On Fri, Mar 03, 2023 at 12:04:09PM -0600, Andrei Warkentin wrote:
> These are implementations of SerialPortLib using SBI console services.
> - SecPeiRiscVSerialPortLibSbi is appropriate for SEC/PEI (XIP) environments
> - PrePiDxeRiscVSerialPortLibSbi is appropriate for PrePI/DXE environments
> 
> Tested with:
> - Qemu RiscVVirt (non-DBCN case, backed by UART)
> - TinyEMU + RiscVVirt (non-DBCN case, HTIF)
> - TinyEMU + RiscVVirt (DBCN case, HTIF)
> 
> Cc: Daniel Schaefer <g...@danielschaefer.me>
> Cc: Sunil V L <suni...@ventanamicro.com>
> Acked-by: Gerd Hoffmann <kra...@redhat.com>
> Signed-off-by: Andrei Warkentin <andrei.warken...@intel.com>
> ---
>  
> MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerialPortLibSbi.inf
>  |  36 +++
>  MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPortLibSbi.inf   
>   |  39 +++
>  MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerialPortLibSbi.c 
>   | 285 ++++++++++++++++++++
>  MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPortLibSbi.c     
>   | 233 ++++++++++++++++
>  
> MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerialPortLibSbi.uni
>  |  16 ++
>  MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPortLibSbi.uni   
>   |  16 ++
>  6 files changed, 625 insertions(+)
> 
> diff --git 
> a/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerialPortLibSbi.inf
>  
> b/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerialPortLibSbi.inf
> new file mode 100644
> index 000000000000..1d8544756bb9
> --- /dev/null
> +++ 
> b/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerialPortLibSbi.inf
> @@ -0,0 +1,36 @@
> +## @file
> +#  Serial Port Library backed by SBI console.
> +#
> +#  Meant for PrePi and DXE environments (where globals are allowed). See
> +#  SecPeiSerialPortLibRiscVSbi for a reduced variant appropriate for SEC
> +#  and PEI (XIP) environments.
> +#
> +#  Copyright (c) 2023, Intel Corporation. All rights reserved.<BR>
> +#
> +#  SPDX-License-Identifier: BSD-2-Clause-Patent
> +#
> +#
> +##
> +
> +[Defines]
> +  INF_VERSION                    = 0x0001001B
> +  BASE_NAME                      = PrePiDxeRiscVSerialPortLibSbi
> +  MODULE_UNI_FILE                = PrePiDxeRiscVSerialPortLibSbi.uni
> +  FILE_GUID                      = 872af743-ab56-45b4-a065-602567f4820c
> +  MODULE_TYPE                    = BASE
> +  VERSION_STRING                 = 1.0
> +  LIBRARY_CLASS                  = SerialPortLib | SEC DXE_CORE DXE_DRIVER 
> DXE_RUNTIME_DRIVER UEFI_DRIVER UEFI_APPLICATION
> +
> +
> +#
> +#  VALID_ARCHITECTURES           = RISCV64
> +#
> +
> +[Sources]
> +  PrePiDxeRiscVSerialPortLibSbi.c
> +
> +[Packages]
> +  MdePkg/MdePkg.dec
> +
> +[LibraryClasses]
> +  RiscVSbiLib
> diff --git 
> a/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPortLibSbi.inf 
> b/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPortLibSbi.inf
> new file mode 100644
> index 000000000000..7bc7cd47c11c
> --- /dev/null
> +++ 
> b/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPortLibSbi.inf
> @@ -0,0 +1,39 @@
> +## @file
> +#  Serial Port Library backed by SBI console.
> +#
> +#  Meant for SEC and PEI (XIP) environments.
> +#
> +#  Due to limitations of SBI console interface and XIP environments
> +#  (on use of globals), this library instance does not implement reading
> +#  and polling the serial port. See PrePiDxeSerialPortLibRiscVSbi for
> +#  the full-featured variant meant for PrePi and DXE environments.
