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DynamicTablesPkg: Add AmlGetEisaIdFromString() to AcpiHelperLib 

Add a function converting a 7 characters string to its UINT32
EISAID. The algorithm used to create the EISAID is described
in the ACPI 6.4 specification, s19.3.4 "ASL Macros".

Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>
Signed-off-by: Pierre Gondois <Pierre.Gondois@arm.com>
This commit is contained in:
Pierre Gondois 2021-09-30 08:48:16 +01:00 committed by mergify[bot]
parent 653113412f
commit 72ab552554
2 changed files with 86 additions and 0 deletions
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17
DynamicTablesPkg/Include/Library/AcpiHelperLib.h
View File

@ -73,4 +73,21 @@ IsValidAcpiId (
IN CONST CHAR8 * Hid
);
/** Convert a EisaId string to its compressed UINT32 equivalent.
Cf. ACPI 6.4 specification, s19.3.4 "ASL Macros": "Eisaid"
@param [in] EisaIdStr Input EisaId string.
@param [out] EisaIdInt Output EisaId UINT32 (compressed).
@retval EFI_SUCCESS The function completed successfully.
@retval EFI_INVALID_PARAMETER Invalid parameter.
**/
EFI_STATUS
EFIAPI
AmlGetEisaIdFromString (
IN CONST CHAR8 * EisaIdStr,
OUT UINT32 * EisaIdInt
);
#endif // ACPI_HELPER_LIB_H_

69
DynamicTablesPkg/Library/Common/AcpiHelperLib/AcpiHelper.c
View File

@ -139,3 +139,72 @@ IsValidAcpiId (
return TRUE;
}
/** Convert a EisaId string to its compressed UINT32 equivalent.
Cf. ACPI 6.4 specification, s19.3.4 "ASL Macros": "Eisaid"
@param [in] EisaIdStr Input EisaId string.
@param [out] EisaIdInt Output EisaId UINT32 (compressed).
@retval EFI_SUCCESS The function completed successfully.
@retval EFI_INVALID_PARAMETER Invalid parameter.
**/
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;
}