MdeModulePkg/Universal/SerialDxe/SerialIo.c - edk2 - Git at Google

 /** @file
   Serial driver that layers on top of a Serial Port Library instance.

   Copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>
   Copyright (c) 2013-2014, ARM Ltd. All rights reserved.<BR>
   Copyright (c) 2015, Intel Corporation. All rights reserved.<BR>

   This program and the accompanying materials
   are licensed and made available under the terms and conditions of the BSD License
   which accompanies this distribution.  The full text of the license may be found at
   http://opensource.org/licenses/bsd-license.php

   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

 **/

 #include <Library/UefiBootServicesTableLib.h>
 #include <Library/SerialPortLib.h>
 #include <Library/DebugLib.h>
 #include <Library/PcdLib.h>

 #include <Protocol/SerialIo.h>
 #include <Protocol/DevicePath.h>

 typedef struct {
   VENDOR_DEVICE_PATH        Guid;
   UART_DEVICE_PATH          Uart;
   EFI_DEVICE_PATH_PROTOCOL  End;
 } SERIAL_DEVICE_PATH;

 /**
   Reset the serial device.

   @param  This              Protocol instance pointer.

   @retval EFI_SUCCESS       The device was reset.
   @retval EFI_DEVICE_ERROR  The serial device could not be reset.

 **/
 EFI_STATUS
 EFIAPI
 SerialReset (
   IN EFI_SERIAL_IO_PROTOCOL *This
   );

 /**
   Sets the baud rate, receive FIFO depth, transmit/receive time out, parity,
   data bits, and stop bits on a serial device.

   @param  This             Protocol instance pointer.
   @param  BaudRate         The requested baud rate. A BaudRate value of 0 will use the the
                            device's default interface speed.
   @param  ReceiveFifoDepth The requested depth of the FIFO on the receive side of the
                            serial interface. A ReceiveFifoDepth value of 0 will use
                            the device's default FIFO depth.
   @param  Timeout          The requested time out for a single character in microseconds.
                            This timeout applies to both the transmit and receive side of the
                            interface. A Timeout value of 0 will use the device's default time
                            out value.
   @param  Parity           The type of parity to use on this serial device. A Parity value of
                            DefaultParity will use the device's default parity value.
   @param  DataBits         The number of data bits to use on the serial device. A DataBits
                            value of 0 will use the device's default data bit setting.
   @param  StopBits         The number of stop bits to use on this serial device. A StopBits
                            value of DefaultStopBits will use the device's default number of
                            stop bits.

   @retval EFI_SUCCESS           The device was reset.
   @retval EFI_INVALID_PARAMETER One or more attributes has an unsupported value.
   @retval EFI_DEVICE_ERROR      The serial device is not functioning correctly.

 **/
 EFI_STATUS
 EFIAPI
 SerialSetAttributes (
   IN EFI_SERIAL_IO_PROTOCOL *This,
   IN UINT64                 BaudRate,
   IN UINT32                 ReceiveFifoDepth,
   IN UINT32                 Timeout,
   IN EFI_PARITY_TYPE        Parity,
   IN UINT8                  DataBits,
   IN EFI_STOP_BITS_TYPE     StopBits
   );

 /**
   Set the control bits on a serial device

   @param  This             Protocol instance pointer.
   @param  Control          Set the bits of Control that are settable.

   @retval EFI_SUCCESS      The new control bits were set on the serial device.
   @retval EFI_UNSUPPORTED  The serial device does not support this operation.
   @retval EFI_DEVICE_ERROR The serial device is not functioning correctly.

 **/
 EFI_STATUS
 EFIAPI
 SerialSetControl (
   IN EFI_SERIAL_IO_PROTOCOL *This,
   IN UINT32                 Control
   );

 /**
   Retrieves the status of the control bits on a serial device

   @param  This              Protocol instance pointer.
   @param  Control           A pointer to return the current Control signals from the serial device.

   @retval EFI_SUCCESS       The control bits were read from the serial device.
   @retval EFI_DEVICE_ERROR  The serial device is not functioning correctly.

 **/
 EFI_STATUS
 EFIAPI
 SerialGetControl (
   IN EFI_SERIAL_IO_PROTOCOL *This,
   OUT UINT32                *Control
   );

 /**
   Writes data to a serial device.

   @param  This              Protocol instance pointer.
   @param  BufferSize        On input, the size of the Buffer. On output, the amount of
                             data actually written.
   @param  Buffer            The buffer of data to write

   @retval EFI_SUCCESS       The data was written.
   @retval EFI_DEVICE_ERROR  The device reported an error.
   @retval EFI_TIMEOUT       The data write was stopped due to a timeout.

 **/
 EFI_STATUS
 EFIAPI
 SerialWrite (
   IN EFI_SERIAL_IO_PROTOCOL *This,
   IN OUT UINTN              *BufferSize,
   IN VOID                   *Buffer
   );

 /**
   Reads data from a serial device.

