Re: [edk2-devel] [PATCH v7 2/3] MdePkg: add SBI-based SerialPortLib for RISC-V

["Andrei Warkentin" <andrei.warkentin@intel.com>]

Hi Sunil,

Not saying it's right, but I followed a specific pattern seen elsewhere, e.g. ./MdeModulePkg/Core/PiSmmCore/PiSmmIpl.uni, where the two sentences are either the same or mildly rephrased.

A 

> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Sunil V L
> Sent: Wednesday, April 12, 2023 2:16 AM
> To: Warkentin, Andrei <andrei.warkentin@intel.com>
> Cc: devel@edk2.groups.io; Daniel Schaefer <git@danielschaefer.me>;
> Kinney, Michael D <michael.d.kinney@intel.com>; Gao, Liming
> <gaoliming@byosoft.com.cn>; Liu, Zhiguang <zhiguang.liu@intel.com>; Gerd
> Hoffmann <kraxel@redhat.com>
> Subject: Re: [edk2-devel] [PATCH v7 2/3] MdePkg: add SBI-based
> SerialPortLib for RISC-V
> 
> Thanks, Andrei. Just one nit comment below.
> 
> Otherwise, LGTM.
> Reviewed-by: Sunil V L <sunilvl@ventanamicro.com>
> 
> On Fri, Apr 07, 2023 at 04:44:24PM -0500, Andrei Warkentin wrote:
> > These are implementations of SerialPortLib using SBI console services.
> > - BaseSerialPortLibRiscVSbiLib is appropriate for SEC/PEI (XIP)
> > environments
> > - BaseSerialPortLibRiscVSbiLibRam 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 <git@danielschaefer.me>
> > Cc: Sunil V L <sunilvl@ventanamicro.com>
> > Cc: Michael D Kinney <michael.d.kinney@intel.com>
> > Cc: Liming Gao <gaoliming@byosoft.com.cn>
> > Cc: Zhiguang Liu <zhiguang.liu@intel.com>
> > Acked-by: Gerd Hoffmann <kraxel@redhat.com>
> > Signed-off-by: Andrei Warkentin <andrei.warkentin@intel.com>
> > ---
> >  MdePkg/MdePkg.dsc                                                               |   2 +
> >
> MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRiscVSbiLib.in
> f    |  41 +++
> >
> MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRiscVSbiLibRa
> m.inf |  38 +++
> >  MdePkg/Library/BaseSerialPortLibRiscVSbiLib/Common.h                            |
> 41 +++
> >
> MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRiscVSbiLib.c
> | 208 ++++++++++++++
> >
> MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRiscVSbiLibRa
> m.c   | 289 ++++++++++++++++++++
> >  MdePkg/Library/BaseSerialPortLibRiscVSbiLib/Common.c                            |
> 132 +++++++++
> >
> MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRiscVSbiLib.u
> ni    |  16 ++
> >  8 files changed, 767 insertions(+)
> >
> > diff --git a/MdePkg/MdePkg.dsc b/MdePkg/MdePkg.dsc index
> > 0ac7618b4623..a810ad0d147d 100644
> > --- a/MdePkg/MdePkg.dsc
> > +++ b/MdePkg/MdePkg.dsc
> > @@ -192,5 +192,7 @@ [Components.ARM, Components.AARCH64]
> >
> >  [Components.RISCV64]
> >    MdePkg/Library/BaseRiscVSbiLib/BaseRiscVSbiLib.inf
> > +
> > + MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRiscVSb
> > + iLib.inf
> > + MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRiscVSb
> > + iLibRam.inf
> >
> >  [BuildOptions]
> > diff --git
> > a/MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRiscVSb
> > iLib.inf
> > b/MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRiscVSb
> > iLib.inf
> > new file mode 100644
> > index 000000000000..2340ac6bfe67
> > --- /dev/null
> > +++ b/MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRis
> > +++ cVSbiLib.inf
> > @@ -0,0 +1,41 @@
> > +## @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
> > +PrePiDxeSerialPortLibRiscVSbiRam.inf
> > +#  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                      = BaseSerialPortLibRiscVSbiLib
> > +  MODULE_UNI_FILE                = BaseSerialPortLibRiscVSbiLib.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]
> > +  BaseSerialPortLibRiscVSbiLib.c
> > +  Common.c
> > +  Common.h
> > +
> > +[Packages]
> > +  MdePkg/MdePkg.dec
> > +
> > +[LibraryClasses]
> > +  RiscVSbiLib
> > diff --git
> > a/MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRiscVSb
> > iLibRam.inf
> > b/MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRiscVSb
> > iLibRam.inf
> > new file mode 100644
> > index 000000000000..d09573ca5b36
> > --- /dev/null
> > +++ b/MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRis
> > +++ cVSbiLibRam.inf
> > @@ -0,0 +1,38 @@
> > +## @file
> > +#  Serial Port Library backed by SBI console.
