev_dbg(&indio_dev->dev,
                                "Buffer not started: buffer preenable failed (%d)\n", ret);
                        goto err_undo_config;
                }
        }

        if (indio_dev->info->update_scan_mode) {
                ret = indio_dev->info
                        ->update_scan_mode(indio_dev,
                                           indio_dev->active_scan_mask);
                if (ret < 0) {
                        dev_dbg(&indio_dev->dev,
                                "Buffer not started: update scan mode failed (%d)\n",
                                ret);
                        goto err_run_postdisable;
                }
        }

        if (indio_dev->info->hwfifo_set_watermark)
                indio_dev->info->hwfifo_set_watermark(indio_dev,
                        config->watermark);

        list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list) {
                ret = iio_buffer_enable(buffer, indio_dev);
                if (ret) {
                        tmp = buffer;
                        goto err_disable_buffers;
                }
        }

        if (iio_dev_opaque->currentmode == INDIO_BUFFER_TRIGGERED) {
                ret = iio_trigger_attach_poll_func(indio_dev->trig,
                                                   indio_dev->pollfunc);
                if (ret)
                        goto err_disable_buffers;
        }

        if (indio_dev->setup_ops->postenable) {
                ret = indio_dev->setup_ops->postenable(indio_dev);
                if (ret) {
                        dev_dbg(&indio_dev->dev,
                                "Buffer not started: postenable failed (%d)\n", ret);
                        goto err_detach_pollfunc;
                }
        }

        return 0;

err_detach_pollfunc:
        if (iio_dev_opaque->currentmode == INDIO_BUFFER_TRIGGERED) {
                iio_trigger_detach_poll_func(indio_dev->trig,
                                             indio_dev->pollfunc);
        }
err_disable_buffers:
        buffer = list_prepare_entry(tmp, &iio_dev_opaque->buffer_list, buffer_list);
        list_for_each_entry_continue_reverse(buffer, &iio_dev_opaque->buffer_list,
                                             buffer_list)
                iio_buffer_disable(buffer, indio_dev);
err_run_postdisable:
        if (indio_dev->setup_ops->postdisable)
                indio_dev->setup_ops->postdisable(indio_dev);
err_undo_config:
        iio_dev_opaque->currentmode = INDIO_DIRECT_MODE;
        indio_dev->active_scan_mask = NULL;

        return ret;
}

static int iio_disable_buffers(struct iio_dev *indio_dev)
{
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
        struct iio_buffer *buffer;
        int ret = 0;
        int ret2;

        /* Wind down existing buffers - iff there are any */
        if (list_empty(&iio_dev_opaque->buffer_list))
                return 0;

        /*
         * If things go wrong at some step in disable we still need to continue
         * to perform the other steps, otherwise we leave the device in a
         * inconsistent state. We return the error code for the first error we
         * encountered.
         */

        if (indio_dev->setup_ops->predisable) {
                ret2 = indio_dev->setup_ops->predisable(indio_dev);
                if (ret2 && !ret)
                        ret = ret2;
        }

        if (iio_dev_opaque->currentmode == INDIO_BUFFER_TRIGGERED) {
                iio_trigger_detach_poll_func(indio_dev->trig,
                                             indio_dev->pollfunc);
        }

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

        if (indio_dev->setup_ops->postdisable) {
                ret2 = indio_dev->setup_ops->postdisable(indio_dev);
                if (ret2 && !ret)
                        ret = ret2;
        }

        iio_free_scan_mask(indio_dev, indio_dev->active_scan_mask);
        indio_dev->active_scan_mask = NULL;
        iio_dev_opaque->currentmode = INDIO_DIRECT_MODE;

        return ret;
}

static int __iio_update_buffers(struct iio_dev *indio_dev,
                                struct iio_buffer *insert_buffer,
                                struct iio_buffer *remove_buffer)
{
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
        struct iio_device_config new_config;
        int ret;

        ret = iio_verify_update(indio_dev, insert_buffer, remove_buffer,
                                &new_config);
        if (ret)
                return ret;

        if (insert_buffer) {
                ret = iio_buffer_request_update(indio_dev, insert_buffer);
                if (ret)
                        goto err_free_config;
        }

        ret = iio_disable_buffers(indio_dev);
        if (ret)
                goto err_deactivate_all;

        if (remove_buffer)
                iio_buffer_deactivate(remove_buffer);
        if (insert_buffer)
                iio_buffer_activate(indio_dev, insert_buffer);

        /* If no buffers in list, we are done */
        if (list_empty(&iio_dev_opaque->buffer_list))
                return 0;

        ret = iio_enable_buffers(indio_dev, &new_config);
        if (ret)
                goto err_deactivate_all;

        return 0;

err_deactivate_all:
        /*
         * We've already verified that the config is valid earlier. If things go
         * wrong in either enable or disable the most likely reason is an IO
         * error from the device. In this case there is no good recovery
         * strategy. Just make sure to disable everything and leave the device
         * in a sane state.  With a bit of luck the device might come back to
         * life again later and userspace can try again.
         */
        iio_buffer_deactivate_all(indio_dev);

err_free_config:
        iio_free_scan_mask(indio_dev, new_config.scan_mask);
        return ret;
}

int iio_update_buffers(struct iio_dev *indio_dev,
                       struct iio_buffer *insert_buffer,
                       struct iio_buffer *remove_buffer)
{
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);

        if (insert_buffer == remove_buffer)
                return 0;

        if (insert_buffer &&
            insert_buffer->direction == IIO_BUFFER_DIRECTION_OUT)
                return -EINVAL;

        guard(mutex)(&iio_dev_opaque->info_exist_lock);
        guard(mutex)(&iio_dev_opaque->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)
                return 0;

        if (!indio_dev->info)
                return -ENODEV;

        return __iio_update_buffers(indio_dev, insert_buffer, remove_buffer);
}
EXPORT_SYMBOL_GPL(iio_update_buffers);

void iio_disable_all_buffers(struct iio_dev *indio_dev)
{
        iio_disable_buffers(indio_dev);
        iio_buffer_deactivate_all(indio_dev);
}

static ssize_t enable_store(struct device *dev, struct device_attribute *attr,
                            const char *buf, size_t len)
{
        int ret;
        bool requested_state;
        struct iio_dev *indio_dev = dev_to_iio_dev(dev);
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
        struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
        bool inlist;

        ret = kstrtobool(buf, &requested_state);
        if (ret < 0)
                return ret;

        guard(mutex)(&iio_dev_opaque->mlock);

