[v2,2/2] leds: trigger: pattern: notify usespace if pattern finished

  In the current moment, userspace caller can schedule LED pattern with
appropriate parameters, but it doesn't have ability to listen to any
events indicated pattern finished. This patch implements such an event
using sysfs node and sysfs_notify_dirent() call.

Signed-off-by: Martin Kurbanov <mmkurbanov@sberdevices.ru>
---
 .../testing/sysfs-class-led-trigger-pattern   | 11 ++++
 drivers/leds/trigger/ledtrig-pattern.c        | 63 ++++++++++++++++++-
 2 files changed, 73 insertions(+), 1 deletion(-)
  

On 21.11.2022 15:38, Martin Kurbanov wrote:
> In the current moment, userspace caller can schedule LED pattern with
> appropriate parameters, but it doesn't have ability to listen to any
> events indicated pattern finished. This patch implements such an event
> using sysfs node and sysfs_notify_dirent() call.
> 
> Signed-off-by: Martin Kurbanov <mmkurbanov@sberdevices.ru>
> ---
>  .../testing/sysfs-class-led-trigger-pattern   | 11 ++++
>  drivers/leds/trigger/ledtrig-pattern.c        | 63 ++++++++++++++++++-
>  2 files changed, 73 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-led-trigger-pattern b/Documentation/ABI/testing/sysfs-class-led-trigger-pattern
> index 8c57d2780554..b2564123b54b 100644
> --- a/Documentation/ABI/testing/sysfs-class-led-trigger-pattern
> +++ b/Documentation/ABI/testing/sysfs-class-led-trigger-pattern
> @@ -38,3 +38,14 @@ Description:
>  
>  		It should be noticed that some leds, like EL15203000 may
>  		only support indefinitely patterns, so they always store -1.
> +
> +What:		/sys/class/leds/<led>/is_running
> +Date:		October 2022
> +KernelVersion:	6.1
> +Description:
> +		Indicates running of a software pattern for the LED.
> +
> +		This file is read only and supports poll() to detect when the
> +		software pattern ended.
> +
> +		1 means pattern is running and number 0 are finish or not run.
> diff --git a/drivers/leds/trigger/ledtrig-pattern.c b/drivers/leds/trigger/ledtrig-pattern.c
> index 354304b404aa..19a6b5dcd7af 100644
> --- a/drivers/leds/trigger/ledtrig-pattern.c
> +++ b/drivers/leds/trigger/ledtrig-pattern.c
> @@ -33,7 +33,9 @@ struct pattern_trig_data {
>  	int delta_t;
>  	bool is_indefinite;
>  	bool is_hw_pattern;
> +	bool is_running;
>  	struct timer_list timer;
> +	struct kernfs_node *is_running_kn;
>  };
>  
>  static void pattern_trig_update_patterns(struct pattern_trig_data *data)
> @@ -76,8 +78,14 @@ static void pattern_trig_timer_function(struct timer_list *t)
>  	struct pattern_trig_data *data = from_timer(data, t, timer);
>  
>  	for (;;) {
> -		if (!data->is_indefinite && !data->repeat)
> +		if (!data->is_indefinite && !data->repeat) {
> +			data->is_running = false;
> +
> +			if (data->is_running_kn)
> +				sysfs_notify_dirent(data->is_running_kn);
> +
>  			break;
> +		}
>  
>  		if (data->curr->brightness == data->next->brightness) {
>  			/* Step change of brightness */
> @@ -137,6 +145,7 @@ static int pattern_trig_start_pattern(struct led_classdev *led_cdev)
>  	data->curr = data->patterns;
>  	data->next = data->patterns + 1;
>  	data->timer.expires = jiffies;
> +	data->is_running = true;
>  	add_timer(&data->timer);
>  
>  	return 0;
> @@ -176,6 +185,7 @@ static ssize_t repeat_store(struct device *dev, struct device_attribute *attr,
>  	mutex_lock(&data->lock);
>  
>  	del_timer_sync(&data->timer);
> +	data->is_running = false;
>  
>  	if (data->is_hw_pattern)
>  		led_cdev->pattern_clear(led_cdev);
> @@ -267,6 +277,7 @@ static ssize_t pattern_trig_store_patterns(struct led_classdev *led_cdev,
>  	mutex_lock(&data->lock);
>  
>  	del_timer_sync(&data->timer);
> +	data->is_running = false;
>  
>  	if (data->is_hw_pattern)
>  		led_cdev->pattern_clear(led_cdev);
> @@ -327,6 +338,16 @@ static ssize_t hw_pattern_store(struct device *dev,
>  }
>  static DEVICE_ATTR_RW(hw_pattern);
>  
> +static ssize_t is_running_show(struct device *dev,
> +			       struct device_attribute *attr, char *buf)
> +{
> +	struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +	struct pattern_trig_data *data = led_get_trigger_data(led_cdev);
> +
> +	return sysfs_emit(buf, "%d\n", data->is_running);
> +}
> +static DEVICE_ATTR_RO(is_running);
> +
>  static umode_t pattern_trig_attrs_mode(struct kobject *kobj,
>  				       struct attribute *attr, int index)
>  {
> @@ -382,9 +403,41 @@ static void pattern_init(struct led_classdev *led_cdev)
>  	kfree(pattern);
>  }
>  
> +static int pattern_trig_add_is_running(struct led_classdev *led_cdev)
> +{
> +	struct pattern_trig_data *data = led_get_trigger_data(led_cdev);
> +	struct device *dev = led_cdev->dev;
> +	int ret;
> +
> +	ret = device_create_file(dev, &dev_attr_is_running);
> +	if (ret) {
> +		dev_err(dev,
> +			"Error creating is_running (%pe)\n", ERR_PTR(ret));
> +		return ret;
> +	}
> +
> +	data->is_running_kn = sysfs_get_dirent(dev->kobj.sd, "is_running");
> +	if (!data->is_running_kn) {
> +		dev_err(dev, "Error getting is_running kernelfs\n");
> +		device_remove_file(dev, &dev_attr_is_running);
> +		return -ENXIO;
> +	}
> +
> +	return 0;
> +}
> +
> +static void pattern_trig_remove_is_running(struct led_classdev *led_cdev)
> +{
> +	struct pattern_trig_data *data = led_get_trigger_data(led_cdev);
> +
> +	sysfs_put(data->is_running_kn);
> +	device_remove_file(led_cdev->dev, &dev_attr_is_running);
> +}
> +
>  static int pattern_trig_activate(struct led_classdev *led_cdev)
>  {
>  	struct pattern_trig_data *data;
> +	int err;
>  
>  	data = kzalloc(sizeof(*data), GFP_KERNEL);
>  	if (!data)
> @@ -403,6 +456,13 @@ static int pattern_trig_activate(struct led_classdev *led_cdev)
>  	data->led_cdev = led_cdev;
>  	led_set_trigger_data(led_cdev, data);
>  	timer_setup(&data->timer, pattern_trig_timer_function, 0);
> +
> +	err = pattern_trig_add_is_running(led_cdev);
> +	if (err)
> +		dev_warn(led_cdev->dev,
> +			 "pattern ended notifications disabled (%pe)\n",
> +			 ERR_PTR(err));
> +
>  	led_cdev->activated = true;
>  
>  	if (led_cdev->flags & LED_INIT_DEFAULT_TRIGGER) {
> @@ -428,6 +488,7 @@ static void pattern_trig_deactivate(struct led_classdev *led_cdev)
>  		led_cdev->pattern_clear(led_cdev);
>  
>  	del_timer_sync(&data->timer);
> +	pattern_trig_remove_is_running(led_cdev);
>  
>  	led_set_brightness(led_cdev, LED_OFF);
>  	kfree(data);

