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Subject[PATCH v5 1/2] leds: core: Introduce generic pattern interface
Date
From: Bjorn Andersson <bjorn.andersson@linaro.org>

Some LED controllers have support for autonomously controlling
brightness over time, according to some preprogrammed pattern or
function.

This adds a new optional operator that LED class drivers can implement
if they support such functionality as well as a new device attribute to
configure the pattern for a given LED.

[Baolin Wang did some improvements.]

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
---
Changes from v4:
- Fix some typos.
- Check if pattern_clear() is initialized.

Changes from v3:
- Move the check in pattern_show() to of_led_classdev_register().
- Add more documentation to explain how to set/clear one pattern.

Changes from v2:
- Change kernel version to 4.19.
- Force user to return error pointer if failed to issue pattern_get().
- Use strstrip() to trim trailing newline.
- Other optimization.

Changes from v1:
- Add some comments suggested by Pavel.
- Change 'delta_t' can be 0.

Note: I removed the pattern repeat check and will get the repeat number by adding
one extra file named 'pattern_repeat' according to previous discussion.
---
Documentation/ABI/testing/sysfs-class-led | 20 +++++
drivers/leds/led-class.c | 118 +++++++++++++++++++++++++++++
include/linux/leds.h | 19 +++++
3 files changed, 157 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-class-led b/Documentation/ABI/testing/sysfs-class-led
index 5f67f7a..a040fd0 100644
--- a/Documentation/ABI/testing/sysfs-class-led
+++ b/Documentation/ABI/testing/sysfs-class-led
@@ -61,3 +61,23 @@ Description:
gpio and backlight triggers. In case of the backlight trigger,
it is useful when driving a LED which is intended to indicate
a device in a standby like state.
+
+What: /sys/class/leds/<led>/pattern
+Date: July 2018
+KernelVersion: 4.19
+Description:
+ Specify a pattern for the LED, for LED hardware that support
+ altering the brightness as a function of time.
+
+ The pattern is given by a series of tuples, of brightness and
+ duration (ms). The LED is expected to traverse the series and
+ each brightness value for the specified duration. Duration of
+ 0 means brightness should immediately change to new value.
+
+ As LED hardware might have different capabilities and precision
+ the requested pattern might be slighly adjusted by the driver
+ and the resulting pattern of such operation should be returned
+ when this file is read.
+
+ Writing non-empty string to this file will activate the pattern,
+ and empty string will disable the pattern.
diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index 3c7e348..5c6d2e9 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -74,6 +74,118 @@ static ssize_t max_brightness_show(struct device *dev,
}
static DEVICE_ATTR_RO(max_brightness);