        /* Find out if it is in the list */
        inlist = iio_buffer_is_active(buffer);
        /* Already in desired state */
        if (inlist == requested_state)
                return len;

        if (requested_state)
                ret = __iio_update_buffers(indio_dev, buffer, NULL);
        else
                ret = __iio_update_buffers(indio_dev, NULL, buffer);
        if (ret)
                return ret;

        return len;
}

static ssize_t watermark_show(struct device *dev, struct device_attribute *attr,
                              char *buf)
{
        struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;

        return sysfs_emit(buf, "%u\n", buffer->watermark);
}

static ssize_t watermark_store(struct device *dev,
                               struct device_attribute *attr,
                               const char *buf, size_t len)
{
        struct iio_dev *indio_dev = dev_to_iio_dev(dev);
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
        struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
        unsigned int val;
        int ret;

        ret = kstrtouint(buf, 10, &val);
        if (ret)
                return ret;
        if (!val)
                return -EINVAL;

        guard(mutex)(&iio_dev_opaque->mlock);

        if (val > buffer->length)
                return -EINVAL;

        if (iio_buffer_is_active(buffer))
                return -EBUSY;

        buffer->watermark = val;

        return len;
}

static ssize_t data_available_show(struct device *dev,
                                   struct device_attribute *attr, char *buf)
{
        struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;

        return sysfs_emit(buf, "%zu\n", iio_buffer_data_available(buffer));
}

static ssize_t direction_show(struct device *dev,
                              struct device_attribute *attr,
                              char *buf)
{
        struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;

        switch (buffer->direction) {
        case IIO_BUFFER_DIRECTION_IN:
                return sysfs_emit(buf, "in\n");
        case IIO_BUFFER_DIRECTION_OUT:
                return sysfs_emit(buf, "out\n");
        default:
                return -EINVAL;
        }
}

static DEVICE_ATTR_RW(length);
static struct device_attribute dev_attr_length_ro = __ATTR_RO(length);
static DEVICE_ATTR_RW(enable);
static DEVICE_ATTR_RW(watermark);
static struct device_attribute dev_attr_watermark_ro = __ATTR_RO(watermark);
static DEVICE_ATTR_RO(data_available);
static DEVICE_ATTR_RO(direction);

/*
 * When adding new attributes here, put the at the end, at least until
 * the code that handles the length/length_ro & watermark/watermark_ro
 * assignments gets cleaned up. Otherwise these can create some weird
 * duplicate attributes errors under some setups.
 */
static struct attribute *iio_buffer_attrs[] = {
        &dev_attr_length.attr,
        &dev_attr_enable.attr,
        &dev_attr_watermark.attr,
        &dev_attr_data_available.attr,
        &dev_attr_direction.attr,
};

#define to_dev_attr(_attr) container_of(_attr, struct device_attribute, attr)

static struct attribute *iio_buffer_wrap_attr(struct iio_buffer *buffer,
                                              struct attribute *attr)
{
        struct device_attribute *dattr = to_dev_attr(attr);
        struct iio_dev_attr *iio_attr;

        iio_attr = kzalloc_obj(*iio_attr);
        if (!iio_attr)
                return NULL;

        iio_attr->buffer = buffer;
        memcpy(&iio_attr->dev_attr, dattr, sizeof(iio_attr->dev_attr));
        iio_attr->dev_attr.attr.name = kstrdup_const(attr->name, GFP_KERNEL);
        if (!iio_attr->dev_attr.attr.name) {
                kfree(iio_attr);
                return NULL;
        }

        sysfs_attr_init(&iio_attr->dev_attr.attr);

        list_add(&iio_attr->l, &buffer->buffer_attr_list);

        return &iio_attr->dev_attr.attr;
}

static int iio_buffer_register_legacy_sysfs_groups(struct iio_dev *indio_dev,
                                                   struct attribute **buffer_attrs,
                                                   int buffer_attrcount,
                                                   int scan_el_attrcount)
{
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
        struct attribute_group *group;
        struct attribute **attrs;
        int ret;

        attrs = kzalloc_objs(*attrs, buffer_attrcount + 1);
        if (!attrs)
                return -ENOMEM;

        memcpy(attrs, buffer_attrs, buffer_attrcount * sizeof(*attrs));

        group = &iio_dev_opaque->legacy_buffer_group;
        group->attrs = attrs;
        group->name = "buffer";

        ret = iio_device_register_sysfs_group(indio_dev, group);
        if (ret)
                goto error_free_buffer_attrs;

        attrs = kzalloc_objs(*attrs, scan_el_attrcount + 1);
        if (!attrs) {
                ret = -ENOMEM;
                goto error_free_buffer_attrs;
        }

        memcpy(attrs, &buffer_attrs[buffer_attrcount],
               scan_el_attrcount * sizeof(*attrs));

        group = &iio_dev_opaque->legacy_scan_el_group;
        group->attrs = attrs;
        group->name = "scan_elements";

