1. 根目录:
2. drivers
3. staging
4. android
5. timed_output.c

/* drivers/misc/timed_output.c
 *
 * Copyright (C) 2009 Google, Inc.
 * Author: Mike Lockwood <lockwood@android.com>
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 */

#define pr_fmt(fmt) "timed_output: " fmt

#include <linux/init.h>
#include <linux/export.h>
#include <linux/types.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/err.h>

#include "timed_output.h"

static struct class *timed_output_class;
static atomic_t device_count;

static ssize_t enable_show(struct device *dev, struct device_attribute *attr,
			   char *buf)
{
	struct timed_output_dev *tdev = dev_get_drvdata(dev);
	int remaining = tdev->get_time(tdev);

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

static ssize_t enable_store(struct device *dev, struct device_attribute *attr,
			    const char *buf, size_t size)
{
	struct timed_output_dev *tdev = dev_get_drvdata(dev);
	int value;
	int rc;

	rc = kstrtoint(buf, 0, &value);
	if (rc != 0)
		return -EINVAL;

	tdev->enable(tdev, value);

	return size;
}
static DEVICE_ATTR_RW(enable);

static struct attribute *timed_output_attrs[] = {
	&dev_attr_enable.attr,
	NULL,
};
ATTRIBUTE_GROUPS(timed_output);

static int create_timed_output_class(void)
{
	if (!timed_output_class) {
		timed_output_class = class_create(THIS_MODULE, "timed_output");
		if (IS_ERR(timed_output_class))
			return PTR_ERR(timed_output_class);
		atomic_set(&device_count, 0);
		timed_output_class->dev_groups = timed_output_groups;
	}

	return 0;
}

int timed_output_dev_register(struct timed_output_dev *tdev)
{
	int ret;

	if (!tdev || !tdev->name || !tdev->enable || !tdev->get_time)
		return -EINVAL;

	ret = create_timed_output_class();
	if (ret < 0)
		return ret;

	tdev->index = atomic_inc_return(&device_count);
	tdev->dev = device_create(timed_output_class, NULL,
		MKDEV(0, tdev->index), NULL, "%s", tdev->name);
	if (IS_ERR(tdev->dev))
		return PTR_ERR(tdev->dev);

	dev_set_drvdata(tdev->dev, tdev);
	tdev->state = 0;
	return 0;
}
EXPORT_SYMBOL_GPL(timed_output_dev_register);

void timed_output_dev_unregister(struct timed_output_dev *tdev)
{
	tdev->enable(tdev, 0);
	device_destroy(timed_output_class, MKDEV(0, tdev->index));
}
EXPORT_SYMBOL_GPL(timed_output_dev_unregister);

static int __init timed_output_init(void)
{
	return create_timed_output_class();
}
device_initcall(timed_output_init);