MdePkg/Library/DxeSmbusLib/SmbusLib.c

   1 /** @file
   2 Implementation of SmBusLib class library for DXE phase.
   3
   4 Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
   5 SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7
   8 **/
   9
  10 #include "InternalSmbusLib.h"
  11
  12 /**
  13   Executes an SMBUS quick read command.
  14
  15   Executes an SMBUS quick read command on the SMBUS device specified by SmBusAddress.
  16   Only the SMBUS slave address field of SmBusAddress is required.
  17   If Status is not NULL, then the status of the executed command is returned in Status.
  18   If PEC is set in SmBusAddress, then ASSERT().
  19   If Command in SmBusAddress is not zero, then ASSERT().
  20   If Length in SmBusAddress is not zero, then ASSERT().
  21   If any reserved bits of SmBusAddress are set, then ASSERT().
  22
  23   @param  SmBusAddress  The address that encodes the SMBUS Slave Address,
  24                         SMBUS Command, SMBUS Data Length, and PEC.
  25   @param  Status        Return status for the executed command.
  26                         This is an optional parameter and may be NULL.
  27                         RETURN_SUCCESS:  The SMBUS command was executed.
  28                         RETURN_TIMEOUT:  A timeout occurred while executing the
  29                         SMBUS command.
  30                         RETURN_DEVICE_ERROR: The request was not
  31                         completed because a failure reflected in the Host Status
  32                         Register bit.  Device errors are a result of a transaction
  33                         collision, illegal command field, unclaimed cycle (host
  34                         initiated), or bus errors (collisions).
  35                         RETURN_UNSUPPORTED: The SMBus operation is not supported.
  36
  37 **/
  38 VOID
  39 EFIAPI
  40 SmBusQuickRead (
  41   IN  UINTN                     SmBusAddress,
  42   OUT RETURN_STATUS             *Status       OPTIONAL
  43   )
  44 {
  45   ASSERT (!SMBUS_LIB_PEC (SmBusAddress));
  46   ASSERT (SMBUS_LIB_COMMAND (SmBusAddress)   == 0);
  47   ASSERT (SMBUS_LIB_LENGTH (SmBusAddress)    == 0);
  48   ASSERT (SMBUS_LIB_RESERVED (SmBusAddress) == 0);
  49
  50   InternalSmBusExec (EfiSmbusQuickRead, SmBusAddress, 0, NULL, Status);
  51 }
  52
  53 /**
  54   Executes an SMBUS quick write command.
  55
  56   Executes an SMBUS quick write command on the SMBUS device specified by SmBusAddress.
  57   Only the SMBUS slave address field of SmBusAddress is required.
  58   If Status is not NULL, then the status of the executed command is returned in Status.
  59   If PEC is set in SmBusAddress, then ASSERT().
  60   If Command in SmBusAddress is not zero, then ASSERT().
  61   If Length in SmBusAddress is not zero, then ASSERT().
  62   If any reserved bits of SmBusAddress are set, then ASSERT().
  63
  64   @param  SmBusAddress  The address that encodes the SMBUS Slave Address,
  65                         SMBUS Command, SMBUS Data Length, and PEC.
  66   @param  Status        Return status for the executed command.
  67                         This is an optional parameter and may be NULL.
  68                         RETURN_SUCCESS: The SMBUS command was executed.
  69                         RETURN_TIMEOUT: A timeout occurred while executing the
  70                         SMBUS command.
  71                         RETURN_DEVICE_ERROR:  The request was not completed because
  72                         a failure reflected in the Host Status Register bit.
  73                         Device errors are a result of a transaction collision,
  74                         illegal command field, unclaimed cycle (host initiated),
  75                         or bus errors (collisions).
