LEDs for 4.11

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Merge tag 'leds_for_4.11' of git://git.kernel.org/pub/scm/linux/kernel/git/j.anaszewski/linux-leds

Pull LED updates from Jacek Anaszewski:
 "New features and improvements:

   - add new optional brightness_hw_changed attribute for the LEDs that
     may have their brightness level changed autonomously (outside of
     kernel control) by hardware / firmware. The attribute supports
     userspace notifications through POLLPRI events

   - add led_brightness_hw_mon tool that demonstrates how to use the
     aforementioned feature

   - add LED_ON enum for LEDs that can be only turned on/off, and don't
     allow setting other brightness levels

   - allow for adjusting heartbeat trigger blink brightness level

  Fixes and cleanups:

   - avoid harmless maybe-uninitialized warning in leds-ktd2692.c

   - add context to the existing example entries in common LED bindings
     to make the documentation more clear"

* tag 'leds_for_4.11' of git://git.kernel.org/pub/scm/linux/kernel/git/j.anaszewski/linux-leds:
  leds: ledtrig-heartbeat: Make top brightness adjustable
  tools/leds: Add led_hw_brightness_mon program
  leds: class: Add new optional brightness_hw_changed attribute
  leds: ktd2692: avoid harmless maybe-uninitialized warning
  leds: add LED_ON brightness as boolean value
  DT: leds: Improve examples by adding some context

Documentation/ABI/testing/sysfs-class-led

@@ -23,6 +23,23 @@ Description:
 		If the LED does not support different brightness levels, this
 		should be 1.
 
+What:		/sys/class/leds/<led>/brightness_hw_changed
+Date:		January 2017
+KernelVersion:	4.11
+Description:
+		Last hardware set brightness level for this LED. Some LEDs
+		may be changed autonomously by hardware/firmware. Only LEDs
+		where this happens and the driver can detect this, will have
+		this file.
+
+		This file supports poll() to detect when the hardware changes
+		the brightness.
+
+		Reading this file will return the last brightness level set
+		by the hardware, this may be different from the current
+		brightness. Reading this file when no hw brightness change
+		event has happened will return an ENODATA error.
+
 What:		/sys/class/leds/<led>/trigger
 Date:		March 2006
 KernelVersion:	2.6.17

Documentation/devicetree/bindings/leds/common.txt

@@ -61,16 +61,24 @@ property can be omitted.
 
 Examples:
 
-system-status {
-	label = "Status";
-	linux,default-trigger = "heartbeat";
-	...
+gpio-leds {
+	compatible = "gpio-leds";
+
+	system-status {
+		label = "Status";
+		linux,default-trigger = "heartbeat";
+		gpios = <&gpio0 0 GPIO_ACTIVE_HIGH>;
+	};
 };
 
-camera-flash {
-	label = "Flash";
-	led-sources = <0>, <1>;
-	led-max-microamp = <50000>;
-	flash-max-microamp = <320000>;
-	flash-max-timeout-us = <500000>;
+max77693-led {
+	compatible = "maxim,max77693-led";
+
+	camera-flash {
+		label = "Flash";
+		led-sources = <0>, <1>;
+		led-max-microamp = <50000>;
+		flash-max-microamp = <320000>;
+		flash-max-timeout-us = <500000>;
+	};
 };

Documentation/leds/leds-class.txt

@@ -65,6 +65,21 @@ LED subsystem core exposes following API for setting brightness:
 		blinking, returns -EBUSY if software blink fallback is enabled.
 
 
+LED registration API
+====================
+
+A driver wanting to register a LED classdev for use by other drivers /
+userspace needs to allocate and fill a led_classdev struct and then call
+[devm_]led_classdev_register. If the non devm version is used the driver
+must call led_classdev_unregister from its remove function before
+free-ing the led_classdev struct.
+
+If the driver can detect hardware initiated brightness changes and thus
+wants to have a brightness_hw_changed attribute then the LED_BRIGHT_HW_CHANGED
+flag must be set in flags before registering. Calling
+led_classdev_notify_brightness_hw_changed on a classdev not registered with
+the LED_BRIGHT_HW_CHANGED flag is a bug and will trigger a WARN_ON.
+
 Hardware accelerated blink of LEDs
 ==================================
 

drivers/leds/Kconfig

@@ -29,6 +29,15 @@ config LEDS_CLASS_FLASH
 	  for the flash related features of a LED device. It can be built
 	  as a module.
 
