/* * 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");