  76                         RETURN_UNSUPPORTED:  The SMBus operation is not supported.
  77
  78 **/
  79 VOID
  80 EFIAPI
  81 SmBusQuickWrite (
  82   IN  UINTN                     SmBusAddress,
  83   OUT RETURN_STATUS             *Status       OPTIONAL
  84   )
  85 {
  86   ASSERT (!SMBUS_LIB_PEC (SmBusAddress));
  87   ASSERT (SMBUS_LIB_COMMAND (SmBusAddress)   == 0);
  88   ASSERT (SMBUS_LIB_LENGTH (SmBusAddress)    == 0);
  89   ASSERT (SMBUS_LIB_RESERVED (SmBusAddress) == 0);
  90
  91   InternalSmBusExec (EfiSmbusQuickWrite, SmBusAddress, 0, NULL, Status);
  92 }
  93
  94 /**
  95   Executes an SMBUS receive byte command.
  96
  97   Executes an SMBUS receive byte command on the SMBUS device specified by SmBusAddress.
  98   Only the SMBUS slave address field of SmBusAddress is required.
  99   The byte received from the SMBUS is returned.
 100   If Status is not NULL, then the status of the executed command is returned in Status.
 101   If Command in SmBusAddress is not zero, then ASSERT().
 102   If Length in SmBusAddress is not zero, then ASSERT().
 103   If any reserved bits of SmBusAddress are set, then ASSERT().
 104
 105   @param  SmBusAddress  The address that encodes the SMBUS Slave Address,
 106                         SMBUS Command, SMBUS Data Length, and PEC.
 107   @param  Status        Return status for the executed command.
 108                         This is an optional parameter and may be NULL.
 109                         RETURN_SUCCESS: The SMBUS command was executed.
 110                         RETURN_TIMEOUT: A timeout occurred while executing the
 111                         SMBUS command.
 112                         RETURN_DEVICE_ERROR:  The request was not completed because
 113                         a failure reflected in the Host Status Register bit.  Device
 114                         errors are a result of a transaction collision, illegal
 115                         command field, unclaimed cycle(host initiated), or bus
 116                         errors (collisions).
 117                         RETURN_CRC_ERROR:  The checksum is not correct. (PEC is incorrect.)
 118                         RETURN_UNSUPPORTED:  The SMBus operation is not supported.
 119
 120   @return The byte received from the SMBUS.
 121
 122 **/
 123 UINT8
 124 EFIAPI
 125 SmBusReceiveByte (
 126   IN  UINTN          SmBusAddress,
 127   OUT RETURN_STATUS  *Status        OPTIONAL
 128   )
 129 {
 130   UINT8   Byte;
 131
 132   ASSERT (SMBUS_LIB_COMMAND (SmBusAddress) == 0);
 133   ASSERT (SMBUS_LIB_LENGTH (SmBusAddress)  == 0);
 134   ASSERT (SMBUS_LIB_RESERVED (SmBusAddress) == 0);
 135
 136   InternalSmBusExec (EfiSmbusReceiveByte, SmBusAddress, 1, &Byte, Status);
 137
 138   return Byte;
 139 }
 140
 141 /**
 142   Executes an SMBUS send byte command.
 143
 144   Executes an SMBUS send byte command on the SMBUS device specified by SmBusAddress.
 145   The byte specified by Value is sent.
 146   Only the SMBUS slave address field of SmBusAddress is required.  Value is returned.
 147   If Status is not NULL, then the status of the executed command is returned in Status.
 148   If Command in SmBusAddress is not zero, then ASSERT().
 149   If Length in SmBusAddress is not zero, then ASSERT().
 150   If any reserved bits of SmBusAddress are set, then ASSERT().
 151
 152   @param  SmBusAddress  The address that encodes the SMBUS Slave Address,
 153                         SMBUS Command, SMBUS Data Length, and PEC.
 154   @param  Value         The 8-bit value to send.
 155   @param  Status        Return status for the executed command.
 156                         This is an optional parameter and may be NULL.
 157                         RETURN_SUCCESS: The SMBUS command was executed.
 158                         RETURN_TIMEOUT: A timeout occurred while executing the
 159                         SMBUS command.
 160                         RETURN_DEVICE_ERROR:  The request was not completed because
 161                         a failure reflected in the Host Status Register bit.  Device
 162                         errors are a result of a transaction collision, illegal
 163                         command field, unclaimed cycle(host initiated), or bus
 164                         errors (collisions).