+config LEDS_BRIGHTNESS_HW_CHANGED
+	bool "LED Class brightness_hw_changed attribute support"
+	depends on LEDS_CLASS
+	help
+	  This option enables support for the brightness_hw_changed attribute
+	  for led sysfs class devices under /sys/class/leds.
+
+	  See Documentation/ABI/testing/sysfs-class-led for details.
+
 comment "LED drivers"
 
 config LEDS_88PM860X

drivers/leds/led-class.c

@@ -103,6 +103,68 @@ static const struct attribute_group *led_groups[] = {
 	NULL,
 };
 
+#ifdef CONFIG_LEDS_BRIGHTNESS_HW_CHANGED
+static ssize_t brightness_hw_changed_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+
+	if (led_cdev->brightness_hw_changed == -1)
+		return -ENODATA;
+
+	return sprintf(buf, "%u\n", led_cdev->brightness_hw_changed);
+}
+
+static DEVICE_ATTR_RO(brightness_hw_changed);
+
+static int led_add_brightness_hw_changed(struct led_classdev *led_cdev)
+{
+	struct device *dev = led_cdev->dev;
+	int ret;
+
+	ret = device_create_file(dev, &dev_attr_brightness_hw_changed);
+	if (ret) {
+		dev_err(dev, "Error creating brightness_hw_changed\n");
+		return ret;
+	}
+
+	led_cdev->brightness_hw_changed_kn =
+		sysfs_get_dirent(dev->kobj.sd, "brightness_hw_changed");
+	if (!led_cdev->brightness_hw_changed_kn) {
+		dev_err(dev, "Error getting brightness_hw_changed kn\n");
+		device_remove_file(dev, &dev_attr_brightness_hw_changed);
+		return -ENXIO;
+	}
+
+	return 0;
+}
+
+static void led_remove_brightness_hw_changed(struct led_classdev *led_cdev)
+{
+	sysfs_put(led_cdev->brightness_hw_changed_kn);
+	device_remove_file(led_cdev->dev, &dev_attr_brightness_hw_changed);
+}
+
+void led_classdev_notify_brightness_hw_changed(struct led_classdev *led_cdev,
+					       enum led_brightness brightness)
+{
+	if (WARN_ON(!led_cdev->brightness_hw_changed_kn))
+		return;
+
+	led_cdev->brightness_hw_changed = brightness;
+	sysfs_notify_dirent(led_cdev->brightness_hw_changed_kn);
+}
+EXPORT_SYMBOL_GPL(led_classdev_notify_brightness_hw_changed);
+#else
+static int led_add_brightness_hw_changed(struct led_classdev *led_cdev)
+{
+	return 0;
+}
+static void led_remove_brightness_hw_changed(struct led_classdev *led_cdev)
+{
+}
+#endif
+
 /**
  * led_classdev_suspend - suspend an led_classdev.
  * @led_cdev: the led_classdev to suspend.
@@ -204,9 +266,20 @@ int led_classdev_register(struct device *parent, struct led_classdev *led_cdev)
 		dev_warn(parent, "Led %s renamed to %s due to name collision",
 				led_cdev->name, dev_name(led_cdev->dev));
 
+	if (led_cdev->flags & LED_BRIGHT_HW_CHANGED) {
+		ret = led_add_brightness_hw_changed(led_cdev);
+		if (ret) {
+			device_unregister(led_cdev->dev);
+			return ret;
+		}
+	}
+
 	led_cdev->work_flags = 0;
 #ifdef CONFIG_LEDS_TRIGGERS
 	init_rwsem(&led_cdev->trigger_lock);
+#endif
+#ifdef CONFIG_LEDS_BRIGHTNESS_HW_CHANGED
+	led_cdev->brightness_hw_changed = -1;
 #endif
 	mutex_init(&led_cdev->led_access);
 	/* add to the list of leds */
@@ -256,6 +329,9 @@ void led_classdev_unregister(struct led_classdev *led_cdev)
 
 	flush_work(&led_cdev->set_brightness_work);
 
