openwrt/package/system/procd/files/hotplug-preinit.json

[
	[ "case", "ACTION", {
		"add": [
			[ "if",
				[ "has", "FIRMWARE" ],
				[
					[ "exec", "/sbin/hotplug-call", "%SUBSYSTEM%" ],
					[ "load-firmware", "/lib/firmware" ],
					[ "return" ]
				]
			]
		]
	} ],
	[ "if",
		[ "eq", "SUBSYSTEM", "button" ],
		[ "exec", "/etc/rc.button/failsafe" ]
	]
]