   @param  This              Protocol instance pointer.
   @param  BufferSize        On input, the size of the Buffer. On output, the amount of
                             data returned in Buffer.
   @param  Buffer            The buffer to return the data into.

   @retval EFI_SUCCESS       The data was read.
   @retval EFI_DEVICE_ERROR  The device reported an error.
   @retval EFI_TIMEOUT       The data write was stopped due to a timeout.

 **/
 EFI_STATUS
 EFIAPI
 SerialRead (
   IN EFI_SERIAL_IO_PROTOCOL *This,
   IN OUT UINTN              *BufferSize,
   OUT VOID                  *Buffer
   );

 EFI_HANDLE mSerialHandle = NULL;

 SERIAL_DEVICE_PATH mSerialDevicePath = {
   {
     { HARDWARE_DEVICE_PATH, HW_VENDOR_DP, { sizeof (VENDOR_DEVICE_PATH), 0} },
     EFI_CALLER_ID_GUID  // Use the driver's GUID
   },
   {
     { MESSAGING_DEVICE_PATH, MSG_UART_DP, { sizeof (UART_DEVICE_PATH), 0} },
     0,                  // Reserved
     0,                  // BaudRate
     0,                  // DataBits
     0,                  // Parity
     0                   // StopBits
   },
   { END_DEVICE_PATH_TYPE, END_ENTIRE_DEVICE_PATH_SUBTYPE, { sizeof (EFI_DEVICE_PATH_PROTOCOL), 0 } }
 };

 //
 // Template used to initialize the Serial IO protocols.
 //
 EFI_SERIAL_IO_MODE mSerialIoMode = {
   //
   //    value  field                set in SerialDxeInitialize()?
   //---------  -------------------  -----------------------------
             0, // ControlMask
   1000 * 1000, // Timeout
             0, // BaudRate          yes
             1, // ReceiveFifoDepth
             0, // DataBits          yes
             0, // Parity            yes
             0  // StopBits          yes
 };

 EFI_SERIAL_IO_PROTOCOL mSerialIoTemplate = {
   SERIAL_IO_INTERFACE_REVISION,
   SerialReset,
   SerialSetAttributes,
   SerialSetControl,
   SerialGetControl,
   SerialWrite,
   SerialRead,
   &mSerialIoMode
 };

 /**
   Reset the serial device.

   @param  This              Protocol instance pointer.

   @retval EFI_SUCCESS       The device was reset.
   @retval EFI_DEVICE_ERROR  The serial device could not be reset.

 **/
 EFI_STATUS
 EFIAPI
 SerialReset (
   IN EFI_SERIAL_IO_PROTOCOL *This
   )
 {
   EFI_STATUS    Status;

   Status = SerialPortInitialize ();
   if (EFI_ERROR (Status)) {
     return Status;
   }

   //
   // Go set the current attributes
   //
   Status = This->SetAttributes (
                    This,
                    This->Mode->BaudRate,
                    This->Mode->ReceiveFifoDepth,
                    This->Mode->Timeout,
                    (EFI_PARITY_TYPE) This->Mode->Parity,
                    (UINT8) This->Mode->DataBits,
                    (EFI_STOP_BITS_TYPE) This->Mode->StopBits
                    );

   //
   // The serial device may not support some of the attributes. To prevent
   // later failure, always return EFI_SUCCESS when SetAttributes is returning
   // EFI_INVALID_PARAMETER.
   //
   if (Status == EFI_INVALID_PARAMETER) {
     return EFI_SUCCESS;
   }

   return Status;
 }

 /**
   Sets the baud rate, receive FIFO depth, transmit/receive time out, parity,
   data bits, and stop bits on a serial device.

   @param  This             Protocol instance pointer.
   @param  BaudRate         The requested baud rate. A BaudRate value of 0 will use the the
                            device's default interface speed.
   @param  ReceiveFifoDepth The requested depth of the FIFO on the receive side of the
                            serial interface. A ReceiveFifoDepth value of 0 will use
                            the device's default FIFO depth.
   @param  Timeout          The requested time out for a single character in microseconds.
                            This timeout applies to both the transmit and receive side of the
                            interface. A Timeout value of 0 will use the device's default time
                            out value.
   @param  Parity           The type of parity to use on this serial device. A Parity value of
                            DefaultParity will use the device's default parity value.
   @param  DataBits         The number of data bits to use on the serial device. A DataBits
                            value of 0 will use the device's default data bit setting.
   @param  StopBits         The number of stop bits to use on this serial device. A StopBits
                            value of DefaultStopBits will use the device's default number of
                            stop bits.

   @retval EFI_SUCCESS           The device was reset.
   @retval EFI_INVALID_PARAMETER One or more attributes has an unsupported value.
   @retval EFI_DEVICE_ERROR      The serial device is not functioning correctly.