 165                         RETURN_CRC_ERROR:  The checksum is not correct (PEC is incorrect)
 166                         RETURN_UNSUPPORTED:  The SMBus operation is not supported.
 167
 168   @return The parameter of Value.
 169
 170 **/
 171 UINT8
 172 EFIAPI
 173 SmBusSendByte (
 174   IN  UINTN          SmBusAddress,
 175   IN  UINT8          Value,
 176   OUT RETURN_STATUS  *Status        OPTIONAL
 177   )
 178 {
 179   UINT8   Byte;
 180
 181   ASSERT (SMBUS_LIB_COMMAND (SmBusAddress)   == 0);
 182   ASSERT (SMBUS_LIB_LENGTH (SmBusAddress)    == 0);
 183   ASSERT (SMBUS_LIB_RESERVED (SmBusAddress) == 0);
 184
 185   Byte   = Value;
 186   InternalSmBusExec (EfiSmbusSendByte, SmBusAddress, 1, &Byte, Status);
 187
 188   return Value;
 189 }
 190
 191 /**
 192   Executes an SMBUS read data byte command.
 193
 194   Executes an SMBUS read data byte command on the SMBUS device specified by SmBusAddress.
 195   Only the SMBUS slave address and SMBUS command fields of SmBusAddress are required.
 196   The 8-bit value read from the SMBUS is returned.
 197   If Status is not NULL, then the status of the executed command is returned in Status.
 198   If Length in SmBusAddress is not zero, then ASSERT().
 199   If any reserved bits of SmBusAddress are set, then ASSERT().
 200
 201   @param  SmBusAddress  The address that encodes the SMBUS Slave Address,
 202                         SMBUS Command, SMBUS Data Length, and PEC.
 203   @param  Status        Return status for the executed command.
 204                         This is an optional parameter and may be NULL.
 205                         RETURN_SUCCESS: The SMBUS command was executed.
 206                         RETURN_TIMEOUT: A timeout occurred while executing the
 207                         SMBUS command.
 208                         RETURN_DEVICE_ERROR:  The request was not completed because
 209                         a failurereflected in the Host Status Register bit.  Device
 210                         errors are a result of a transaction collision, illegal
 211                         command field, unclaimed cycle (host initiated), or bus
 212                         errors (collisions).
 213                         RETURN_CRC_ERROR:  The checksum is not correct (PEC is incorrect)
 214                         RETURN_UNSUPPORTED:  The SMBus operation is not supported.
 215
 216   @return The byte read from the SMBUS.
 217
 218 **/
 219 UINT8
 220 EFIAPI
 221 SmBusReadDataByte (
 222   IN  UINTN          SmBusAddress,
 223   OUT RETURN_STATUS  *Status        OPTIONAL
 224   )
 225 {
 226   UINT8   Byte;
 227
 228   ASSERT (SMBUS_LIB_LENGTH (SmBusAddress)    == 0);
 229   ASSERT (SMBUS_LIB_RESERVED (SmBusAddress) == 0);
 230
 231   InternalSmBusExec (EfiSmbusReadByte, SmBusAddress, 1, &Byte, Status);
 232
 233   return Byte;
 234 }
 235
 236 /**
 237   Executes an SMBUS write data byte command.
 238
 239   Executes an SMBUS write data byte command on the SMBUS device specified by SmBusAddress.
 240   The 8-bit value specified by Value is written.
 241   Only the SMBUS slave address and SMBUS command fields of SmBusAddress are required.
 242   Value is returned.
 243   If Status is not NULL, then the status of the executed command is returned in Status.
 244   If Length in SmBusAddress is not zero, then ASSERT().
 245   If any reserved bits of SmBusAddress are set, then ASSERT().
 246
 247   @param  SmBusAddress  The address that encodes the SMBUS Slave Address,
 248                         SMBUS Command, SMBUS Data Length, and PEC.
 249   @param  Value         The 8-bit value to write.
 250   @param  Status        Return status for the executed command.
