leds: class: Don't expose color sysfs entry

The commit c7d8005 ("leds: class: Store the color index in struct
led_classdev") introduced a new sysfs entry "color" that is commonly
created for the led classdev.  Unfortunately, this conflicts with the
"color" sysfs entry of already existing drivers such as Logitech HID
or System76 ACPI drivers.  The driver probe fails due to the conflict,
hence it leads to a severe regression with the missing keyboard, for
example.

This patch reverts partially the change in the commit above for
removing the led class color sysfs entries again for addressing the
regressions.  The newly introduced led_classdev.color field is kept as
it's already used by other driver.

Fixes: c7d8005 ("leds: class: Store the color index in struct led_classdev")
Reported-by: Johannes Penßel <johannes.penssel@gmail.com>
Closes: https://lore.kernel.org/r/b5646db3-acff-45aa-baef-df3f660486fb@gmail.com
Link: https://bugzilla.kernel.org/show_bug.cgi?id=218045
Link: https://bugzilla.kernel.org/show_bug.cgi?id=218155
Link: https://bugzilla.suse.com/show_bug.cgi?id=1217172
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20231121162359.9332-1-tiwai@suse.de
Signed-off-by: Lee Jones <lee@kernel.org>

Documentation/ABI/testing/sysfs-class-led

@@ -59,15 +59,6 @@ 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 (e.g: "red", "green", "multicolor").
-
 What:		/sys/class/leds/<led>/trigger
 Date:		March 2006
 KernelVersion:	2.6.17

drivers/leds/led-class.c

@@ -75,19 +75,6 @@ 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[] = {
@@ -102,7 +89,6 @@ 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,
 };