base-files: add ucidef for LEDs with configurable brightness

Add ucidef_set_led_brightness() to set up a static LED with an optional
brightness level, complementing ucidef_set_led_default() for hardware
that supports per-channel current or PWM control.

The function writes a "brightness" type to board.json alongside the
default on/off state. config_generate picks this up and writes the
brightness option to the UCI LED config, where the led init script
already knows to apply it.

Signed-off-by: Manuel Fombuena <fombuena@outlook.com>
Link: https://github.com/openwrt/openwrt/pull/23457
Signed-off-by: Robert Marko <robimarko@gmail.com>

package/base-files/files/bin/config_generate

@@ -405,6 +405,12 @@ generate_led() {
 	EOF
 
 	case "$type" in
+		brightness)
+			local brightness
+			json_get_vars brightness
+			[ -n "$brightness" ] && uci -q set system.$cfg.brightness="$brightness"
+		;;
+
 		gpio)
 			local gpio inverted
 			json_get_vars gpio inverted

package/base-files/files/lib/functions/uci-defaults.sh

@@ -416,6 +416,17 @@ ucidef_set_led_ataport() {
 	_ucidef_set_led_trigger "$1" "$2" "$3" ata"$4"
 }
 
+ucidef_set_led_brightness() {
+	_ucidef_set_led_common "$1" "$2" "$3"
+
+	json_add_string type brightness
+	json_add_string default "$4"
+	[ -n "$5" ] && json_add_string brightness "$5"
+	json_select ..
+
+	json_select ..
+}
+
 _ucidef_set_led_common() {
 	local cfg="led_$1"
 	local name="$2"