> +#
> +#  Copyright (c) 2023, Intel Corporation. All rights reserved.<BR>
> +#
> +#  SPDX-License-Identifier: BSD-2-Clause-Patent
> +#
> +#
> +##
> +
> +[Defines]
> +  INF_VERSION                    = 0x0001001B
> +  BASE_NAME                      = SecPeiRiscVSerialPortLibSbi
> +  MODULE_UNI_FILE                = SecPeiRiscVSerialPortLibSbi.uni
> +  FILE_GUID                      = 639fad38-4bfd-4eb9-9f09-e97c7947d480
> +  MODULE_TYPE                    = BASE
> +  VERSION_STRING                 = 1.0
> +  LIBRARY_CLASS                  = SerialPortLib | SEC PEI_CORE PEIM
> +
> +
> +#
> +#  VALID_ARCHITECTURES           = RISCV64
> +#
> +
> +[Sources]
> +  SecPeiRiscVSerialPortLibSbi.c
> +
> +[Packages]
> +  MdePkg/MdePkg.dec
> +
> +[LibraryClasses]
> +  RiscVSbiLib
> diff --git 
> a/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerialPortLibSbi.c
>  
> b/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerialPortLibSbi.c
> new file mode 100644
> index 000000000000..cedda04ee5aa
> --- /dev/null
> +++ 
> b/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerialPortLibSbi.c
> @@ -0,0 +1,285 @@
> +/** @file
> +  Serial Port Library backed by SBI console.
> +
> +  Meant for PrePi and DXE environments (where globals are allowed). See
> +  SecPeiSerialPortLibRiscVSbi for a reduced variant appropriate for SEC
> +  and PEI (XIP) environments.
> +
> +  Copyright (c) 2023, Intel Corporation. All rights reserved.<BR>
> +  SPDX-License-Identifier: BSD-2-Clause-Patent
> +
> +**/
> +
> +#include <Base.h>
> +#include <Library/SerialPortLib.h>
> +#include <Library/BaseRiscVSbiLib.h>
> +
> +STATIC BOOLEAN  mHaveDbcn          = FALSE;
> +STATIC BOOLEAN  mHaveLegacyPutchar = FALSE;
> +STATIC BOOLEAN  mHaveLegacyGetchar = FALSE;
> +STATIC INT64    mLastGetChar       = -1;
> +
> +/**
> +  Initialize the serial device hardware.
> +
> +  If no initialization is required, then return RETURN_SUCCESS.
> +  If the serial device was successfully initialized, then return 
> RETURN_SUCCESS.
> +  If the serial device could not be initialized, then return 
> RETURN_DEVICE_ERROR.
> +
> +  @retval RETURN_SUCCESS        The serial device was initialized.
> +  @retval RETURN_DEVICE_ERROR   The serial device could not be initialized.
> +
> +**/
> +RETURN_STATUS
> +EFIAPI
> +SerialPortInitialize (
> +  VOID
> +  )
> +{
> +  SBI_RET  Ret;
> +
> +  Ret = SbiCall (SBI_EXT_BASE, SBI_EXT_BASE_PROBE_EXT, 1, SBI_EXT_DBCN);
> +  if ((TranslateError (Ret.Error) == EFI_SUCCESS) &&
> +      (Ret.Value != 0))
> +  {
> +    mHaveDbcn = TRUE;
> +  } else {
> +    Ret = SbiCall (SBI_EXT_BASE, SBI_EXT_BASE_PROBE_EXT, 1, 
> SBI_EXT_0_1_CONSOLE_PUTCHAR);
> +    if ((TranslateError (Ret.Error) == EFI_SUCCESS) &&
> +        (Ret.Value != 0))
> +    {
> +      mHaveLegacyPutchar = TRUE;
> +    }
> +
> +    Ret = SbiCall (SBI_EXT_BASE, SBI_EXT_BASE_PROBE_EXT, 1, 
> SBI_EXT_0_1_CONSOLE_GETCHAR);
> +    if ((TranslateError (Ret.Error) == EFI_SUCCESS) &&
> +        (Ret.Value != 0))
> +    {
> +      mHaveLegacyGetchar = TRUE;
> +    }
> +  }
> +
> +  return RETURN_SUCCESS;
> +}
> +
> +/**
> +  Write data from buffer to serial device.
> +
> +  Writes NumberOfBytes data bytes from Buffer to the serial device.
> +  The number of bytes actually written to the serial device is returned.
> +  If the return value is less than NumberOfBytes, then the write operation 
> failed.
> +  If Buffer is NULL, then ASSERT().
> +  If NumberOfBytes is zero, then return 0.
> +
> +  @param  Buffer           The pointer to the data buffer to be written.
> +  @param  NumberOfBytes    The number of bytes to written to the serial 
> device.
> +
> +  @retval 0                NumberOfBytes is 0.
> +  @retval >0               The number of bytes written to the serial device.
> +                           If this value is less than NumberOfBytes, then 
> the write operation failed.
