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

// 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/kernel.h>
#include <linux/export.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/slab.h>
#include <linux/poll.h>
#include <linux/sched/signal.h>

#include <linux/iio/iio.h>
#include <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>

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

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

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

	datum_size = rb->bytes_per_datum;

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

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

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

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

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

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

	return ret;
}

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

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

	poll_wait(filp, &rb->pollq, wait);
	if (iio_buffer_ready(indio_dev, rb, rb->watermark, 0))
		return EPOLLIN | EPOLLRDNORM;
	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)
{
	struct iio_buffer *buffer = indio_dev->buffer;

	if (!buffer)
		return;

	wake_up(&buffer->pollq);
}

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

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

static ssize_t iio_show_fixed_type(struct device *dev,
				   struct device_attribute *attr,
				   char *buf)
{
	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
	u8 type = this_attr->c->scan_type.endianness;

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

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

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

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

/* Note NULL used as error indicator as it doesn't make sense. */
static const unsigned long *iio_scan_mask_match(const unsigned long *av_masks,
					  unsigned int masklength,
					  const unsigned long *mask,
					  bool strict)
{
	if (bitmap_empty(mask, masklength))
		return NULL;
	while (*av_masks) {
		if (strict) {
			if (bitmap_equal(mask, av_masks, masklength))
				return av_masks;
		} else {
			if (bitmap_subset(mask, av_masks, masklength))
				return av_masks;
		}
		av_masks += BITS_TO_LONGS(masklength);
	}
	return NULL;
}

static bool iio_validate_scan_mask(struct iio_dev *indio_dev,
	const unsigned long *mask)
{
	if (!indio_dev->setup_ops->validate_scan_mask)
		return true;

	return indio_dev->setup_ops->validate_scan_mask(indio_dev, mask);
}

/**
 * iio_scan_mask_set() - set particular bit in the scan mask
 * @indio_dev: the iio device
 * @buffer: the buffer whose scan mask we are interested in
 * @bit: the bit to be set.
 *
 * Note that at this point we have no way of knowing what other
 * buffers might request, hence this code only verifies that the
 * individual buffers request is plausible.
 */
static int iio_scan_mask_set(struct iio_dev *indio_dev,
		      struct iio_buffer *buffer, int bit)
{
	const unsigned long *mask;
	unsigned long *trialmask;

	trialmask = bitmap_zalloc(indio_dev->masklength, GFP_KERNEL);
	if (trialmask == NULL)
		return -ENOMEM;
	if (!indio_dev->masklength) {
		WARN(1, "Tryin