        ret = iio_device_register_sysfs_group(indio_dev, group);
        if (ret)
                goto error_free_scan_el_attrs;

        return 0;

error_free_scan_el_attrs:
        kfree(iio_dev_opaque->legacy_scan_el_group.attrs);
error_free_buffer_attrs:
        kfree(iio_dev_opaque->legacy_buffer_group.attrs);

        return ret;
}

static void iio_buffer_unregister_legacy_sysfs_groups(struct iio_dev *indio_dev)
{
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);

        kfree(iio_dev_opaque->legacy_buffer_group.attrs);
        kfree(iio_dev_opaque->legacy_scan_el_group.attrs);
}

static void iio_buffer_dmabuf_release(struct kref *ref)
{
        struct iio_dmabuf_priv *priv = container_of(ref, struct iio_dmabuf_priv, ref);
        struct dma_buf_attachment *attach = priv->attach;
        struct iio_buffer *buffer = priv->buffer;
        struct dma_buf *dmabuf = attach->dmabuf;

        dma_buf_unmap_attachment_unlocked(attach, priv->sgt, priv->dir);

        buffer->access->detach_dmabuf(buffer, priv->block);

        dma_buf_detach(attach->dmabuf, attach);
        dma_buf_put(dmabuf);
        kfree(priv);
}

static void iio_buffer_dmabuf_get(struct dma_buf_attachment *attach)
{
        struct iio_dmabuf_priv *priv = attach->importer_priv;

        kref_get(&priv->ref);
}

static void iio_buffer_dmabuf_put(struct dma_buf_attachment *attach)
{
        struct iio_dmabuf_priv *priv = attach->importer_priv;

        kref_put(&priv->ref, iio_buffer_dmabuf_release);
}

static int iio_buffer_chrdev_release(struct inode *inode, struct file *filep)
{
        struct iio_dev_buffer_pair *ib = filep->private_data;
        struct iio_dev *indio_dev = ib->indio_dev;
        struct iio_buffer *buffer = ib->buffer;
        struct iio_dmabuf_priv *priv, *tmp;

        wake_up(&buffer->pollq);

        guard(mutex)(&buffer->dmabufs_mutex);

        /* Close all attached DMABUFs */
        list_for_each_entry_safe(priv, tmp, &buffer->dmabufs, entry) {
                list_del_init(&priv->entry);
                iio_buffer_dmabuf_put(priv->attach);
        }

        kfree(ib);
        clear_bit(IIO_BUSY_BIT_POS, &buffer->flags);
        iio_device_put(indio_dev);

        return 0;
}

static int iio_dma_resv_lock(struct dma_buf *dmabuf, bool nonblock)
{
        if (!nonblock)
                return dma_resv_lock_interruptible(dmabuf->resv, NULL);

        if (!dma_resv_trylock(dmabuf->resv))
                return -EBUSY;

        return 0;
}

static struct device *iio_buffer_get_dma_dev(const struct iio_dev *indio_dev,
                                             struct iio_buffer *buffer)
{
        if (buffer->access->get_dma_dev)
                return buffer->access->get_dma_dev(buffer);

        return indio_dev->dev.parent;
}

static struct dma_buf_attachment *
iio_buffer_find_attachment(struct iio_dev_buffer_pair *ib,
                           struct dma_buf *dmabuf, bool nonblock)
{
        struct iio_buffer *buffer = ib->buffer;
        struct device *dma_dev = iio_buffer_get_dma_dev(ib->indio_dev, buffer);
        struct dma_buf_attachment *attach = NULL;
        struct iio_dmabuf_priv *priv;

        guard(mutex)(&buffer->dmabufs_mutex);

        list_for_each_entry(priv, &buffer->dmabufs, entry) {
                if (priv->attach->dev == dma_dev
                    && priv->attach->dmabuf == dmabuf) {
                        attach = priv->attach;
                        break;
                }
        }

        if (attach)
                iio_buffer_dmabuf_get(attach);

        return attach ?: ERR_PTR(-EPERM);
}

static int iio_buffer_attach_dmabuf(struct iio_dev_buffer_pair *ib,
                                    int __user *user_fd, bool nonblock)
{
        struct iio_dev *indio_dev = ib->indio_dev;
        struct iio_buffer *buffer = ib->buffer;
        struct device *dma_dev = iio_buffer_get_dma_dev(indio_dev, buffer);
        struct dma_buf_attachment *attach;
        struct iio_dmabuf_priv *priv, *each;
        struct dma_buf *dmabuf;
        int err, fd;

        if (!buffer->access->attach_dmabuf
            || !buffer->access->detach_dmabuf
            || !buffer->access->enqueue_dmabuf)
                return -EPERM;

        if (copy_from_user(&fd, user_fd, sizeof(fd)))
                return -EFAULT;

        priv = kzalloc_obj(*priv);
        if (!priv)
                return -ENOMEM;

        spin_lock_init(&priv->lock);
        priv->context = dma_fence_context_alloc(1);

        dmabuf = dma_buf_get(fd);
        if (IS_ERR(dmabuf)) {
                err = PTR_ERR(dmabuf);
                goto err_free_priv;
        }

        attach = dma_buf_attach(dmabuf, dma_dev);
        if (IS_ERR(attach)) {
                err = PTR_ERR(attach);
                goto err_dmabuf_put;
        }

        err = iio_dma_resv_lock(dmabuf, nonblock);
        if (err)
                goto err_dmabuf_detach;

        priv->dir = buffer->direction == IIO_BUFFER_DIRECTION_IN
                ? DMA_FROM_DEVICE : DMA_TO_DEVICE;

        priv->sgt = dma_buf_map_attachment(attach, priv->dir);
        if (IS_ERR(priv->sgt)) {
                err = PTR_ERR(priv->sgt);
                dev_err(&indio_dev->dev, "Unable to map attachment: %d\n", err);
                goto err_resv_unlock;
        }

        kref_init(&priv->ref);
        priv->buffer = buffer;
        priv->attach = attach;
        attach->importer_priv = priv;

        priv->block = buffer->access->attach_dmabuf(buffer, attach);
        if (IS_ERR(priv->block)) {
                err = PTR_ERR(priv->block);
                goto err_dmabuf_unmap_attachment;
        }

        dma_resv_unlock(dmabuf->resv);

        mutex_lock(&buffer->dmabufs_mutex);