 **/
 EFI_STATUS
 EFIAPI
 SerialSetAttributes (
   IN EFI_SERIAL_IO_PROTOCOL *This,
   IN UINT64                 BaudRate,
   IN UINT32                 ReceiveFifoDepth,
   IN UINT32                 Timeout,
   IN EFI_PARITY_TYPE        Parity,
   IN UINT8                  DataBits,
   IN EFI_STOP_BITS_TYPE     StopBits
   )
 {
   EFI_STATUS                Status;
   EFI_TPL                   Tpl;
   UINT64                    OriginalBaudRate;
   UINT32                    OriginalReceiveFifoDepth;
   UINT32                    OriginalTimeout;
   EFI_PARITY_TYPE           OriginalParity;
   UINT8                     OriginalDataBits;
   EFI_STOP_BITS_TYPE        OriginalStopBits;

   //
   // Preserve the original input values in case
   // SerialPortSetAttributes() updates the input/output
   // parameters even on error.
   //
   OriginalBaudRate = BaudRate;
   OriginalReceiveFifoDepth = ReceiveFifoDepth;
   OriginalTimeout = Timeout;
   OriginalParity = Parity;
   OriginalDataBits = DataBits;
   OriginalStopBits = StopBits;
   Status = SerialPortSetAttributes (&BaudRate, &ReceiveFifoDepth, &Timeout, &Parity, &DataBits, &StopBits);
   if (EFI_ERROR (Status)) {
     //
     // If it is just to set Timeout value and unsupported is returned,
     // do not return error.
     //
     if ((Status == EFI_UNSUPPORTED) &&
         (This->Mode->Timeout          != OriginalTimeout) &&
         (This->Mode->ReceiveFifoDepth == OriginalReceiveFifoDepth) &&
         (This->Mode->BaudRate         == OriginalBaudRate) &&
         (This->Mode->DataBits         == (UINT32) OriginalDataBits) &&
         (This->Mode->Parity           == (UINT32) OriginalParity) &&
         (This->Mode->StopBits         == (UINT32) OriginalStopBits)) {
       //
       // Restore to the original input values.
       //
       BaudRate = OriginalBaudRate;
       ReceiveFifoDepth = OriginalReceiveFifoDepth;
       Timeout = OriginalTimeout;
       Parity = OriginalParity;
       DataBits = OriginalDataBits;
       StopBits = OriginalStopBits;
       Status = EFI_SUCCESS;
     } else if (Status == EFI_INVALID_PARAMETER || Status == EFI_UNSUPPORTED) {
       return EFI_INVALID_PARAMETER;
     } else {
       return EFI_DEVICE_ERROR;
     }
   }

   //
   // Set the Serial I/O mode and update the device path
   //

   Tpl = gBS->RaiseTPL (TPL_NOTIFY);

   //
   // Set the Serial I/O mode
   //
   This->Mode->ReceiveFifoDepth  = ReceiveFifoDepth;
   This->Mode->Timeout           = Timeout;
   This->Mode->BaudRate          = BaudRate;
   This->Mode->DataBits          = (UINT32) DataBits;
   This->Mode->Parity            = (UINT32) Parity;
   This->Mode->StopBits          = (UINT32) StopBits;

   //
   // Check if the device path has actually changed
   //
   if (mSerialDevicePath.Uart.BaudRate == BaudRate &&
       mSerialDevicePath.Uart.DataBits == DataBits &&
       mSerialDevicePath.Uart.Parity   == (UINT8) Parity &&
       mSerialDevicePath.Uart.StopBits == (UINT8) StopBits
      ) {
     gBS->RestoreTPL (Tpl);
     return EFI_SUCCESS;
   }

   //
   // Update the device path
   //
   mSerialDevicePath.Uart.BaudRate = BaudRate;
   mSerialDevicePath.Uart.DataBits = DataBits;
   mSerialDevicePath.Uart.Parity   = (UINT8) Parity;
   mSerialDevicePath.Uart.StopBits = (UINT8) StopBits;

   Status = gBS->ReinstallProtocolInterface (
                   mSerialHandle,
                   &gEfiDevicePathProtocolGuid,
                   &mSerialDevicePath,
                   &mSerialDevicePath
                   );

   gBS->RestoreTPL (Tpl);

   return Status;
 }

 /**
   Set the control bits on a serial device

   @param  This             Protocol instance pointer.
   @param  Control          Set the bits of Control that are settable.

   @retval EFI_SUCCESS      The new control bits were set on the serial device.
   @retval EFI_UNSUPPORTED  The serial device does not support this operation.
   @retval EFI_DEVICE_ERROR The serial device is not functioning correctly.

