leds: Introduce userspace LED class driver
This driver creates a userspace leds driver similar to uinput. New LEDs are created by opening /dev/uleds and writing a uleds_user_dev struct. A new LED class device is registered with the name given in the struct. Reading will return a single byte that is the current brightness. The poll() syscall is also supported. It will be triggered whenever the brightness changes. Closing the file handle to /dev/uleds will remove the leds class device. Signed-off-by: David Lechner <david@lechnology.com> Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
This commit is contained in:
David Lechner
Jacek Anaszewski
parent
1001354ca3
commit
e381322b01
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@ -0,0 +1,36 @@
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Userspace LEDs
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==============
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The uleds driver supports userspace LEDs. This can be useful for testing
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triggers and can also be used to implement virtual LEDs.
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Usage
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=====
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When the driver is loaded, a character device is created at /dev/uleds. To
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create a new LED class device, open /dev/uleds and write a uleds_user_dev
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structure to it (found in kernel public header file linux/uleds.h).
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#define LED_MAX_NAME_SIZE 64
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struct uleds_user_dev {
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char name[LED_MAX_NAME_SIZE];
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};
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A new LED class device will be created with the name given. The name can be
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any valid sysfs device node name, but consider using the LED class naming
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convention of "devicename:color:function".
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The current brightness is found by reading a single byte from the character
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device. Values are unsigned: 0 to 255. Reading will block until the brightness
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changes. The device node can also be polled to notify when the brightness value
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changes.
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The LED class device will be removed when the open file handle to /dev/uleds
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is closed.
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Multiple LED class devices are created by opening additional file handles to
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/dev/uleds.
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See tools/leds/uledmon.c for an example userspace program.
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@ -659,6 +659,14 @@ config LEDS_MLXCPLD
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This option enabled support for the LEDs on the Mellanox
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boards. Say Y to enabled these.
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config LEDS_USER
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tristate "Userspace LED support"
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depends on LEDS_CLASS
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help
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This option enables support for userspace LEDs. Say 'y' to enable this
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support in kernel. To compile this driver as a module, choose 'm' here:
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the module will be called uleds.
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comment "LED Triggers"
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source "drivers/leds/trigger/Kconfig"
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@ -75,5 +75,8 @@ obj-$(CONFIG_LEDS_MLXCPLD) += leds-mlxcpld.o
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# LED SPI Drivers
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obj-$(CONFIG_LEDS_DAC124S085) += leds-dac124s085.o
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# LED Userspace Drivers
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obj-$(CONFIG_LEDS_USER) += uleds.o
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# LED Triggers
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obj-$(CONFIG_LEDS_TRIGGERS) += trigger/
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@ -0,0 +1,235 @@
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/*
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* Userspace driver for the LED subsystem
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*
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* Copyright (C) 2016 David Lechner <david@lechnology.com>
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*
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* Based on uinput.c: Aristeu Sergio Rozanski Filho <aris@cathedrallabs.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#include <linux/fs.h>
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#include <linux/init.h>
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#include <linux/leds.h>
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#include <linux/miscdevice.h>
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#include <linux/module.h>
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#include <linux/poll.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <uapi/linux/uleds.h>
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#define ULEDS_NAME "uleds"
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enum uleds_state {
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ULEDS_STATE_UNKNOWN,
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ULEDS_STATE_REGISTERED,
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};
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struct uleds_device {
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struct uleds_user_dev user_dev;
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struct led_classdev led_cdev;
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struct mutex mutex;
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enum uleds_state state;
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wait_queue_head_t waitq;
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int brightness;
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bool new_data;
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};
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static struct miscdevice uleds_misc;
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static void uleds_brightness_set(struct led_classdev *led_cdev,
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enum led_brightness brightness)
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{
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struct uleds_device *udev = container_of(led_cdev, struct uleds_device,
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led_cdev);
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if (udev->brightness != brightness) {
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udev->brightness = brightness;
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udev->new_data = true;
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wake_up_interruptible(&udev->waitq);
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}
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}
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static int uleds_open(struct inode *inode, struct file *file)
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{
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struct uleds_device *udev;
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udev = kzalloc(sizeof(*udev), GFP_KERNEL);
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if (!udev)
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return -ENOMEM;
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udev->led_cdev.name = udev->user_dev.name;
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udev->led_cdev.brightness_set = uleds_brightness_set;
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mutex_init(&udev->mutex);
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init_waitqueue_head(&udev->waitq);
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udev->state = ULEDS_STATE_UNKNOWN;
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file->private_data = udev;
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nonseekable_open(inode, file);
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return 0;
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}
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static ssize_t uleds_write(struct file *file, const char __user *buffer,
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size_t count, loff_t *ppos)
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{
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struct uleds_device *udev = file->private_data;
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const char *name;
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int ret;
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if (count == 0)
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return 0;
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ret = mutex_lock_interruptible(&udev->mutex);
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if (ret)
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return ret;
