selftests: add media controller regression test scripts and document

#!/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

#!/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

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.