        /*
         * Check whether we already have an attachment for this driver/DMABUF
         * combo. If we do, refuse to attach.
         */
        list_for_each_entry(each, &buffer->dmabufs, entry) {
                if (each->attach->dev == dma_dev
                    && each->attach->dmabuf == dmabuf) {
                        /*
                         * We unlocked the reservation object, so going through
                         * the cleanup code would mean re-locking it first.
                         * At this stage it is simpler to free the attachment
                         * using iio_buffer_dma_put().
                         */
                        mutex_unlock(&buffer->dmabufs_mutex);
                        iio_buffer_dmabuf_put(attach);
                        return -EBUSY;
                }
        }

        /* Otherwise, add the new attachment to our dmabufs list. */
        list_add(&priv->entry, &buffer->dmabufs);
        mutex_unlock(&buffer->dmabufs_mutex);

        return 0;

err_dmabuf_unmap_attachment:
        dma_buf_unmap_attachment(attach, priv->sgt, priv->dir);
err_resv_unlock:
        dma_resv_unlock(dmabuf->resv);
err_dmabuf_detach:
        dma_buf_detach(dmabuf, attach);
err_dmabuf_put:
        dma_buf_put(dmabuf);
err_free_priv:
        kfree(priv);

        return err;
}

static int iio_buffer_detach_dmabuf(struct iio_dev_buffer_pair *ib,
                                    int __user *user_req, bool nonblock)
{
        struct iio_buffer *buffer = ib->buffer;
        struct iio_dev *indio_dev = ib->indio_dev;
        struct device *dma_dev = iio_buffer_get_dma_dev(indio_dev, buffer);
        struct iio_dmabuf_priv *priv;
        struct dma_buf *dmabuf;
        int dmabuf_fd, ret = -EPERM;

        if (copy_from_user(&dmabuf_fd, user_req, sizeof(dmabuf_fd)))
                return -EFAULT;

        dmabuf = dma_buf_get(dmabuf_fd);
        if (IS_ERR(dmabuf))
                return PTR_ERR(dmabuf);

        guard(mutex)(&buffer->dmabufs_mutex);

        list_for_each_entry(priv, &buffer->dmabufs, entry) {
                if (priv->attach->dev == dma_dev
                    && priv->attach->dmabuf == dmabuf) {
                        list_del(&priv->entry);

                        /* Unref the reference from iio_buffer_attach_dmabuf() */
                        iio_buffer_dmabuf_put(priv->attach);
                        ret = 0;
                        break;
                }
        }

        dma_buf_put(dmabuf);

        return ret;
}

static const char *
iio_buffer_dma_fence_get_driver_name(struct dma_fence *fence)
{
        return "iio";
}

static void iio_buffer_dma_fence_release(struct dma_fence *fence)
{
        struct iio_dma_fence *iio_fence =
                container_of(fence, struct iio_dma_fence, base);

        kfree(iio_fence);
}

static const struct dma_fence_ops iio_buffer_dma_fence_ops = {
        .get_driver_name        = iio_buffer_dma_fence_get_driver_name,
        .get_timeline_name      = iio_buffer_dma_fence_get_driver_name,
        .release                = iio_buffer_dma_fence_release,
};

static int iio_buffer_enqueue_dmabuf(struct iio_dev_buffer_pair *ib,
                                     struct iio_dmabuf __user *iio_dmabuf_req,
                                     bool nonblock)
{
        struct iio_buffer *buffer = ib->buffer;
        struct iio_dmabuf iio_dmabuf;
        struct dma_buf_attachment *attach;
        struct iio_dmabuf_priv *priv;
        struct iio_dma_fence *fence;
        struct dma_buf *dmabuf;
        unsigned long timeout;
        bool cookie, cyclic, dma_to_ram;
        long retl;
        u32 seqno;
        int ret;

        if (copy_from_user(&iio_dmabuf, iio_dmabuf_req, sizeof(iio_dmabuf)))
                return -EFAULT;

        if (iio_dmabuf.flags & ~IIO_BUFFER_DMABUF_SUPPORTED_FLAGS)
                return -EINVAL;

        cyclic = iio_dmabuf.flags & IIO_BUFFER_DMABUF_CYCLIC;

        /* Cyclic flag is only supported on output buffers */
        if (cyclic && buffer->direction != IIO_BUFFER_DIRECTION_OUT)
                return -EINVAL;

        dmabuf = dma_buf_get(iio_dmabuf.fd);
        if (IS_ERR(dmabuf))
                return PTR_ERR(dmabuf);

        if (!iio_dmabuf.bytes_used || iio_dmabuf.bytes_used > dmabuf->size) {
                ret = -EINVAL;
                goto err_dmabuf_put;
        }

        attach = iio_buffer_find_attachment(ib, dmabuf, nonblock);
        if (IS_ERR(attach)) {
                ret = PTR_ERR(attach);
                goto err_dmabuf_put;
        }

        priv = attach->importer_priv;

        fence = kmalloc_obj(*fence);
        if (!fence) {
                ret = -ENOMEM;
                goto err_attachment_put;
        }

        fence->priv = priv;

        seqno = atomic_add_return(1, &priv->seqno);

