port: read/write now not mutable self

[fox0]

No description provided.

[Freax13]

Hi there, sorry for the delay in reviewing this!

I'm not sure how to feel about this. I think requiring a unique reference to the port is more often useful than not, so I'm a bit hesitant to remove that. If your primary goal is to use a port stored in a const, note that this is already possible today by just making a local copy:

const DATA_PORT: PortGeneric<u8, ReadWriteAccess> = Port::<u8>::new(0x0060);
const COMMAND_REGISTER: PortGeneric<u8, WriteOnlyAccess> = PortWriteOnly::<u8>::new(0x0064);
const STATUS_REGISTER: PortGeneric<u8, ReadOnlyAccess> = PortReadOnly::<u8>::new(0x0064);

fn foo() {
    let mut data_port = DATA_PORT;
    let mut command_register = COMMAND_REGISTER;
    let umt status_register = STATUS_REGISTER;
    unsafe {
        let _ = data_port.read();
        data_port.write(0x42);
        command_register.write(0x42);
        let _ = status_register.read();
    }
}

Thoughts?

[fox0]

Made a wrapper over PortGeneric for my private project.

use core::marker::PhantomData;
use x86_64::instructions::port::{
    PortReadAccess, PortWriteAccess, ReadOnlyAccess, ReadWriteAccess, WriteOnlyAccess,
};
use x86_64::structures::port::{PortRead, PortWrite};

pub struct PortGeneric<T, A> {
    port: u16,
    phantom: PhantomData<(T, A)>,
}

pub type Port<T> = PortGeneric<T, ReadWriteAccess>;
pub type PortReadOnly<T> = PortGeneric<T, ReadOnlyAccess>;
pub type PortWriteOnly<T> = PortGeneric<T, WriteOnlyAccess>;

impl<T, A> PortGeneric<T, A> {
    #[inline]
    pub const fn new(port: u16) -> PortGeneric<T, A> {
        PortGeneric {
            port,
            phantom: PhantomData,
        }
    }
}

impl<T: PortRead, A: PortReadAccess> PortGeneric<T, A> {
    #[inline]
    #[must_use]
    pub unsafe fn read(&self) -> T {
        unsafe { T::read_from_port(self.port) }
    }
}

impl<T: PortWrite, A: PortWriteAccess> PortGeneric<T, A> {
    #[inline]
    pub unsafe fn write(&self, value: T) {
        unsafe { T::write_to_port(self.port, value) }
    }
}

const DATA_PORT: PortGeneric<u8, ReadWriteAccess> = Port::<u8>::new(0x0060);
const COMMAND_REGISTER: PortGeneric<u8, WriteOnlyAccess> = PortWriteOnly::<u8>::new(0x0064);
const STATUS_REGISTER: PortGeneric<u8, ReadOnlyAccess> = PortReadOnly::<u8>::new(0x0064);

#[deny(const_item_mutation)]
fn foo() {
    unsafe {
        let _ = DATA_PORT.read();
        DATA_PORT.write(0x42);
        COMMAND_REGISTER.write(0x42);
        let _ = STATUS_REGISTER.read();
    }
}