+	if (led_cdev->flags & LED_BRIGHT_HW_CHANGED)
+		led_remove_brightness_hw_changed(led_cdev);
+
 	device_unregister(led_cdev->dev);
 
 	down_write(&leds_list_lock);

drivers/leds/leds-ktd2692.c

@@ -270,15 +270,15 @@ static int ktd2692_parse_dt(struct ktd2692_context *led, struct device *dev,
 		return -ENXIO;
 
 	led->ctrl_gpio = devm_gpiod_get(dev, "ctrl", GPIOD_ASIS);
-	if (IS_ERR(led->ctrl_gpio)) {
-		ret = PTR_ERR(led->ctrl_gpio);
+	ret = PTR_ERR_OR_ZERO(led->ctrl_gpio);
+	if (ret) {
 		dev_err(dev, "cannot get ctrl-gpios %d\n", ret);
 		return ret;
 	}
 
 	led->aux_gpio = devm_gpiod_get(dev, "aux", GPIOD_ASIS);
-	if (IS_ERR(led->aux_gpio)) {
-		ret = PTR_ERR(led->aux_gpio);
+	ret = PTR_ERR_OR_ZERO(led->aux_gpio);
+	if (ret) {
 		dev_err(dev, "cannot get aux-gpios %d\n", ret);
 		return ret;
 	}

drivers/leds/trigger/ledtrig-heartbeat.c

@@ -43,6 +43,9 @@ static void led_heartbeat_function(unsigned long data)
 		return;
 	}
 
+	if (test_and_clear_bit(LED_BLINK_BRIGHTNESS_CHANGE, &led_cdev->work_flags))
+		led_cdev->blink_brightness = led_cdev->new_blink_brightness;
+
 	/* acts like an actual heart beat -- ie thump-thump-pause... */
 	switch (heartbeat_data->phase) {
 	case 0:
@@ -59,26 +62,26 @@ static void led_heartbeat_function(unsigned long data)
 		delay = msecs_to_jiffies(70);
 		heartbeat_data->phase++;
 		if (!heartbeat_data->invert)
-			brightness = led_cdev->max_brightness;
+			brightness = led_cdev->blink_brightness;
 		break;
 	case 1:
 		delay = heartbeat_data->period / 4 - msecs_to_jiffies(70);
 		heartbeat_data->phase++;
 		if (heartbeat_data->invert)
-			brightness = led_cdev->max_brightness;
+			brightness = led_cdev->blink_brightness;
 		break;
 	case 2:
 		delay = msecs_to_jiffies(70);
 		heartbeat_data->phase++;
 		if (!heartbeat_data->invert)
-			brightness = led_cdev->max_brightness;
+			brightness = led_cdev->blink_brightness;
 		break;
 	default:
 		delay = heartbeat_data->period - heartbeat_data->period / 4 -
 			msecs_to_jiffies(70);
 		heartbeat_data->phase = 0;
 		if (heartbeat_data->invert)
-			brightness = led_cdev->max_brightness;
+			brightness = led_cdev->blink_brightness;
 		break;
 	}
 
@@ -133,7 +136,10 @@ static void heartbeat_trig_activate(struct led_classdev *led_cdev)
 	setup_timer(&heartbeat_data->timer,
 		    led_heartbeat_function, (unsigned long) led_cdev);
 	heartbeat_data->phase = 0;
+	if (!led_cdev->blink_brightness)
+		led_cdev->blink_brightness = led_cdev->max_brightness;
 	led_heartbeat_function(heartbeat_data->timer.data);
+	set_bit(LED_BLINK_SW, &led_cdev->work_flags);
 	led_cdev->activated = true;
 }
 
@@ -145,6 +151,7 @@ static void heartbeat_trig_deactivate(struct led_classdev *led_cdev)
 		del_timer_sync(&heartbeat_data->timer);
 		device_remove_file(led_cdev->dev, &dev_attr_invert);
 		kfree(heartbeat_data);
+		clear_bit(LED_BLINK_SW, &led_cdev->work_flags);
 		led_cdev->activated = false;
 	}
 }

include/linux/leds.h

@@ -13,6 +13,7 @@
 #define __LINUX_LEDS_H_INCLUDED
 
 #include <linux/device.h>
+#include <linux/kernfs.h>
 #include <linux/list.h>
 #include <linux/mutex.h>
 #include <linux/rwsem.h>
@@ -27,6 +28,7 @@ struct device;
 
 enum led_brightness {
 	LED_OFF		= 0,
+	LED_ON		= 1,
 	LED_HALF	= 127,
 	LED_FULL	= 255,
 };
@@ -46,6 +48,7 @@ struct led_classdev {
 #define LED_DEV_CAP_FLASH	(1 << 18)
 #define LED_HW_PLUGGABLE	(1 << 19)
 #define LED_PANIC_INDICATOR	(1 << 20)
+#define LED_BRIGHT_HW_CHANGED	(1 << 21)
 
