path: root/drivers/iio/industrialio-buffer.c

/* The industrial I/O core
 *
 * Copyright (c) 2008 Jonathan Cameron
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 *
 * Handling of buffer allocation / resizing.
 *
 *
 * Things to look at here.
 * - Better memory allocation techniques?
 * - Alternative access techniques?
 */
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/slab.h>
#include <linux/poll.h>
#include <linux/sched.h>

#include <linux/iio/iio.h>
#include "iio_core.h"
#include <linux/iio/sysfs.h>
#include <linux/iio/buffer.h>

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

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

static bool iio_buffer_data_available(struct iio_buffer *buf)
{
	if (buf->access->data_available)
		return buf->access->data_available(buf);

	return buf->stufftoread;
}

/**
 * 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;
	int ret;

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

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

	do {
		if (!iio_buffer_data_available(rb)) {
			if (filp->f_flags & O_NONBLOCK)
				return -EAGAIN;

			ret = wait_event_interruptible(rb->pollq,
					iio_buffer_data_available(rb) ||
					indio_dev->info == NULL);
			if (ret)
				return ret;
			if (indio_dev->info == NULL)
				return -ENODEV;
		}

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

	return ret;
}

/**
 * iio_buffer_poll() - poll the buffer to find out if it has data
 */
unsigned int iio_buffer_poll(struct file *filp,
			     struct poll_table_struct *wait)
{
	struct iio_dev *indio_dev = filp->private_data;
	struct iio_buffer *rb = indio_dev->buffer;

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

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

/**
 * iio_buffer_wakeup_poll - Wakes up the buffer waitqueue
 * @indio_dev: The IIO device
 *
 * Wakes up the event waitqueue used for poll(). Should usually
 * be called when the device is unregistered.
 */
void iio_buffer_wakeup_poll(struct iio_dev *indio_dev)
{
	if (!indio_dev->buffer)
		return;

	wake_up(&indio_dev->buffer->pollq);
}

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