Hi all,
Following our discussion about [PATCH RFC] leds: Add status code trigger,
here is a patch allowing arbitrary patterns. This is intended for
embedded systems without screen or network access to show a status (or
error) code to a human.
It's been tested on an ARM architecture (Xilinx Zynq 7010 SoC,
which CPU is a dual ARM Cortex-A9), with a non-mainline
kernel (xilinx-v2014.4, based of a 3.17.0 kernel).
Unfortunately, I don't have other hardware to test it on.
It compiles fine in a 3.19.0-rc1 source tree.
Additional testing and comments would be appreciated.
Add a new led trigger supporting arbitrary patterns.
This is useful for embedded systems with no screen or network access.
Export two sysfs attributes: "pattern", and "repeat".
When "repeat"=-1, repeat the pattern indefinitely. Otherwise,
repeat it the specified number of times. "pattern" specifies
the pattern as comma separated couples of "brightness duration"
values. See detailed documentation in patch.
Signed-off-by: Raphaël Teysseyre <rteysseyre@xxxxxxxxx>
---
Documentation/leds/ledtrig-pattern.txt | 80 +++++++
drivers/leds/trigger/Kconfig | 10 +
drivers/leds/trigger/Makefile | 1 +
drivers/leds/trigger/ledtrig-pattern.c | 388 ++++++++++++++++++++++++++++++++
4 files changed, 479 insertions(+), 0 deletions(-)
create mode 100644 Documentation/leds/ledtrig-pattern.txt
create mode 100644 drivers/leds/trigger/ledtrig-pattern.c
diff --git a/Documentation/leds/ledtrig-pattern.txt b/Documentation/leds/ledtrig-pattern.txt
new file mode 100644
index 0000000..68d11d2
--- /dev/null
+++ b/Documentation/leds/ledtrig-pattern.txt
@@ -0,0 +1,80 @@
+LED Pattern Trigger
+===================
+
+This is a LED trigger allowing arbitrary pattern execution. It can do gradual
+dimming. This trigger can be configured to repeat the pattern a number of
+times or indefinitely. This is intended as a way of communication for embedded
+systems with no screen.
+
+The trigger can be activated from user space on led class devices as shown
+below:
+
+ echo pattern > trigger
+
+This adds the following sysfs attributes to the LED:
+
+ pattern - specifies the pattern. See syntax below.
+
+ repeat - number of times the pattern must be repeated.
+ writing -1 to this file will make the pattern
+ repeat indefinitely.
+
+The pattern will be restarted each time a new value is written to
+the pattern or repeat attribute. When dimming, the LED brightness
+is set every 50 ms.
+
+pattern syntax:
+The pattern is specified in the pattern attribute with an array of comma-
+separated "brightness/length in miliseconds" values. The two components
+of each value are to be separated by a space.
+
+For example, assuming the driven LED supports
+intensity value from 0 to 255:
+
+ echo 0 1000, 255 2000 > pattern
+
+Will make the LED go gradually from zero-intensity to max (255) intensity
+in 1000 milliseconds, then back to zero intensity in 2000 milliseconds:
+
+LED brightness
+ ^
+255-| / \ / \ /
+ | / \ / \ /
+ | / \ / \ /
+ | / \ / \ /
+ 0-| / \/ \/
+ +---0----1----2----3----4----5----6------------> time (s)
+
+
+
+To make the LED go instantly from one brigntess value to another,
+use zero-time lengths. For example:
+
+ echo 0 1000, 0 0, 255 2000, 255 0 > pattern
+
+Will make the LED stay off for one second, then stay at max brightness
+for two seconds:
+
+LED brightness
+ ^
+255-| +---------+ +---------+
+ | | | | |
+ | | | | |
+ | | | | |
+ 0-| -----+ +----+ +----
+ +---0----1----2----3----4----5----6------------> time (s)
+
+
+
+Patterns with less than two values, no value with time length > 50
+milliseconds, or no two values with differing brightnesses will
+result in the LED being set at the brightness of the first value,
+or zero if the pattern contains no value.
+
+Patterns with invalid syntax are silently swallowed and will result
+in undefined behavior of the LED brightness.
