media: rc: self test for IR encoders and decoders

ir-loopback can transmit IR on one rc device and check the correct
scancode and protocol is decoded on a different rc device. This can be
used to check IR transmission between two rc devices. Using rc-loopback,
we use it to check the IR encoders and decoders themselves.

No hardware is required for this test.

Signed-off-by: Sean Young <sean@mess.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Shuah Khan <shuah@kernel.org>

tools/testing/selftests/ir/ir_loopback.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
+if ! /sbin/modprobe -q -n rc-loopback; then
+        echo "ir_loopback: module rc-loopback is not found [SKIP]"
+        exit $ksft_skip
+fi
+
+/sbin/modprobe rc-loopback
+if [ $? -ne 0 ]; then
+	exit
+fi
+
+RCDEV=$(grep -l DRV_NAME=rc-loopback /sys/class/rc/rc*/uevent | grep -o 'rc[0-9]\+')
+
+./ir_loopback $RCDEV $RCDEV
+exit