> +
> +**/
> +UINTN
> +EFIAPI
> +SerialPortWrite (
> +  IN UINT8  *Buffer,
> +  IN UINTN  NumberOfBytes
> +  )
> +{
> +  UINTN  Index;
> +
> +  if (mHaveDbcn) {
> +    SBI_RET  Ret;
> +    Ret = SbiCall (
> +            SBI_EXT_DBCN,
> +            SBI_EXT_DBCN_WRITE,
> +            3,
> +            NumberOfBytes,
> +            ((UINTN)Buffer),
> +            0
> +            );
> +    if (TranslateError (Ret.Error) != EFI_SUCCESS) {
> +      return 0;
> +    }
> +
> +    return Ret.Value;
> +  } else if (mHaveLegacyPutchar) {
> +    for (Index = 0; Index < NumberOfBytes; Index++) {
> +      SbiCall (SBI_EXT_0_1_CONSOLE_PUTCHAR, 0, 1, Buffer[Index]);
Should there be a check for return value and return?

> +    }
> +
> +    return Index;
> +  }
> +
> +  /*
> +   * Neither DBCN or legacy extension were present.
> +   */
> +  return NumberOfBytes;

Shouldn't this return 0?

> +}
> +
> +/**
> +  Read data from serial device and save the datas in buffer.
> +
> +  Reads NumberOfBytes data bytes from a serial device into the buffer
> +  specified by Buffer. The number of bytes actually read is returned.
> +  If the return value is less than NumberOfBytes, then the rest operation 
> failed.
> +  If Buffer is NULL, then ASSERT().
> +  If NumberOfBytes is zero, then return 0.
> +
> +  @param  Buffer           The pointer to the data buffer to store the data 
> read from the serial device.
> +  @param  NumberOfBytes    The number of bytes which will be read.
> +
> +  @retval 0                Read data failed; No data is to be read.
> +  @retval >0               The actual number of bytes read from serial 
> device.
> +
> +**/
> +UINTN
> +EFIAPI
> +SerialPortRead (
> +  OUT UINT8  *Buffer,
> +  IN  UINTN  NumberOfBytes
> +  )
> +{
> +  UINTN  Index = 0;
> +
> +  while ((Index < NumberOfBytes) && SerialPortPoll ()) {
> +    Buffer[Index++] = (UINT8)mLastGetChar;
> +    mLastGetChar    = -1;
> +  }
> +
> +  return Index;
> +}
> +
> +/**
> +  Polls a serial device to see if there is any data waiting to be read.
> +
> +  Polls a serial device to see if there is any data waiting to be read.
> +  If there is data waiting to be read from the serial device, then TRUE is 
> returned.
> +  If there is no data waiting to be read from the serial device, then FALSE 
> is returned.
> +
> +  @retval TRUE             Data is waiting to be read from the serial device.
> +  @retval FALSE            There is no data waiting to be read from the 
> serial device.
> +
> +**/
> +BOOLEAN
> +EFIAPI
> +SerialPortPoll (
> +  VOID
> +  )
> +{
> +  /*
> +   * Careful. OpenSBI with HTIF console will return -1 followed by -2
> +   * if there is no character received. So just check for values >= 0.
> +   */
> +
> +  if (mLastGetChar >= 0) {
> +    return TRUE;
> +  }
> +
> +  if (mHaveDbcn) {
> +    UINT8    Buffer;
> +    SBI_RET  Ret = SbiCall (
> +                     SBI_EXT_DBCN,
> +                     SBI_EXT_DBCN_READ,
> +                     3,
> +                     1,
> +                     ((UINTN)&Buffer),
> +                     0
> +                     );
> +    if ((TranslateError (Ret.Error) == EFI_SUCCESS) &&
> +        (Ret.Value == 1))
> +    {
> +      mLastGetChar = Buffer;
> +    }
> +  } else if (mHaveLegacyGetchar) {
> +    mLastGetChar = (INT64)SbiCall (SBI_EXT_0_1_CONSOLE_GETCHAR, 0, 0).Error;
Isn't it better to use SBI_RET?

> +  }
> +
> +  return mLastGetChar >= 0;
> +}
> +
> +/**
> +  Sets the control bits on a serial device.
> +
> +  @param Control                Sets the bits of Control that are settable.
> +
> +  @retval RETURN_SUCCESS        The new control bits were set on the serial 
> device.
> +  @retval RETURN_UNSUPPORTED    The serial device does not support this 
> operation.
> +  @retval RETURN_DEVICE_ERROR   The serial device is not functioning 
> correctly.
