#ifndef IOCTL_H #define IOCTL_H #include /* Structs are the way to pass multiple arguments. */ typedef struct { int i; int j; } lkmc_ioctl_struct; /* Some random number I can't understand how to choose. */ #define LKMC_IOCTL_MAGIC 0x33 /* * I think those number does not *need* to be unique across, that is just to help debugging: * https://stackoverflow.com/questions/22496123/what-is-the-meaning-of-this-macro-iormy-macig-0-int * * However, the ioctl syscall highjacks several low values at do_vfs_ioctl, e.g. * This "forces" use to use the _IOx macros... * https://stackoverflow.com/questions/10071296/ioctl-is-not-called-if-cmd-2 * * Some of those magic low values are used for fnctl, which can also be used on regular files: * e.g. FIOCLEX for close-on-exec: * https://stackoverflow.com/questions/6125068/what-does-the-fd-cloexec-fcntl-flag-do * * TODO are the W or R of _IOx and type functional, or only to help with uniqueness? * */ #define LKMC_IOCTL_INC _IOWR(LKMC_IOCTL_MAGIC, 0, int) #define LKMC_IOCTL_INC_DEC _IOWR(LKMC_IOCTL_MAGIC, 1, lkmc_ioctl_struct) #endif