Function _IOC

pub const fn _IOC<T: ?Sized>(dir: Dir, ty: u8, nr: u8, size: usize) -> Ioctl<T>

Manually constructs an Ioctl from its components.

Also see Ioctl::from_raw for a way to interface with “legacy” ioctls that don’t yet follow this scheme.

Prefer to use _IO, _IOR, _IOW, or _IOWR where possible.

Arguments

• dir: Direction of the ioctl. One of _IOC_NONE, _IOC_READ, _IOC_WRITE, or _IOC_READ | _IOC_WRITE (aka _IOC_READ_WRITE).
• ty: the ioctl group or type to identify the driver or subsystem. You can find a list here.
• nr: the ioctl number within its group.
• size: the size of the ioctl’s indirect argument. ioctls that take an argument directly (without passing a pointer to it) typically set this to 0.

Panics

This function may panic when size exceeds the (platform-specific) maximum parameter size.

Example

UI_GET_SYSNAME is a polymorphic ioctl that can be invoked with a variety of buffer lengths. This function can be used to bind to it.

From linux/uinput.h:

/* ioctl */
#define UINPUT_IOCTL_BASE	'U'
...
#define UI_GET_SYSNAME(len)	_IOC(_IOC_READ, UINPUT_IOCTL_BASE, 44, len)

use std::ffi::c_char;
use linux_ioctl::*;

const UINPUT_IOCTL_BASE: u8 = b'U';
const fn UI_GET_SYSNAME(len: usize) -> Ioctl<*mut c_char> {
    _IOC(_IOC_READ, UINPUT_IOCTL_BASE, 44, len)
}

// Use it like this:
unsafe {
    let mut buffer = [0 as c_char; 16];
    UI_GET_SYSNAME(16).ioctl(fd, buffer.as_mut_ptr())?;
}