 251                         This is an optional parameter and may be NULL.
 252                         RETURN_SUCCESS: The SMBUS command was executed.
 253                         RETURN_TIMEOUT: A timeout occurred while executing the
 254                         SMBUS command.
 255                         RETURN_DEVICE_ERROR:  The request was not completed because
 256                         a failure reflected in the Host Status Register bit.  Device
 257                         errors are a result of a transaction collision, illegal
 258                         command field, unclaimed cycle host initiated), or bus
 259                         errors (collisions).
 260                         RETURN_CRC_ERROR:  The checksum is not correct. (PEC is incorrect.)
 261                         RETURN_UNSUPPORTED:  The SMBus operation is not supported.
 262
 263   @return The parameter of Value.
 264
 265 **/
 266 UINT8
 267 EFIAPI
 268 SmBusWriteDataByte (
 269   IN  UINTN          SmBusAddress,
 270   IN  UINT8          Value,
 271   OUT RETURN_STATUS  *Status        OPTIONAL
 272   )
 273 {
 274   UINT8   Byte;
 275
 276   ASSERT (SMBUS_LIB_LENGTH (SmBusAddress)    == 0);
 277   ASSERT (SMBUS_LIB_RESERVED (SmBusAddress) == 0);
 278
 279   Byte = Value;
 280   InternalSmBusExec (EfiSmbusWriteByte, SmBusAddress, 1, &Byte, Status);
 281
 282   return Value;
 283 }
 284
 285 /**
 286   Executes an SMBUS read data word command.
 287
 288   Executes an SMBUS read data word command on the SMBUS device specified by SmBusAddress.
 289   Only the SMBUS slave address and SMBUS command fields of SmBusAddress are required.
 290   The 16-bit value read from the SMBUS is returned.
 291   If Status is not NULL, then the status of the executed command is returned in Status.
 292   If Length in SmBusAddress is not zero, then ASSERT().
 293   If any reserved bits of SmBusAddress are set, then ASSERT().
 294
 295   @param  SmBusAddress  The address that encodes the SMBUS Slave Address,
 296                         SMBUS Command, SMBUS Data Length, and PEC.
 297   @param  Status        Return status for the executed command.
 298                         This is an optional parameter and may be NULL.
 299                         RETURN_SUCCESS: The SMBUS command was executed.
 300                         RETURN_TIMEOUT: A timeout occurred while executing the
 301                         SMBUS command.
 302                         RETURN_DEVICE_ERROR:  The request was not completed because
 303                         a failure reflected in the Host Status Register bit.
 304                         Device errors are a result of a transaction collision,
 305                         illegal command field, unclaimed cycle (host initiated),
 306                         or bus errors (collisions).
 307                         RETURN_CRC_ERROR:  The checksum is not correct. (PEC is
 308                         incorrect.)
 309                         RETURN_UNSUPPORTED:  The SMBus operation is not supported.
 310
 311   @return The byte read from the SMBUS.
 312
 313 **/
 314 UINT16
 315 EFIAPI
 316 SmBusReadDataWord (
 317   IN  UINTN          SmBusAddress,
 318   OUT RETURN_STATUS  *Status        OPTIONAL
 319   )
 320 {
 321   UINT16  Word;
 322
 323   ASSERT (SMBUS_LIB_LENGTH (SmBusAddress)    == 0);
 324   ASSERT (SMBUS_LIB_RESERVED (SmBusAddress) == 0);
 325
 326   InternalSmBusExec (EfiSmbusReadWord, SmBusAddress, 2, &Word, Status);
 327
 328   return Word;
 329 }
 330
 331 /**
 332   Executes an SMBUS write data word command.
 333
 334   Executes an SMBUS write data word command on the SMBUS device specified by SmBusAddress.
 335   The 16-bit value specified by Value is written.
 336   Only the SMBUS slave address and SMBUS command fields of SmBusAddress are required.
 337   Value is returned.
 338   If Status is not NULL, then the status of the executed command is returned in Status.
 339   If Length in SmBusAddress is not zero, then ASSERT().
 340   If any reserved bits of SmBusAddress are set, then ASSERT().
 341
 342   @param  SmBusAddress  The address that encodes the SMBUS Slave Address,
 343                         SMBUS Command, SMBUS Data Length, and PEC.
 344   @param  Value         The 16-bit value to write.
