// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * 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>
 */
#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_obj(*udev);
        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;
        stream_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,
};

static struct miscdevice uleds_misc = {
        .fops           = &uleds_fops,
        .minor          = MISC_DYNAMIC_MINOR,
        .name           = ULEDS_NAME,
};

module_misc_device(uleds_misc);

MODULE_AUTHOR("David Lechner <david@lechnology.com>");
MODULE_DESCRIPTION("Userspace driver for the LED subsystem");
MODULE_LICENSE("GPL");