In this section, we'll write a bit of a more interesting driver (the code's for this can be found at ch5/sed1/sed1_driver). We'll design it so that it encrypts and/or decrypts a given message (very trivially, of course). The basic idea is that a user mode app (this can be found in ch5/userapp_sed) serves as its user interface. When run, it opens our misc character driver's device file (/dev/sed1_drv) and issues an ioctl(2) system call upon it.
We have provided material online to help you understand how to interface a kernel module or device driver to a user space process via several common methods: via procfs, sysfs, debugfs, netlink sockets, and the ioctl() system call (https://github.com/PacktPublishing/Learn-Linux-Kernel-Development/blob/master/User_kernel_communication_pathways.pdf)!
The ioctl() call passes a data structure that encapsulates the data...
