audk/ArmPkg/Library/SemiHostingSerialPortLib/SerialPortLib.c

/** @file
  Serial I/O Port library functions with no library constructor/destructor

  Copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>
  Copyright (c) 2021, Arm Limited. All rights reserved.<BR>

  SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include <Uefi.h>
#include <Library/DebugLib.h>
#include <Library/SemihostLib.h>
#include <Library/SerialPortLib.h>

/*

  Programmed hardware of Serial port.

  @return    Always return EFI_UNSUPPORTED.

**/
RETURN_STATUS
EFIAPI
SerialPortInitialize (
  VOID
  )
{
  if (SemihostConnectionSupported ()) {
    return RETURN_SUCCESS;
  } else {
    return RETURN_UNSUPPORTED;
  }
}

/**
  Write data to serial device.

  @param  Buffer           Point of data buffer which need to be written.
  @param  NumberOfBytes    Number of output bytes which are cached in Buffer.

  @retval 0                Write data failed.
  @retval !0               Actual number of bytes written to serial device.

**/

#define PRINT_BUFFER_SIZE       512
#define PRINT_BUFFER_THRESHOLD  (PRINT_BUFFER_SIZE - 4)

UINTN
EFIAPI
SerialPortWrite (
  IN UINT8  *Buffer,
  IN UINTN  NumberOfBytes
  )
{
  UINT8  PrintBuffer[PRINT_BUFFER_SIZE];
  UINTN  SourceIndex;
  UINTN  DestinationIndex;
  UINT8  CurrentCharacter;

  SourceIndex      = 0;
  DestinationIndex = 0;

  while (SourceIndex < NumberOfBytes) {
    CurrentCharacter = Buffer[SourceIndex++];

    switch (CurrentCharacter) {
      case '\r':
        continue;

      case '\n':
        PrintBuffer[DestinationIndex++] = ' ';
      // fall through

      default:
        PrintBuffer[DestinationIndex++] = CurrentCharacter;
        break;
    }

    if (DestinationIndex > PRINT_BUFFER_THRESHOLD) {
      PrintBuffer[DestinationIndex] = '\0';
      SemihostWriteString ((CHAR8 *)PrintBuffer);

      DestinationIndex = 0;
    }
  }

  if (DestinationIndex > 0) {
    PrintBuffer[DestinationIndex] = '\0';
    SemihostWriteString ((CHAR8 *)PrintBuffer);
  }

  return NumberOfBytes;
}

/**
  Read data from serial device and save the datas in buffer.

  @param  Buffer           Point of data buffer which need to be written.
  @param  NumberOfBytes    Number of output bytes which are cached in Buffer.

  @retval 0                Read data failed.
  @retval !0               Actual number of bytes read from serial device.

**/
UINTN
EFIAPI
SerialPortRead (
  OUT UINT8  *Buffer,
  IN  UINTN  NumberOfBytes
  )
{
  *Buffer = SemihostReadCharacter ();
  return 1;
}

/**
  Check to see if any data is available to be read from the debug device.

  @retval TRUE       At least one byte of data is available to be read
  @retval FALSE      No data is available to be read

**/
BOOLEAN
EFIAPI
SerialPortPoll (
  VOID
  )
{
  // Since SemiHosting read character is blocking always say we have a char ready?
  return SemihostConnectionSupported ();
}