selftests: add media controller regression test scripts and document

Add regression test scripts open_loop_test.sh, and bind_unbind_sample.sh.
Also add regression_test.txt that describes the regression test procedure.
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>

tools/testing/selftests/media_tests/bind_unbind_sample.sh

+#!/bin/bash
+# Find device number in /sys/bus/usb/drivers/drivername
+# Edit this file to update the driver numer and name
+# Example test for uvcvideo driver
+#i=0
+# while :; do
+#  i=$((i+1))
+#  echo 1-5:1.0 > /sys/bus/usb/drivers/uvcvideo/unbind;
+#  echo 1-5:1.0 > /sys/bus/usb/drivers/uvcvideo/bind;
+#  clear
+#	echo $i
+#done

tools/testing/selftests/media_tests/open_loop_test.sh

+#!/bin/bash
+ i=0
+file=/dev/media$1
+ while :; do
+  echo $file
+  i=$((i+1))
+  R=$(./media_device_open -d $file);
+ # clear
+  echo -e "Loop $i\n$R"
+ done

tools/testing/selftests/media_tests/regression_test.txt

+Testing for regressions in Media Controller API register, ioctl, syscall,
+and unregister paths. There have a few problems that result in user-after
+free on media_device, media_devnode, and cdev pointers when the driver is
+unbound while ioctl is in progress.
+
+Test Procedure:
+
+Run bin/unbind loop while ioctls are in progress.
+Run rmmod and modprobe.
+Disconnect the device.
+
+Setup:
+
+Build media_device_test
+cd tools/testing/selftests/media_tests
+make
+
+Regressions test for cdev user-after free error on /dev/mediaX when driver
+is unbound:
+
+Start media_device_test to regression test media devnode dynamic alloc
+and cdev user-after-free fixes. This opens media dev files and sits in
+a loop running media ioctl MEDIA_IOC_DEVICE_INFO command once every 10
+seconds. The idea is when device file goes away, media devnode and cdev
+should stick around until this test exits.
+
+The test for a random number of iterations or until user kills it with a
+sleep 10 in between the ioctl calls.
+
+sudo ./media_device_test -d /dev/mediaX
+
+Regression test for media_devnode unregister race with ioctl_syscall:
+
+Start 6 open_loop_test.sh tests with different /dev/mediaX files. When
+device file goes away after unbind, device file name changes. Start the
+test with possible device names. If we start with /dev/media0 for example,
+after unbind, /dev/media1 or /dev/media2 could get created. The idea is
+keep ioctls going while bind/unbind runs.
+
+Copy bind_unbind_sample.txt and make changes to specify the driver name
+and number to run bind and unbind. Start the bind_unbind.sh
+
+Run dmesg looking for any user-after free errors or mutex lock errors.