Hi David,
On 09/16/2016 09:16 PM, 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. Closing the file handle to /dev/uleds will remove
> the leds class device.
>
> Signed-off-by: David Lechner <[email protected]>
> ---
> Documentation/leds/uleds.txt | 36 +++++++
> drivers/leds/Kconfig | 8 ++
> drivers/leds/Makefile | 3 +
> drivers/leds/uleds.c | 230 +++++++++++++++++++++++++++++++++++++++++++
> include/uapi/linux/Kbuild | 1 +
> include/uapi/linux/uleds.h | 23 +++++
> 6 files changed, 301 insertions(+)
> create mode 100644 Documentation/leds/uleds.txt
> create mode 100644 drivers/leds/uleds.c
> create mode 100644 include/uapi/linux/uleds.h
>
> diff --git a/Documentation/leds/uleds.txt b/Documentation/leds/uleds.txt
> new file mode 100644
> index 0000000..486d473
> --- /dev/null
> +++ b/Documentation/leds/uleds.txt
> @@ -0,0 +1,36 @@
> +Userspace LEDs
> +==============
> +
> +The uleds driver supports userspace LEDs. This can be useful for testing
> +triggers and can also be used to implement virtual LEDs.
> +
> +
> +Usage
> +=====
> +
> +When the driver is loaded, a character device is created at /dev/uleds. To
> +create a new LED class device, open /dev/uleds and write a uleds_user_dev
> +structure to it (found in kernel public header file linux/uleds.h).
> +
> + #define LEDS_MAX_NAME_SIZE 64
> +
> + struct uleds_user_dev {
> + char name[LEDS_MAX_NAME_SIZE];
> + };
> +
> +A new LED class device will be created with the name given. The name can be
> +any valid sysfs device node name, but consider using the LED class naming
> +convention of "devicename:color:function".
> +
> +The current brightness is found by reading a single byte from the character
> +device. Values are unsigned: 0 to 255. Reading will block until the brightness
> +changes. The device node can also be polled to notify when the brightness value
> +changes.
> +
> +The LED class device will be removed when the open file handle to /dev/uleds
> +is closed.
> +
> +Multiple LED class devices are created by opening additional file handles to
> +/dev/uleds.
> +
> +See tools/leds/uledmon.c for an example userspace program.
> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
> index 7a628c6..5fd3f4c 100644
> --- a/drivers/leds/Kconfig
> +++ b/drivers/leds/Kconfig
> @@ -659,6 +659,14 @@ config LEDS_MLXCPLD
> This option enabled support for the LEDs on the Mellanox
> 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 uleds.
> +
> comment "LED Triggers"
> source "drivers/leds/trigger/Kconfig"
>
> diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
> index 3965070..d5331ff 100644
> --- a/drivers/leds/Makefile
> +++ b/drivers/leds/Makefile
> @@ -75,5 +75,8 @@ obj-$(CONFIG_LEDS_MLXCPLD) += leds-mlxcpld.o
> # LED SPI Drivers
> obj-$(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..59ea23e
> --- /dev/null
> +++ b/drivers/leds/uleds.c
> @@ -0,0 +1,229 @@
> +/*
> + * Userspace driver for leds subsystem
> + *
> + * Copyright (C) 2016 David Lechner <[email protected]>
> + *
> + * Based on uinput.c: Aristeu Sergio Rozanski Filho <[email protected]>
> + *
> + * 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;
> + unsigned char brightness;
I've just noticed that this is wrong, since LED subsystem
brightness type is enum led_brightness, i.e. int.
LED_FULL (255) value is a legacy enum value that can be overridden
by max_brightness property.
Please submit a fix so that I could merge it with the original
patch before sending it upstream.
Thanks,
Jacek Anaszewski
> + 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.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;
> + 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;
> + }
> +
> + 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 == 0)
> + 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, 1);
> + udev->new_data = false;
> + retval = 1;
> + }
> +
> + 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 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;
> + 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 <[email protected]>");
> +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..6f277f3
> --- /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 LEDS_MAX_NAME_SIZE 64
> +
> +struct uleds_user_dev {
> + char name[LEDS_MAX_NAME_SIZE];
> +};
> +
> +#endif /* _UAPI__ULEDS_H_ */
>
On 11/8/16 5:26 AM, Jacek Anaszewski wrote:
> Hi David,
>
>> +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;
>
> I've just noticed that this is wrong, since LED subsystem
> brightness type is enum led_brightness, i.e. int.
> LED_FULL (255) value is a legacy enum value that can be overridden
> by max_brightness property.
>
> Please submit a fix so that I could merge it with the original
> patch before sending it upstream.
>
> Thanks,
> Jacek Anaszewski
>
The brightness should be a 32-bit integer then?
On 11/08/2016 08:08 PM, David Lechner wrote:
>
>
> On 11/8/16 5:26 AM, Jacek Anaszewski wrote:
>> Hi David,
>>
>
>>> +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;
>>
>> I've just noticed that this is wrong, since LED subsystem
>> brightness type is enum led_brightness, i.e. int.
>> LED_FULL (255) value is a legacy enum value that can be overridden
>> by max_brightness property.
>>
>> Please submit a fix so that I could merge it with the original
>> patch before sending it upstream.
>>
>> Thanks,
>> Jacek Anaszewski
>>
>
> The brightness should be a 32-bit integer then?
Exactly.
--
Best regards,
Jacek Anaszewski
Hi!
> >+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;
>
> I've just noticed that this is wrong, since LED subsystem
> brightness type is enum led_brightness, i.e. int.
> LED_FULL (255) value is a legacy enum value that can be overridden
> by max_brightness property.
>
> Please submit a fix so that I could merge it with the original
> patch before sending it upstream.
Actually... perhaps you want to wait with merging the userspace driver
till the locking is solved in the LED subsystem? Maybe I'm wrong, but
I have feeling that userspace driver will have unusual requirements
w.r.t. locking, and that it would be good to have that solved,
first...
Best regards,
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
Hi,
On 11/09/2016 08:05 AM, Pavel Machek wrote:
> Hi!
>
>>> +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;
>>
>> I've just noticed that this is wrong, since LED subsystem
>> brightness type is enum led_brightness, i.e. int.
>> LED_FULL (255) value is a legacy enum value that can be overridden
>> by max_brightness property.
>>
>> Please submit a fix so that I could merge it with the original
>> patch before sending it upstream.
>
> Actually... perhaps you want to wait with merging the userspace driver
> till the locking is solved in the LED subsystem? Maybe I'm wrong, but
> I have feeling that userspace driver will have unusual requirements
> w.r.t. locking, and that it would be good to have that solved,
> first...
If you think about locking between led_set_brightness() and
led_update_brightness() then we have no ready solution for that.
Do you have any?
If not then we have to live with that until one is devised.
After adding the locking in brightness_show the risk of races will be
only in case of concurrent calls to led_set_brightness() and
led_update_brightness() from kernel, whereas currently there are no
such use cases.
--
Best regards,
Jacek Anaszewski