[PATCH 4/5] leds: add /sys/class/triggers/ that contains trigger sub-directories

[Akinobu Mita <akinobu.mita@gmail.com>]

Reading /sys/class/leds/<led>/trigger returns all available LED triggers.
However, this violates the "one value per file" rule of sysfs.

This provides /sys/class/leds/triggers directory that contains a number of
sub-directories, each representing an LED trigger. The name of the
sub-directory matches the LED trigger name.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Dan Murphy <dmurphy@ti.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
---
 Documentation/ABI/testing/sysfs-class-led |  9 +++++++++
 drivers/leds/led-class.c                  | 32 +++++++++++++++++++++++++++++++
 drivers/leds/led-triggers.c               | 19 ++++++++++++++++++
 drivers/leds/leds.h                       |  1 +
 include/linux/leds.h                      |  1 +
 5 files changed, 62 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-class-led b/Documentation/ABI/testing/sysfs-class-led
index 5f67f7a..14d91af 100644
--- a/Documentation/ABI/testing/sysfs-class-led
+++ b/Documentation/ABI/testing/sysfs-class-led
@@ -61,3 +61,12 @@ Description:
 		gpio and backlight triggers. In case of the backlight trigger,
 		it is useful when driving a LED which is intended to indicate
 		a device in a standby like state.
+
+What:		/sys/class/leds/triggers/
+Date:		September 2019
+KernelVersion:	5.5
+Contact:	linux-leds@vger.kernel.org
+Description:
+		This directory contains a number of sub-directories, each
+		representing an LED trigger. The name of the sub-directory
+		matches the LED trigger name.
diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index 7d85181..04e6c14 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -81,6 +81,28 @@ static struct bin_attribute *led_trigger_bin_attrs[] = {
 static const struct attribute_group led_trigger_group = {
 	.bin_attrs = led_trigger_bin_attrs,
 };
+
+static int led_triggers_kobj_create(void)
+{
+	led_triggers_kobj = class_kobject_create_and_add("triggers",
+							 leds_class);
+
+	return led_triggers_kobj ? 0 : -ENOMEM;
+}
+
+static void led_triggers_kobj_destroy(void)
+{
+	kobject_put(led_triggers_kobj);
+}
+
+#else
+static inline int led_triggers_kobj_create(void)
+{
+	return 0;
+}
+static void led_triggers_kobj_destroy(void)
+{
+}
 #endif
 
 static struct attribute *led_class_attrs[] = {
@@ -411,16 +433,26 @@ EXPORT_SYMBOL_GPL(devm_led_classdev_unregister);
 
 static int __init leds_init(void)
 {
+	int ret;
+
 	leds_class = class_create(THIS_MODULE, "leds");
 	if (IS_ERR(leds_class))
 		return PTR_ERR(leds_class);
 	leds_class->pm = &leds_class_dev_pm_ops;
 	leds_class->dev_groups = led_groups;
+
+	ret = led_triggers_kobj_create();
+	if (ret) {
+		class_unregister(leds_class);
+		return ret;
+	}
+
 	return 0;
 }
 
 static void __exit leds_exit(void)
 {
+	led_triggers_kobj_destroy();
 	class_destroy(leds_class);
 }
 
diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
index ed5a311..4a86964 100644
--- a/drivers/leds/led-triggers.c
+++ b/drivers/leds/led-triggers.c
@@ -268,16 +268,26 @@ void led_trigger_rename_static(const char *name, struct led_trigger *trig)
 }
 EXPORT_SYMBOL_GPL(led_trigger_rename_static);
 
+static struct kobj_type led_trigger_kobj_type = {
+	.sysfs_ops = &kobj_sysfs_ops,
+};
+
+struct kobject *led_triggers_kobj;
+EXPORT_SYMBOL_GPL(led_triggers_kobj);
+
 /* LED Trigger Interface */
 
 int led_trigger_register(struct led_trigger *trig)
 {
 	struct led_classdev *led_cdev;
 	struct led_trigger *_trig;
+	int ret;
 
 	rwlock_init(&trig->leddev_list_lock);
 	INIT_LIST_HEAD(&trig->led_cdevs);
 
+	kobject_init(&trig->kobj, &led_trigger_kobj_type);
+
 	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) {
@@ -286,6 +296,14 @@ int led_trigger_register(struct led_trigger *trig)
 			return -EEXIST;
 		}
 	}
+
+	WARN_ON_ONCE(!led_triggers_kobj);
+	ret = kobject_add(&trig->kobj, led_triggers_kobj, "%s", trig->name);
+	if (ret) {
+		up_write(&triggers_list_lock);
+		return ret;
+	}
+
 	/* Add to the list of led triggers */
 	list_add_tail(&trig->next_trig, &trigger_list);
 	up_write(&triggers_list_lock);
@@ -316,6 +334,7 @@ void led_trigger_unregister(struct led_trigger *trig)
 
 	/* Remove from the list of led triggers */
 	down_write(&triggers_list_lock);
+	kobject_put(&trig->kobj);
 	list_del_init(&trig->next_trig);
 	up_write(&triggers_list_lock);
 
diff --git a/drivers/leds/leds.h b/drivers/leds/leds.h
index a0ee33c..52debe0 100644
--- a/drivers/leds/leds.h
+++ b/drivers/leds/leds.h
@@ -33,5 +33,6 @@ ssize_t led_trigger_write(struct file *filp, struct kobject *kobj,
 extern struct rw_semaphore leds_list_lock;
 extern struct list_head leds_list;
 extern struct list_head trigger_list;
+extern struct kobject *led_triggers_kobj;
 
 #endif	/* __LEDS_H_INCLUDED */
diff --git a/include/linux/leds.h b/include/linux/leds.h
index 33ae825..379f282 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -279,6 +279,7 @@ struct led_trigger {
 	struct list_head  next_trig;
 
 	const struct attribute_group **groups;
+	struct kobject kobj;
 };
 
 /*
-- 
2.7.4