Re: [PATCH] leds: Introduce userspace leds driver
From: Jacek Anaszewski
Date: Thu Sep 08 2016 - 05:59:06 EST
Hi David,
Thanks for the patch. It is very nice. I have only one minor remark
in the code.
I think that it would be good to add a documentation for this
driver to Documentation/leds, with exemplary C program instead
of python one. The program could poll the dev node in a loop,
which allows to conveniently check the impact of setting particular
triggers and all other brightness change events.
On 09/06/2016 04:15 AM, David Lechner wrote:
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 leds 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.
Signed-off-by: David Lechner <david@xxxxxxxxxxxxxx>
---
Here is a sample python program that I used to test that it works as expected.
#!/usr/bin/env python3
import select
from threading import Timer
ULEDS_MAX_NAME_SIZE = 80
name = 'test'
def change_brightness(b):
with open('/sys/class/leds/{}/brightness'.format(name) , 'w') as f:
f.write(str(b))
with open('/dev/uleds', 'rb+', 0) as uleds:
bname = name.encode("ascii")
# create the leds class device
uleds.write(bname + b'\0' * (ULEDS_MAX_NAME_SIZE - len(bname)))
# test that it works
print(uleds.read(1))
# schedule some brighness changes at 1 second intervals
Timer(1, change_brightness, (1,)).start()
# this won't trigger poll since brighness does not change
Timer(2, change_brightness, (1,)).start()
Timer(3, change_brightness, (2,)).start()
# wait for the scheduled changes
p = select.poll()
p.register(uleds.fileno(), select.POLLIN)
p.poll()
print(uleds.read(1))
p.poll()
print(uleds.read(1))
drivers/leds/Kconfig | 8 ++
drivers/leds/Makefile | 3 +
drivers/leds/uleds.c | 224 +++++++++++++++++++++++++++++++++++++++++++++
include/uapi/linux/Kbuild | 1 +
include/uapi/linux/uleds.h | 23 +++++
5 files changed, 259 insertions(+)
create mode 100644 drivers/leds/uleds.c
create mode 100644 include/uapi/linux/uleds.h
diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index 9dcc9b1..25c6168 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -631,6 +631,14 @@ config LEDS_VERSATILE
This option enabled support for the LEDs on the ARM Versatile
and RealView boards. Say Y to enabled these.
+config LEDS_USER
+ tristate "Userspace LED support"
+ depends on LEDS_CLASS
+ help
+ This option enables support for userspace LEDs. Say 'y' to enable this
+ support in kernel. To compile this driver as a module, choose 'm' here:
+ the module will be called leds-user.
+
comment "LED Triggers"
source "drivers/leds/trigger/Kconfig"
diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
index 0684c86..d723eeb 100644
--- a/drivers/leds/Makefile
+++ b/drivers/leds/Makefile
@@ -72,5 +72,8 @@ obj-$(CONFIG_LEDS_IS31FL32XX) += leds-is31fl32xx.o
# LED SPI Drivers
obj-$(CONFIG_LEDS_DAC124S085) += leds-dac124s085.o
+# LED Userspace Drivers
+obj-$(CONFIG_LEDS_USER) += uleds.o
+
# LED Triggers
obj-$(CONFIG_LEDS_TRIGGERS) += trigger/
diff --git a/drivers/leds/uleds.c b/drivers/leds/uleds.c
new file mode 100644
index 0000000..992bca4
--- /dev/null
+++ b/drivers/leds/uleds.c
@@ -0,0 +1,224 @@
+/*
+ * Userspace driver for leds subsystem
+ *
+ * Copyright (C) 2016 David Lechner <david@xxxxxxxxxxxxxx>
+ *
+ * Based on uinput.c: Aristeu Sergio Rozanski Filho <aris@xxxxxxxxxxxxxxxxx>
+ *
+ * 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/poll.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/leds.h>
+#include <linux/miscdevice.h>
Please arrange include directives in alphabetical order.
+#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;
+ unsigned char brightness;
+ unsigned char new_data;
+};
+
+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 = 1;
+ 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.max_brightness = LED_FULL;
+ 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;
+ 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;
+ }
+
+ if (!udev->user_dev.name[0]) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ ret = led_classdev_register(NULL, &udev->led_cdev);
+ if (ret < 0)
+ goto out;
+
+ 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 == 0)
+ return 0;
+
+ if (count != 1)
+ return -EINVAL;
+
+ 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 {
+ retval = copy_to_user(buffer, &udev->brightness, 1);
+ udev->new_data = 0;
+ retval = 1;
+ }
+
+ mutex_unlock(&udev->mutex);
+
+ if (retval || count == 0)
+ 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 unsigned int 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 POLLIN | POLLRDNORM;
+
+ 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;
+ led_classdev_unregister(&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@xxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Userspace driver for leds subsystem");
+MODULE_LICENSE("GPL");
diff --git a/include/uapi/linux/Kbuild b/include/uapi/linux/Kbuild
index 185f8ea..416f5e6 100644
--- a/include/uapi/linux/Kbuild
+++ b/include/uapi/linux/Kbuild
@@ -421,6 +421,7 @@ header-y += udp.h
header-y += uhid.h
header-y += uinput.h
header-y += uio.h
+header-y += uleds.h
header-y += ultrasound.h
header-y += un.h
header-y += unistd.h
diff --git a/include/uapi/linux/uleds.h b/include/uapi/linux/uleds.h
new file mode 100644
index 0000000..e78ed46
--- /dev/null
+++ b/include/uapi/linux/uleds.h
@@ -0,0 +1,23 @@
+/*
+ * Userspace driver support for leds subsystem
+ *
+ * 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.
+ */
+#ifndef _UAPI__ULEDS_H_
+#define _UAPI__ULEDS_H_
+
+#define ULEDS_MAX_NAME_SIZE 80
+
+struct uleds_user_dev {
+ char name[ULEDS_MAX_NAME_SIZE];
+};
+
+#endif /* _UAPI__ULEDS_H_ */
--
Best regards,
Jacek Anaszewski