FM / ttyS0

/sys/devices/pnp0/00:00/tty/ttyS0

Name	Size	Mode	Actions
device/	-	0755	rm
power/	-	0755	rm
subsystem/	-	0755	rm
close_delay	4096	0440	edit dl rm
closing_wait	4096	0440	edit dl rm
custom_divisor	4096	0440	edit dl rm
dev	4096	0444	edit dl rm
flags	4096	0440	edit dl rm
iomem_base	4096	0440	edit dl rm
iomem_reg_shift	4096	0440	edit dl rm
io_type	4096	0440	edit dl rm
irq	4096	0440	edit dl rm
line	4096	0440	edit dl rm
port	4096	0440	edit dl rm
rx_trig_bytes	4096	0640	edit dl rm
type	4096	0440	edit dl rm
uartclk	4096	0440	edit dl rm
uevent	4096	0644	edit dl rm
xmit_fifo_size	4096	0440	edit dl rm

Edit: /sys/devices/pnp0/00:00/tty/ttyS0/closing_wait (4096B)