[PATCH 1/3] leds: add device activity LED triggers

[Maciek Borzecki <maciek.borzecki@gmail.com>]

The patch adds LED triggers for indicating an activity on a selected
device. The drivers that intend to use triggers need to register
respective devices using ledtrig_dev_add(). Triggers are generated by
explicitly calling ledtrig_dev_activity().

Signed-off-by: Maciek Borzecki <maciek.borzecki@gmail.com>
---
 drivers/leds/trigger/Kconfig          |   8 ++
 drivers/leds/trigger/Makefile         |   1 +
 drivers/leds/trigger/ledtrig-device.c | 185 ++++++++++++++++++++++++++++++++++
 include/linux/leds.h                  |  10 ++
 4 files changed, 204 insertions(+)
 create mode 100644 drivers/leds/trigger/ledtrig-device.c

diff --git a/drivers/leds/trigger/Kconfig b/drivers/leds/trigger/Kconfig
index 5bda6a9b56bbd90b4a3749f87bc0c6fda8dd5034..c6ecfbd7c0876f21688140aa9afc7eb5b9fec3a2 100644
--- a/drivers/leds/trigger/Kconfig
+++ b/drivers/leds/trigger/Kconfig
@@ -108,4 +108,12 @@ config LEDS_TRIGGER_CAMERA
 	  This enables direct flash/torch on/off by the driver, kernel space.
 	  If unsure, say Y.
 