        /*
         * The transfers are guaranteed to be processed in the order they are
         * enqueued, so we can use a simple incrementing sequence number for
         * the dma_fence.
         */
        dma_fence_init(&fence->base, &iio_buffer_dma_fence_ops,
                       &priv->lock, priv->context, seqno);

        ret = iio_dma_resv_lock(dmabuf, nonblock);
        if (ret)
                goto err_fence_put;

        timeout = nonblock ? 0 : msecs_to_jiffies(DMABUF_ENQUEUE_TIMEOUT_MS);
        dma_to_ram = buffer->direction == IIO_BUFFER_DIRECTION_IN;

        /* Make sure we don't have writers */
        retl = dma_resv_wait_timeout(dmabuf->resv,
                                     dma_resv_usage_rw(dma_to_ram),
                                     true, timeout);
        if (retl == 0)
                retl = -EBUSY;
        if (retl < 0) {
                ret = (int)retl;
                goto err_resv_unlock;
        }

        if (buffer->access->lock_queue)
                buffer->access->lock_queue(buffer);

        ret = dma_resv_reserve_fences(dmabuf->resv, 1);
        if (ret)
                goto err_queue_unlock;

        dma_resv_add_fence(dmabuf->resv, &fence->base,
                           dma_to_ram ? DMA_RESV_USAGE_WRITE : DMA_RESV_USAGE_READ);
        dma_resv_unlock(dmabuf->resv);

        cookie = dma_fence_begin_signalling();

        ret = buffer->access->enqueue_dmabuf(buffer, priv->block, &fence->base,
                                             priv->sgt, iio_dmabuf.bytes_used,
                                             cyclic);
        if (ret) {
                /*
                 * DMABUF enqueue failed, but we already added the fence.
                 * Signal the error through the fence completion mechanism.
                 */
                iio_buffer_signal_dmabuf_done(&fence->base, ret);
        }

        if (buffer->access->unlock_queue)
                buffer->access->unlock_queue(buffer);

        dma_fence_end_signalling(cookie);
        dma_buf_put(dmabuf);

        return ret;

err_queue_unlock:
        if (buffer->access->unlock_queue)
                buffer->access->unlock_queue(buffer);
err_resv_unlock:
        dma_resv_unlock(dmabuf->resv);
err_fence_put:
        dma_fence_put(&fence->base);
err_attachment_put:
        iio_buffer_dmabuf_put(attach);
err_dmabuf_put:
        dma_buf_put(dmabuf);

        return ret;
}

static void iio_buffer_cleanup(struct work_struct *work)
{
        struct iio_dma_fence *fence =
                container_of(work, struct iio_dma_fence, work);
        struct iio_dmabuf_priv *priv = fence->priv;
        struct dma_buf_attachment *attach = priv->attach;

        dma_fence_put(&fence->base);
        iio_buffer_dmabuf_put(attach);
}

void iio_buffer_signal_dmabuf_done(struct dma_fence *fence, int ret)
{
        struct iio_dma_fence *iio_fence =
                container_of(fence, struct iio_dma_fence, base);
        bool cookie = dma_fence_begin_signalling();

        /*
         * Get a reference to the fence, so that it's not freed as soon as
         * it's signaled.
         */
        dma_fence_get(fence);

        fence->error = ret;
        dma_fence_signal(fence);
        dma_fence_end_signalling(cookie);

        /*
         * The fence will be unref'd in iio_buffer_cleanup.
         * It can't be done here, as the unref functions might try to lock the
         * resv object, which can deadlock.
         */
        INIT_WORK(&iio_fence->work, iio_buffer_cleanup);
        schedule_work(&iio_fence->work);
}
EXPORT_SYMBOL_GPL(iio_buffer_signal_dmabuf_done);

static long iio_buffer_chrdev_ioctl(struct file *filp,
                                    unsigned int cmd, unsigned long arg)
{
        struct iio_dev_buffer_pair *ib = filp->private_data;
        void __user *_arg = (void __user *)arg;
        bool nonblock = filp->f_flags & O_NONBLOCK;

        switch (cmd) {
        case IIO_BUFFER_DMABUF_ATTACH_IOCTL:
                return iio_buffer_attach_dmabuf(ib, _arg, nonblock);
        case IIO_BUFFER_DMABUF_DETACH_IOCTL:
                return iio_buffer_detach_dmabuf(ib, _arg, nonblock);
        case IIO_BUFFER_DMABUF_ENQUEUE_IOCTL:
                return iio_buffer_enqueue_dmabuf(ib, _arg, nonblock);
        default:
                return -EINVAL;
        }
}

static const struct file_operations iio_buffer_chrdev_fileops = {
        .owner = THIS_MODULE,
        .llseek = noop_llseek,
        .read = iio_buffer_read,
        .write = iio_buffer_write,
        .unlocked_ioctl = iio_buffer_chrdev_ioctl,
        .compat_ioctl = compat_ptr_ioctl,
        .poll = iio_buffer_poll,
        .release = iio_buffer_chrdev_release,
};

static long iio_device_buffer_getfd(struct iio_dev *indio_dev, unsigned long arg)
{
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
        int __user *ival = (int __user *)arg;
        struct iio_dev_buffer_pair *ib;
        struct iio_buffer *buffer;
        int fd, idx, ret;

        if (copy_from_user(&idx, ival, sizeof(idx)))
                return -EFAULT;

        if (idx >= iio_dev_opaque->attached_buffers_cnt)
                return -ENODEV;

        iio_device_get(indio_dev);

        buffer = iio_dev_opaque->attached_buffers[idx];

