// SPDX-License-Identifier: MIT OR Apache-2.0
//
// Copyright (c) 2018-2022 Andre Richter <andre.o.richter@gmail.com>

// Rust embedded logo for `make doc`.
#![doc(
    html_logo_url = "https://raw.githubusercontent.com/rust-embedded/wg/master/assets/logo/ewg-logo-blue-white-on-transparent.png"
)]

//! The `kernel` binary.

#![feature(format_args_nl)]
#![no_main]
#![no_std]

use libkernel::{bsp, console, driver, exception, info, memory, time};

/// Early init code.
///
/// # Safety
///
/// - Only a single core must be active and running this function.
/// - The init calls in this function must appear in the correct order:
///     - MMU + Data caching must be activated at the earliest. Without it, any atomic operations,
///       e.g. the yet-to-be-introduced spinlocks in the device drivers (which currently employ
///       NullLocks instead of spinlocks), will fail to work (properly) on the RPi SoCs.
#[no_mangle]
unsafe fn kernel_init() -> ! {
    use memory::mmu::interface::MMU;

    exception::handling_init();

    if let Err(string) = memory::mmu::mmu().enable_mmu_and_caching() {
        panic!("MMU: {}", string);
    }

    // Initialize the BSP driver subsystem.
    if let Err(x) = bsp::driver::init() {
        panic!("Error initializing BSP driver subsystem: {}", x);
    }

    // Initialize all device drivers.
    driver::driver_manager().init_drivers();
    // println! is usable from here on.

    // Transition from unsafe to safe.
    kernel_main()
}

/// The main function running after the early init.
fn kernel_main() -> ! {
    use console::console;

    info!("{}", libkernel::version());
    info!("Booting on: {}", bsp::board_name());

    info!("MMU online. Special regions:");
    bsp::memory::mmu::virt_mem_layout().print_layout();

    let (_, privilege_level) = exception::current_privilege_level();
    info!("Current privilege level: {}", privilege_level);

    info!("Exception handling state:");
    exception::asynchronous::print_state();

    info!(
        "Architectural timer resolution: {} ns",
        time::time_manager().resolution().as_nanos()
    );

    info!("Drivers loaded:");
    driver::driver_manager().enumerate();

    info!("Echoing input now");

    // Discard any spurious received characters before going into echo mode.
    console().clear_rx();
    loop {
        let c = console().read_char();
        console().write_char(c);
    }
}