 	/* set_brightness_work / blink_timer flags, atomic, private. */
 	unsigned long		work_flags;
@@ -110,6 +113,11 @@ struct led_classdev {
 	bool			activated;
 #endif
 
+#ifdef CONFIG_LEDS_BRIGHTNESS_HW_CHANGED
+	int			 brightness_hw_changed;
+	struct kernfs_node	*brightness_hw_changed_kn;
+#endif
+
 	/* Ensures consistent access to the LED Flash Class device */
 	struct mutex		led_access;
 };
@@ -422,4 +430,12 @@ static inline void ledtrig_cpu(enum cpu_led_event evt)
 }
 #endif
 
+#ifdef CONFIG_LEDS_BRIGHTNESS_HW_CHANGED
+extern void led_classdev_notify_brightness_hw_changed(
+	struct led_classdev *led_cdev, enum led_brightness brightness);
+#else
+static inline void led_classdev_notify_brightness_hw_changed(
+	struct led_classdev *led_cdev, enum led_brightness brightness) { }
+#endif
+
 #endif		/* __LINUX_LEDS_H_INCLUDED */

tools/leds/Makefile

@@ -3,11 +3,11 @@
 CC = $(CROSS_COMPILE)gcc
 CFLAGS = -Wall -Wextra -g -I../../include/uapi
 
-all: uledmon
+all: uledmon led_hw_brightness_mon
 %: %.c
 	$(CC) $(CFLAGS) -o $@ $^
 
 clean:
-	$(RM) uledmon
+	$(RM) uledmon led_hw_brightness_mon
 
 .PHONY: all clean

tools/leds/led_hw_brightness_mon.c

@@ -0,0 +1,84 @@
+/*
+ * led_hw_brightness_mon.c
+ *
+ * This program monitors LED brightness level changes having its origin
+ * in hardware/firmware, i.e. outside of kernel control.
+ * A timestamp and brightness value is printed each time the brightness changes.
+ *
+ * Usage: led_hw_brightness_mon <device-name>
+ *
+ * <device-name> is the name of the LED class device to be monitored. Pressing
+ * CTRL+C will exit.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+
+#include <linux/uleds.h>
+
+int main(int argc, char const *argv[])
+{
+	int fd, ret;
+	char brightness_file_path[LED_MAX_NAME_SIZE + 11];
+	struct pollfd pollfd;
+	struct timespec ts;
+	char buf[11];
+
+	if (argc != 2) {
+		fprintf(stderr, "Requires <device-name> argument\n");
+		return 1;
+	}
+
+	snprintf(brightness_file_path, LED_MAX_NAME_SIZE,
+		 "/sys/class/leds/%s/brightness_hw_changed", argv[1]);
+
+	fd = open(brightness_file_path, O_RDONLY);
+	if (fd == -1) {
+		printf("Failed to open %s file\n", brightness_file_path);
+		return 1;
+	}
+
+	/*
+	 * read may fail if no hw brightness change has occurred so far,
+	 * but it is required to avoid spurious poll notifications in
+	 * the opposite case.
+	 */
+	read(fd, buf, sizeof(buf));
+
+	pollfd.fd = fd;
+	pollfd.events = POLLPRI;
+
+	while (1) {
+		ret = poll(&pollfd, 1, -1);
+		if (ret == -1) {
+			printf("Failed to poll %s file (%d)\n",
+				brightness_file_path, ret);
+			ret = 1;
+			break;
+		}
+
+		clock_gettime(CLOCK_MONOTONIC, &ts);
+
+		ret = read(fd, buf, sizeof(buf));
+		if (ret < 0)
+			break;
+
+		ret = lseek(pollfd.fd, 0, SEEK_SET);
+		if (ret < 0) {
+			printf("lseek failed (%d)\n", ret);
+			break;
+		}
+
+		printf("[%ld.%09ld] %d\n", ts.tv_sec, ts.tv_nsec, atoi(buf));
+	}
+
+	close(fd);
+
+	return ret;
+}