 **/
 EFI_STATUS
 EFIAPI
 SerialSetControl (
   IN EFI_SERIAL_IO_PROTOCOL *This,
   IN UINT32                 Control
   )
 {
   return SerialPortSetControl (Control);
 }

 /**
   Retrieves the status of the control bits on a serial device

   @param  This              Protocol instance pointer.
   @param  Control           A pointer to return the current Control signals from the serial device.

   @retval EFI_SUCCESS       The control bits were read from the serial device.
   @retval EFI_DEVICE_ERROR  The serial device is not functioning correctly.

 **/
 EFI_STATUS
 EFIAPI
 SerialGetControl (
   IN EFI_SERIAL_IO_PROTOCOL *This,
   OUT UINT32                *Control
   )
 {
   return SerialPortGetControl (Control);
 }

 /**
   Writes data to a serial device.

   @param  This              Protocol instance pointer.
   @param  BufferSize        On input, the size of the Buffer. On output, the amount of
                             data actually written.
   @param  Buffer            The buffer of data to write

   @retval EFI_SUCCESS       The data was written.
   @retval EFI_DEVICE_ERROR  The device reported an error.
   @retval EFI_TIMEOUT       The data write was stopped due to a timeout.

 **/
 EFI_STATUS
 EFIAPI
 SerialWrite (
   IN EFI_SERIAL_IO_PROTOCOL *This,
   IN OUT UINTN              *BufferSize,
   IN VOID                   *Buffer
   )
 {
   UINTN Count;

   Count = SerialPortWrite (Buffer, *BufferSize);

   if (Count != *BufferSize) {
     *BufferSize = Count;
     return EFI_TIMEOUT;
   }

   return EFI_SUCCESS;
 }

 /**
   Reads data from a serial device.

   @param  This              Protocol instance pointer.
   @param  BufferSize        On input, the size of the Buffer. On output, the amount of
                             data returned in Buffer.
   @param  Buffer            The buffer to return the data into.

   @retval EFI_SUCCESS       The data was read.
   @retval EFI_DEVICE_ERROR  The device reported an error.
   @retval EFI_TIMEOUT       The data write was stopped due to a timeout.

 **/
 EFI_STATUS
 EFIAPI
 SerialRead (
   IN EFI_SERIAL_IO_PROTOCOL *This,
   IN OUT UINTN              *BufferSize,
   OUT VOID                  *Buffer
   )
 {
   UINTN Count;
   UINTN TimeOut;

   Count = 0;

   while (Count < *BufferSize) {
     TimeOut = 0;
     while (TimeOut < mSerialIoMode.Timeout) {
       if (SerialPortPoll ()) {
         break;
       }
       gBS->Stall (10);
       TimeOut += 10;
     }
     if (TimeOut >= mSerialIoMode.Timeout) {
       break;
     }
     SerialPortRead (Buffer, 1);
     Count++;
     Buffer = (VOID *) ((UINT8 *) Buffer + 1);
   }

   if (Count != *BufferSize) {
     *BufferSize = Count;
     return EFI_TIMEOUT;
   }

   return EFI_SUCCESS;
 }

 /**
   Initialization for the Serial Io Protocol.

   @param[in] ImageHandle    The firmware allocated handle for the EFI image.
   @param[in] SystemTable    A pointer to the EFI System Table.

   @retval EFI_SUCCESS       The entry point is executed successfully.
   @retval other             Some error occurs when executing this entry point.

 **/
 EFI_STATUS
 EFIAPI
 SerialDxeInitialize (
   IN EFI_HANDLE         ImageHandle,
   IN EFI_SYSTEM_TABLE   *SystemTable
   )
 {
   EFI_STATUS            Status;

   mSerialIoMode.BaudRate = PcdGet64 (PcdUartDefaultBaudRate);
   mSerialIoMode.DataBits = (UINT32) PcdGet8 (PcdUartDefaultDataBits);
   mSerialIoMode.Parity   = (UINT32) PcdGet8 (PcdUartDefaultParity);
   mSerialIoMode.StopBits = (UINT32) PcdGet8 (PcdUartDefaultStopBits);
   mSerialIoMode.ReceiveFifoDepth = PcdGet16 (PcdUartDefaultReceiveFifoDepth);
   mSerialDevicePath.Uart.BaudRate = PcdGet64 (PcdUartDefaultBaudRate);
   mSerialDevicePath.Uart.DataBits = PcdGet8 (PcdUartDefaultDataBits);
   mSerialDevicePath.Uart.Parity   = PcdGet8 (PcdUartDefaultParity);
   mSerialDevicePath.Uart.StopBits = PcdGet8 (PcdUartDefaultStopBits);

   //
   // Issue a reset to initialize the Serial Port
   //
   Status = mSerialIoTemplate.Reset (&mSerialIoTemplate);
   if (EFI_ERROR (Status)) {
     return Status;
   }

   //
   // Make a new handle with Serial IO protocol and its device path on it.
   //
   Status = gBS->InstallMultipleProtocolInterfaces (
                   &mSerialHandle,
                   &gEfiSerialIoProtocolGuid,   &mSerialIoTemplate,
                   &gEfiDevicePathProtocolGuid, &mSerialDevicePath,
                   NULL
                   );
   ASSERT_EFI_ERROR (Status);

   return Status;
 }
	/** @file
	Serial driver that layers on top of a Serial Port Library instance.

	Copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>
	Copyright (c) 2013-2014, ARM Ltd. All rights reserved.<BR>
	Copyright (c) 2015, Intel Corporation. All rights reserved.<BR>

	This program and the accompanying materials
	are licensed and made available under the terms and conditions of the BSD License
	which accompanies this distribution. The full text of the license may be found at
	http://opensource.org/licenses/bsd-license.php

	THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
	WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

	**/

	#include <Library/UefiBootServicesTableLib.h>
	#include <Library/SerialPortLib.h>
	#include <Library/DebugLib.h>
	#include <Library/PcdLib.h>

	#include <Protocol/SerialIo.h>
	#include <Protocol/DevicePath.h>

	typedef struct {
	VENDOR_DEVICE_PATH Guid;
	UART_DEVICE_PATH Uart;
	EFI_DEVICE_PATH_PROTOCOL End;
	} SERIAL_DEVICE_PATH;

	/**
	Reset the serial device.

	@param This Protocol instance pointer.

	@retval EFI_SUCCESS The device was reset.
	@retval EFI_DEVICE_ERROR The serial device could not be reset.

	**/
	EFI_STATUS
	EFIAPI
	SerialReset (
	IN EFI_SERIAL_IO_PROTOCOL *This
	);

	/**
	Sets the baud rate, receive FIFO depth, transmit/receive time out, parity,
	data bits, and stop bits on a serial device.

	@param This Protocol instance pointer.
	@param BaudRate The requested baud rate. A BaudRate value of 0 will use the the
	device's default interface speed.
	@param ReceiveFifoDepth The requested depth of the FIFO on the receive side of the
	serial interface. A ReceiveFifoDepth value of 0 will use
	the device's default FIFO depth.
	@param Timeout The requested time out for a single character in microseconds.
	This timeout applies to both the transmit and receive side of the
	interface. A Timeout value of 0 will use the device's default time
	out value.
	@param Parity The type of parity to use on this serial device. A Parity value of
	DefaultParity will use the device's default parity value.
	@param DataBits The number of data bits to use on the serial device. A DataBits
	value of 0 will use the device's default data bit setting.
	@param StopBits The number of stop bits to use on this serial device. A StopBits
	value of DefaultStopBits will use the device's default number of
	stop bits.

	@retval EFI_SUCCESS The device was reset.
	@retval EFI_INVALID_PARAMETER One or more attributes has an unsupported value.
	@retval EFI_DEVICE_ERROR The serial device is not functioning correctly.

	**/
	EFI_STATUS
	EFIAPI
	SerialSetAttributes (
	IN EFI_SERIAL_IO_PROTOCOL *This,
	IN UINT64 BaudRate,
	IN UINT32 ReceiveFifoDepth,
	IN UINT32 Timeout,
	IN EFI_PARITY_TYPE Parity,
	IN UINT8 DataBits,
	IN EFI_STOP_BITS_TYPE StopBits
	);

	/**
	Set the control bits on a serial device

	@param This Protocol instance pointer.
	@param Control Set the bits of Control that are settable.

	@retval EFI_SUCCESS The new control bits were set on the serial device.
	@retval EFI_UNSUPPORTED The serial device does not support this operation.
	@retval EFI_DEVICE_ERROR The serial device is not functioning correctly.

	**/
	EFI_STATUS
	EFIAPI
	SerialSetControl (
	IN EFI_SERIAL_IO_PROTOCOL *This,
	IN UINT32 Control
	);

	/**
	Retrieves the status of the control bits on a serial device

	@param This Protocol instance pointer.
	@param Control A pointer to return the current Control signals from the serial device.

	@retval EFI_SUCCESS The control bits were read from the serial device.
	@retval EFI_DEVICE_ERROR The serial device is not functioning correctly.

	**/
	EFI_STATUS
	EFIAPI
	SerialGetControl (
	IN EFI_SERIAL_IO_PROTOCOL *This,
	OUT UINT32 *Control
	);

	/**
	Writes data to a serial device.

	@param This Protocol instance pointer.
	@param BufferSize On input, the size of the Buffer. On output, the amount of
	data actually written.
	@param Buffer The buffer of data to write

	@retval EFI_SUCCESS The data was written.
	@retval EFI_DEVICE_ERROR The device reported an error.
	@retval EFI_TIMEOUT The data write was stopped due to a timeout.

