leds: core: Introduce LED pattern trigger

This patch adds a new LED trigger that LED device can configure
to employ software or hardware pattern engine.

Consumers can write 'pattern' file to enable the software pattern
which alters the brightness for the specified duration with one
software timer.

Moreover consumers can write 'hw_pattern' file to enable the hardware
pattern for some LED controllers which can autonomously control
brightness over time, according to some preprogrammed hardware
patterns.

Signed-off-by: Raphael Teysseyre <rteysseyre@gmail.com>
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>

3 files changed, 419 insertions, 0 deletions

diff --git a/drivers/leds/trigger/Kconfig b/drivers/leds/trigger/Kconfig
index 4018af769969..b76fc3cdc8f8 100644
--- a/drivers/leds/trigger/Kconfig
+++ b/drivers/leds/trigger/Kconfig
@@ -129,4 +129,11 @@ config LEDS_TRIGGER_NETDEV
 	  This allows LEDs to be controlled by network device activity.
 	  If unsure, say Y.
 
+config LEDS_TRIGGER_PATTERN
+	tristate "LED Pattern Trigger"
+	help
+	  This allows LEDs to be controlled by a software or hardware pattern
+	  which is a series of tuples, of brightness and duration (ms).
+	  If unsure, say N
+
 endif # LEDS_TRIGGERS
diff --git a/drivers/leds/trigger/Makefile b/drivers/leds/trigger/Makefile
index f3cfe1950538..9bcb64ee8123 100644
--- a/drivers/leds/trigger/Makefile
+++ b/drivers/leds/trigger/Makefile
@@ -13,3 +13,4 @@ obj-$(CONFIG_LEDS_TRIGGER_TRANSIENT)	+= ledtrig-transient.o
 obj-$(CONFIG_LEDS_TRIGGER_CAMERA)	+= ledtrig-camera.o
 obj-$(CONFIG_LEDS_TRIGGER_PANIC)	+= ledtrig-panic.o
 obj-$(CONFIG_LEDS_TRIGGER_NETDEV)	+= ledtrig-netdev.o
+obj-$(CONFIG_LEDS_TRIGGER_PATTERN)	+= ledtrig-pattern.o
diff --git a/drivers/leds/trigger/ledtrig-pattern.c b/drivers/leds/trigger/ledtrig-pattern.c
new file mode 100644
index 000000000000..ce7acd115dd8
--- /dev/null
+++ b/drivers/leds/trigger/ledtrig-pattern.c
@@ -0,0 +1,411 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * LED pattern trigger
+ *
+ * Idea discussed with Pavel Machek. Raphael Teysseyre implemented
+ * the first version, Baolin Wang simplified and improved the approach.
+ */
+
+#include <linux/kernel.h>
+#include <linux/leds.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/timer.h>
+
+#define MAX_PATTERNS		1024
+/*
+ * When doing gradual dimming, the led brightness will be updated
+ * every 50 milliseconds.
+ */
+#define UPDATE_INTERVAL		50
+
+struct pattern_trig_data {
+	struct led_classdev *led_cdev;
+	struct led_pattern patterns[MAX_PATTERNS];
+	struct led_pattern *curr;
+	struct led_pattern *next;
+	struct mutex lock;
+	u32 npatterns;
+	int repeat;
+	int last_repeat;
+	int delta_t;
+	bool is_indefinite;
+	bool is_hw_pattern;
+	struct timer_list timer;
+};
+
+static void pattern_trig_update_patterns(struct pattern_trig_data *data)
+{
+	data->curr = data->next;
+	if (!data->is_indefinite && data->curr == data->patterns)
+		data->repeat--;
+
+	if (data->next == data->patterns + data->npatterns - 1)
+		data->next = data->patterns;
+	else
+		data->next++;
+
+	data->delta_t = 0;
+}
+
+static int pattern_trig_compute_brightness(struct pattern_trig_data *data)
+{
+	int step_brightness;
+
+	/*
+	 * If current tuple's duration is less than the dimming interval,
+	 * we should treat it as a step change of brightness instead of
+	 * doing gradual dimming.
+	 */
+	if (data->delta_t == 0 || data->curr->delta_t < UPDATE_INTERVAL)
+		return data->curr->brightness;
+
+	step_brightness = abs(data->next->brightness - data->curr->brightness);
+	step_brightness = data->delta_t * step_brightness / data->curr->delta_t;
+
+	if (data->next->brightness > data->curr->brightness)
+		return data->curr->brightness + step_brightness;
+	else
+		return data->curr->brightness - step_brightness;
+}
+
+static void pattern_trig_timer_function(struct timer_list *t)
+{
+	struct pattern_trig_data *data = from_timer(data, t, timer);
+
+	mutex_lock(&data->lock);
+
+	for (;;) {
+		if (!data->is_indefinite && !data->repeat)
