safe-mmio

The safe-mmio crate provides types to wrap registers that can be read or written safely.

// Copyright 2025 Google LLC
// SPDX-License-Identifier: Apache-2.0

use safe_mmio::fields::{ReadPure, ReadPureWrite, ReadWrite, WriteOnly};

#[repr(C, align(4))]
pub struct Registers {
    dr: ReadWrite<u16>,
    _reserved0: [u8; 2],
    rsr: ReadPure<ReceiveStatus>,
    _reserved1: [u8; 19],
    fr: ReadPure<Flags>,
    _reserved2: [u8; 6],
    ilpr: ReadPureWrite<u8>,
    _reserved3: [u8; 3],
    ibrd: ReadPureWrite<u16>,
    _reserved4: [u8; 2],
    fbrd: ReadPureWrite<u8>,
    _reserved5: [u8; 3],
    lcr_h: ReadPureWrite<u8>,
    _reserved6: [u8; 3],
    cr: ReadPureWrite<u16>,
    _reserved7: [u8; 3],
    ifls: ReadPureWrite<u8>,
    _reserved8: [u8; 3],
    imsc: ReadPureWrite<u16>,
    _reserved9: [u8; 2],
    ris: ReadPure<u16>,
    _reserved10: [u8; 2],
    mis: ReadPure<u16>,
    _reserved11: [u8; 2],
    icr: WriteOnly<u16>,
    _reserved12: [u8; 2],
    dmacr: ReadPureWrite<u8>,
    _reserved13: [u8; 3],
}

• Reading dr has a side effect: it pops a byte from the receive FIFO.
• Reading rsr (and other registers) has no side-effects. It is a ‘pure’ read.