+
+Because sysfs is used to define the pattern, patterns that need more than
+PAGE_SIZE characters to describe aren't supported. PAGE_SIZE is system
+dependent.
+
diff --git a/drivers/leds/trigger/Kconfig b/drivers/leds/trigger/Kconfig
index 49794b4..ce27bdb 100644
--- a/drivers/leds/trigger/Kconfig
+++ b/drivers/leds/trigger/Kconfig
@@ -108,4 +108,14 @@ config LEDS_TRIGGER_CAMERA
This enables direct flash/torch on/off by the driver, kernel space.
If unsure, say Y.
+config LEDS_TRIGGER_PATTERN
+ tristate "LED Pattern Trigger"
+ depends on LEDS_TRIGGERS
+ help
+ This allows LEDs blinking with an arbitrary pattern. Can be useful
+ on embedded systems with no screen to give out a status code to
+ a human.
+
+ If unsure, say N
+
endif # LEDS_TRIGGERS
diff --git a/drivers/leds/trigger/Makefile b/drivers/leds/trigger/Makefile
index 1abf48d..a739429 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_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 0000000..da290b3
--- /dev/null
+++ b/drivers/leds/trigger/ledtrig-pattern.c
@@ -0,0 +1,388 @@
+/*
+ * Arbitrary pattern trigger
+ *
+ * Copyright 2015, Epsiline
+ *
+ * Author : Raphaël Teysseyre <rteysseyre@xxxxxxxxx>
+ *
+ * Idea discussed with Pavel Machek <pavel@xxxxxx> on
+ * <linux-leds@xxxxxxxxxxxxxxx> (march 2015, thread title
+ * [PATCH RFC] leds: Add status code trigger)
+ *
+ * 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/types.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/leds.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include "../leds.h"
+
+struct pattern_step {
+ int brightness;
+ int time_ms;
+};
+
+struct pattern_trig_data {
+ struct pattern_step *steps; /* Array describing the pattern */
+ struct mutex lock;
+ char is_sane;
+ struct pattern_step *curr;
+ struct pattern_step *next;
+ int time_ms; /* Time in current step */
+ int nsteps; /* Number of steps */
+ int repeat; /* < 0 means repeat indefinitely */
+ struct timer_list timer; /* Used for scheduling updates to
+ the led brightness */
+};
+
+#define MAX_NSTEPS (PAGE_SIZE/4)
+/* The "pattern" attribute contains at most PAGE_SIZE characters.
+ Each line in this attribute is at least 4 characters long
+ (a 1-digit number for the led brighntess, a space,
+ a 1-digit number for the time, a semi-colon).
+ Therefore, there is at most PAGE_SIZE/4 steps. */
+
+#define UPDATE_INTERVAL 50
+/* When doing gradual dimming, the led brightness
+ will be updated every UPDATE_INTERVAL milliseconds */
+
+#define PATTERN_SEPARATOR ","
+
+static int pattern_trig_initialize_data(struct pattern_trig_data *data)
+{
+ mutex_init(&data->lock);
+ mutex_lock(&data->lock);
+
+ data->is_sane = 0;
+ data->steps = kzalloc(MAX_NSTEPS*sizeof(struct pattern_step),
+ GFP_KERNEL);
+ if (!data->steps)
+ return -ENOMEM;
+
+ data->curr = NULL;
+ data->next = NULL;
+ data->time_ms = 0;
+ data->nsteps = 0;
+ data->repeat = -1;
+ init_timer(&data->timer);
+
+ mutex_unlock(&data->lock);
+ return 0;
+}
+
+static void pattern_trig_clear_data(struct pattern_trig_data *data)
+{
+ data->is_sane = 0;
+ kfree(data->steps);
+}
+
+/*
+ * is_sane : pattern checking.
+ * A pattern satisfaying these three conditions is reported as sane :
+ * - At least two steps
+ * - At least one step with time >= UPDATE_INTERVAL
+ * - At least two steps with differing brightnesses
+ * When @data isn't sane, a sensible brightness
+ * default is suggested in @brightness
+ *
+ * DO NOT call pattern_trig_update on a not-sane pattern,
+ * you'll be punished with an infinite loop in the kernel.
