AcpiHelper.c

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#include <Library/BaseLib.h>
#include <Library/DebugLib.h>
 
// Module specific include files.
#include <Library/AcpiHelperLib.h>
 
UINT8
EFIAPI
AsciiFromHex (
  IN  UINT8  Hex
  )
{
  if (Hex < 10) {
    return (UINT8)(Hex + '0');
  }
 
  if (Hex < 16) {
    return (UINT8)(Hex - 10 + 'A');
  }
 
  ASSERT (FALSE);
  return (UINT8)-1;
}
 
UINT8
EFIAPI
HexFromAscii (
  IN  CHAR8  Char
  )
{
  if ((Char >= '0') && (Char <= '9')) {
    return (UINT8)(Char - '0');
  }
 
  if ((Char >= 'A') && (Char <= 'F')) {
    return (UINT8)(Char - 'A' + 10);
  }
 
  if ((Char >= 'a') && (Char <= 'f')) {
    return (UINT8)(Char - 'a' + 10);
  }
 
  ASSERT (FALSE);
  return (UINT8)-1;
}
 
BOOLEAN
IsValidPnpId (
  IN  CONST CHAR8  *Hid
  )
{
  UINTN  Index;
 
  if (AsciiStrLen (Hid) != 7) {
    return FALSE;
  }
 
  // A valid PNP ID must be of the form "AAA####"
  // where A is an uppercase letter and # is a hex digit.
  for (Index = 0; Index < 3; Index++) {
    if (!IS_UPPER_CHAR (Hid[Index])) {
      return FALSE;
    }
  }
 
  for (Index = 3; Index < 7; Index++) {
    if (!IS_UPPER_HEX (Hid[Index])) {
      return FALSE;
    }
  }
 
  return TRUE;
}
 
BOOLEAN
IsValidAcpiId (
  IN  CONST CHAR8  *Hid
  )
{
  UINTN  Index;
 
  if (AsciiStrLen (Hid) != 8) {
    return FALSE;
  }
 
  // A valid ACPI ID must be of the form "NNNN####"
  // where N is an uppercase letter or a digit ('0'-'9')
  // and # is a hex digit.
  for (Index = 0; Index < 4; Index++) {
    if (!(IS_UPPER_CHAR (Hid[Index]) || IS_DIGIT (Hid[Index]))) {
      return FALSE;
    }
  }
 
  for (Index = 4; Index < 8; Index++) {
    if (!IS_UPPER_HEX (Hid[Index])) {
      return FALSE;
    }
  }
 
  return TRUE;
}
 
EFI_STATUS
EFIAPI
AmlGetEisaIdFromString (
  IN  CONST CHAR8   *EisaIdStr,
  OUT       UINT32  *EisaIdInt
  )
{
  if ((EisaIdStr == NULL)         ||
      (!IsValidPnpId (EisaIdStr)) ||
      (EisaIdInt == NULL))
  {
    ASSERT (0);
    return EFI_INVALID_PARAMETER;
  }
 
  /* Cf. ACPI 6.4 specification, s19.3.4 "ASL Macros": "Eisaid"
 
  Converts and compresses the 7-character text argument into its corresponding
  4-byte numeric EISA ID encoding (Integer). This can be used when declaring
  IDs for devices that are EISA IDs.
 
  The algorithm used to convert the TextID is as shown in the following
  example:
    Starting with a seven character input string "PNP0303", we want to create
    a DWordConst. This string contains a three character manufacturer code
    "PNP", a three character hex product identifier "030", and a one character
    revision identifier "3".
    The compressed manufacturer code is created as follows:
      1) Find hex ASCII value for each letter
      2) Subtract 40h from each ASCII value
      3) Retain 5 least significant bits for each letter and discard remaining
         0's:
 
      Byte 0:
        Bit 7: reserved (0)
        Bit 6-2: 1st character of compressed mfg code "P"
        Bit 1-0: Upper 2 bits of 2nd character of mfg code "N"
      Byte 1:
        Bit 7-5: Lower 3 bits of 2nd character of mfg code "N"
        Bit 4-0: 3rd character of mfg code "P"
      Byte 2:
        Bit 7-4: 1st hex digit of product number "0"
        Bit 3-0: 2nd hex digit of product number "3"
      Byte 3:
        Bit 7-4: 3rd hex digit of product number "0"
        Bit 3-0: 4th hex digit of product number "3"
  */
  *EisaIdInt = SwapBytes32 (
                 ((EisaIdStr[0] - 0x40) << 26)       |
                 ((EisaIdStr[1] - 0x40) << 21)       |
                 ((EisaIdStr[2] - 0x40) << 16)       |
                 (HexFromAscii (EisaIdStr[3]) << 12) |
                 (HexFromAscii (EisaIdStr[4]) << 8)  |
                 (HexFromAscii (EisaIdStr[5]) << 4)  |
                 (HexFromAscii (EisaIdStr[6]))
                 );
 
  return EFI_SUCCESS;
}