leds: add RGB color option, as that is different from multicolor.

Multicolor is a bit too abstract. Yes, we can have
Green-Magenta-Ultraviolet LED, but so far all the LEDs we support are
RGB, and not even RGB-White or RGB-Yellow variants emerged.

Multicolor is not a good fit for RGB LED. It does not really know
about LED color.  In particular, there's no way to make LED "white".

Userspace is interested in knowing "this LED can produce arbitrary
color", which not all multicolor LEDs can.
Signed-off-by: Pavel Machek <pavel@ucw.cz>

drivers/leds/led-core.c

@@ -35,6 +35,7 @@ const char * const led_colors[LED_COLOR_ID_MAX] = {
 	[LED_COLOR_ID_YELLOW] = "yellow",
 	[LED_COLOR_ID_IR] = "ir",
 	[LED_COLOR_ID_MULTI] = "multicolor",
+	[LED_COLOR_ID_RGB] = "rgb",
 };
 EXPORT_SYMBOL_GPL(led_colors);
 

drivers/leds/leds-lp55xx-common.c

@@ -638,7 +638,7 @@ static int lp55xx_parse_logical_led(struct device_node *np,
 	if (ret)
 		return ret;
 
-	if (led_color == LED_COLOR_ID_MULTI)
+	if (led_color == LED_COLOR_ID_RGB)
 		return lp55xx_parse_multi_led(np, cfg, child_number);
 
 	ret =  lp55xx_parse_common_child(np, cfg, child_number, &chan_nr);

include/dt-bindings/leds/common.h

@@ -30,8 +30,10 @@
 #define LED_COLOR_ID_VIOLET	5
 #define LED_COLOR_ID_YELLOW	6
 #define LED_COLOR_ID_IR		7
-#define LED_COLOR_ID_MULTI	8
-#define LED_COLOR_ID_MAX	9
+#define LED_COLOR_ID_MULTI	8	/* For multicolor LEDs */
+#define LED_COLOR_ID_RGB	9	/* For multicolor LEDs that can do arbitrary color,
+					   so this would include RGBW and similar */
+#define LED_COLOR_ID_MAX	10
 
 /* Standard LED functions */
 /* Keyboard LEDs, usually it would be input4::capslock etc. */