leds: core: add generic support for RGB LED's

Add generic support for RGB LED's.

Basic idea is to use enum led_brightness also for the hue and saturation color components.This allows to implement the color extension w/o changes to struct led_classdev.

Select LEDS_CLASS_RGB to enable building drivers using the RGB extension.

Flag LED_SET_HUE_SAT allows to specify that hue / saturation should be overridden even if the provided values are zero.

Some examples for writing values to /sys/class/leds/<xx>/brightness:
(now also hex notation can be used)

255 -> set full brightness and keep existing color if set
0 -> switch LED off but keep existing color so that it can be restored
if the LED is switched on again later
0x1000000 -> switch LED off and set also hue and saturation to 0 0x00ffff -> set full brightness, full saturation and set hue to 0 (red)

Signed-off-by Heiner Kallweit <[email protected]>

---
v2:
- move extension-specific code into a separate source file and introduce config symbol LEDS_HSV for it
- create separate patch for the extension to sysfs
- use variable name led_cdev as in the rest if the core
- rename to_hsv to led_validate_brightness
- rename LED_BRIGHTNESS_SET_COLOR to LED_SET_HSV
- introduce helper is_off for checking whether V part
of a HSV value is zero
v3:
- change Kconfig to use depend instead of select, add help message, and change config symbol to LEDS_COLOR
- change LED core object file name in Makefile
- rename flag LED_SET_HSV to LED_SET_COLOR
- rename is_off to led_is_off
- rename led_validate-brightness to led_confine_brightness
- rename variable in led_confine_brightness
- add dummy enum led_brightness value to enforce 32bit enum
- rename led-hsv-core.c to led-color-core.c
- move check of provided brightness value to led_confine_brightness v4:
- change config symbol name to LEDS_RGB
- change name of new file to led-rgb-core.c
- factor out part of led_confine_brightness
- change led_is_off to __is_set_brightness
- in led_set_software_blink pass led_cdev->max_brightness instead of LED_FULL
- rename LED_SET_COLOR to LED_SET_HUE_SAT
v5:
- change "RGB Color LED" to "RGB LED" in Kconfig
- move definition of LED_HUE_SAT_MASK to drivers/leds/leds.h
- rename LED_DEV_CAP_HSV to LED_DEV_CAP_RGB
v6:
- no change
v7:
- removed "Color" from RGB Color LED in commit message and title
- don't include linux/kernel.h in led-rgb-core.c
- keep definition of LED_DEV_CAP_[] flags together
v8:
- rename LEDS_RGB to LEDS_CLASS_RGB

---
  drivers/leds/Kconfig        | 12 ++++++++++++
  drivers/leds/Makefile       |  4 +++-
  drivers/leds/led-class.c    |  2 +-
  drivers/leds/led-core.c     | 16 +++++++++-------
  drivers/leds/led-rgb-core.c | 39 +++++++++++++++++++++++++++++++++++++++
  drivers/leds/leds.h         | 18 ++++++++++++++++++
  include/linux/leds.h        | 11 ++++++++++-
  7 files changed, 92 insertions(+), 10 deletions(-)

create mode 100644 drivers/leds/led-rgb-core.c

drivers/leds/Kconfig +12 -0

index 7f940c2..20697a2 100644
@@ -19,6 +19,14 @@ config LEDS_CLASS
  	  This option enables the led sysfs class in /sys/class/leds.  You'll
  	  need this to do anything useful with LEDs.  If unsure, say N.
 
+config LEDS_CLASS_RGB
+	bool "RGB LED Class Support"
+	depends on LEDS_CLASS
+	help
+	  This option enables support for RGB LED devices.
+	  Sysfs attribute brightness is interpreted as a HSV color value.
+	  For details see Documentation/leds/leds-class.txt.
+
  config LEDS_CLASS_FLASH
  	tristate "LED Flash Class Support"
  	depends on LEDS_CLASS

@@ -29,6 +37,10 @@ config LEDS_CLASS_FLASH
  	  for the flash related features of a LED device. It can be built
  	  as a module.
 
+if LEDS_CLASS_RGB
+comment "RGB LED drivers"
+endif # LEDS_CLASS_RGB
+
  comment "LED drivers"
 
  config LEDS_88PM860X

drivers/leds/Makefile +3 -1

index e9d5309..7f1b2be 100644
@@ -1,6 +1,8 @@
 
  # LED Core
-obj-$(CONFIG_NEW_LEDS)			+= led-core.o
+obj-$(CONFIG_NEW_LEDS)			+= led-core-objs.o
+led-core-objs-y				:= led-core.o
+led-core-objs-$(CONFIG_LEDS_CLASS_RGB)	+= led-rgb-core.o
  obj-$(CONFIG_LEDS_CLASS)		+= led-class.o
  obj-$(CONFIG_LEDS_CLASS_FLASH)		+= led-class-flash.o
  obj-$(CONFIG_LEDS_TRIGGERS)		+= led-triggers.o

drivers/leds/led-class.c +1 -1

index aa84e5b..007a5b3 100644
@@ -53,7 +53,7 @@ static ssize_t brightness_store(struct device *dev,
  	if (ret)
  		goto unlock;
 
-	if (state == LED_OFF)
+	if (!__is_brightness_set(state))
  		led_trigger_remove(led_cdev);
  	led_set_brightness(led_cdev, state);
 

drivers/leds/led-core.c +9 -7

index 3495d5d..e75b0c8 100644
@@ -62,7 +62,7 @@ static void led_timer_function(unsigned long data)
  	}
 
  	brightness = led_get_brightness(led_cdev);
-	if (!brightness) {
+	if (!__is_brightness_set(brightness)) {
  		/* Time to switch the LED on. */
  		brightness = led_cdev->blink_brightness;
  		delay = led_cdev->blink_delay_on;