+			break;
+
+		if (data->curr->brightness == data->next->brightness) {
+			/* Step change of brightness */
+			led_set_brightness(data->led_cdev,
+					   data->curr->brightness);
+			mod_timer(&data->timer,
+				  jiffies + msecs_to_jiffies(data->curr->delta_t));
+
+			/* Skip the tuple with zero duration */
+			pattern_trig_update_patterns(data);
+			/* Select next tuple */
+			pattern_trig_update_patterns(data);
+		} else {
+			/* Gradual dimming */
+
+			/*
+			 * If the accumulation time is larger than current
+			 * tuple's duration, we should go next one and re-check
+			 * if we repeated done.
+			 */
+			if (data->delta_t > data->curr->delta_t) {
+				pattern_trig_update_patterns(data);
+				continue;
+			}
+
+			led_set_brightness(data->led_cdev,
+					   pattern_trig_compute_brightness(data));
+			mod_timer(&data->timer,
+				  jiffies + msecs_to_jiffies(UPDATE_INTERVAL));
+
+			/* Accumulate the gradual dimming time */
+			data->delta_t += UPDATE_INTERVAL;
+		}
+
+		break;
+	}
+
+	mutex_unlock(&data->lock);
+}
+
+static int pattern_trig_start_pattern(struct led_classdev *led_cdev)
+{
+	struct pattern_trig_data *data = led_cdev->trigger_data;
+
+	if (!data->npatterns)
+		return 0;
+
+	if (data->is_hw_pattern) {
+		return led_cdev->pattern_set(led_cdev, data->patterns,
+					     data->npatterns, data->repeat);
+	}
+
+	/* At least 2 tuples for software pattern. */
+	if (data->npatterns < 2)
+		return -EINVAL;
+
+	data->delta_t = 0;
+	data->curr = data->patterns;
+	data->next = data->patterns + 1;
+	data->timer.expires = jiffies;
+	add_timer(&data->timer);
+
+	return 0;
+}
+
+static ssize_t repeat_show(struct device *dev, struct device_attribute *attr,
+			   char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct pattern_trig_data *data = led_cdev->trigger_data;
+	int repeat;
+
+	mutex_lock(&data->lock);
+
+	repeat = data->last_repeat;
+
+	mutex_unlock(&data->lock);
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n", repeat);
+}
+
+static ssize_t repeat_store(struct device *dev, struct device_attribute *attr,
+			    const char *buf, size_t count)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct pattern_trig_data *data = led_cdev->trigger_data;
+	int err, res;
+
+	err = kstrtos32(buf, 10, &res);
+	if (err)
+		return err;
+
+	/* Number 0 and negative numbers except -1 are invalid. */
+	if (res < -1 || res == 0)
+		return -EINVAL;
+
+	/*
+	 * Clear previous patterns' performence firstly, and remove the timer
+	 * without mutex lock to avoid dead lock.
+	 */
+	del_timer_sync(&data->timer);
+
+	mutex_lock(&data->lock);
+
+	if (data->is_hw_pattern)
+		led_cdev->pattern_clear(led_cdev);
+
+	data->last_repeat = data->repeat = res;
+	/* -1 means repeat indefinitely */
+	if (data->repeat == -1)
+		data->is_indefinite = true;
+	else
+		data->is_indefinite = false;
+
+	err = pattern_trig_start_pattern(led_cdev);
+
+	mutex_unlock(&data->lock);
+	return err < 0 ? err : count;
+}
+
+static DEVICE_ATTR_RW(repeat);
+
+static ssize_t pattern_trig_show_patterns(struct pattern_trig_data *data,
+					  char *buf, bool hw_pattern)
+{
+	ssize_t count = 0;
+	int i;
+
+	mutex_lock(&data->lock);
+
+	if (!data->npatterns || (data->is_hw_pattern ^ hw_pattern))
+		goto out;
+
+	for (i = 0; i < data->npatterns; i++) {
+		count += scnprintf(buf + count, PAGE_SIZE - count,
+				   "%d %u ",
+				   data->patterns[i].brightness,
+				   data->patterns[i].delta_t);
+	}
+
+	buf[count - 1] = '\n';
+
+out:
+	mutex_unlock(&data->lock);
+	return count;
+}
+
+static ssize_t pattern_trig_store_patterns(struct led_classdev *led_cdev,
+					   const char *buf, size_t count,
+					   bool hw_pattern)
+{
+	struct pattern_trig_data *data = led_cdev->trigger_data;
+	int ccount, cr, offset = 0, err = 0;
+
+	/*
+	 * Clear previous patterns' performence firstly, and remove the timer
+	 * without mutex lock to avoid dead lock.
+	 */
+	del_timer_sync(&data->timer);
+
+	mutex_lock(&data->lock);
+
+	if (data->is_hw_pattern)
+		led_cdev->pattern_clear(led_cdev);
+
