Solution to Challenge #6 - misc char device

In this challenge, I was asked to implement a small misc char device which controls the return code of the syscall write based on the given data from the user. If the given data matches the secret then the return code should be valid, otherwise EINVAL should be returned, The testing flow is as follows:

dmesg -c > /dev/null                # clear the current kernel log.
lsmod                               # see the module isn't loaded yet.
ls /dev/eudyptula                   # verify there is no such device yet.

modprobe solution_6                 # load the kernel module.
dmesg -c                            # see the loading logs of the module.
lsmod                               # see that the module is currently loaded.
ls /dev/eudyptula                   # verify that there is char device.
cat /dev/eudyptula                  # see roeey777 (i.e. the id) printed out.
echo -n eudyptula > /dev/eudyptula  # write the "secret" into the device.
echo $?                             # expect to see 0, indicating success.
dmesg -c                            # verify there is no error logs.

echo -n nonsense > /dev/eudyptula   # write something else than the "secret" into the device.
echo $?                             # expect to see 1, indicating failure.
dmesg -c                            # verify there is an error log indicating that nonsense isn't the "secret".

modprobe -r solution_6              # unload the kernel module.
dmesg -c                            # see the unloading logs of the module.
lsmod                               # see that the module isn't loaded.
ls /dev/eudyptula                   # verify that there is no such char device.