	**/
	EFI_STATUS
	EFIAPI
	SerialWrite (
	IN EFI_SERIAL_IO_PROTOCOL *This,
	IN OUT UINTN *BufferSize,
	IN VOID *Buffer
	);

	/**
	Reads data from a serial device.

	@param This Protocol instance pointer.
	@param BufferSize On input, the size of the Buffer. On output, the amount of
	data returned in Buffer.
	@param Buffer The buffer to return the data into.

	@retval EFI_SUCCESS The data was read.
	@retval EFI_DEVICE_ERROR The device reported an error.
	@retval EFI_TIMEOUT The data write was stopped due to a timeout.

	**/
	EFI_STATUS
	EFIAPI
	SerialRead (
	IN EFI_SERIAL_IO_PROTOCOL *This,
	IN OUT UINTN *BufferSize,
	OUT VOID *Buffer
	);

	EFI_HANDLE mSerialHandle = NULL;

	SERIAL_DEVICE_PATH mSerialDevicePath = {
	{
	{ HARDWARE_DEVICE_PATH, HW_VENDOR_DP, { sizeof (VENDOR_DEVICE_PATH), 0} },
	EFI_CALLER_ID_GUID // Use the driver's GUID
	},
	{
	{ MESSAGING_DEVICE_PATH, MSG_UART_DP, { sizeof (UART_DEVICE_PATH), 0} },
	0, // Reserved
	0, // BaudRate
	0, // DataBits
	0, // Parity
	0 // StopBits
	},
	{ END_DEVICE_PATH_TYPE, END_ENTIRE_DEVICE_PATH_SUBTYPE, { sizeof (EFI_DEVICE_PATH_PROTOCOL), 0 } }
	};

	//
	// Template used to initialize the Serial IO protocols.
	//
	EFI_SERIAL_IO_MODE mSerialIoMode = {
	//
	// value field set in SerialDxeInitialize()?
	//--------- ------------------- -----------------------------
	0, // ControlMask
	1000 * 1000, // Timeout
	0, // BaudRate yes
	1, // ReceiveFifoDepth
	0, // DataBits yes
	0, // Parity yes
	0 // StopBits yes
	};

	EFI_SERIAL_IO_PROTOCOL mSerialIoTemplate = {
	SERIAL_IO_INTERFACE_REVISION,
	SerialReset,
	SerialSetAttributes,
	SerialSetControl,
	SerialGetControl,
	SerialWrite,
	SerialRead,
	&mSerialIoMode
	};

	/**
	Reset the serial device.

	@param This Protocol instance pointer.

	@retval EFI_SUCCESS The device was reset.
	@retval EFI_DEVICE_ERROR The serial device could not be reset.

	**/
	EFI_STATUS
	EFIAPI
	SerialReset (
	IN EFI_SERIAL_IO_PROTOCOL *This
	)
	{
	EFI_STATUS Status;

	Status = SerialPortInitialize ();
	if (EFI_ERROR (Status)) {
	return Status;
	}

	//
	// Go set the current attributes
	//
	Status = This->SetAttributes (
	This,
	This->Mode->BaudRate,
	This->Mode->ReceiveFifoDepth,
	This->Mode->Timeout,
	(EFI_PARITY_TYPE) This->Mode->Parity,
	(UINT8) This->Mode->DataBits,
	(EFI_STOP_BITS_TYPE) This->Mode->StopBits
	);

	//
	// The serial device may not support some of the attributes. To prevent
	// later failure, always return EFI_SUCCESS when SetAttributes is returning
	// EFI_INVALID_PARAMETER.
	//
	if (Status == EFI_INVALID_PARAMETER) {
	return EFI_SUCCESS;
	}

	return Status;
	}

	/**
	Sets the baud rate, receive FIFO depth, transmit/receive time out, parity,
	data bits, and stop bits on a serial device.

	@param This Protocol instance pointer.
	@param BaudRate The requested baud rate. A BaudRate value of 0 will use the the
	device's default interface speed.
	@param ReceiveFifoDepth The requested depth of the FIFO on the receive side of the
	serial interface. A ReceiveFifoDepth value of 0 will use
	the device's default FIFO depth.
	@param Timeout The requested time out for a single character in microseconds.
	This timeout applies to both the transmit and receive side of the
	interface. A Timeout value of 0 will use the device's default time
	out value.
	@param Parity The type of parity to use on this serial device. A Parity value of
	DefaultParity will use the device's default parity value.
	@param DataBits The number of data bits to use on the serial device. A DataBits
	value of 0 will use the device's default data bit setting.
	@param StopBits The number of stop bits to use on this serial device. A StopBits
	value of DefaultStopBits will use the device's default number of
	stop bits.

	@retval EFI_SUCCESS The device was reset.
	@retval EFI_INVALID_PARAMETER One or more attributes has an unsupported value.
	@retval EFI_DEVICE_ERROR The serial device is not functioning correctly.