Hello Andy,

In the previous patch series feedback you mentioned two main problems:
sysfs node creation time and life cycle, and sysfs node creation method.
Let me explain why I didn't fix the above items.

1) About sysfs node creation time and its life cycle. In my opinion,
sysfs node should exist only when user has activated pattern explicitly;
otherwise, it will mislead potential user in the case when pattern is
not activated, but sysfs node existed.
2) About pattern_trig_attrs. We need to use sysfs_notify_dirent()
instead of sysfs_notify(), cause sysfs_notify() can sleep on the lock,
but it's not acceptable for the pattern code in the timer context.
Considering this, we have to create sysfs node in the
pattern_trig_activate() directly and retrieve kernfs_node for required
sysfs_notify_dirent() routine.
  

On Mon, Nov 21, 2022 at 2:44 PM Martin Kurbanov
<MMKurbanov@sberdevices.ru> wrote:
> On 21.11.2022 15:38, Martin Kurbanov wrote:

> In the previous patch series feedback you mentioned two main problems:
> sysfs node creation time and life cycle, and sysfs node creation method.
> Let me explain why I didn't fix the above items.
>
> 1) About sysfs node creation time and its life cycle. In my opinion,
> sysfs node should exist only when user has activated pattern explicitly;
> otherwise, it will mislead potential user in the case when pattern is
> not activated, but sysfs node existed.

OK.

> 2) About pattern_trig_attrs. We need to use sysfs_notify_dirent()
> instead of sysfs_notify(), cause sysfs_notify() can sleep on the lock,
> but it's not acceptable for the pattern code in the timer context.
> Considering this, we have to create sysfs node in the
> pattern_trig_activate() directly and retrieve kernfs_node for required
> sysfs_notify_dirent() routine.

Is there a guarantee that nobody is using the removed node?
If no, what would be the problems with that if any?
  

On Mon, Nov 21, 2022 at 2:39 PM Martin Kurbanov
<mmkurbanov@sberdevices.ru> wrote:
>
> In the current moment, userspace caller can schedule LED pattern with

a LED pattern

> appropriate parameters, but it doesn't have ability to listen to any
> events indicated pattern finished. This patch implements such an event
> using sysfs node and sysfs_notify_dirent() call.

...

> +Date:          October 2022
> +KernelVersion: 6.1

It can't be. Have you read my previous comments?

...

> +               1 means pattern is running and number 0 are finish or not run.

are finished

...

> +static void pattern_trig_remove_is_running(struct led_classdev *led_cdev)
> +{
> +       struct pattern_trig_data *data = led_get_trigger_data(led_cdev);
> +
> +       sysfs_put(data->is_running_kn);
> +       device_remove_file(led_cdev->dev, &dev_attr_is_running);
> +}

If the file is opened at this time, what would happen during execution
of this function?