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if (udev->state == ULEDS_STATE_REGISTERED) {
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ret = -EBUSY;
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goto out;
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}
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if (count != sizeof(struct uleds_user_dev)) {
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ret = -EINVAL;
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goto out;
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}
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if (copy_from_user(&udev->user_dev, buffer,
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sizeof(struct uleds_user_dev))) {
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ret = -EFAULT;
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goto out;
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}
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name = udev->user_dev.name;
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if (!name[0] || !strcmp(name, ".") || !strcmp(name, "..") ||
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strchr(name, '/')) {
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ret = -EINVAL;
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goto out;
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}
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if (udev->user_dev.max_brightness <= 0) {
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ret = -EINVAL;
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goto out;
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}
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udev->led_cdev.max_brightness = udev->user_dev.max_brightness;
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ret = devm_led_classdev_register(uleds_misc.this_device,
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&udev->led_cdev);
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if (ret < 0)
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goto out;
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udev->new_data = true;
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udev->state = ULEDS_STATE_REGISTERED;
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ret = count;
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out:
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mutex_unlock(&udev->mutex);
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return ret;
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}
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static ssize_t uleds_read(struct file *file, char __user *buffer, size_t count,
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loff_t *ppos)
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{
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struct uleds_device *udev = file->private_data;
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ssize_t retval;
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if (count < sizeof(udev->brightness))
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return 0;
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do {
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retval = mutex_lock_interruptible(&udev->mutex);
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if (retval)
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return retval;
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if (udev->state != ULEDS_STATE_REGISTERED) {
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retval = -ENODEV;
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} else if (!udev->new_data && (file->f_flags & O_NONBLOCK)) {
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retval = -EAGAIN;
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} else if (udev->new_data) {
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retval = copy_to_user(buffer, &udev->brightness,
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sizeof(udev->brightness));
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udev->new_data = false;
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retval = sizeof(udev->brightness);
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}
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mutex_unlock(&udev->mutex);
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if (retval)
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break;
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if (!(file->f_flags & O_NONBLOCK))
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retval = wait_event_interruptible(udev->waitq,
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udev->new_data ||
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udev->state != ULEDS_STATE_REGISTERED);
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} while (retval == 0);
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return retval;
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}
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static unsigned int uleds_poll(struct file *file, poll_table *wait)
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{
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struct uleds_device *udev = file->private_data;
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poll_wait(file, &udev->waitq, wait);
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if (udev->new_data)
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return POLLIN | POLLRDNORM;
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return 0;
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}
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static int uleds_release(struct inode *inode, struct file *file)
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{
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struct uleds_device *udev = file->private_data;
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if (udev->state == ULEDS_STATE_REGISTERED) {
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udev->state = ULEDS_STATE_UNKNOWN;
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devm_led_classdev_unregister(uleds_misc.this_device,
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&udev->led_cdev);
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}
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kfree(udev);
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return 0;
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}
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static const struct file_operations uleds_fops = {
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.owner = THIS_MODULE,
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.open = uleds_open,
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.release = uleds_release,
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.read = uleds_read,
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.write = uleds_write,
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.poll = uleds_poll,
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.llseek = no_llseek,
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};
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static struct miscdevice uleds_misc = {
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.fops = &uleds_fops,
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.minor = MISC_DYNAMIC_MINOR,
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.name = ULEDS_NAME,
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};
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static int __init uleds_init(void)
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{
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return misc_register(&uleds_misc);
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}
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module_init(uleds_init);
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static void __exit uleds_exit(void)
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{
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misc_deregister(&uleds_misc);
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}
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module_exit(uleds_exit);
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MODULE_AUTHOR("David Lechner <david@lechnology.com>");
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MODULE_DESCRIPTION("Userspace driver for the LED subsystem");
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MODULE_LICENSE("GPL");
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@ -425,6 +425,7 @@ header-y += udp.h
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header-y += uhid.h
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header-y += uinput.h
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header-y += uio.h
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header-y += uleds.h
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header-y += ultrasound.h
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header-y += un.h
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header-y += unistd.h
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@ -0,0 +1,24 @@
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/*
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* Userspace driver support for the LED subsystem
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#ifndef _UAPI__ULEDS_H_
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#define _UAPI__ULEDS_H_
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#define LED_MAX_NAME_SIZE 64
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struct uleds_user_dev {
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char name[LED_MAX_NAME_SIZE];
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int max_brightness;
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};
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#endif /* _UAPI__ULEDS_H_ */
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