@@ -133,8 +133,9 @@ static void led_set_software_blink(struct led_classdev *led_cdev,
  	if (current_brightness)
  		led_cdev->blink_brightness = current_brightness;
  	if (!led_cdev->blink_brightness)
-		led_cdev->blink_brightness = led_cdev->max_brightness;
-
+		led_cdev->blink_brightness =
+				led_confine_brightness(led_cdev,
+						led_cdev->max_brightness);
  	led_cdev->blink_delay_on = delay_on;
  	led_cdev->blink_delay_off = delay_off;
 

@@ -235,12 +236,13 @@ void led_set_brightness(struct led_classdev *led_cdev,
  		 * work queue task to avoid problems in case we are called
  		 * from hard irq context.
  		 */
-		if (brightness == LED_OFF) {
+		if (!__is_brightness_set(brightness)) {
  			led_cdev->flags |= LED_BLINK_DISABLE;
  			schedule_work(&led_cdev->set_brightness_work);
  		} else {
  			led_cdev->flags |= LED_BLINK_BRIGHTNESS_CHANGE;
-			led_cdev->blink_brightness = brightness;
+			led_cdev->blink_brightness =
+				led_confine_brightness(led_cdev, brightness);
  		}
  		return;
  	}

@@ -265,7 +267,7 @@ EXPORT_SYMBOL_GPL(led_set_brightness_nopm);
  void led_set_brightness_nosleep(struct led_classdev *led_cdev,
  				enum led_brightness value)
  {
-	led_cdev->brightness = min(value, led_cdev->max_brightness);
+	led_cdev->brightness = led_confine_brightness(led_cdev, value);
 
  	if (led_cdev->flags & LED_SUSPENDED)
  		return;

@@ -280,7 +282,7 @@ int led_set_brightness_sync(struct led_classdev *led_cdev,
  	if (led_cdev->blink_delay_on || led_cdev->blink_delay_off)
  		return -EBUSY;
 
-	led_cdev->brightness = min(value, led_cdev->max_brightness);
+	led_cdev->brightness = led_confine_brightness(led_cdev, value);
 
  	if (led_cdev->flags & LED_SUSPENDED)
  		return 0;

drivers/leds/led-rgb-core.c new file +39 -0

new file mode 100644
index 0000000..cbd8b35
@@ -0,0 +1,39 @@
+/*
+ * RGB LED Class Support
+ *
+ * Author: Heiner Kallweit <[email protected]>
+ *
+ * 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/leds.h>
+#include "leds.h"
+
+/*
+ * The color extension handles RGB LEDs but uses a HSV color model internally.
+ * led_rgb_adjust_hue_sat sets hue and saturation part of the HSV color value.
+ */
+static enum led_brightness led_rgb_adjust_hue_sat(struct led_classdev *led_cdev,
+						  enum led_brightness value)
+{
+	/* LED_SET_HUE_SAT sets hue and saturation even if both are zero */
+	if (value & LED_SET_HUE_SAT || value > LED_FULL)
+		return value & LED_HUE_SAT_MASK;
+	else
+		return led_cdev->brightness & ~LED_BRIGHTNESS_MASK;
+}
+
+enum led_brightness led_confine_brightness(struct led_classdev *led_cdev,
+					   enum led_brightness value)
+{
+	enum led_brightness brightness = 0;
+
+	if (led_cdev->flags & LED_DEV_CAP_RGB)
+		brightness = led_rgb_adjust_hue_sat(led_cdev, value);
+
+	return brightness |
+	       min(value & LED_BRIGHTNESS_MASK, led_cdev->max_brightness);
+}

drivers/leds/leds.h +18 -0

index db3f20d..9c5f3fe 100644
@@ -16,17 +16,35 @@
  #include <linux/rwsem.h>
  #include <linux/leds.h>
 
+#define LED_BRIGHTNESS_MASK	0x000000ff
+#define LED_HUE_SAT_MASK	0x00ffff00
+
  static inline int led_get_brightness(struct led_classdev *led_cdev)
  {
  	return led_cdev->brightness;
  }
 
+static inline bool __is_brightness_set(enum led_brightness brightness)
+{
+	return (brightness & LED_BRIGHTNESS_MASK) != LED_OFF;
+}
+
  void led_init_core(struct led_classdev *led_cdev);
  void led_stop_software_blink(struct led_classdev *led_cdev);
  void led_set_brightness_nopm(struct led_classdev *led_cdev,
  				enum led_brightness value);
  void led_set_brightness_nosleep(struct led_classdev *led_cdev,
  				enum led_brightness value);
+#if IS_ENABLED(CONFIG_LEDS_CLASS_RGB)
+enum led_brightness led_confine_brightness(struct led_classdev *led_cdev,
+					   enum led_brightness value);
+#else
+static inline enum led_brightness led_confine_brightness(
+		struct led_classdev *led_cdev, enum led_brightness value)
+{
+	return min(value, led_cdev->max_brightness);
+}
+#endif
 
  extern struct rw_semaphore leds_list_lock;
  extern struct list_head leds_list;

include/linux/leds.h +8 -0

index f203a8f..58e8299 100644
@@ -29,8 +29,16 @@ enum led_brightness {
  	LED_OFF		= 0,
  	LED_HALF	= 127,
  	LED_FULL	= 255,
+	/*
+	 * dummy enum value to make gcc use a 32 bit type for the enum
+	 * even if compiled with -fshort-enums. This is needed for
+	 * the enum to store hsv values.
+	 */
+	LED_LEVEL_DUMMY	= 0xffffffff,
  };
 
+#define LED_SET_HUE_SAT		BIT(24)
+
  struct led_classdev {
  	const char		*name;
  	enum led_brightness	 brightness;