> +
> +**/
> +RETURN_STATUS
> +EFIAPI
> +SerialPortSetControl (
> +  IN UINT32  Control
> +  )
> +{
> +  return RETURN_SUCCESS;
> +}
> +
> +/**
> +  Retrieve the status of the control bits on a serial device.
> +
> +  @param Control                A pointer to return the current control 
> signals from the serial device.
> +
> +  @retval RETURN_SUCCESS        The control bits were read from the serial 
> device.
> +  @retval RETURN_UNSUPPORTED    The serial device does not support this 
> operation.
> +  @retval RETURN_DEVICE_ERROR   The serial device is not functioning 
> correctly.
> +
> +**/
> +RETURN_STATUS
> +EFIAPI
> +SerialPortGetControl (
> +  OUT UINT32  *Control
> +  )
> +{
> +  *Control = 0;
> +  return RETURN_SUCCESS;
> +}
> +
> +/**
> +  Sets the baud rate, receive FIFO depth, transmit/receice time out, parity,
> +  data bits, and stop bits on a serial device.
> +
> +  @param BaudRate           The requested baud rate. A BaudRate value of 0 
> will use the
> +                            device's default interface speed.
> +                            On output, the value actually set.
> +  @param ReveiveFifoDepth   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.
> +                            On output, the value actually set.
> +  @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.
> +                            On output, the value actually set.
> +  @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.
> +                            On output, the value actually set.
> +  @param DataBits           The number of data bits to use on the serial 
> device. A DataBits
> +                            vaule of 0 will use the device's default data 
> bit setting.
> +                            On output, the value actually set.
> +  @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.
> +                            On output, the value actually set.
> +
> +  @retval RETURN_SUCCESS            The new attributes were set on the 
> serial device.
> +  @retval RETURN_UNSUPPORTED        The serial device does not support this 
> operation.
> +  @retval RETURN_INVALID_PARAMETER  One or more of the attributes has an 
> unsupported value.
> +  @retval RETURN_DEVICE_ERROR       The serial device is not functioning 
> correctly.
> +
> +**/
> +RETURN_STATUS
> +EFIAPI
> +SerialPortSetAttributes (
> +  IN OUT UINT64              *BaudRate,
> +  IN OUT UINT32              *ReceiveFifoDepth,
> +  IN OUT UINT32              *Timeout,
> +  IN OUT EFI_PARITY_TYPE     *Parity,
> +  IN OUT UINT8               *DataBits,
> +  IN OUT EFI_STOP_BITS_TYPE  *StopBits
> +  )
> +{
> +  return RETURN_SUCCESS;
> +}
> diff --git 
> a/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPortLibSbi.c 
> b/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPortLibSbi.c
> new file mode 100644
> index 000000000000..0ad5931be3ae
> --- /dev/null
> +++ b/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPortLibSbi.c
> @@ -0,0 +1,233 @@
> +/** @file
> +  Serial Port Library backed by SBI console.
> +
> +  Meant for SEC and PEI (XIP) environments.
> +
> +  Due to limitations of SBI console interface and XIP environments
> +  (on use of globals), this library instance does not implement reading
> +  and polling the serial port. See PrePiDxeSerialPortLibRiscVSbi for
> +  the full-featured variant meant for PrePi and DXE environments.
> +
> +  Copyright (c) 2023, Intel Corporation. All rights reserved.<BR>
> +  SPDX-License-Identifier: BSD-2-Clause-Patent
> +
> +**/
> +
> +#include <Base.h>
> +#include <Library/SerialPortLib.h>
> +#include <Library/BaseRiscVSbiLib.h>
> +
> +/**
> +  Initialize the serial device hardware.
> +
> +  If no initialization is required, then return RETURN_SUCCESS.
> +  If the serial device was successfully initialized, then return 
> RETURN_SUCCESS.
> +  If the serial device could not be initialized, then return 
> RETURN_DEVICE_ERROR.
> +
> +  @retval RETURN_SUCCESS        The serial device was initialized.
> +  @retval RETURN_DEVICE_ERROR   The serial device could not be initialized.
> +
> +**/
> +RETURN_STATUS
> +EFIAPI
> +SerialPortInitialize (
> +  VOID
> +  )
> +{
> +  return RETURN_SUCCESS;
> +}
> +
> +/**
> +  Write data from buffer to serial device.
> +
> +  Writes NumberOfBytes data bytes from Buffer to the serial device.
> +  The number of bytes actually written to the serial device is returned.
> +  If the return value is less than NumberOfBytes, then the write operation 
> failed.