        if (test_and_set_bit(IIO_BUSY_BIT_POS, &buffer->flags)) {
                ret = -EBUSY;
                goto error_iio_dev_put;
        }

        ib = kzalloc_obj(*ib);
        if (!ib) {
                ret = -ENOMEM;
                goto error_clear_busy_bit;
        }

        ib->indio_dev = indio_dev;
        ib->buffer = buffer;

        fd = anon_inode_getfd("iio:buffer", &iio_buffer_chrdev_fileops,
                              ib, O_RDWR | O_CLOEXEC);
        if (fd < 0) {
                ret = fd;
                goto error_free_ib;
        }

        if (copy_to_user(ival, &fd, sizeof(fd))) {
                /*
                 * "Leak" the fd, as there's not much we can do about this
                 * anyway. 'fd' might have been closed already, as
                 * anon_inode_getfd() called fd_install() on it, which made
                 * it reachable by userland.
                 *
                 * Instead of allowing a malicious user to play tricks with
                 * us, rely on the process exit path to do any necessary
                 * cleanup, as in releasing the file, if still needed.
                 */
                return -EFAULT;
        }

        return 0;

error_free_ib:
        kfree(ib);
error_clear_busy_bit:
        clear_bit(IIO_BUSY_BIT_POS, &buffer->flags);
error_iio_dev_put:
        iio_device_put(indio_dev);
        return ret;
}

static long iio_device_buffer_ioctl(struct iio_dev *indio_dev, struct file *filp,
                                    unsigned int cmd, unsigned long arg)
{
        switch (cmd) {
        case IIO_BUFFER_GET_FD_IOCTL:
                return iio_device_buffer_getfd(indio_dev, arg);
        default:
                return IIO_IOCTL_UNHANDLED;
        }
}

static int iio_channel_validate_scan_type(struct device *dev, int ch,
                                          const struct iio_scan_type *scan_type)
{
        /* Verify that sample bits fit into storage */
        if (scan_type->storagebits < scan_type->realbits + scan_type->shift) {
                dev_err(dev,
                        "Channel %d storagebits (%d) < shifted realbits (%d + %d)\n",
                        ch, scan_type->storagebits,
                        scan_type->realbits,
                        scan_type->shift);
                return -EINVAL;
        }

        return 0;
}

static int __iio_buffer_alloc_sysfs_and_mask(struct iio_buffer *buffer,
                                             struct iio_dev *indio_dev,
                                             int index)
{
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
        unsigned int masklength = iio_get_masklength(indio_dev);
        struct iio_dev_attr *p;
        const struct iio_dev_attr *id_attr;
        struct attribute **attr;
        int ret, i, attrn, scan_el_attrcount, buffer_attrcount;
        const struct iio_chan_spec *channels;

        buffer_attrcount = 0;
        if (buffer->attrs) {
                while (buffer->attrs[buffer_attrcount])
                        buffer_attrcount++;
        }
        buffer_attrcount += ARRAY_SIZE(iio_buffer_attrs);

        scan_el_attrcount = 0;
        INIT_LIST_HEAD(&buffer->buffer_attr_list);
        channels = indio_dev->channels;
        if (channels) {
                /* new magic */
                for (i = 0; i < indio_dev->num_channels; i++) {
                        const struct iio_scan_type *scan_type;

                        if (channels[i].scan_index < 0)
                                continue;

                        if (channels[i].has_ext_scan_type) {
                                int j;

                                /*
                                 * get_current_scan_type is required when using
                                 * extended scan types.
                                 */
                                if (!indio_dev->info->get_current_scan_type) {
                                        ret = -EINVAL;
                                        goto error_cleanup_dynamic;
                                }

                                for (j = 0; j < channels[i].num_ext_scan_type; j++) {
                                        scan_type = &channels[i].ext_scan_type[j];

                                        ret = iio_channel_validate_scan_type(
                                                &indio_dev->dev, i, scan_type);
                                        if (ret)
                                                goto error_cleanup_dynamic;
                                }
                        } else {
                                scan_type = &channels[i].scan_type;

                                ret = iio_channel_validate_scan_type(
                                                &indio_dev->dev, i, scan_type);
                                if (ret)
                                        goto error_cleanup_dynamic;
                        }

                        ret = iio_buffer_add_channel_sysfs(indio_dev, buffer,
                                                           &channels[i]);
                        if (ret < 0)
                                goto error_cleanup_dynamic;
                        scan_el_attrcount += ret;
                        if (channels[i].type == IIO_TIMESTAMP)
                                iio_dev_opaque->scan_index_timestamp =
                                        channels[i].scan_index;
                }
                if (masklength && !buffer->scan_mask) {
                        buffer->scan_mask = bitmap_zalloc(masklength,
                                                          GFP_KERNEL);
                        if (!buffer->scan_mask) {
                                ret = -ENOMEM;
                                goto error_cleanup_dynamic;
                        }
                }
        }

        attrn = buffer_attrcount + scan_el_attrcount;
        attr = kzalloc_objs(*attr, attrn + 1);
        if (!attr) {
                ret = -ENOMEM;
                goto error_free_scan_mask;
        }

        memcpy(attr, iio_buffer_attrs, sizeof(iio_buffer_attrs));
        if (!buffer->access->set_length)
                attr[0] = &dev_attr_length_ro.attr;

        if (buffer->access->flags & INDIO_BUFFER_FLAG_FIXED_WATERMARK)
                attr[2] = &dev_attr_watermark_ro.attr;

        if (buffer->attrs)
                for (i = 0, id_attr = buffer->attrs[i];
                     (id_attr = buffer->attrs[i]); i++)
                        attr[ARRAY_SIZE(iio_buffer_attrs) + i] =
                                (struct attribute *)&id_attr->dev_attr.attr;

        buffer->buffer_group.attrs = attr;