+ */
+static int is_sane(struct pattern_trig_data *data, int *brightness)
+{
+ int i;
+ char stept_ok = 0;
+ char stepb_ok = 0;
+
+ *brightness = 0;
+ if (data->nsteps < 1)
+ return 0;
+
+ *brightness = data->steps[0].brightness;
+ if (data->nsteps < 2)
+ return 0;
+
+ for (i = 0; i < data->nsteps; i++) {
+ if (data->steps[i].time_ms >= UPDATE_INTERVAL) {
+ if (stepb_ok)
+ return 1;
+ stept_ok = 1;
+ }
+ if (data->steps[i].brightness != data->steps[0].brightness) {
+ if (stept_ok)
+ return 1;
+ stepb_ok = 1;
+ }
+ }
+
+ return 0;
+}
+
+static void reset_pattern(struct pattern_trig_data *data,
+ struct led_classdev *led_cdev)
+{
+ int brightness;
+
+ del_timer_sync(&data->timer);
+
+ if (is_sane(data, &brightness)) {
+ data->curr = data->steps;
+ data->next = data->steps + 1;
+ data->time_ms = 0;
+ data->is_sane = 1;
+
+ data->timer.expires = jiffies;
+ add_timer(&data->timer);
+ } else
+ led_set_brightness(led_cdev, brightness);
+}
+
+/* --- Sysfs handling --- */
+
+static ssize_t pattern_trig_show_repeat(
+ 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 scnprintf(buf, PAGE_SIZE, "%d\n", data->repeat);
+}
+
+static ssize_t pattern_trig_store_repeat(
+ 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;
+ long res;
+ int err;
+
+ err = kstrtol(buf, 10, &res);
+ if (err)
+ return err;
+
+ data->repeat = res < 0 ? -1 : res;
+ reset_pattern(data, led_cdev);
+
+ return count;
+}
+
+DEVICE_ATTR(repeat, S_IRUGO | S_IWUSR,
+ pattern_trig_show_repeat, pattern_trig_store_repeat);
+
+static ssize_t pattern_trig_show_pattern(
+ 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;
+ ssize_t count = 0;
+ int i;
+
+ if (!data->steps || !data->nsteps)
+ return 0;
+
+ for (i = 0; i < data->nsteps; i++)
+ count += scnprintf(buf + count, PAGE_SIZE - count,
+ "%d %d" PATTERN_SEPARATOR,
+ data->steps[i].brightness,
+ data->steps[i].time_ms);
+ buf[count - 1] = '\n';
+ buf[count] = '\0';
+
+ return count + 1;
+}
+
+static ssize_t pattern_trig_store_pattern(
+ 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 cr = 0; /* Characters read on one conversion */
+ int tcr = 0; /* Total characters read */
+ int ccount; /* Number of successful conversions */
+
+ mutex_lock(&data->lock);
+ data->is_sane = 0;
+
+ for (data->nsteps = 0; data->nsteps < MAX_NSTEPS; data->nsteps++) {
+ cr = 0;
+ ccount = sscanf(buf + tcr, "%d %d " PATTERN_SEPARATOR "%n",
+ &data->steps[data->nsteps].brightness,
+ &data->steps[data->nsteps].time_ms, &cr);
+
+ if (!cr) { /* Invalid syntax or end of pattern */
+ if (ccount == 2)
+ data->nsteps++;
+ mutex_unlock(&data->lock);
+ reset_pattern(data, led_cdev);
+ return count;
+ }
+
+ tcr += cr;
+ }
+
+ /* Shouldn't reach that */
+ WARN(1, "MAX_NSTEP too small. Please report\n");
+ mutex_unlock(&data->lock);
+ return count;
+}
+
+DEVICE_ATTR(pattern, S_IRUGO | S_IWUSR,
+ pattern_trig_show_pattern, pattern_trig_store_pattern);
+
+static int pattern_trig_create_sysfs_files(struct device *dev)
+{
+ int err;
+
+ err = device_create_file(dev, &dev_attr_repeat);
+ if (err)
+ return err;
+
+ err = device_create_file(dev, &dev_attr_pattern);
+ if (err)
+ device_remove_file(dev, &dev_attr_repeat);
+
+ return err;
