selftests: firmware: add empty string and async tests

BugLink: http://bugs.launchpad.net/bugs/1732698

commit 1b1fe542 upstream.

Now that we've added a 'trigger_async_request' knob to test the
request_firmware_nowait() API, let's use it. Also add tests for the
empty ("") string, since there have been a couple errors in that
handling already.

Since we now have real ways that the sysfs write might fail, let's add
the appropriate check on the 'echo' lines too.
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
[AmitP: Dropped the async trigger testing parts from original commit]
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

tools/testing/selftests/firmware/fw_filesystem.sh

@@ -48,8 +48,16 @@ echo "ABCD0123" >"$FW"
 
 NAME=$(basename "$FW")
 
+if printf '\000' >"$DIR"/trigger_request; then
+	echo "$0: empty filename should not succeed" >&2
+	exit 1
+fi
+
 # Request a firmware that doesn't exist, it should fail.
-echo -n "nope-$NAME" >"$DIR"/trigger_request
+if echo -n "nope-$NAME" >"$DIR"/trigger_request; then
+	echo "$0: firmware shouldn't have loaded" >&2
+	exit 1
+fi
 if diff -q "$FW" /dev/test_firmware >/dev/null ; then
 	echo "$0: firmware was not expected to match" >&2
 	exit 1