artiq/artiq/firmware/libboard_artiq/mailbox.rs

use core::ptr::{read_volatile, write_volatile};
use board_misoc::{mem, cache};

const MAILBOX: *mut usize = mem::MAILBOX_BASE as *mut usize;
static mut LAST: usize = 0;

pub unsafe fn send(data: usize) {
    LAST = data;
    write_volatile(MAILBOX, data)
}

pub fn acknowledged() -> bool {
    unsafe {
        let data = read_volatile(MAILBOX);
        data == 0 || data != LAST
    }
}

pub fn receive() -> usize {
    unsafe {
        let data = read_volatile(MAILBOX);
        if data == LAST {
            0
        } else {
            if data != 0 {
                cache::flush_cpu_dcache()
            }
            data
        }
    }
}

pub fn acknowledge() {
    unsafe { write_volatile(MAILBOX, 0) }
}