leds: add oneshot trigger

Add oneshot trigger to blink a led with configurale parameters via
sysfs.

Signed-off-by: Fabio Baltieri <[e-mail]>
Cc: Shuah Khan <[e-mail]>
Signed-off-by: Bryan Wu <[e-mail]>

Documentation/leds/ledtrig-oneshot.txt

···
+One-shot LED Trigger
+====================
+
+This is a LED trigger useful for signaling the user of an event where there are
+no clear trap points to put standard led-on and led-off settings.  Using this
+trigger, the application needs only to signal the trigger when an event has
+happened, than the trigger turns the LED on and than keeps it off for a
+specified amount of time.
+
+This trigger is meant to be usable both for sporadic and dense events.  In the
+first case, the trigger produces a clear single controlled blink for each
+event, while in the latter it keeps blinking at constant rate, as to signal
+that the events are arriving continuously.
+
+A one-shot LED only stays in a constant state when there are no events.  An
+additional "invert" property specifies if the LED has to stay off (normal) or
+on (inverted) when not rearmed.
+
+The trigger can be activated from user space on led class devices as shown
+below:
+
+  echo oneshot > trigger
+
+This adds the following sysfs attributes to the LED:
+
+  delay_on - specifies for how many milliseconds the LED has to stay at
+             LED_FULL brightness after it has been armed.
+             Default to 100 ms.
+
+  delay_off - specifies for how many milliseconds the LED has to stay at
+              LED_OFF brightness after it has been armed.
+              Default to 100 ms.
+
+  invert - reverse the blink logic.  If set to 0 (default) blink on for delay_on
+           ms, then blink off for delay_off ms, leaving the LED normally off.  If
+           set to 1, blink off for delay_off ms, then blink on for delay_on ms,
+           leaving the LED normally on.
+           Setting this value also immediately change the LED state.
+
+  shot - write any non-empty string to signal an events, this starts a blink
+         sequence if not already running.
+
+Example use-case: network devices, initialization:
+
+  echo oneshot > trigger # set trigger for this led
+  echo 33 > delay_on     # blink at 1 / (33 + 33) Hz on continuous traffic
+  echo 33 > delay_off
+
+interface goes up:
+
+  echo 1 > invert # set led as normally-on, turn the led on
+
+packet received/transmitted:
+
+  echo 1 > shot # led starts blinking, ignored if already blinking
+
+interface goes down
+
+  echo 0 > invert # set led as normally-off, turn the led off

drivers/leds/Kconfig

···
 
 	  If unsure, say Y.
 
+config LEDS_TRIGGER_ONESHOT
+	tristate "LED One-shot Trigger"
+	depends on LEDS_TRIGGERS
+	help
+	  This allows LEDs to blink in one-shot pulses with parameters
+	  controlled via sysfs.  It's useful to notify the user on
+	  sporadic events, when there are no clear begin and end trap points,
+	  or on dense events, where this blinks the LED at constant rate if
+	  rearmed continuously.
+
+	  It also shows how to use the led_blink_set_oneshot() function.
+
+	  If unsure, say Y.
+
 config LEDS_TRIGGER_IDE_DISK
 	bool "LED IDE Disk Trigger"
 	depends on IDE_GD_ATA

drivers/leds/Makefile

···
 
 # LED Triggers
 obj-$(CONFIG_LEDS_TRIGGER_TIMER)	+= ledtrig-timer.o
+obj-$(CONFIG_LEDS_TRIGGER_ONESHOT)	+= ledtrig-oneshot.o
 obj-$(CONFIG_LEDS_TRIGGER_IDE_DISK)	+= ledtrig-ide-disk.o
 obj-$(CONFIG_LEDS_TRIGGER_HEARTBEAT)	+= ledtrig-heartbeat.o
 obj-$(CONFIG_LEDS_TRIGGER_BACKLIGHT)	+= ledtrig-backlight.o