+config LEDS_TRIGGER_DEVICE
+	bool "LED Device Activity Trigger"
+	depends on LEDS_TRIGGERS
+	help
+	  This allows LEDs to be triggered by an actvity on a selected
+          device.
+	  If unsure, say Y.
+
 endif # LEDS_TRIGGERS
diff --git a/drivers/leds/trigger/Makefile b/drivers/leds/trigger/Makefile
index 1abf48dacf7ebfcfb8208f7ae7bdf29d7c11ba32..86beeacd5403afc163873d7c3f817ee082b64e04 100644
--- a/drivers/leds/trigger/Makefile
+++ b/drivers/leds/trigger/Makefile
@@ -8,3 +8,4 @@ obj-$(CONFIG_LEDS_TRIGGER_CPU)		+= ledtrig-cpu.o
 obj-$(CONFIG_LEDS_TRIGGER_DEFAULT_ON)	+= ledtrig-default-on.o
 obj-$(CONFIG_LEDS_TRIGGER_TRANSIENT)	+= ledtrig-transient.o
 obj-$(CONFIG_LEDS_TRIGGER_CAMERA)	+= ledtrig-camera.o
+obj-$(CONFIG_LEDS_TRIGGER_DEVICE)	+= ledtrig-device.o
diff --git a/drivers/leds/trigger/ledtrig-device.c b/drivers/leds/trigger/ledtrig-device.c
new file mode 100644
index 0000000000000000000000000000000000000000..dbb8d7d2b4a0258149c581a040c416d412d9ceeb
--- /dev/null
+++ b/drivers/leds/trigger/ledtrig-device.c
@@ -0,0 +1,185 @@
+/*
+ * LED Device Activity Trigger
+ *
+ * Copyright 2015 Maciej Borzecki <maciek.borzecki@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/leds.h>
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <linux/rwsem.h>
+#include <linux/kdev_t.h>
+
+#define BLINK_DELAY 30
+static unsigned long blink_delay = BLINK_DELAY;
+
+static DECLARE_RWSEM(devs_list_lock);
+static LIST_HEAD(devs_list);
+
+#define MAX_NAME_LEN 20
+
+struct ledtrig_dev_data {
+	char name[MAX_NAME_LEN];
+	dev_t dev;
+	struct led_trigger *trig;
+	struct list_head node;
+};
+
+/**
+ * ledtrig_dev_activity - signal activity on device
+ * @dev: device
+ *
+ * Fires a trigger assigned to @dev device.
+ */
+void ledtrig_dev_activity(dev_t dev)
+{
+	struct ledtrig_dev_data *dev_trig;
+
+	if (!down_read_trylock(&devs_list_lock))
+		return;
+
+	list_for_each_entry(dev_trig, &devs_list, node) {
+		if (dev_trig->dev == dev) {
+			led_trigger_blink_oneshot(dev_trig->trig,
+						  &blink_delay,
+						  &blink_delay,
+						  0);
+			break;
+		}
+	}
+	up_read(&devs_list_lock);
+}
+EXPORT_SYMBOL(ledtrig_dev_activity);
+
+static struct ledtrig_dev_data *ledtrig_dev_new(dev_t dev)
+{
+	struct ledtrig_dev_data *dev_trig;
+
+	dev_trig = kzalloc(sizeof(*dev_trig), GFP_KERNEL);
+	if (!dev_trig)
+		return NULL;
+
+	INIT_LIST_HEAD(&dev_trig->node);
+	dev_trig->dev = dev;
+	snprintf(dev_trig->name, sizeof(dev_trig->name),
+		 "dev-%u:%u", MAJOR(dev), MINOR(dev));
+
+	return dev_trig;
+}
+
+static void ledtrig_dev_release(struct ledtrig_dev_data *dev_trig)
+{
+	led_trigger_unregister_simple(dev_trig->trig);
+
+	kfree(dev_trig);
+}
+
+/**
+ * ledtrig_dev_add - add a trigger for device
+ * @dev: device for which the trigger is to be added
+ *
+ * Create and register a new trigger for device @dev. The trigger will
+ * show up as dev-<major>:<minor> in the list of avaialble LED
+ * triggers.
+ */
+void ledtrig_dev_add(dev_t dev)
+{
+	int found = 0;
+	struct ledtrig_dev_data *new_dev_trig;
+	struct ledtrig_dev_data *dev_trig;
+
+	new_dev_trig = ledtrig_dev_new(dev);
+	if (!new_dev_trig)
+		return;
+
+	down_write(&devs_list_lock);
+	list_for_each_entry(dev_trig, &devs_list, node) {
+		if (dev_trig->dev == dev) {
+			found = 1;
+			break;
+		}
+	}
+	if (!found)
+		list_add(&new_dev_trig->node, &devs_list);
+	up_write(&devs_list_lock);
+
+	if (!found)
+		/* register with led triggers */
+		led_trigger_register_simple(new_dev_trig->name,
+					    &new_dev_trig->trig);
+	else
+		kfree(new_dev_trig);
+}
+EXPORT_SYMBOL(ledtrig_dev_add);
+
+/**
+ * ledtrig_dev_del - delete a trigger
+ * @dev: device for which to delete a trigger
+ */
+void ledtrig_dev_del(dev_t dev)
+{
+
+	struct ledtrig_dev_data *dev_trig;
+
+	down_write(&devs_list_lock);
+	list_for_each_entry(dev_trig, &devs_list, node) {
+		if (dev_trig->dev == dev) {
+			/* remove from devs list */
+			list_del(&dev_trig->node);
+
+			/* unregister & release data */
+			ledtrig_dev_release(dev_trig);
+			break;
+		}
+	}
+	up_write(&devs_list_lock);
+
+}
+EXPORT_SYMBOL(ledtrig_dev_del);
+
+static void ledtrig_dev_remove_all(void)
+{
+	struct list_head *en;
+
+	down_write(&devs_list_lock);
+	list_for_each(en, &devs_list) {
+		struct list_head *prev = en->prev;
+		struct ledtrig_dev_data *dev_trig;
+
+		dev_trig = list_entry(en, struct ledtrig_dev_data,
+				      node);
+		/* remove from list */
+		list_del(en);
+
+		/* unregister & release data */
+		ledtrig_dev_release(dev_trig);
+
+		/* and go back */
+		en = prev;
+	}
+	up_write(&devs_list_lock);
+}
+
+static int __init ledtrig_dev_init(void)
+{
+	return 0;
+}
+
+static void __exit ledtrig_dev_exit(void)
+{
+	ledtrig_dev_remove_all();
+}
+
+module_init(ledtrig_dev_init);
+module_exit(ledtrig_dev_exit);
+
+MODULE_AUTHOR("Maciej Borzecki <maciek.borzecki@gmail.com>");
+MODULE_DESCRIPTION("LED Device Activity Trigger");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/leds.h b/include/linux/leds.h
index b122eeafb5dc17b8a8b1a1852dc1c420ecf0f8d2..e487d5b2ac556bdb2f1525d8b5e84df0c245d4c9 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -369,4 +369,14 @@ static inline void ledtrig_cpu(enum cpu_led_event evt)
 }
 #endif
 
+#ifdef CONFIG_LEDS_TRIGGER_DEVICE
+extern void ledtrig_dev_add(dev_t dev);
+extern void ledtrig_dev_del(dev_t dev);
+extern void ledtrig_dev_activity(dev_t dev);
+#else
+static inline void ledtrig_dev_add(dev_t dev) {}
+static inline void ledtrig_dev_del(dev_t dev) {}
+static inline void ledtrig_dev_activity(dev_t dev) {}
+#endif
+
 #endif		/* __LINUX_LEDS_H_INCLUDED */
-- 
2.5.3