        for (i = 0; i < buffer_attrcount; i++) {
                struct attribute *wrapped;

                wrapped = iio_buffer_wrap_attr(buffer, attr[i]);
                if (!wrapped) {
                        ret = -ENOMEM;
                        goto error_free_buffer_attrs;
                }
                attr[i] = wrapped;
        }

        attrn = 0;
        list_for_each_entry(p, &buffer->buffer_attr_list, l)
                attr[attrn++] = &p->dev_attr.attr;

        buffer->buffer_group.name = kasprintf(GFP_KERNEL, "buffer%d", index);
        if (!buffer->buffer_group.name) {
                ret = -ENOMEM;
                goto error_free_buffer_attrs;
        }

        ret = iio_device_register_sysfs_group(indio_dev, &buffer->buffer_group);
        if (ret)
                goto error_free_buffer_attr_group_name;

        /* we only need to register the legacy groups for the first buffer */
        if (index > 0)
                return 0;

        ret = iio_buffer_register_legacy_sysfs_groups(indio_dev, attr,
                                                      buffer_attrcount,
                                                      scan_el_attrcount);
        if (ret)
                goto error_free_buffer_attr_group_name;

        return 0;

error_free_buffer_attr_group_name:
        kfree(buffer->buffer_group.name);
error_free_buffer_attrs:
        kfree(buffer->buffer_group.attrs);
error_free_scan_mask:
        bitmap_free(buffer->scan_mask);
error_cleanup_dynamic:
        iio_free_chan_devattr_list(&buffer->buffer_attr_list);

        return ret;
}

static void __iio_buffer_free_sysfs_and_mask(struct iio_buffer *buffer,
                                             struct iio_dev *indio_dev,
                                             int index)
{
        if (index == 0)
                iio_buffer_unregister_legacy_sysfs_groups(indio_dev);
        bitmap_free(buffer->scan_mask);
        kfree(buffer->buffer_group.name);
        kfree(buffer->buffer_group.attrs);
        iio_free_chan_devattr_list(&buffer->buffer_attr_list);
}

int iio_buffers_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
{
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
        const struct iio_chan_spec *channels;
        struct iio_buffer *buffer;
        int ret, i, idx;
        size_t sz;

        channels = indio_dev->channels;
        if (channels) {
                int ml = 0;

                for (i = 0; i < indio_dev->num_channels; i++)
                        ml = max(ml, channels[i].scan_index + 1);
                ACCESS_PRIVATE(indio_dev, masklength) = ml;
        }

        if (!iio_dev_opaque->attached_buffers_cnt)
                return 0;

        for (idx = 0; idx < iio_dev_opaque->attached_buffers_cnt; idx++) {
                buffer = iio_dev_opaque->attached_buffers[idx];
                ret = __iio_buffer_alloc_sysfs_and_mask(buffer, indio_dev, idx);
                if (ret)
                        goto error_unwind_sysfs_and_mask;
        }

        sz = sizeof(*iio_dev_opaque->buffer_ioctl_handler);
        iio_dev_opaque->buffer_ioctl_handler = kzalloc(sz, GFP_KERNEL);
        if (!iio_dev_opaque->buffer_ioctl_handler) {
                ret = -ENOMEM;
                goto error_unwind_sysfs_and_mask;
        }

        iio_dev_opaque->buffer_ioctl_handler->ioctl = iio_device_buffer_ioctl;
        iio_device_ioctl_handler_register(indio_dev,
                                          iio_dev_opaque->buffer_ioctl_handler);

        return 0;

error_unwind_sysfs_and_mask:
        while (idx--) {
                buffer = iio_dev_opaque->attached_buffers[idx];
                __iio_buffer_free_sysfs_and_mask(buffer, indio_dev, idx);
        }
        return ret;
}

void iio_buffers_free_sysfs_and_mask(struct iio_dev *indio_dev)
{
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
        struct iio_buffer *buffer;
        int i;

        if (!iio_dev_opaque->attached_buffers_cnt)
                return;

        iio_device_ioctl_handler_unregister(iio_dev_opaque->buffer_ioctl_handler);
        kfree(iio_dev_opaque->buffer_ioctl_handler);

        for (i = iio_dev_opaque->attached_buffers_cnt - 1; i >= 0; i--) {
                buffer = iio_dev_opaque->attached_buffers[i];
                __iio_buffer_free_sysfs_and_mask(buffer, indio_dev, i);
        }
}

/**
 * iio_validate_scan_mask_onehot() - Validates that exactly one channel is selected
 * @indio_dev: the iio device
 * @mask: scan mask to be checked
 *
 * Return true if exactly one bit is set in the scan mask, false otherwise. It
 * can be used for devices where only one channel can be active for sampling at
 * a time.
 */
bool iio_validate_scan_mask_onehot(struct iio_dev *indio_dev,
                                   const unsigned long *mask)
{
        return bitmap_weight(mask, iio_get_masklength(indio_dev)) == 1;
}
EXPORT_SYMBOL_GPL(iio_validate_scan_mask_onehot);

static const void *iio_demux(struct iio_buffer *buffer,
                             const void *datain)
{
        struct iio_demux_table *t;

        if (list_empty(&buffer->demux_list))
                return datain;
        list_for_each_entry(t, &buffer->demux_list, l)
                memcpy(buffer->demux_bounce + t->to,
                       datain + t->from, t->length);

        return buffer->demux_bounce;
}

static int iio_push_to_buffer(struct iio_buffer *buffer, const void *data)
{
        const void *dataout = iio_demux(buffer, data);
        int ret;

        ret = buffer->access->store_to(buffer, dataout);
        if (ret)
                return ret;

