drivers/staging/iio/iio_hwmon.c

/* Hwmon client for industrial I/O devices
 *
 * Copyright (c) 2011 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.
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/err.h>
#include <linux/platform_device.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/iio/consumer.h>
#include <linux/iio/types.h>

/**
 * struct iio_hwmon_state - device instance state
 * @channels:		filled with array of channels from iio
 * @num_channels:	number of channels in channels (saves counting twice)
 * @hwmon_dev:		associated hwmon device
 * @attr_group:	the group of attributes
 * @attrs:		null terminated array of attribute pointers.
 */
struct iio_hwmon_state {
	struct iio_channel *channels;
	int num_channels;
	struct device *hwmon_dev;
	struct attribute_group attr_group;
	struct attribute **attrs;
};

/*
 * Assumes that IIO and hwmon operate in the same base units.
 * This is supposed to be true, but needs verification for
 * new channel types.
 */
static ssize_t iio_hwmon_read_val(struct device *dev,
				  struct device_attribute *attr,
				  char *buf)
{
	long result;
	int val, ret, scaleint, scalepart;
	struct sensor_device_attribute *sattr = to_sensor_dev_attr(attr);
	struct iio_hwmon_state *state = dev_get_drvdata(dev);

	/*
	 * No locking between this pair, so theoretically possible
	 * the scale has changed.
	 */
	ret = iio_read_channel_raw(&state->channels[sattr->index],
				      &val);
	if (ret < 0)
		return ret;

	ret = iio_read_channel_scale(&state->channels[sattr->index],
					&scaleint, &scalepart);
	if (ret < 0)
		return ret;
	switch (ret) {
	case IIO_VAL_INT:
		result = val * scaleint;
		break;
	case IIO_VAL_INT_PLUS_MICRO:
		result = (s64)val * (s64)scaleint +
			div_s64((s64)val * (s64)scalepart, 1000000LL);
		break;
	case IIO_VAL_INT_PLUS_NANO:
		result = (s64)val * (s64)scaleint +
			div_s64((s64)val * (s64)scalepart, 1000000000LL);
		break;
	default:
		return -EINVAL;
	}
	return sprintf(buf, "%ld\n", result);
}

static void iio_hwmon_free_attrs(struct iio_hwmon_state *st)
{
	int i;
	struct sensor_device_attribute *a;
	for (i = 0; i < st->num_channels; i++)
		if (st->attrs[i]) {
			a = to_sensor_dev_attr(
				container_of(st->attrs[i],
					     struct device_attribute,
					     attr));
			kfree(a);
		}
}

static int __devinit iio_hwmon_probe(struct platform_device *pdev)
{
	struct iio_hwmon_state *st;
	struct sensor_device_attribute *a;
	int ret, i;
	int in_i = 1, temp_i = 1, curr_i = 1;
	enum iio_chan_type type;

	st = kzalloc(sizeof(*st), GFP_KERNEL);
	if (st == NULL) {
		ret = -ENOMEM;
		goto error_ret;
	}

	st->channels = iio_channel_get_all(dev_name(&pdev->dev));
	if (IS_ERR(st->channels)) {
		ret = PTR_ERR(st->channels);
		goto error_free_state;
	}

	/* count how many attributes we have */
	while (st->channels[st->num_channels].indio_dev)
		st->num_channels++;

	st->attrs = kzalloc(sizeof(st->attrs) * (st->num_channels + 1),
			    GFP_KERNEL);
	if (st->attrs == NULL) {
		ret = -ENOMEM;
		goto error_release_channels;
	}
	for (i = 0; i < st->num_channels; i++) {
		a = kzalloc(sizeof(*a), GFP_KERNEL);
		if (a == NULL) {
			ret = -ENOMEM;
			goto error_free_attrs;
		}

		sysfs_attr_init(&a->dev_attr.attr);
		ret = iio_get_channel_type(&st->channels[i], &type);
		if (ret < 0) {
			kfree(a);
			goto error_free_attrs;
		}
		switch (type) {
		case IIO_VOLTAGE:
			a->dev_attr.attr.name = kasprintf(GFP_KERNEL,
							  "in%d_input",
							  in_i++);
			break;
		case IIO_TEMP:
			a->dev_attr.attr.name = kasprintf(GFP_KERNEL,
							  "temp%d_input",
							  temp_i++);
			break;
		case IIO_CURRENT:
			a->dev_attr.attr.name = kasprintf(GFP_KERNEL,
							  "curr%d_input",
							  curr_i++);
			break;
		default:
			ret = -EINVAL;
			kfree(a);
			goto error_free_attrs;
		}
		if (a->dev_attr.attr.name == NULL) {
			kfree(a);
			ret = -ENOMEM;
			goto error_free_attrs;
		}
		a->dev_attr.show = iio_hwmon_read_val;
		a->dev_attr.attr.mode = S_IRUGO;
		a->index = i;
		st->attrs[i] = &a->dev_attr.attr;
	}

	st->attr_group.attrs = st->attrs;
	platform_set_drvdata(pdev, st);
	ret = sysfs_create_group(&pdev->dev.kobj, &st->attr_group);
	if (ret < 0)
		goto error_free_attrs;

	st->hwmon_dev = hwmon_device_register(&pdev->dev);
	if (IS_ERR(st->hwmon_dev)) {
		ret = PTR_ERR(st->hwmon_dev);
		goto error_remove_group;
	}
	return 0;

error_remove_group:
	sysfs_remove_group(&pdev->dev.kobj, &st->attr_group);
error_free_attrs:
	iio_hwmon_free_attrs(st);
	kfree(st->attrs);
error_release_channels:
	iio_channel_release_all(st->channels);
error_free_state:
	kfree(st);
error_ret:
	return ret;
}

static int __devexit iio_hwmon_remove(struct platform_device *pdev)
{
	struct iio_hwmon_state *st = platform_get_drvdata(pdev);

	hwmon_device_unregister(st->hwmon_dev);
	sysfs_remove_group(&pdev->dev.kobj, &st->attr_group);
	iio_hwmon_free_attrs(st);
	kfree(st->attrs);
	iio_channel_release_all(st->channels);

	return 0;
}

static struct platform_driver __refdata iio_hwmon_driver = {
	.driver = {
		.name = "iio_hwmon",
		.owner = THIS_MODULE,
	},
	.probe = iio_hwmon_probe,
	.remove = __devexit_p(iio_hwmon_remove),
};

static int iio_inkern_init(void)
{
	return platform_driver_register(&iio_hwmon_driver);
}
module_init(iio_inkern_init);

static void iio_inkern_exit(void)
{
	platform_driver_unregister(&iio_hwmon_driver);
}
module_exit(iio_inkern_exit);

MODULE_AUTHOR("Jonathan Cameron <jic23@cam.ac.uk>");
MODULE_DESCRIPTION("IIO to hwmon driver");
MODULE_LICENSE("GPL v2");