fw_fallback.sh test failed in Debian 11

[Zhou, Jie2X]

hi,

fw_fallback.sh test failed.
The error may caused by failed to write /sys/devices/virtual/misc/test_firmware/trigger_request.

diff firmware/fw_fallback.sh_org firmware/fw_fallback.sh
165c164,165
<       echo -n "nope-$NAME" >"$DIR"/trigger_request 2>/dev/null &
---
>       echo "echo -n \"nope-$NAME\" >\"$DIR\"/trigger_request &"
>       echo -n "nope-$NAME" >"$DIR"/trigger_request &

# Test request_partial_firmware_into_buf() off=1 size=6 nofile: OK
# Test request_partial_firmware_into_buf() off=2 size=10 nofile: OK
# echo -n "nope-test-firmware.bin" >"/sys/devices/virtual/misc/test_firmware"/trigger_request &
# ./fw_fallback.sh: line 165: echo: write error: No such file or directory
# ./fw_fallback.sh: fallback mechanism immediately cancelled

$ echo -n "nope-test-firmware.bin" >/sys/devices/virtual/misc/test_firmware/trigger_request 
-bash: echo: write error: No such file or directory

test OS: Debian 11
test kernel: v6.1-rc6

test output:
# ./fw_fallback.sh: fallback mechanism immediately cancelled
# 
# The file never appeared: /sys/devices/virtual/misc/test_firmware/nope-test-firmware.bin/loading
# 
# This might be a distribution udev rule setup by your distribution
# to immediately cancel all fallback requests, this must be
# removed before running these tests. To confirm look for
# a firmware rule like /lib/udev/rules.d/50-firmware.rules
# and see if you have something like this:
# 
# SUBSYSTEM=="firmware", ACTION=="add", ATTR{loading}="-1"
# 
# If you do remove this file or comment out this line before
# proceeding with these tests.
not ok 1 selftests: firmware: fw_run_tests.sh # exit=1

There is not /lib/udev/rules.d/50-firmware.rules in Debian 11.
How can fw_run_tests.sh run successfully in Debian 11?

best regards,