drivers/leds/ledtrig-oneshot.c

···
+/*
+ * One-shot LED Trigger
+ *
+ * Copyright 2012, Fabio Baltieri <[e-mail]>
+ *
+ * Based on ledtrig-timer.c by Richard Purdie <[e-mail]>
+ *
+ * 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/kernel.h>
+#include <linux/init.h>
+#include <linux/device.h>
+#include <linux/ctype.h>
+#include <linux/slab.h>
+#include <linux/leds.h>
+#include "leds.h"
+
+#define DEFAULT_DELAY 100
+
+struct oneshot_trig_data {
+	unsigned int invert;
+};
+
+static ssize_t led_shot(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct oneshot_trig_data *oneshot_data = led_cdev->trigger_data;
+
+	led_blink_set_oneshot(led_cdev,
+			&led_cdev->blink_delay_on, &led_cdev->blink_delay_off,
+			oneshot_data->invert);
+
+	/* content is ignored */
+	return size;
+}
+static ssize_t led_invert_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct oneshot_trig_data *oneshot_data = led_cdev->trigger_data;
+
+	return sprintf(buf, "%u\n", oneshot_data->invert);
+}
+
+static ssize_t led_invert_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct oneshot_trig_data *oneshot_data = led_cdev->trigger_data;
+	unsigned long state;
+	int ret;
+
+	ret = kstrtoul(buf, 0, &state);
+	if (ret)
+		return ret;
+
+	oneshot_data->invert = !!state;
+
+	if (oneshot_data->invert)
+		led_set_brightness(led_cdev, LED_FULL);
+	else
+		led_set_brightness(led_cdev, LED_OFF);
+
+	return size;
+}
+
+static ssize_t led_delay_on_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%lu\n", led_cdev->blink_delay_on);
+}
+
+static ssize_t led_delay_on_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	unsigned long state;
+	int ret;
+
+	ret = kstrtoul(buf, 0, &state);
+	if (ret)
+		return ret;
+
+	led_cdev->blink_delay_on = state;
+
+	return size;
+}
+static ssize_t led_delay_off_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%lu\n", led_cdev->blink_delay_off);
+}
+
+static ssize_t led_delay_off_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	unsigned long state;
+	int ret;
+
+	ret = kstrtoul(buf, 0, &state);
+	if (ret)
+		return ret;
+
+	led_cdev->blink_delay_off = state;
+
+	return size;
+}
+
+static DEVICE_ATTR(delay_on, 0644, led_delay_on_show, led_delay_on_store);
+static DEVICE_ATTR(delay_off, 0644, led_delay_off_show, led_delay_off_store);
+static DEVICE_ATTR(invert, 0644, led_invert_show, led_invert_store);
+static DEVICE_ATTR(shot, 0200, NULL, led_shot);
+
+static void oneshot_trig_activate(struct led_classdev *led_cdev)
+{
+	struct oneshot_trig_data *oneshot_data;
+	int rc;
+
+	oneshot_data = kzalloc(sizeof(*oneshot_data), GFP_KERNEL);
+	if (!oneshot_data)
+		return;
+
+	led_cdev->trigger_data = oneshot_data;
+
+	rc = device_create_file(led_cdev->dev, &dev_attr_delay_on);
+	if (rc)
+		goto err_out_trig_data;
+	rc = device_create_file(led_cdev->dev, &dev_attr_delay_off);
+	if (rc)
+		goto err_out_delayon;
+	rc = device_create_file(led_cdev->dev, &dev_attr_invert);
+	if (rc)
+		goto err_out_delayoff;
+	rc = device_create_file(led_cdev->dev, &dev_attr_shot);
+	if (rc)
+		goto err_out_invert;
+
+	led_cdev->blink_delay_on = DEFAULT_DELAY;
+	led_cdev->blink_delay_off = DEFAULT_DELAY;
+
+	led_cdev->activated = true;
+
+	return;
+
+err_out_invert:
+	device_remove_file(led_cdev->dev, &dev_attr_invert);
+err_out_delayoff:
+	device_remove_file(led_cdev->dev, &dev_attr_delay_off);
+err_out_delayon:
+	device_remove_file(led_cdev->dev, &dev_attr_delay_on);
+err_out_trig_data:
+	kfree(led_cdev->trigger_data);
+}
+
+static void oneshot_trig_deactivate(struct led_classdev *led_cdev)
+{
+	struct oneshot_trig_data *oneshot_data = led_cdev->trigger_data;
+
+	if (led_cdev->activated) {
+		device_remove_file(led_cdev->dev, &dev_attr_delay_on);
+		device_remove_file(led_cdev->dev, &dev_attr_delay_off);
+		device_remove_file(led_cdev->dev, &dev_attr_invert);
+		device_remove_file(led_cdev->dev, &dev_attr_shot);
+		kfree(oneshot_data);
+		led_cdev->activated = false;
+	}
+
+	/* Stop blinking */
+	led_brightness_set(led_cdev, LED_OFF);
+}
+
+static struct led_trigger oneshot_led_trigger = {
+	.name     = "oneshot",
+	.activate = oneshot_trig_activate,
+	.deactivate = oneshot_trig_deactivate,
+};
+
+static int __init oneshot_trig_init(void)
+{
+	return led_trigger_register(&oneshot_led_trigger);
+}
+
+static void __exit oneshot_trig_exit(void)
+{
+	led_trigger_unregister(&oneshot_led_trigger);
+}
+
+module_init(oneshot_trig_init);
+module_exit(oneshot_trig_exit);
+
+MODULE_AUTHOR("Fabio Baltieri <[e-mail]>");
+MODULE_DESCRIPTION("One-shot LED trigger");
+MODULE_LICENSE("GPL");