ioctl decoding

I was interested to know how to decode an ioctl hex string, I worked through the example described in the kernel documentation at /ioctl/ioctl-decoding.txt
Then I tested it out on an ioctl code listed in an error message in a server log, here is my working (this is for an x86_64 server, other architectures may vary)

ioctl code in hex is
cc770002

Which in binary is
11001100011101110000000000000010

First two bits gives us the macro used
11
this according to the document is _IOWR (Read/Write)

The next 14 bits give the size of the arguments
00110001110111
which in decimal is 3191

The next 8 bits are an ascii character, which in my example gives NULL (could well be an issue and why the message appears in the logs for that application)
00000000

The final 8 bits gives the function number, in my example this is
00000010
which in decimal is 2

If I had the sourcecode of the application I could go and look up this function using the character and the function number. In the example above, looks like a bug in the application is generating the wrong character and the ioctl call will fail.