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Subject[PATCH -next 1/2] leds: add /sys/devices/virtual/led-trigger/
Date
Reading /sys/class/leds/<led>/trigger returns all available LED triggers.
However, this violates the "one value per file" rule of sysfs.

This makes led_triggers "real" devices and provides an
/sys/devices/virtual/led-trigger/ directory that contains a sub-directoriy
for each LED trigger device. The name of the sub-directory matches the LED
trigger name.

We can find all available LED triggers by listing this directory contents.

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>
---
.../ABI/testing/sysfs-devices-virtual-led-trigger | 8 +++
drivers/leds/led-triggers.c | 57 ++++++++++++++++++++++
include/linux/leds.h | 3 ++
3 files changed, 68 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-devices-virtual-led-trigger

diff --git a/Documentation/ABI/testing/sysfs-devices-virtual-led-trigger b/Documentation/ABI/testing/sysfs-devices-virtual-led-trigger
new file mode 100644
index 0000000..b8eb8f3
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-devices-virtual-led-trigger
@@ -0,0 +1,8 @@
+What: /sys/devices/virtual/leds-trigger/
+Date: September 2019
+KernelVersion: 5.5
+Contact: linux-leds@vger.kernel.org
+Description:
+ This directory contains a sub-directoriy for each LED trigger
+ device. The name of the sub-directory matches the LED trigger
+ name.
diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
index 79e30d2..0b810cf 100644
--- a/drivers/leds/led-triggers.c
+++ b/drivers/leds/led-triggers.c
@@ -267,21 +267,76 @@ void led_trigger_rename_static(const char *name, struct led_trigger *trig)
}
EXPORT_SYMBOL_GPL(led_trigger_rename_static);

+struct ledtrig_device {
+ struct device dev;
+};
+
+static void ledtrig_device_release(struct device *dev)
+{
+ struct ledtrig_device *trig_dev =
+ container_of(dev, struct ledtrig_device, dev);
+
+ kfree(trig_dev);
+}
+
+static struct bus_type led_trigger_subsys = {
+ .name = "led-trigger",
+};
+
+static int led_trigger_subsys_init(void)
+{
+ static DEFINE_MUTEX(init_mutex);
+ static bool init_done;
+ int ret = 0;
+
+ mutex_lock(&init_mutex);
+ if (!init_done) {
+ ret = subsys_virtual_register(&led_trigger_subsys, NULL);
+ if (!ret)
+ init_done = true;
+ }
+ mutex_unlock(&init_mutex);
+
+ return ret;
+}
+
/* LED Trigger Interface */

int led_trigger_register(struct led_trigger *trig)
{
struct led_classdev *led_cdev;
struct led_trigger *_trig;
+ struct ledtrig_device *trig_dev;
+ int ret;

rwlock_init(&trig->leddev_list_lock);
INIT_LIST_HEAD(&trig->led_cdevs);

+ ret = led_trigger_subsys_init();
+ if (ret)
+ return ret;
+ trig_dev = kzalloc(sizeof(*trig_dev), GFP_KERNEL);
+ if (!trig_dev)
+ return -ENOMEM;
+
+ trig_dev->dev.bus = &led_trigger_subsys;
+ trig_dev->dev.release = ledtrig_device_release;
+ dev_set_name(&trig_dev->dev, "%s", trig->name);
+
+ ret = device_register(&trig_dev->dev);
+ if (ret) {
+ put_device(&trig_dev->dev);
+ return ret;
+ }
+
+ trig->trig_dev = trig_dev;
+
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)) {
up_write(&triggers_list_lock);
+ device_unregister(&trig_dev->dev);
return -EEXIST;
}
}
@@ -327,6 +382,8 @@ void led_trigger_unregister(struct led_trigger *trig)
up_write(&led_cdev->trigger_lock);
}
up_read(&leds_list_lock);
+
+ device_unregister(&trig->trig_dev->dev);
}
EXPORT_SYMBOL_GPL(led_trigger_unregister);

diff --git a/include/linux/leds.h b/include/linux/leds.h
index da78b27..d63c8e7 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -336,6 +336,8 @@ static inline bool led_sysfs_is_disabled(struct led_classdev *led_cdev)

#define TRIG_NAME_MAX 50

+struct ledtrig_device;
+
struct led_trigger {
/* Trigger Properties */
const char *name;
@@ -350,6 +352,7 @@ struct led_trigger {
struct list_head next_trig;

const struct attribute_group **groups;
+ struct ledtrig_device *trig_dev;
};

/*
--
2.7.4
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