Interface Ioctl

src/ioctl/mod.rs:147–190

A trait defining the properties of an `ioctl` command. Objects implementing this trait can be passed to [`ioctl`] to make an `ioctl` call. The contents of the object represent the inputs to the `ioctl` call. The inputs must be convertible to a pointer through the `as_ptr` method. In most cases, this involves either casting a number to a pointer, or creating a pointer to the actual data. The latte

///  - If `IS_MUTATING` is false, that no userspace data will be modified by
///    the `ioctl` call.
pub unsafe trait Ioctl {
    /// The type of the output data.
    ///
    /// Given a pointer, one should be able to construct an instance of this
    /// type.
    type Output;

    /// Does the `ioctl` mutate any data in the userspace?
    ///
    /// If the `ioctl` call does not mutate any data in the userspace, then
    /// making this `false` enables optimizations that can make the call
    /// faster. When in doubt, set this to `true`.
    ///
    /// # Safety
    ///
    /// This should only be set to `false` if the `ioctl` call does not mutate
    /// any data in the userspace. Undefined behavior may occur if this is set
    /// to `false` when it should be `true`.
    const IS_MUTATING: bool;

    /// Get the opcode used by this `ioctl` command.
    ///
    /// There are different types of opcode depending on the operation. See
    /// documentation for [`opcode`] for more information.
    fn opcode(&self) -> Opcode;

    /// Get a pointer to the data to be passed to the `ioctl` command.
    ///
    /// See trait-level documentation for more information.
    fn as_ptr(&mut self) -> *mut c::c_void;

    /// Cast the output data to the correct type.
    ///
    /// # Safety
    ///
    /// The `extract_output` value must be the resulting value after a
    /// successful `ioctl` call, and `out` is the direct return value of an
    /// `ioctl` call that did not fail. In this case `extract_output` is the
    /// pointer that was passed to the `ioctl` call.
    unsafe fn output_from_ptr(
        out: IoctlOutput,
        extract_output: *mut c::c_void,
    ) -> Result<Self::Output>;
}

/// Const functions for computing opcode values.
///