[PATCH v9 3/5] leds: class: store the color index in struct led_classdev

[Jean-Jacques Hiblot <jjhiblot@xxxxxxxxxxxxxxx>]

This information might be useful for more than only deriving the led's
name. And since we have this information, we can expose it in the sysfs.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@xxxxxxxxxxxxxxx>
---
 Documentation/ABI/testing/sysfs-class-led |  9 +++++++++
 drivers/leds/led-class.c                  | 20 ++++++++++++++++++++
 include/linux/leds.h                      |  1 +
 3 files changed, 30 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-class-led b/Documentation/ABI/testing/sysfs-class-led
index 2e24ac3bd7ef..1509e71fcde1 100644
--- a/Documentation/ABI/testing/sysfs-class-led
+++ b/Documentation/ABI/testing/sysfs-class-led
@@ -59,6 +59,15 @@ Description:
 		brightness. Reading this file when no hw brightness change
 		event has happened will return an ENODATA error.
 
+What:		/sys/class/leds/<led>/color
+Date:		June 2023
+KernelVersion:	6.5
+Description:
+		Color of the led.
+
+		This is a read-only file. Reading this file returns the color
+		of the led as a string (ex: "red", "green", "multicolor").
+
 What:		/sys/class/leds/<led>/trigger
 Date:		March 2006
 KernelVersion:	2.6.17
diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index eb1a8494dc5b..6cca21b227dd 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -76,6 +76,18 @@ static ssize_t max_brightness_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(max_brightness);
 
+static ssize_t color_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	const char *color_text = "invalid";
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+
+	if (led_cdev->color < LED_COLOR_ID_MAX)
+		color_text = led_colors[led_cdev->color];
+	return sysfs_emit(buf, "%s\n", color_text);
+}
+static DEVICE_ATTR_RO(color);
+
 #ifdef CONFIG_LEDS_TRIGGERS
 static BIN_ATTR(trigger, 0644, led_trigger_read, led_trigger_write, 0);
 static struct bin_attribute *led_trigger_bin_attrs[] = {
@@ -90,6 +102,7 @@ static const struct attribute_group led_trigger_group = {
 static struct attribute *led_class_attrs[] = {
 	&dev_attr_brightness.attr,
 	&dev_attr_max_brightness.attr,
+	&dev_attr_color.attr,
 	NULL,
 };
 
@@ -482,6 +495,10 @@ int led_classdev_register_ext(struct device *parent,
 			if (fwnode_property_present(init_data->fwnode,
 						    "retain-state-shutdown"))
 				led_cdev->flags |= LED_RETAIN_AT_SHUTDOWN;
+
+			if (fwnode_property_present(init_data->fwnode, "color"))
+				fwnode_property_read_u32(init_data->fwnode, "color",
+							 &led_cdev->color);
 		}
 	} else {
 		proposed_name = led_cdev->name;
@@ -491,6 +508,9 @@ int led_classdev_register_ext(struct device *parent,
 	if (ret < 0)
 		return ret;
 
+	if (led_cdev->color >= LED_COLOR_ID_MAX)
+		dev_warn(parent, "LED %s color identifier out of range\n", final_name);
+
 	mutex_init(&led_cdev->led_access);
 	mutex_lock(&led_cdev->led_access);
 	led_cdev->dev = device_create_with_groups(leds_class, parent, 0,
diff --git a/include/linux/leds.h b/include/linux/leds.h
index 95311c70d95c..487d00dac4de 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -100,6 +100,7 @@ struct led_classdev {
 	const char		*name;
 	unsigned int brightness;
 	unsigned int max_brightness;
+	unsigned int color;
 	int			 flags;
 
 	/* Lower 16 bits reflect status */
-- 
2.34.1