+static ssize_t pattern_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct led_classdev *led_cdev = dev_get_drvdata(dev);
+ struct led_pattern *pattern;
+ size_t offset = 0;
+ int count, n, i;
+
+ pattern = led_cdev->pattern_get(led_cdev, &count);
+ if (IS_ERR(pattern))
+ return PTR_ERR(pattern);
+
+ for (i = 0; i < count; i++) {
+ n = snprintf(buf + offset, PAGE_SIZE - offset, "%d %d ",
+ pattern[i].brightness, pattern[i].delta_t);
+
+ if (offset + n >= PAGE_SIZE)
+ goto err_nospc;
+
+ offset += n;
+ }
+
+ buf[offset - 1] = '\n';
+
+ kfree(pattern);
+ return offset;
+
+err_nospc:
+ kfree(pattern);
+ return -ENOSPC;
+}
+
+static ssize_t pattern_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t size)
+{
+ struct led_classdev *led_cdev = dev_get_drvdata(dev);
+ struct led_pattern *pattern = NULL;
+ char *sbegin, *elem, *s;
+ unsigned long val;
+ int ret = 0, len = 0;
+ bool odd = true;
+
+ sbegin = kstrndup(buf, size, GFP_KERNEL);
+ if (!sbegin)
+ return -ENOMEM;
+
+ /*
+ * Trim trailing newline, if the remaining string is empty,
+ * clear the pattern.
+ */
+ s = strstrip(sbegin);
+ if (!*s) {
+ ret = led_cdev->pattern_clear(led_cdev);
+ goto out;
+ }
+
+ pattern = kcalloc(size, sizeof(*pattern), GFP_KERNEL);
+ if (!pattern) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ /* Parse out the brightness & delta_t touples */
+ while ((elem = strsep(&s, " ")) != NULL) {
+ ret = kstrtoul(elem, 10, &val);
+ if (ret)
+ goto out;
+
+ if (odd) {
+ pattern[len].brightness = val;
+ } else {
+ pattern[len].delta_t = val;
+ len++;
+ }
+
+ odd = !odd;
+ }
+
+ /*
+ * Fail if we didn't find any data points or last data point was partial
+ */
+ if (!len || !odd) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ ret = led_cdev->pattern_set(led_cdev, pattern, len);
+
+out:
+ kfree(pattern);
+ kfree(sbegin);
+ return ret < 0 ? ret : size;
+}
+static DEVICE_ATTR_RW(pattern);
+
+static umode_t led_class_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_brightness.attr)
+ return attr->mode;
+ if (attr == &dev_attr_max_brightness.attr)
+ return attr->mode;
+ if (attr == &dev_attr_pattern.attr && led_cdev->pattern_set)
+ return attr->mode;
+
+ return 0;
+}
+
#ifdef CONFIG_LEDS_TRIGGERS
static DEVICE_ATTR(trigger, 0644, led_trigger_show, led_trigger_store);
static struct attribute *led_trigger_attrs[] = {
@@ -88,11 +200,13 @@ static ssize_t max_brightness_show(struct device *dev,
static struct attribute *led_class_attrs[] = {
&dev_attr_brightness.attr,
&dev_attr_max_brightness.attr,
+ &dev_attr_pattern.attr,
NULL,
};

static const struct attribute_group led_group = {
.attrs = led_class_attrs,
+ .is_visible = led_class_attrs_mode,
};

static const struct attribute_group *led_groups[] = {
@@ -256,6 +370,10 @@ int of_led_classdev_register(struct device *parent, struct device_node *np,
char name[LED_MAX_NAME_SIZE];
int ret;

+ if (led_cdev->pattern_set &&
+ (!led_cdev->pattern_get || !led_cdev->pattern_clear))
+ return -EINVAL;
+
ret = led_classdev_next_name(led_cdev->name, name, sizeof(name));
if (ret < 0)
return ret;
diff --git a/include/linux/leds.h b/include/linux/leds.h
index b7e8255..5f1c751 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -22,6 +22,7 @@
#include <linux/workqueue.h>

struct device;
+struct led_pattern;
/*
* LED Core
*/
@@ -88,6 +89,14 @@ struct led_classdev {
unsigned long *delay_on,
unsigned long *delay_off);

+ int (*pattern_set)(struct led_classdev *led_cdev,
+ struct led_pattern *pattern, int len);
+
+ int (*pattern_clear)(struct led_classdev *led_cdev);
+
+ struct led_pattern *(*pattern_get)(struct led_classdev *led_cdev,
+ int *len);
+
struct device *dev;
const struct attribute_group **groups;

@@ -446,4 +455,14 @@ static inline void led_classdev_notify_brightness_hw_changed(
struct led_classdev *led_cdev, enum led_brightness brightness) { }
#endif

+/**
+ * struct led_pattern - brightness value in a pattern
+ * @delta_t: delay until next entry, in milliseconds
+ * @brightness: brightness at time = 0
+ */
+struct led_pattern {
+ int delta_t;
+ int brightness;
+};
+
#endif /* __LINUX_LEDS_H_INCLUDED */
--
1.7.9.5
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