ns16550a.hpp

Go to the documentation of this file.

 
#pragma once
 
#include <cstdint>
#include <optional>
 
#include "expected.hpp"
#include "mmio_accessor.hpp"
 
namespace ns16550a {
 
class Ns16550a {
 public:
  [[nodiscard]] static auto Create(uint64_t dev_addr) -> Expected<Ns16550a> {
    if (dev_addr == 0) {
      return std::unexpected(Error{ErrorCode::kInvalidArgument});
    }
 
    Ns16550a uart(dev_addr);
 
    // UART 初始化序列
    uart.mmio_.Write<uint8_t>(kRegIER, 0x00);   // 禁用所有中断
    uart.mmio_.Write<uint8_t>(kRegLCR, 0x80);   // 启用 DLAB（设置波特率）
    uart.mmio_.Write<uint8_t>(kUartDLL, 0x03);  // 波特率低字节（38400）
    uart.mmio_.Write<uint8_t>(kUartDLM, 0x00);  // 波特率高字节
    uart.mmio_.Write<uint8_t>(kRegLCR, 0x03);   // 8 位，无校验，1 停止位
    uart.mmio_.Write<uint8_t>(kRegFCR, 0x07);   // 启用并清除 FIFO
    uart.mmio_.Write<uint8_t>(kRegIER, 0x01);   // 启用接收中断
 
    return uart;
  }
 
  auto PutChar(uint8_t c) const -> void {
    while ((mmio_.Read<uint8_t>(kRegLSR) & (1 << 5)) == 0) {
    }
    mmio_.Write<uint8_t>(kRegTHR, c);
  }
 
  [[nodiscard]] auto GetChar() const -> uint8_t {
    while ((mmio_.Read<uint8_t>(kRegLSR) & (1 << 0)) == 0) {
    }
    return mmio_.Read<uint8_t>(kRegRHR);
  }
 
  [[nodiscard]] auto TryGetChar() const -> std::optional<uint8_t> {
    if ((mmio_.Read<uint8_t>(kRegLSR) & (1 << 0)) != 0) {
      return mmio_.Read<uint8_t>(kRegRHR);
    }
    return std::nullopt;
  }
 
  [[nodiscard]] auto HasData() const -> bool {
    return (mmio_.Read<uint8_t>(kRegLSR) & (1 << 0)) != 0;
  }
 
  [[nodiscard]] auto GetInterruptId() const -> uint8_t {
    return mmio_.Read<uint8_t>(kRegISR);
  }
 
  [[nodiscard]] auto IsInterruptPending() const -> bool {
    return (mmio_.Read<uint8_t>(kRegISR) & 0x01) == 0;
  }
 
  Ns16550a() = default;
  Ns16550a(const Ns16550a&) = delete;
  Ns16550a(Ns16550a&&) = default;
  auto operator=(const Ns16550a&) -> Ns16550a& = delete;
  auto operator=(Ns16550a&&) -> Ns16550a& = default;
  ~Ns16550a() = default;
 
 private:
  static constexpr uint8_t kRegRHR = 0;
  static constexpr uint8_t kRegTHR = 0;
  static constexpr uint8_t kRegIER = 1;
  static constexpr uint8_t kRegFCR = 2;
  static constexpr uint8_t kRegISR = 2;
  static constexpr uint8_t kRegLCR = 3;
  static constexpr uint8_t kRegMCR = 4;
  static constexpr uint8_t kRegLSR = 5;
  static constexpr uint8_t kRegMSR = 6;
 
  static constexpr uint8_t kUartDLL = 0;
  static constexpr uint8_t kUartDLM = 1;
 
  MmioAccessor mmio_{};
 
  explicit Ns16550a(uint64_t dev_addr) : mmio_(dev_addr) {}
};
 
}  // namespace ns16550a