[PATCH v2 1/4] leds: core: add generic support for color LED's

[Heiner Kallweit <hkallweit1@gmail.com>]

Add generic support for color 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.
A driver that wants to use this extension has to select LEDS_HSV
in its Kconfig entry.

Flag LED_SET_HSV 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 <hkallweit1@gmail.com>
---
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
---
 drivers/leds/Kconfig        |  5 +++++
 drivers/leds/Makefile       |  4 +++-
 drivers/leds/led-core.c     | 17 ++++++++++-------
 drivers/leds/led-hsv-core.c | 30 ++++++++++++++++++++++++++++++
 drivers/leds/leds.h         | 17 +++++++++++++++++
 include/linux/leds.h        |  9 +++++++++
 6 files changed, 74 insertions(+), 8 deletions(-)
 create mode 100644 drivers/leds/led-hsv-core.c

diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index 7f940c2..01c0b35 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -29,6 +29,11 @@ config LEDS_CLASS_FLASH
 	  for the flash related features of a LED device. It can be built
 	  as a module.
 
+config LEDS_HSV
+	bool
+	depends on LEDS_CLASS
+	default n
+
 comment "LED drivers"
 
 config LEDS_88PM860X
diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
index e9d5309..748d650 100644
--- a/drivers/leds/Makefile
+++ b/drivers/leds/Makefile
@@ -1,6 +1,8 @@
 
 # LED Core
-obj-$(CONFIG_NEW_LEDS)			+= led-core.o
+obj-$(CONFIG_NEW_LEDS)			+= ledcore.o
+ledcore-y				:= led-core.o
+ledcore-$(CONFIG_LEDS_HSV)		+= led-hsv-core.o
 obj-$(CONFIG_LEDS_CLASS)		+= led-class.o
 obj-$(CONFIG_LEDS_CLASS_FLASH)		+= led-class-flash.o
 obj-$(CONFIG_LEDS_TRIGGERS)		+= led-triggers.o
diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
index 3495d5d..64b627a 100644
--- a/drivers/leds/led-core.c
+++ b/drivers/leds/led-core.c
@@ -62,7 +62,7 @@ static void led_timer_function(unsigned long data)
 	}
 
 	brightness = led_get_brightness(led_cdev);
-	if (!brightness) {
+	if (is_off(brightness)) {
 		/* Time to switch the LED on. */
 		brightness = led_cdev->blink_brightness;
 		delay = led_cdev->blink_delay_on;
@@ -133,8 +133,8 @@ 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_validate_brightness(led_cdev, LED_FULL);
 	led_cdev->blink_delay_on = delay_on;
 	led_cdev->blink_delay_off = delay_off;
 
@@ -225,6 +225,8 @@ EXPORT_SYMBOL_GPL(led_stop_software_blink);
 void led_set_brightness(struct led_classdev *led_cdev,
 			enum led_brightness brightness)
 {
+	if (!(led_cdev->flags & LED_DEV_CAP_HSV))
+		brightness &= LED_BRIGHTNESS_MASK;
 	/*
 	 * In case blinking is on delay brightness setting
 	 * until the next timer tick.
@@ -235,12 +237,13 @@ 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_off(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_validate_brightness(led_cdev, brightness);
 		}
 		return;
 	}
@@ -265,7 +268,7 @@ 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_validate_brightness(led_cdev, value);
 
 	if (led_cdev->flags & LED_SUSPENDED)
 		return;
@@ -280,7 +283,7 @@ 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_validate_brightness(led_cdev, value);
 
 	if (led_cdev->flags & LED_SUSPENDED)
 		return 0;
diff --git a/drivers/leds/led-hsv-core.c b/drivers/leds/led-hsv-core.c
new file mode 100644
index 0000000..3c31139
--- /dev/null
+++ b/drivers/leds/led-hsv-core.c
@@ -0,0 +1,30 @@
+/*
+ * LED Class Color Support
+ *
+ * Author: Heiner Kallweit <hkallweit1@gmail.com>
+ *
+ * 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/kernel.h>
+#include <linux/leds.h>
+#include "leds.h"
+
+#define LED_HUE_SAT_MASK	0x00ffff00
+
+enum led_brightness led_validate_brightness(struct led_classdev *led_cdev,
+					    enum led_brightness value)
+{
+	enum led_brightness ret;
+
+	/* Use LED_SET_HSV to set hue and saturation even if both are zero */
+	if (value & LED_SET_HSV || value > LED_FULL)
+		ret = value & LED_HUE_SAT_MASK;
+	else
+		ret = led_cdev->brightness & ~LED_BRIGHTNESS_MASK;
+
+	return ret | min(value & LED_BRIGHTNESS_MASK, led_cdev->max_brightness);
+}
diff --git a/drivers/leds/leds.h b/drivers/leds/leds.h
index db3f20d..ac3f1be 100644
--- a/drivers/leds/leds.h
+++ b/drivers/leds/leds.h
@@ -16,17 +16,34 @@
 #include <linux/rwsem.h>
 #include <linux/leds.h>
 
+#define LED_BRIGHTNESS_MASK	0x000000ff
+
 static inline int led_get_brightness(struct led_classdev *led_cdev)
 {
 	return led_cdev->brightness;
 }
 
+static inline bool is_off(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_HSV)
+enum led_brightness led_validate_brightness(struct led_classdev *led_cdev,
+					    enum led_brightness value);
+#else
+static inline enum led_brightness led_validate_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;
diff --git a/include/linux/leds.h b/include/linux/leds.h
index f203a8f..d72dfd9 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -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_SIZE_DUMMY	= 0xffffffff,
 };
 
+#define LED_SET_HSV		BIT(24)
+
 struct led_classdev {
 	const char		*name;
 	enum led_brightness	 brightness;
@@ -50,6 +58,7 @@ struct led_classdev {
 #define LED_SYSFS_DISABLE	(1 << 22)
 #define LED_DEV_CAP_FLASH	(1 << 23)
 #define LED_HW_PLUGGABLE	(1 << 24)
+#define LED_DEV_CAP_HSV		(1 << 25)
 
 	/* Set LED brightness level
 	 * Must not sleep. Use brightness_set_blocking for drivers
-- 
2.7.1