leds: core: Introduce led_get_color_name() function

This is similar to the existing led_colors[] array but is safer to use and
usable by everyone.

Getting string representations of color ids is useful for drivers
which are handling color IDs anyways, for example for the multicolor API.

Signed-off-by: Thomas Weißschuh <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Lee Jones <[e-mail]>

drivers/leds/led-core.c

···
 }
 EXPORT_SYMBOL_GPL(led_compose_name);
 
+const char *led_get_color_name(u8 color_id)
+{
+	if (color_id >= ARRAY_SIZE(led_colors))
+		return NULL;
+
+	return led_colors[color_id];
+}
+EXPORT_SYMBOL_GPL(led_get_color_name);
+
 enum led_default_state led_init_default_state_get(struct fwnode_handle *fwnode)
 {
 	const char *state = NULL;

include/linux/leds.h

···
 		     char *led_classdev_name);
 
 /**
+ * led_get_color_name - get string representation of color ID
+ * @color_id: The LED_COLOR_ID_* constant
+ *
+ * Get the string name of a LED_COLOR_ID_* constant.
+ *
+ * Returns: A string constant or NULL on an invalid ID.
+ */
+const char *led_get_color_name(u8 color_id);
+
+/**
  * led_sysfs_is_disabled - check if LED sysfs interface is disabled
  * @led_cdev: the LED to query
  *