> > +#
> > +#  Meant for PrePi and DXE environments (where globals are allowed).
> > +See #  BaseSerialPortLibRiscVSbiLib.inf 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                      = BaseSerialPortLibRiscVSbiLibRam
> > +  MODULE_UNI_FILE                = BaseSerialPortLibRiscVSbiLib.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]
> > +  BaseSerialPortLibRiscVSbiLibRam.c
> > +  Common.c
> > +  Common.h
> > +
> > +[Packages]
> > +  MdePkg/MdePkg.dec
> > +
> > +[LibraryClasses]
> > +  RiscVSbiLib
> > diff --git a/MdePkg/Library/BaseSerialPortLibRiscVSbiLib/Common.h
> > b/MdePkg/Library/BaseSerialPortLibRiscVSbiLib/Common.h
> > new file mode 100644
> > index 000000000000..98c1a5d3865e
> > --- /dev/null
> > +++ b/MdePkg/Library/BaseSerialPortLibRiscVSbiLib/Common.h
> > @@ -0,0 +1,41 @@
> > +/** @file
> > +  Serial Port Library backed by SBI console.
> > +
> > +  Common functionality shared by PrePiDxeSerialPortLibRiscVSbi and
> > + PrePiDxeSerialPortLibRiscVSbiRam implementations.
> > +
> > +  Copyright (c) 2023, Intel Corporation. All rights reserved.<BR>
> > +  SPDX-License-Identifier: BSD-2-Clause-Patent
> > +
> > +**/
> > +
> > +#ifndef SERIAL_PORT_SBI_COMMON_H_
> > +#define SERIAL_PORT_SBI_COMMON_H_
> > +
> > +#include <Base.h>
> > +#include <Library/SerialPortLib.h>
> > +#include <Library/BaseRiscVSbiLib.h>
> > +
> > +BOOLEAN
> > +SbiImplementsDbcn (
> > +  VOID
> > +  );
> > +
> > +BOOLEAN
> > +SbiImplementsLegacyPutchar (
> > +  VOID
> > +  );
> > +
> > +UINTN
> > +SbiLegacyPutchar (
> > +  IN  UINT8  *Buffer,
> > +  IN  UINTN  NumberOfBytes
> > +  );
> > +
> > +UINTN
> > +SbiDbcnWrite (
> > +  IN  UINT8  *Buffer,
> > +  IN  UINTN  NumberOfBytes
> > +  );
> > +
> > +#endif /* SERIAL_PORT_SBI_COMMON_H_ */
> > diff --git
> > a/MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRiscVSb
> > iLib.c
> > b/MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRiscVSb
> > iLib.c
> > new file mode 100644
> > index 000000000000..f4f2959cf8cc
> > --- /dev/null
> > +++ b/MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRis
> > +++ cVSbiLib.c
> > @@ -0,0 +1,208 @@
> > +/** @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
> > + BaseSerialPortLibRiscVSbiLibRam.c 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 "Common.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 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
> > +  )
> > +{
> > +  if (NumberOfBytes == 0) {
> > +    return 0;
> > +  }
> > +
> > +  if (SbiImplementsDbcn ()) {
> > +    return SbiDbcnWrite (Buffer, NumberOfBytes);  }
> > +
> > +  if (SbiImplementsLegacyPutchar ()) {
> > +    return SbiLegacyPutchar (Buffer, NumberOfBytes);  }
> > +
> > +  /*
> > +   * Neither DBCN or legacy extension were present.
