UART initialization failed on Raspberry Pi 4

[matsujirushi]

Hi,
When I try to use UART on Raspberry Pi 4, the following error occurs.

Error message:

$ sudo python3 uart-test.py
Traceback (most recent call last):
  File "/home/pi/work/uart-test.py", line 6, in <module>
    uart = mraa.Uart(0)
  File "/usr/local/lib/python3.9/dist-packages/mraa.py", line 601, in __init__
    _mraa.Uart_swiginit(self, _mraa.new_Uart(*args))
ValueError: Error initialising UART

Code:

#!/usr/bin/env python3

import mraa
import time

uart = mraa.Uart(0)

It seems that device_path is not set.

mraa/src/uart/uart.c

Line 240 in 046bdd0

if (!path) {

path == NULL

mraa/src/uart/uart.c

Line 217 in 046bdd0

mraa_uart_context dev = mraa_uart_init_raw((char*)plat->uart_dev[index].device_path);

plat->uart_dev[index].device_path == NULL

Does anyone know the cause?