linux_kernel/tools/testing/selftests/firmware/fw_userhelper.sh

#!/bin/sh
# This validates that the kernel will fall back to using the user helper
# to load firmware it can't find on disk itself. We must request a firmware
# that the kernel won't find, and any installed helper (e.g. udev) also
# won't find so that we can do the load ourself manually.
set -e

modprobe test_firmware

DIR=/sys/devices/virtual/misc/test_firmware

# CONFIG_FW_LOADER_USER_HELPER has a sysfs class under /sys/class/firmware/
# These days no one enables CONFIG_FW_LOADER_USER_HELPER so check for that
# as an indicator for CONFIG_FW_LOADER_USER_HELPER.
HAS_FW_LOADER_USER_HELPER=$(if [ -d /sys/class/firmware/ ]; then echo yes; else echo no; fi)

if [ "$HAS_FW_LOADER_USER_HELPER" = "yes" ]; then
       OLD_TIMEOUT=$(cat /sys/class/firmware/timeout)
else
	echo "usermode helper disabled so ignoring test"
	exit 0
fi

FWPATH=$(mktemp -d)
FW="$FWPATH/test-firmware.bin"

test_finish()
{
	echo "$OLD_TIMEOUT" >/sys/class/firmware/timeout
	rm -f "$FW"
	rmdir "$FWPATH"
}

load_fw()
{
	local name="$1"
	local file="$2"

	# This will block until our load (below) has finished.
	echo -n "$name" >"$DIR"/trigger_request &

	# Give kernel a chance to react.
	local timeout=10
	while [ ! -e "$DIR"/"$name"/loading ]; do
		sleep 0.1
		timeout=$(( $timeout - 1 ))
		if [ "$timeout" -eq 0 ]; then
			echo "$0: firmware interface never appeared" >&2
			exit 1
		fi
	done

	echo 1 >"$DIR"/"$name"/loading
	cat "$file" >"$DIR"/"$name"/data
	echo 0 >"$DIR"/"$name"/loading

	# Wait for request to finish.
	wait
}

trap "test_finish" EXIT

# This is an unlikely real-world firmware content. :)
echo "ABCD0123" >"$FW"
NAME=$(basename "$FW")

# Test failure when doing nothing (timeout works).
echo 1 >/sys/class/firmware/timeout
echo -n "$NAME" >"$DIR"/trigger_request
if diff -q "$FW" /dev/test_firmware >/dev/null ; then
	echo "$0: firmware was not expected to match" >&2
	exit 1
else
	echo "$0: timeout works"
fi

# Put timeout high enough for us to do work but not so long that failures
# slow down this test too much.
echo 4 >/sys/class/firmware/timeout

# Load this script instead of the desired firmware.
load_fw "$NAME" "$0"
if diff -q "$FW" /dev/test_firmware >/dev/null ; then
	echo "$0: firmware was not expected to match" >&2
	exit 1
else
	echo "$0: firmware comparison works"
fi

# Do a proper load, which should work correctly.
load_fw "$NAME" "$FW"
if ! diff -q "$FW" /dev/test_firmware >/dev/null ; then
	echo "$0: firmware was not loaded" >&2
	exit 1
else
	echo "$0: user helper firmware loading works"
fi

exit 0