+	data->is_hw_pattern = hw_pattern;
+	data->npatterns = 0;
+
+	while (offset < count - 1 && data->npatterns < MAX_PATTERNS) {
+		cr = 0;
+		ccount = sscanf(buf + offset, "%d %u %n",
+				&data->patterns[data->npatterns].brightness,
+				&data->patterns[data->npatterns].delta_t, &cr);
+		if (ccount != 2) {
+			data->npatterns = 0;
+			err = -EINVAL;
+			goto out;
+		}
+
+		offset += cr;
+		data->npatterns++;
+	}
+
+	err = pattern_trig_start_pattern(led_cdev);
+	if (err)
+		data->npatterns = 0;
+
+out:
+	mutex_unlock(&data->lock);
+	return err < 0 ? err : count;
+}
+
+static ssize_t pattern_show(struct device *dev, struct device_attribute *attr,
+			    char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct pattern_trig_data *data = led_cdev->trigger_data;
+
+	return pattern_trig_show_patterns(data, buf, false);
+}
+
+static ssize_t pattern_store(struct device *dev, struct device_attribute *attr,
+			     const char *buf, size_t count)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+
+	return pattern_trig_store_patterns(led_cdev, buf, count, false);
+}
+
+static DEVICE_ATTR_RW(pattern);
+
+static ssize_t hw_pattern_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct pattern_trig_data *data = led_cdev->trigger_data;
+
+	return pattern_trig_show_patterns(data, buf, true);
+}
+
+static ssize_t hw_pattern_store(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t count)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+
+	return pattern_trig_store_patterns(led_cdev, buf, count, true);
+}
+
+static DEVICE_ATTR_RW(hw_pattern);
+
+static umode_t pattern_trig_attrs_mode(struct kobject *kobj,
+				       struct attribute *attr, int index)
+{
+	struct device *dev = container_of(kobj, struct device, kobj);
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+
+	if (attr == &dev_attr_repeat.attr || attr == &dev_attr_pattern.attr)
+		return attr->mode;
+	else if (attr == &dev_attr_hw_pattern.attr && led_cdev->pattern_set)
+		return attr->mode;
+
+	return 0;
+}
+
+static struct attribute *pattern_trig_attrs[] = {
+	&dev_attr_pattern.attr,
+	&dev_attr_hw_pattern.attr,
+	&dev_attr_repeat.attr,
+	NULL
+};
+
+static const struct attribute_group pattern_trig_group = {
+	.attrs = pattern_trig_attrs,
+	.is_visible = pattern_trig_attrs_mode,
+};
+
+static const struct attribute_group *pattern_trig_groups[] = {
+	&pattern_trig_group,
+	NULL,
+};
+
+static int pattern_trig_activate(struct led_classdev *led_cdev)
+{
+	struct pattern_trig_data *data;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	if (!!led_cdev->pattern_set ^ !!led_cdev->pattern_clear) {
+		dev_warn(led_cdev->dev,
+			 "Hardware pattern ops validation failed\n");
+		led_cdev->pattern_set = NULL;
+		led_cdev->pattern_clear = NULL;
+	}
+
+	data->is_indefinite = true;
+	data->last_repeat = -1;
+	mutex_init(&data->lock);
+	data->led_cdev = led_cdev;
+	led_set_trigger_data(led_cdev, data);
+	timer_setup(&data->timer, pattern_trig_timer_function, 0);
+	led_cdev->activated = true;
+
+	return 0;
+}
+
+static void pattern_trig_deactivate(struct led_classdev *led_cdev)
+{
+	struct pattern_trig_data *data = led_cdev->trigger_data;
+
+	if (!led_cdev->activated)
+		return;
+
+	if (led_cdev->pattern_clear)
+		led_cdev->pattern_clear(led_cdev);
+
+	del_timer_sync(&data->timer);
+
+	led_set_brightness(led_cdev, LED_OFF);
+	kfree(data);
+	led_cdev->activated = false;
+}
+
+static struct led_trigger pattern_led_trigger = {
+	.name = "pattern",
+	.activate = pattern_trig_activate,
+	.deactivate = pattern_trig_deactivate,
+	.groups = pattern_trig_groups,
+};
+
+static int __init pattern_trig_init(void)
+{
+	return led_trigger_register(&pattern_led_trigger);
+}
+
+static void __exit pattern_trig_exit(void)
+{
+	led_trigger_unregister(&pattern_led_trigger);
+}
+
+module_init(pattern_trig_init);
+module_exit(pattern_trig_exit);
+
+MODULE_AUTHOR("Raphael Teysseyre <rteysseyre@gmail.com");
+MODULE_AUTHOR("Baolin Wang <baolin.wang@linaro.org");
+MODULE_DESCRIPTION("LED Pattern trigger");
+MODULE_LICENSE("GPL v2");