 345   @param  Status        Return status for the executed command.
 346                         This is an optional parameter and may be NULL.
 347                         RETURN_SUCCESS: The SMBUS command was executed.
 348                         RETURN_TIMEOUT: A timeout occurred while executing the SMBUS
 349                         command.
 350                         RETURN_DEVICE_ERROR:  The request was not completed because
 351                         a failure reflected in the Host Status Register bit.
 352                         Device errors are a result of a transaction collision,
 353                         illegal command field, unclaimed cycle (host initiated),
 354                         or bus errors (collisions).
 355                         RETURN_CRC_ERROR:  The checksum is not correct.
 356                         (PEC is incorrect.)
 357                         RETURN_UNSUPPORTED:  The SMBus operation is not supported.
 358
 359   @return The parameter of Value.
 360
 361 **/
 362 UINT16
 363 EFIAPI
 364 SmBusWriteDataWord (
 365   IN  UINTN          SmBusAddress,
 366   IN  UINT16         Value,
 367   OUT RETURN_STATUS  *Status        OPTIONAL
 368   )
 369 {
 370   UINT16  Word;
 371
 372   ASSERT (SMBUS_LIB_LENGTH (SmBusAddress)    == 0);
 373   ASSERT (SMBUS_LIB_RESERVED (SmBusAddress) == 0);
 374
 375   Word = Value;
 376   InternalSmBusExec (EfiSmbusWriteWord, SmBusAddress, 2, &Word, Status);
 377
 378   return Value;
 379 }
 380
 381 /**
 382   Executes an SMBUS process call command.
 383
 384   Executes an SMBUS process call command on the SMBUS device specified by SmBusAddress.
 385   The 16-bit value specified by Value is written.
 386   Only the SMBUS slave address and SMBUS command fields of SmBusAddress are required.
 387   The 16-bit value returned by the process call command is returned.
 388   If Status is not NULL, then the status of the executed command is returned in Status.
 389   If Length in SmBusAddress is not zero, then ASSERT().
 390   If any reserved bits of SmBusAddress are set, then ASSERT().
 391
 392   @param  SmBusAddress  The address that encodes the SMBUS Slave Address,
 393                         SMBUS Command, SMBUS Data Length, and PEC.
 394   @param  Value         The 16-bit value to write.
 395   @param  Status        Return status for the executed command.
 396                         This is an optional parameter and may be NULL.
 397                         RETURN_SUCCESS: The SMBUS command was executed.
 398                         RETURN_TIMEOUT: A timeout occurred while executing the
 399                         SMBUS command.
 400                         RETURN_DEVICE_ERROR:  The request was not completed because
 401                         a failure reflected in the Host Status Register bit.
 402                         Device errors are a result of a transaction collision,
 403                         illegal command field, unclaimed cycle (host initiated),
 404                         or bus errors (collisions).
 405                         RETURN_CRC_ERROR:  The checksum is not correct. (PEC is
 406                         incorrect.)
 407                         RETURN_UNSUPPORTED:  The SMBus operation is not supported.
 408
 409   @return The 16-bit value returned by the process call command.
 410
 411 **/
 412 UINT16
 413 EFIAPI
 414 SmBusProcessCall (
 415   IN  UINTN          SmBusAddress,
 416   IN  UINT16         Value,
 417   OUT RETURN_STATUS  *Status        OPTIONAL
 418   )
 419 {
 420   ASSERT (SMBUS_LIB_LENGTH (SmBusAddress)    == 0);
 421   ASSERT (SMBUS_LIB_RESERVED (SmBusAddress) == 0);
 422
 423   InternalSmBusExec (EfiSmbusProcessCall, SmBusAddress, 2, &Value, Status);
 424
 425   return Value;