> +  If Buffer is NULL, then ASSERT().
> +  If NumberOfBytes is zero, then return 0.
> +
> +  @param  Buffer           The pointer to the data buffer to be written.
> +  @param  NumberOfBytes    The number of bytes to written to the serial 
> device.
> +
> +  @retval 0                NumberOfBytes is 0.
> +  @retval >0               The number of bytes written to the serial device.
> +                           If this value is less than NumberOfBytes, then 
> the write operation failed.
> +
> +**/
> +UINTN
> +EFIAPI
> +SerialPortWrite (
> +  IN UINT8  *Buffer,
> +  IN UINTN  NumberOfBytes
> +  )
> +{
> +  SBI_RET  Ret;
> +  UINTN    Index;
> +
> +  Ret = SbiCall (SBI_EXT_BASE, SBI_EXT_BASE_PROBE_EXT, 1, SBI_EXT_DBCN);
> +  if ((TranslateError (Ret.Error) == EFI_SUCCESS) &&
> +      (Ret.Value != 0))
> +  {
> +    Ret = SbiCall (
> +            SBI_EXT_DBCN,
> +            SBI_EXT_DBCN_WRITE,
> +            3,
> +            NumberOfBytes,
> +            ((UINTN)Buffer),
> +            0
> +            );
> +    if (TranslateError (Ret.Error) != EFI_SUCCESS) {
> +      return 0;
> +    }
> +
> +    return Ret.Value;
> +  }
> +
> +  Ret = SbiCall (SBI_EXT_BASE, SBI_EXT_BASE_PROBE_EXT, 1, 
> SBI_EXT_0_1_CONSOLE_PUTCHAR);
> +  if ((TranslateError (Ret.Error) == EFI_SUCCESS) &&
> +      (Ret.Value != 0))
> +  {
> +    for (Index = 0; Index < NumberOfBytes; Index++) {
> +      SbiCall (SBI_EXT_0_1_CONSOLE_PUTCHAR, 0, 1, Buffer[Index]);

Same as above. Should we check for return value?

> +    }
> +
> +    return Index;
> +  }
> +
> +  /*
> +   * Neither DBCN or legacy extension were present.
> +   */
> +  return NumberOfBytes;
Failure to write should return 0 right?

> +}
> +
> +/**
> +  Read data from serial device and save the datas in buffer.
> +
> +  Reads NumberOfBytes data bytes from a serial device into the buffer
> +  specified by Buffer. The number of bytes actually read is returned.
> +  If the return value is less than NumberOfBytes, then the rest operation 
> failed.
> +  If Buffer is NULL, then ASSERT().
> +  If NumberOfBytes is zero, then return 0.
> +
> +  @param  Buffer           The pointer to the data buffer to store the data 
> read from the serial device.
> +  @param  NumberOfBytes    The number of bytes which will be read.
> +
> +  @retval 0                Read data failed; No data is to be read.
> +  @retval >0               The actual number of bytes read from serial 
> device.
> +
> +**/
> +UINTN
> +EFIAPI
> +SerialPortRead (
> +  OUT UINT8  *Buffer,
> +  IN  UINTN  NumberOfBytes
> +  )
> +{
> +  return 0;
> +}
> +
> +/**
> +  Polls a serial device to see if there is any data waiting to be read.
> +
> +  Polls a serial device to see if there is any data waiting to be read.
> +  If there is data waiting to be read from the serial device, then TRUE is 
> returned.
> +  If there is no data waiting to be read from the serial device, then FALSE 
> is returned.
> +
> +  @retval TRUE             Data is waiting to be read from the serial device.
> +  @retval FALSE            There is no data waiting to be read from the 
> serial device.
> +
> +**/
> +BOOLEAN
> +EFIAPI
> +SerialPortPoll (
> +  VOID
> +  )
> +{
> +  return FALSE;
> +}
> +
> +/**
> +  Sets the control bits on a serial device.
> +
> +  @param Control                Sets the bits of Control that are settable.
> +
> +  @retval RETURN_SUCCESS        The new control bits were set on the serial 
> device.
> +  @retval RETURN_UNSUPPORTED    The serial device does not support this 
> operation.
> +  @retval RETURN_DEVICE_ERROR   The serial device is not functioning 
> correctly.
> +
> +**/
> +RETURN_STATUS
> +EFIAPI
> +SerialPortSetControl (
> +  IN UINT32  Control
> +  )
> +{
> +  return RETURN_SUCCESS;
> +}
> +
> +/**
> +  Retrieve the status of the control bits on a serial device.
