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/*
* Userspace driver for the LED subsystem
*
* Copyright (C) 2016 David Lechner <david@lechnology.com>
*
* Based on uinput.c: Aristeu Sergio Rozanski Filho <aris@cathedrallabs.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* 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.
*/
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/leds.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/poll.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <uapi/linux/uleds.h>
#define ULEDS_NAME "uleds"
enum uleds_state {
ULEDS_STATE_UNKNOWN,
ULEDS_STATE_REGISTERED,
};
struct uleds_device {
struct uleds_user_dev user_dev;
struct led_classdev led_cdev;
struct mutex mutex;
enum uleds_state state;
wait_queue_head_t waitq;
int brightness;
bool new_data;
};
static struct miscdevice uleds_misc;
static void uleds_brightness_set(struct led_classdev *led_cdev,
enum led_brightness brightness)
{
struct uleds_device *udev = container_of(led_cdev, struct uleds_device,
led_cdev);
if (udev->brightness != brightness) {
udev->brightness = brightness;
udev->new_data = true;
wake_up_interruptible(&udev->waitq);
}
}
static int uleds_open(struct inode *inode, struct file *file)
{
struct uleds_device *udev;
udev = kzalloc(sizeof(*udev), GFP_KERNEL);
if (!udev)
return -ENOMEM;
udev->led_cdev.name = udev->user_dev.name;
udev->led_cdev.brightness_set = uleds_brightness_set;
mutex_init(&udev->mutex);
init_waitqueue_head(&udev->waitq);
udev->state = ULEDS_STATE_UNKNOWN;
file->private_data = udev;
nonseekable_open(inode, file);
return 0;
}
static ssize_t uleds_write(struct file *file, const char __user *buffer,
size_t count, loff_t *ppos)
{
struct uleds_device *udev = file->private_data;
const char *name;
int ret;
if (count == 0)
return 0;
ret = mutex_lock_interruptible(&udev->mutex);
if (ret)
return ret;
if (udev->state == ULEDS_STATE_REGISTERED) {
ret = -EBUSY;
goto out;
}
if (count != sizeof(struct uleds_user_dev)) {
ret = -EINVAL;
goto out;
}
if (copy_from_user(&udev->user_dev, buffer,
sizeof(struct uleds_user_dev))) {
ret = -EFAULT;
goto out;
}
name = udev->user_dev.name;
if (!name[0] || !strcmp(name, ".") || !strcmp(name, "..") ||
strchr(name, '/')) {
ret = -EINVAL;
goto out;
}
if (udev->user_dev.max_brightness <= 0) {
ret = -EINVAL;
goto out;
}
udev->led_cdev.max_brightness = udev->user_dev.max_brightness;
ret = devm_led_classdev_register(uleds_misc.this_device,
&udev->led_cdev);
if (ret < 0)
goto out;
udev->new_data = true;
udev->state = ULEDS_STATE_REGISTERED;
ret = count;
out:
mutex_unlock(&udev->mutex);
return ret;
}
static ssize_t uleds_read(struct file *file, char __user *buffer, size_t count,
loff_t *ppos)
{
struct uleds_device *udev = file->private_data;
ssize_t retval;
if (count < sizeof(udev->brightness))
return 0;
do {
retval = mutex_lock_interruptible(&udev->mutex);
if (retval)
return retval;
if (udev->state != ULEDS_STATE_REGISTERED) {
retval = -ENODEV;
} else if (!udev->new_data && (file->f_flags & O_NONBLOCK)) {
retval = -EAGAIN;
} else if (udev->new_data) {
retval = copy_to_user(buffer, &udev->brightness,
sizeof(udev->brightness));
udev->new_data = false;
retval = sizeof(udev->brightness);
}
mutex_unlock(&udev->mutex);
if (retval)
break;
if (!(file->f_flags & O_NONBLOCK))
retval = wait_event_interruptible(udev->waitq,
udev->new_data ||
udev->state != ULEDS_STATE_REGISTERED);
} while (retval == 0);
return retval;
}
static __poll_t uleds_poll(struct file *file, poll_table *wait)
{
struct uleds_device *udev = file->private_data;
poll_wait(file, &udev->waitq, wait);
if (udev->new_data)
return EPOLLIN | EPOLLRDNORM;
return 0;
}
static int uleds_release(struct inode *inode, struct file *file)
{
struct uleds_device *udev = file->private_data;
if (udev->state == ULEDS_STATE_REGISTERED) {
udev->state = ULEDS_STATE_UNKNOWN;
devm_led_classdev_unregister(uleds_misc.this_device,
&udev->led_cdev);
}
kfree(udev);
return 0;
}
static const struct file_operations uleds_fops = {
.owner = THIS_MODULE,
.open = uleds_open,
.release = uleds_release,
.read = uleds_read,
.write = uleds_write,
.poll = uleds_poll,
.llseek = no_llseek,
};
static struct miscdevice uleds_misc = {
.fops = &uleds_fops,
.minor = MISC_DYNAMIC_MINOR,
.name = ULEDS_NAME,
};
static int __init uleds_init(void)
{
return misc_register(&uleds_misc);
}
module_init(uleds_init);
static void __exit uleds_exit(void)
{
misc_deregister(&uleds_misc);
}
module_exit(uleds_exit);
MODULE_AUTHOR("David Lechner <david@lechnology.com>");
MODULE_DESCRIPTION("Userspace driver for the LED subsystem");
MODULE_LICENSE("GPL");
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