        /*
         * We can't just test for watermark to decide if we wake the poll queue
         * because read may request less samples than the watermark.
         */
        wake_up_interruptible_poll(&buffer->pollq, EPOLLIN | EPOLLRDNORM);
        return 0;
}

/**
 * iio_push_to_buffers() - push to a registered buffer.
 * @indio_dev:          iio_dev structure for device.
 * @data:               Full scan.
 *
 * Context: Any context.
 * Return: 0 on success, negative error code on failure.
 */
int iio_push_to_buffers(struct iio_dev *indio_dev, const void *data)
{
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
        int ret;
        struct iio_buffer *buf;

        list_for_each_entry(buf, &iio_dev_opaque->buffer_list, buffer_list) {
                ret = iio_push_to_buffer(buf, data);
                if (ret < 0)
                        return ret;
        }

        return 0;
}
EXPORT_SYMBOL_GPL(iio_push_to_buffers);

/**
 * iio_push_to_buffers_with_ts_unaligned() - push to registered buffer,
 *    no alignment or space requirements.
 * @indio_dev:          iio_dev structure for device.
 * @data:               channel data excluding the timestamp.
 * @data_sz:            size of data.
 * @timestamp:          timestamp for the sample data.
 *
 * This special variant of iio_push_to_buffers_with_timestamp() does
 * not require space for the timestamp, or 8 byte alignment of data.
 * It does however require an allocation on first call and additional
 * copies on all calls, so should be avoided if possible.
 *
 * Context: May sleep.
 * Return: 0 on success, negative error code on failure.
 */
int iio_push_to_buffers_with_ts_unaligned(struct iio_dev *indio_dev,
                                          const void *data,
                                          size_t data_sz,
                                          int64_t timestamp)
{
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);

        might_sleep();

        /*
         * Conservative estimate - we can always safely copy the minimum
         * of either the data provided or the length of the destination buffer.
         * This relaxed limit allows the calling drivers to be lax about
         * tracking the size of the data they are pushing, at the cost of
         * unnecessary copying of padding.
         */
        data_sz = min_t(size_t, indio_dev->scan_bytes, data_sz);
        if (iio_dev_opaque->bounce_buffer_size !=  indio_dev->scan_bytes) {
                void *bb;

                bb = devm_krealloc(&indio_dev->dev,
                                   iio_dev_opaque->bounce_buffer,
                                   indio_dev->scan_bytes, GFP_KERNEL);
                if (!bb)
                        return -ENOMEM;
                iio_dev_opaque->bounce_buffer = bb;
                iio_dev_opaque->bounce_buffer_size = indio_dev->scan_bytes;
        }
        memcpy(iio_dev_opaque->bounce_buffer, data, data_sz);
        return iio_push_to_buffers_with_timestamp(indio_dev,
                                                  iio_dev_opaque->bounce_buffer,
                                                  timestamp);
}
EXPORT_SYMBOL_GPL(iio_push_to_buffers_with_ts_unaligned);

/**
 * iio_buffer_release() - Free a buffer's resources
 * @ref: Pointer to the kref embedded in the iio_buffer struct
 *
 * This function is called when the last reference to the buffer has been
 * dropped. It will typically free all resources allocated by the buffer. Do not
 * call this function manually, always use iio_buffer_put() when done using a
 * buffer.
 */
static void iio_buffer_release(struct kref *ref)
{
        struct iio_buffer *buffer = container_of(ref, struct iio_buffer, ref);

        mutex_destroy(&buffer->dmabufs_mutex);
        buffer->access->release(buffer);
}

/**
 * iio_buffer_get() - Grab a reference to the buffer
 * @buffer: The buffer to grab a reference for, may be NULL
 *
 * Returns the pointer to the buffer that was passed into the function.
 */
struct iio_buffer *iio_buffer_get(struct iio_buffer *buffer)
{
        if (buffer)
                kref_get(&buffer->ref);

        return buffer;
}
EXPORT_SYMBOL_GPL(iio_buffer_get);

/**
 * iio_buffer_put() - Release the reference to the buffer
 * @buffer: The buffer to release the reference for, may be NULL
 */
void iio_buffer_put(struct iio_buffer *buffer)
{
        if (buffer)
                kref_put(&buffer->ref, iio_buffer_release);
}
EXPORT_SYMBOL_GPL(iio_buffer_put);

/**
 * iio_device_attach_buffer - Attach a buffer to a IIO device
 * @indio_dev: The device the buffer should be attached to
 * @buffer: The buffer to attach to the device
 *
 * Return 0 if successful, negative if error.
 *
 * This function attaches a buffer to a IIO device. The buffer stays attached to
 * the device until the device is freed. For legacy reasons, the first attached
 * buffer will also be assigned to 'indio_dev->buffer'.
 * The array allocated here, will be free'd via the iio_device_detach_buffers()
 * call which is handled by the iio_device_free().
 */
int iio_device_attach_buffer(struct iio_dev *indio_dev,
                             struct iio_buffer *buffer)
{
        struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
        struct iio_buffer **new, **old = iio_dev_opaque->attached_buffers;
        unsigned int cnt = iio_dev_opaque->attached_buffers_cnt;

        cnt++;

        new = krealloc(old, sizeof(*new) * cnt, GFP_KERNEL);
        if (!new)
                return -ENOMEM;
        iio_dev_opaque->attached_buffers = new;

        buffer = iio_buffer_get(buffer);

        /* first buffer is legacy; attach it to the IIO device directly */
        if (!indio_dev->buffer)
                indio_dev->buffer = buffer;

        iio_dev_opaque->attached_buffers[cnt - 1] = buffer;
        iio_dev_opaque->attached_buffers_cnt = cnt;

        return 0;
}
EXPORT_SYMBOL_GPL(iio_device_attach_buffer);