I am using ioctl command in linux for just playing with transferring data from kernel to user and from user to kernel.
It works fine if I give
#define cmd0 _IO(42,0).
upto my knowledge 42 is magic number here.
but when I give different magic number it does not work.why so?
and if I am getting wrong then what exactly this magic number is? and for what purpose do we need to use it?
please help me out friends.
hoping for quick reply.