	**/
	EFI_STATUS
	EFIAPI
	SerialSetAttributes (
	IN EFI_SERIAL_IO_PROTOCOL *This,
	IN UINT64 BaudRate,
	IN UINT32 ReceiveFifoDepth,
	IN UINT32 Timeout,
	IN EFI_PARITY_TYPE Parity,
	IN UINT8 DataBits,
	IN EFI_STOP_BITS_TYPE StopBits
	)
	{
	EFI_STATUS Status;
	EFI_TPL Tpl;
	UINT64 OriginalBaudRate;
	UINT32 OriginalReceiveFifoDepth;
	UINT32 OriginalTimeout;
	EFI_PARITY_TYPE OriginalParity;
	UINT8 OriginalDataBits;
	EFI_STOP_BITS_TYPE OriginalStopBits;

	//
	// Preserve the original input values in case
	// SerialPortSetAttributes() updates the input/output
	// parameters even on error.
	//
	OriginalBaudRate = BaudRate;
	OriginalReceiveFifoDepth = ReceiveFifoDepth;
	OriginalTimeout = Timeout;
	OriginalParity = Parity;
	OriginalDataBits = DataBits;
	OriginalStopBits = StopBits;
	Status = SerialPortSetAttributes (&BaudRate, &ReceiveFifoDepth, &Timeout, &Parity, &DataBits, &StopBits);
	if (EFI_ERROR (Status)) {
	//
	// If it is just to set Timeout value and unsupported is returned,
	// do not return error.
	//
	if ((Status == EFI_UNSUPPORTED) &&
	(This->Mode->Timeout != OriginalTimeout) &&
	(This->Mode->ReceiveFifoDepth == OriginalReceiveFifoDepth) &&
	(This->Mode->BaudRate == OriginalBaudRate) &&
	(This->Mode->DataBits == (UINT32) OriginalDataBits) &&
	(This->Mode->Parity == (UINT32) OriginalParity) &&
	(This->Mode->StopBits == (UINT32) OriginalStopBits)) {
	//
	// Restore to the original input values.
	//
	BaudRate = OriginalBaudRate;
	ReceiveFifoDepth = OriginalReceiveFifoDepth;
	Timeout = OriginalTimeout;
	Parity = OriginalParity;
	DataBits = OriginalDataBits;
	StopBits = OriginalStopBits;
	Status = EFI_SUCCESS;
	} else if (Status == EFI_INVALID_PARAMETER \|\| Status == EFI_UNSUPPORTED) {
	return EFI_INVALID_PARAMETER;
	} else {
	return EFI_DEVICE_ERROR;
	}
	}

	//
	// Set the Serial I/O mode and update the device path
	//

	Tpl = gBS->RaiseTPL (TPL_NOTIFY);

	//
	// Set the Serial I/O mode
	//
	This->Mode->ReceiveFifoDepth = ReceiveFifoDepth;
	This->Mode->Timeout = Timeout;
	This->Mode->BaudRate = BaudRate;
	This->Mode->DataBits = (UINT32) DataBits;
	This->Mode->Parity = (UINT32) Parity;
	This->Mode->StopBits = (UINT32) StopBits;

	//
	// Check if the device path has actually changed
	//
	if (mSerialDevicePath.Uart.BaudRate == BaudRate &&
	mSerialDevicePath.Uart.DataBits == DataBits &&
	mSerialDevicePath.Uart.Parity == (UINT8) Parity &&
	mSerialDevicePath.Uart.StopBits == (UINT8) StopBits
	) {
	gBS->RestoreTPL (Tpl);
	return EFI_SUCCESS;
	}

	//
	// Update the device path
	//
	mSerialDevicePath.Uart.BaudRate = BaudRate;
	mSerialDevicePath.Uart.DataBits = DataBits;
	mSerialDevicePath.Uart.Parity = (UINT8) Parity;
	mSerialDevicePath.Uart.StopBits = (UINT8) StopBits;

	Status = gBS->ReinstallProtocolInterface (
	mSerialHandle,
	&gEfiDevicePathProtocolGuid,
	&mSerialDevicePath,
	&mSerialDevicePath
	);

	gBS->RestoreTPL (Tpl);

	return Status;
	}

	/**
	Set the control bits on a serial device

	@param This Protocol instance pointer.
	@param Control Set the bits of Control that are settable.

	@retval EFI_SUCCESS The new control bits were set on the serial device.
	@retval EFI_UNSUPPORTED The serial device does not support this operation.
	@retval EFI_DEVICE_ERROR The serial device is not functioning correctly.

	**/
	EFI_STATUS
	EFIAPI
	SerialSetControl (
	IN EFI_SERIAL_IO_PROTOCOL *This,
	IN UINT32 Control
	)
	{
	return SerialPortSetControl (Control);
	}

	/**
	Retrieves the status of the control bits on a serial device

	@param This Protocol instance pointer.
	@param Control A pointer to return the current Control signals from the serial device.