 426 }
 427
 428 /**
 429   Executes an SMBUS read block command.
 430
 431   Executes an SMBUS read block command on the SMBUS device specified by SmBusAddress.
 432   Only the SMBUS slave address and SMBUS command fields of SmBusAddress are required.
 433   Bytes are read from the SMBUS and stored in Buffer.
 434   The number of bytes read is returned, and will never return a value larger than 32-bytes.
 435   If Status is not NULL, then the status of the executed command is returned in Status.
 436   It is the caller's responsibility to make sure Buffer is large enough for the total number of bytes read.
 437   SMBUS supports a maximum transfer size of 32 bytes, so Buffer does not need to be any larger than 32 bytes.
 438   If Length in SmBusAddress is not zero, then ASSERT().
 439   If Buffer is NULL, then ASSERT().
 440   If any reserved bits of SmBusAddress are set, then ASSERT().
 441
 442   @param  SmBusAddress  The address that encodes the SMBUS Slave Address,
 443                         SMBUS Command, SMBUS Data Length, and PEC.
 444   @param  Buffer        The pointer to the buffer to store the bytes read from
 445                         the SMBUS.
 446   @param  Status        Return status for the executed command.
 447                         This is an optional parameter and may be NULL.
 448                         RETURN_SUCCESS: The SMBUS command was executed.
 449                         RETURN_TIMEOUT: A timeout occurred while executing the SMBUS
 450                         command.
 451                         RETURN_DEVICE_ERROR:  The request was not completed because
 452                         a failure reflected in the Host Status Register bit.  Device
 453                         errors are a result of a transaction collision, illegal
 454                         command field, unclaimed cycle (host initiated), or bus
 455                         errors (collisions).
 456                         RETURN_CRC_ERROR:  The checksum is not correct. (PEC is
 457                         incorrect.)
 458                         RETURN_UNSUPPORTED:  The SMBus operation is not supported.
 459
 460   @return The number of bytes read.
 461
 462 **/
 463 UINTN
 464 EFIAPI
 465 SmBusReadBlock (
 466   IN  UINTN          SmBusAddress,
 467   OUT VOID           *Buffer,
 468   OUT RETURN_STATUS  *Status        OPTIONAL
 469   )
 470 {
 471   ASSERT (Buffer != NULL);
 472   ASSERT (SMBUS_LIB_LENGTH (SmBusAddress)    == 0);
 473   ASSERT (SMBUS_LIB_RESERVED (SmBusAddress) == 0);
 474
 475   return InternalSmBusExec (EfiSmbusReadBlock, SmBusAddress, 0x20, Buffer, Status);
 476 }
 477
 478 /**
 479   Executes an SMBUS write block command.
 480
 481   Executes an SMBUS write block command on the SMBUS device specified by SmBusAddress.
 482   The SMBUS slave address, SMBUS command, and SMBUS length fields of SmBusAddress are required.
 483   Bytes are written to the SMBUS from Buffer.
 484   The number of bytes written is returned, and will never return a value larger than 32-bytes.
 485   If Status is not NULL, then the status of the executed command is returned in Status.
 486   If Length in SmBusAddress is zero or greater than 32, then ASSERT().
 487   If Buffer is NULL, then ASSERT().
 488   If any reserved bits of SmBusAddress are set, then ASSERT().
 489
 490   @param  SmBusAddress  The address that encodes the SMBUS Slave Address,
 491                         MBUS Command, SMBUS Data Length, and PEC.
 492   @param  Buffer        The pointer to the buffer to store the bytes read from
 493                         the SMBUS.
 494   @param  Status        Return status for the executed command.
 495                         This is an optional parameter and may be NULL.
 496                         RETURN_TIMEOUT: A timeout occurred while executing the
 497                         SMBUS command.
 498                         RETURN_DEVICE_ERROR:  The request was not completed because
 499                         a failure reflected in the Host Status Register bit.  Device
 500                         errors are a result of a transaction collision, illegal
 501                         command field, unclaimed cycle (host initiated), or bus
 502                         errors (collisions).
 503                         RETURN_CRC_ERROR:  The checksum is not correct. (PEC is
 504                         incorrect.)
 505                         RETURN_UNSUPPORTED:  The SMBus operation is not supported.
 506
 507   @return The number of bytes written.