+}
+
+static void pattern_trig_remove_sysfs_files(struct device *dev)
+{
+ device_remove_file(dev, &dev_attr_pattern);
+ device_remove_file(dev, &dev_attr_repeat);
+}
+
+/* --- Led intensity updating --- */
+
+static int compute_brightness(struct pattern_trig_data *data)
+{
+ if (data->time_ms == 0)
+ return data->curr->brightness;
+
+ if (data->curr->time_ms == 0)
+ return data->next->brightness;
+
+ return data->curr->brightness + data->time_ms
+ * (data->next->brightness - data->curr->brightness)
+ / data->curr->time_ms;
+}
+
+static void update_to_next_step(struct pattern_trig_data *data)
+{
+ data->curr = data->next;
+ if (data->curr == data->steps)
+ data->repeat--;
+
+ if (data->next == data->steps + data->nsteps - 1)
+ data->next = data->steps;
+ else
+ data->next++;
+
+ data->time_ms = 0;
+}
+
+static void pattern_trig_update(unsigned long led_cdev_ptr)
+{
+ struct led_classdev *led_cdev = (struct led_classdev *) led_cdev_ptr;
+ struct pattern_trig_data *data = led_cdev->trigger_data;
+
+ mutex_lock(&data->lock);
+
+ if (!data->is_sane || !data->repeat) {
+ mutex_unlock(&data->lock);
+ return;
+ }
+
+ if (data->time_ms > data->curr->time_ms)
+ update_to_next_step(data);
+
+ /* is_sane() checked that there is at least
+ one step with time_ms >= UPDATE_INTERVAL
+ so we won't go in an infinite loop */
+ while (data->curr->time_ms < UPDATE_INTERVAL)
+ update_to_next_step(data);
+
+ if (data->next->brightness == data->curr->brightness) {
+ /* Constant brightness for this step */
+ led_set_brightness(led_cdev, data->curr->brightness);
+ mod_timer(&data->timer, jiffies
+ + msecs_to_jiffies(data->curr->time_ms));
+ update_to_next_step(data);
+ } else {
+ /* Gradual dimming */
+ led_set_brightness(led_cdev, compute_brightness(data));
+ data->time_ms += UPDATE_INTERVAL;
+ mod_timer(&data->timer, jiffies
+ + msecs_to_jiffies(UPDATE_INTERVAL));
+ }
+
+ mutex_unlock(&data->lock);
+}
+
+/* --- Trigger activation --- */
+
+static void pattern_trig_activate(struct led_classdev *led_cdev)
+{
+ struct pattern_trig_data *data = NULL;
+ int err;
+
+ data = kzalloc(sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return;
+
+ err = pattern_trig_initialize_data(data);
+ if (err) {
+ kfree(data);
+ return;
+ }
+
+ led_cdev->trigger_data = data;
+ setup_timer(&data->timer, pattern_trig_update,
+ (unsigned long) led_cdev);
+ pattern_trig_create_sysfs_files(led_cdev->dev);
+}
+
+static void pattern_trig_deactivate(struct led_classdev *led_cdev)
+{
+ struct pattern_trig_data *data = led_cdev->trigger_data;
+
+ if (data) {
+ pattern_trig_remove_sysfs_files(led_cdev->dev);
+ del_timer_sync(&data->timer);
+ led_set_brightness(led_cdev, LED_OFF);
+ pattern_trig_clear_data(data);
+ kfree(data);
+ led_cdev->trigger_data = NULL;
+ }
+}
+
+static struct led_trigger pattern_led_trigger = {
+ .name = "pattern",
+ .activate = pattern_trig_activate,
+ .deactivate = pattern_trig_deactivate,
+};
+
+/* --- Module loading/unloading --- */
+
+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@xxxxxxxxx");
+MODULE_DESCRIPTION("Statuscode LED trigger");
+MODULE_LICENSE("GPL");
--
1.7.1
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