> +
> +  @param Control                A pointer to return the current control 
> signals from the serial device.
> +
> +  @retval RETURN_SUCCESS        The control bits were read from the serial 
> device.
> +  @retval RETURN_UNSUPPORTED    The serial device does not support this 
> operation.
> +  @retval RETURN_DEVICE_ERROR   The serial device is not functioning 
> correctly.
> +
> +**/
> +RETURN_STATUS
> +EFIAPI
> +SerialPortGetControl (
> +  OUT UINT32  *Control
> +  )
> +{
> +  *Control = 0;
> +  return RETURN_SUCCESS;
> +}
> +
> +/**
> +  Sets the baud rate, receive FIFO depth, transmit/receice time out, parity,
> +  data bits, and stop bits on a serial device.
> +
> +  @param BaudRate           The requested baud rate. A BaudRate value of 0 
> will use the
> +                            device's default interface speed.
> +                            On output, the value actually set.
> +  @param ReveiveFifoDepth   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.
> +                            On output, the value actually set.
> +  @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.
> +                            On output, the value actually set.
> +  @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.
> +                            On output, the value actually set.
> +  @param DataBits           The number of data bits to use on the serial 
> device. A DataBits
> +                            vaule of 0 will use the device's default data 
> bit setting.
> +                            On output, the value actually set.
> +  @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.
> +                            On output, the value actually set.
> +
> +  @retval RETURN_SUCCESS            The new attributes were set on the 
> serial device.
> +  @retval RETURN_UNSUPPORTED        The serial device does not support this 
> operation.
> +  @retval RETURN_INVALID_PARAMETER  One or more of the attributes has an 
> unsupported value.
> +  @retval RETURN_DEVICE_ERROR       The serial device is not functioning 
> correctly.
> +
> +**/
> +RETURN_STATUS
> +EFIAPI
> +SerialPortSetAttributes (
> +  IN OUT UINT64              *BaudRate,
> +  IN OUT UINT32              *ReceiveFifoDepth,
> +  IN OUT UINT32              *Timeout,
> +  IN OUT EFI_PARITY_TYPE     *Parity,
> +  IN OUT UINT8               *DataBits,
> +  IN OUT EFI_STOP_BITS_TYPE  *StopBits
> +  )
> +{
> +  return RETURN_SUCCESS;
> +}
> diff --git 
> a/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerialPortLibSbi.uni
>  
> b/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerialPortLibSbi.uni
> new file mode 100644
> index 000000000000..7b22caa5a090
> --- /dev/null
> +++ 
> b/MdePkg/Library/PrePiDxeRiscVSerialPortLibSbi/PrePiDxeRiscVSerialPortLibSbi.uni
> @@ -0,0 +1,16 @@
> +// /** @file
> +// Serial Port Library backed by SBI console.
> +//
> +// Serial Port Library backed by SBI console.
> +//
> +// Copyright (c) 2023, Intel Corporation. All rights reserved.<BR>
> +//
> +// SPDX-License-Identifier: BSD-2-Clause-Patent
> +//
> +// **/
> +
> +
> +#string STR_MODULE_ABSTRACT             #language en-US "Serial Port Library 
> backed by SBI console"
> +
> +#string STR_MODULE_DESCRIPTION          #language en-US "Serial Port Library 
> backed by SBI console."
> +
> diff --git 
> a/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPortLibSbi.uni 
> b/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPortLibSbi.uni
> new file mode 100644
> index 000000000000..7b22caa5a090
> --- /dev/null
> +++ 
> b/MdePkg/Library/SecPeiRiscVSerialPortLibSbi/SecPeiRiscVSerialPortLibSbi.uni
> @@ -0,0 +1,16 @@
> +// /** @file
> +// Serial Port Library backed by SBI console.
> +//
> +// Serial Port Library backed by SBI console.
> +//
> +// Copyright (c) 2023, Intel Corporation. All rights reserved.<BR>
> +//
> +// SPDX-License-Identifier: BSD-2-Clause-Patent
> +//
> +// **/
> +
> +
> +#string STR_MODULE_ABSTRACT             #language en-US "Serial Port Library 
> backed by SBI console"
> +
> +#string STR_MODULE_DESCRIPTION          #language en-US "Serial Port Library 
> backed by SBI console."
> +
> -- 
> 2.25.1
> 
Please update MdePkg.dsc for these new libraries. Also, we need ACK from
MdePkg maintainers.


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