 508
 509 **/
 510 UINTN
 511 EFIAPI
 512 SmBusWriteBlock (
 513   IN  UINTN          SmBusAddress,
 514   OUT VOID           *Buffer,
 515   OUT RETURN_STATUS  *Status        OPTIONAL
 516   )
 517 {
 518   UINTN  Length;
 519
 520   ASSERT (Buffer != NULL);
 521   ASSERT (SMBUS_LIB_LENGTH (SmBusAddress) >= 1);
 522   ASSERT (SMBUS_LIB_LENGTH (SmBusAddress) <= 32);
 523   ASSERT (SMBUS_LIB_RESERVED (SmBusAddress) == 0);
 524
 525   Length = SMBUS_LIB_LENGTH (SmBusAddress);
 526   return InternalSmBusExec (EfiSmbusWriteBlock, SmBusAddress, Length, Buffer, Status);
 527 }
 528
 529 /**
 530   Executes an SMBUS block process call command.
 531
 532   Executes an SMBUS block process call command on the SMBUS device specified by SmBusAddress.
 533   The SMBUS slave address, SMBUS command, and SMBUS length fields of SmBusAddress are required.
 534   Bytes are written to the SMBUS from WriteBuffer.  Bytes are then read from the SMBUS into ReadBuffer.
 535   If Status is not NULL, then the status of the executed command is returned in Status.
 536   It is the caller's responsibility to make sure ReadBuffer is large enough for the total number of bytes read.
 537   SMBUS supports a maximum transfer size of 32 bytes, so Buffer does not need to be any larger than 32 bytes.
 538   If Length in SmBusAddress is zero or greater than 32, then ASSERT().
 539   If WriteBuffer is NULL, then ASSERT().
 540   If ReadBuffer is NULL, then ASSERT().
 541   If any reserved bits of SmBusAddress are set, then ASSERT().
 542
 543   @param  SmBusAddress  The address that encodes the SMBUS Slave Address,
 544                         SMBUS Command, SMBUS Data Length, and PEC.
 545   @param  WriteBuffer   The pointer to the buffer of bytes to write to the SMBUS.
 546   @param  ReadBuffer    The pointer to the buffer of bytes to read from the SMBUS.
 547   @param  Status        Return status for the executed command.
 548                         This is an optional parameter and may be NULL.
 549                         RETURN_TIMEOUT: A timeout occurred while executing the
 550                         SMBUS command.
 551                         RETURN_DEVICE_ERROR: The request was not completed because
 552                         a failure reflected in the Host Status Register bit.  Device
 553                         errors are a result of a transaction collision, illegal
 554                         command field, unclaimed cycle (host initiated), or bus
 555                         errors (collisions).
 556                         RETURN_CRC_ERROR:  The checksum is not correct. (PEC is
 557                         incorrect.)
 558                         RETURN_UNSUPPORTED:  The SMBus operation is not supported.
 559
 560   @return The number of bytes written.
 561
 562 **/
 563 UINTN
 564 EFIAPI
 565 SmBusBlockProcessCall (
 566   IN  UINTN          SmBusAddress,
 567   IN  VOID           *WriteBuffer,
 568   OUT VOID           *ReadBuffer,
 569   OUT RETURN_STATUS  *Status        OPTIONAL
 570   )
 571 {
 572   UINTN   Length;
 573
 574   ASSERT (WriteBuffer != NULL);
 575   ASSERT (ReadBuffer  != NULL);
 576   ASSERT (SMBUS_LIB_LENGTH (SmBusAddress) >= 1);
 577   ASSERT (SMBUS_LIB_LENGTH (SmBusAddress) <= 32);
 578   ASSERT (SMBUS_LIB_RESERVED (SmBusAddress) == 0);
 579
 580   Length = SMBUS_LIB_LENGTH (SmBusAddress);
 581   //
 582   // Assuming that ReadBuffer is large enough to save another memory copy.
 583   //
 584   ReadBuffer = CopyMem (ReadBuffer, WriteBuffer, Length);
 585   return InternalSmBusExec (EfiSmbusBWBRProcessCall, SmBusAddress, Length, ReadBuffer, Status);
 586 }