> > +   */
> > +  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 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/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRiscVSb
> > iLibRam.c
> > b/MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRiscVSb
> > iLibRam.c
> > new file mode 100644
> > index 000000000000..fafba87b7cd1
> > --- /dev/null
> > +++ b/MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRis
> > +++ cVSbiLibRam.c
> > @@ -0,0 +1,289 @@
> > +/** @file
> > +  Serial Port Library backed by SBI console.
> > +
> > +  Meant for PrePi and DXE environments (where globals are allowed).
> > + See  BaseSerialPortLibRiscVSbiLib.c 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>
> > +#include "Common.h"
> > +
> > +STATIC BOOLEAN  mHaveDbcn          = FALSE;
> > +STATIC BOOLEAN  mHaveLegacyPutchar = FALSE; STATIC BOOLEAN
> > +mHaveLegacyGetchar = FALSE;
> > +STATIC INT64    mLastGetChar       = -1;
> > +
> > +/**
> > +  Return whether the legacy console getchar extension is implemented.
> > +
> > +  @retval TRUE                  Extension is implemented.
> > +  @retval FALSE                 Extension is not implemented.
> > +
> > +**/
> > +STATIC
> > +BOOLEAN
> > +SbiImplementsLegacyGetchar (
> > +  VOID
> > +  )
> > +{
> > +  SBI_RET  Ret;
> > +
> > +  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))
> > +  {
> > +    return TRUE;
> > +  }
> > +
> > +  return FALSE;
> > +}
> > +
> > +/**
> > +  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
> > +  )
> > +{
> > +  if (SbiImplementsDbcn ()) {
> > +    mHaveDbcn = TRUE;
> > +    return RETURN_SUCCESS;
> > +  }
> > +
> > +  if (SbiImplementsLegacyPutchar ()) {
> > +    mHaveLegacyPutchar = TRUE;
> > +  }
> > +
> > +  if (SbiImplementsLegacyGetchar ()) {
> > +    mHaveLegacyGetchar = TRUE;
> > +  }
> > +
> > +  return (mHaveLegacyGetchar && mHaveLegacyPutchar) ?
> > +         RETURN_SUCCESS :
> > +         RETURN_DEVICE_ERROR;
> > +}
> > +
> > +/**
> > +  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 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
> > +  )
> > +{
> > +  if (NumberOfBytes == 0) {
> > +    return 0;
> > +  }
> > +
> > +  if (mHaveDbcn) {
> > +    return SbiDbcnWrite (Buffer, NumberOfBytes);  } else if
> > + (mHaveLegacyPutchar) {
> > +    return SbiLegacyPutchar (Buffer, NumberOfBytes);  }
> > +
> > +  /*
> > +   * Neither DBCN or legacy extension were present.
> > +   */
> > +  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 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;
> > +
> > +  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;
> > +
> > +    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;  }
> > +
> > +  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/BaseSerialPortLibRiscVSbiLib/Common.c
> > b/MdePkg/Library/BaseSerialPortLibRiscVSbiLib/Common.c
> > new file mode 100644
> > index 000000000000..4926ac675b62
> > --- /dev/null
> > +++ b/MdePkg/Library/BaseSerialPortLibRiscVSbiLib/Common.c
> > @@ -0,0 +1,132 @@
> > +/** @file
> > +  Serial Port Library backed by SBI console.
> > +
> > +  Common functionality shared by PrePiDxeSerialPortLibRiscVSbi and
> > + PrePiDxeSerialPortLibRiscVSbiRam implementations.
