linux-kernel - Re: [PATCH RFC] leds: Add support for per-LED device triggers

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Date:   Sat, 11 Jul 2020 12:04:09 +0200
From:   Pavel Machek <pavel@....cz>
To:     Ondrej Jirman <megous@...ous.com>
Cc:     linux-kernel@...r.kernel.org,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Dan Murphy <dmurphy@...com>,
        "open list:LED SUBSYSTEM" <linux-leds@...r.kernel.org>
Subject: Re: [PATCH RFC] leds: Add support for per-LED device triggers

Hi!

> Some LED controllers may come with an internal HW triggering mechanism
> for the LED and an ability to switch between user control of the LED,
> or the internal control. One such example is AXP20X PMIC, that allows
> wither for user control of the LED, or for internal control based on
> the state of the battery charger.
> 
> Add support for registering per-LED device trigger.
> 
> Names of private triggers need to be globally unique, but may clash
> with other private triggers. This is enforced during trigger
> registration. Developers can register private triggers just like
> the normal triggers, by setting private_led to a classdev
> of the LED the trigger is associated with.

What about this? Should address Marek's concerns about resource use...

Best regards,
     	   	 				       		Pavel

diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
index 79e30d2cb7a5..e8333675959c 100644
--- a/drivers/leds/led-triggers.c
+++ b/drivers/leds/led-triggers.c
@@ -27,6 +27,12 @@ LIST_HEAD(trigger_list);
 
  /* Used by LED Class */
 
+static inline bool
+trigger_relevant(struct led_classdev *led_cdev, struct led_trigger *trig)
+{
+	return !trig->trigger_type || trig->trigger_type == led_cdev->trigger_type;
+}
+
 ssize_t led_trigger_write(struct file *filp, struct kobject *kobj,
 			  struct bin_attribute *bin_attr, char *buf,
 			  loff_t pos, size_t count)
@@ -50,7 +56,8 @@ ssize_t led_trigger_write(struct file *filp, struct kobject *kobj,
 
 	down_read(&triggers_list_lock);
 	list_for_each_entry(trig, &trigger_list, next_trig) {
-		if (sysfs_streq(buf, trig->name)) {
+		if (sysfs_streq(buf, trig->name) &&
+		    trigger_relevant(led_cdev, trig)) {
 			down_write(&led_cdev->trigger_lock);
 			led_trigger_set(led_cdev, trig);
 			up_write(&led_cdev->trigger_lock);
@@ -96,6 +103,9 @@ static int led_trigger_format(char *buf, size_t size,
 		bool hit = led_cdev->trigger &&
 			!strcmp(led_cdev->trigger->name, trig->name);
 
+		if (!trigger_relevant(led_cdev, trig))
+			continue;
+
 		len += led_trigger_snprintf(buf + len, size - len,
 					    " %s%s%s", hit ? "[" : "",
 					    trig->name, hit ? "]" : "");
@@ -243,7 +253,8 @@ void led_trigger_set_default(struct led_classdev *led_cdev)
 	down_read(&triggers_list_lock);
 	down_write(&led_cdev->trigger_lock);
 	list_for_each_entry(trig, &trigger_list, next_trig) {
-		if (!strcmp(led_cdev->default_trigger, trig->name)) {
+		if (!strcmp(led_cdev->default_trigger, trig->name) &&
+		    trigger_relevant(led_cdev, trig)) {
 			led_cdev->flags |= LED_INIT_DEFAULT_TRIGGER;
 			led_trigger_set(led_cdev, trig);
 			break;
@@ -280,7 +291,8 @@ int led_trigger_register(struct led_trigger *trig)
 	down_write(&triggers_list_lock);
 	/* Make sure the trigger's name isn't already in use */
 	list_for_each_entry(_trig, &trigger_list, next_trig) {
-		if (!strcmp(_trig->name, trig->name)) {
+		if (!strcmp(_trig->name, trig->name) &&
+		    (!_trig->private_led || _trig->private_led == trig->private_led)) {
 			up_write(&triggers_list_lock);
 			return -EEXIST;
 		}
diff --git a/include/linux/leds.h b/include/linux/leds.h
index 2451962d1ec5..cba52714558f 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -57,6 +57,10 @@ struct led_init_data {
 	bool devname_mandatory;
 };
 
+struct led_hw_trigger_type {
+	int dummy;
+}
+
 struct led_classdev {
 	const char		*name;
 	enum led_brightness	 brightness;
@@ -150,6 +154,8 @@ struct led_classdev {
 
 	/* Ensures consistent access to the LED Flash Class device */
 	struct mutex		led_access;
+
+	struct led_hw_trigger_type *trigger_type;
 };
 
 /**
@@ -345,6 +351,9 @@ struct led_trigger {
 	int		(*activate)(struct led_classdev *led_cdev);
 	void		(*deactivate)(struct led_classdev *led_cdev);
 
+	/* LED-private triggers have this set. */
+	struct led_hw_trigger_type *trigger_type;
+
 	/* LEDs under control by this trigger (for simple triggers) */
 	rwlock_t	  leddev_list_lock;
 	struct list_head  led_cdevs;

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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