Macro ioctl_ioc_nr

macro_rules! ioctl_ioc_nr {
    ($name:ident, $dir:expr, $ty:expr, $nr:expr, $size:expr) => { ... };
    ($name:ident, $dir:expr, $ty:expr, $nr:expr, $size:expr, $($v:ident),+) => { ... };
}

Raw macro to declare a function that returns an ioctl number.