> > +
> > +  Copyright (c) 2023, Intel Corporation. All rights reserved.<BR>
> > +  SPDX-License-Identifier: BSD-2-Clause-Patent
> > +
> > +**/
> > +
> > +#include "Common.h"
> > +
> > +/**
> > +  Return whether the DBCN extension is implemented.
> > +
> > +  @retval TRUE                  Extension is implemented.
> > +  @retval FALSE                 Extension is not implemented.
> > +
> > +**/
> > +BOOLEAN
> > +SbiImplementsDbcn (
> > +  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))
> > +  {
> > +    return TRUE;
> > +  }
> > +
> > +  return FALSE;
> > +}
> > +
> > +/**
> > +  Return whether the legacy console putchar extension is implemented.
> > +
> > +  @retval TRUE                  Extension is implemented.
> > +  @retval FALSE                 Extension is not implemented.
> > +
> > +**/
> > +BOOLEAN
> > +SbiImplementsLegacyPutchar (
> > +  VOID
> > +  )
> > +{
> > +  SBI_RET  Ret;
> > +
> > +  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))
> > +  {
> > +    return TRUE;
> > +  }
> > +
> > +  return FALSE;
> > +}
> > +
> > +/**
> > +  Write data from buffer to console via SBI legacy putchar extension.
> > +
> > +  The number of bytes actually written to the SBI console is returned.
> > +  If the return value is less than NumberOfBytes, then the write operation
> failed.
> > +
> > +  @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              The number of bytes written to the serial device.
> > +                           If this value is less than NumberOfBytes, then the
> > +                           write operation failed.
> > +
> > +**/
> > +UINTN
> > +SbiLegacyPutchar (
> > +  IN  UINT8  *Buffer,
> > +  IN  UINTN  NumberOfBytes
> > +  )
> > +{
> > +  SBI_RET  Ret;
> > +  UINTN    Index;
> > +
> > +  for (Index = 0; Index < NumberOfBytes; Index++) {
> > +    Ret =  SbiCall (SBI_EXT_0_1_CONSOLE_PUTCHAR, 0, 1, Buffer[Index]);
> > +    if ((INT64)Ret.Error < 0) {
> > +      break;
> > +    }
> > +  }
> > +
> > +  return Index;
> > +}
> > +
> > +/**
> > +  Write data from buffer to console via SBI DBCN.
> > +
> > +  The number of bytes actually written to the SBI console is returned.
> > +  If the return value is less than NumberOfBytes, then the write operation
> failed.
> > +
> > +  @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              The number of bytes written to the serial device.
> > +                           If this value is less than NumberOfBytes, then the
> > +                           write operation failed.
> > +
> > +**/
> > +UINTN
> > +SbiDbcnWrite (
> > +  IN  UINT8  *Buffer,
> > +  IN  UINTN  NumberOfBytes
> > +  )
> > +{
> > +  SBI_RET  Ret;
> > +
> > +  Ret = SbiCall (
> > +          SBI_EXT_DBCN,
> > +          SBI_EXT_DBCN_WRITE,
> > +          3,
> > +          NumberOfBytes,
> > +          ((UINTN)Buffer),
> > +          0
> > +          );
> > +
> > +  /*
> > +   * May do partial writes. Don't bother decoding
> > +   * Ret.Error as we're only interested in number of
> > +   * bytes written to console.
> > +   */
> > +  return Ret.Value;
> > +}
> > diff --git
> > a/MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRiscVSb
> > iLib.uni
> > b/MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRiscVSb
> > iLib.uni
> > new file mode 100644
> > index 000000000000..7b22caa5a090
> > --- /dev/null
> > +++ b/MdePkg/Library/BaseSerialPortLibRiscVSbiLib/BaseSerialPortLibRis
> > +++ cVSbiLib.uni
> > @@ -0,0 +1,16 @@
> > +// /** @file
> > +// Serial Port Library backed by SBI console.
> > +//
> > +// Serial Port Library backed by SBI console.
> Duplicate sentence.
> 
> 
> 
> 
>