	@retval EFI_SUCCESS The control bits were read from the serial device.
	@retval EFI_DEVICE_ERROR The serial device is not functioning correctly.

	**/
	EFI_STATUS
	EFIAPI
	SerialGetControl (
	IN EFI_SERIAL_IO_PROTOCOL *This,
	OUT UINT32 *Control
	)
	{
	return SerialPortGetControl (Control);
	}

	/**
	Writes data to a serial device.

	@param This Protocol instance pointer.
	@param BufferSize On input, the size of the Buffer. On output, the amount of
	data actually written.
	@param Buffer The buffer of data to write

	@retval EFI_SUCCESS The data was written.
	@retval EFI_DEVICE_ERROR The device reported an error.
	@retval EFI_TIMEOUT The data write was stopped due to a timeout.

	**/
	EFI_STATUS
	EFIAPI
	SerialWrite (
	IN EFI_SERIAL_IO_PROTOCOL *This,
	IN OUT UINTN *BufferSize,
	IN VOID *Buffer
	)
	{
	UINTN Count;

	Count = SerialPortWrite (Buffer, *BufferSize);

	if (Count != *BufferSize) {
	*BufferSize = Count;
	return EFI_TIMEOUT;
	}

	return EFI_SUCCESS;
	}

	/**
	Reads data from a serial device.

	@param This Protocol instance pointer.
	@param BufferSize On input, the size of the Buffer. On output, the amount of
	data returned in Buffer.
	@param Buffer The buffer to return the data into.

	@retval EFI_SUCCESS The data was read.
	@retval EFI_DEVICE_ERROR The device reported an error.
	@retval EFI_TIMEOUT The data write was stopped due to a timeout.

	**/
	EFI_STATUS
	EFIAPI
	SerialRead (
	IN EFI_SERIAL_IO_PROTOCOL *This,
	IN OUT UINTN *BufferSize,
	OUT VOID *Buffer
	)
	{
	UINTN Count;
	UINTN TimeOut;

	Count = 0;

	while (Count < *BufferSize) {
	TimeOut = 0;
	while (TimeOut < mSerialIoMode.Timeout) {
	if (SerialPortPoll ()) {
	break;
	}
	gBS->Stall (10);
	TimeOut += 10;
	}
	if (TimeOut >= mSerialIoMode.Timeout) {
	break;
	}
	SerialPortRead (Buffer, 1);
	Count++;
	Buffer = (VOID ) ((UINT8 ) Buffer + 1);
	}

	if (Count != *BufferSize) {
	*BufferSize = Count;
	return EFI_TIMEOUT;
	}

	return EFI_SUCCESS;
	}

	/**
	Initialization for the Serial Io Protocol.

	@param[in] ImageHandle The firmware allocated handle for the EFI image.
	@param[in] SystemTable A pointer to the EFI System Table.

	@retval EFI_SUCCESS The entry point is executed successfully.
	@retval other Some error occurs when executing this entry point.

	**/
	EFI_STATUS
	EFIAPI
	SerialDxeInitialize (
	IN EFI_HANDLE ImageHandle,
	IN EFI_SYSTEM_TABLE *SystemTable
	)
	{
	EFI_STATUS Status;

	mSerialIoMode.BaudRate = PcdGet64 (PcdUartDefaultBaudRate);
	mSerialIoMode.DataBits = (UINT32) PcdGet8 (PcdUartDefaultDataBits);
	mSerialIoMode.Parity = (UINT32) PcdGet8 (PcdUartDefaultParity);
	mSerialIoMode.StopBits = (UINT32) PcdGet8 (PcdUartDefaultStopBits);
	mSerialIoMode.ReceiveFifoDepth = PcdGet16 (PcdUartDefaultReceiveFifoDepth);
	mSerialDevicePath.Uart.BaudRate = PcdGet64 (PcdUartDefaultBaudRate);
	mSerialDevicePath.Uart.DataBits = PcdGet8 (PcdUartDefaultDataBits);
	mSerialDevicePath.Uart.Parity = PcdGet8 (PcdUartDefaultParity);
	mSerialDevicePath.Uart.StopBits = PcdGet8 (PcdUartDefaultStopBits);

	//
	// Issue a reset to initialize the Serial Port
	//
	Status = mSerialIoTemplate.Reset (&mSerialIoTemplate);
	if (EFI_ERROR (Status)) {
	return Status;
	}

	//
	// Make a new handle with Serial IO protocol and its device path on it.
	//
	Status = gBS->InstallMultipleProtocolInterfaces (
	&mSerialHandle,
	&gEfiSerialIoProtocolGuid, &mSerialIoTemplate,
	&gEfiDevicePathProtocolGuid, &mSerialDevicePath,
	NULL
	);
	ASSERT_EFI_ERROR (Status);

	return Status;
	}