Re: [PATCH v2 05/21] DynamicTablesPkg: Add AmlSetRdListCheckSum()

["Sami Mujawar" <sami.mujawar@arm.com>]

Hi Pierre,

Thank you for this patch.

Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>

Regards,

Sami Mujawar

On 07/10/2021 04:31 PM, Pierre.Gondois@arm.com wrote:
> From: Pierre Gondois <Pierre.Gondois@arm.com>
>
> Lists of Resource Data elements end with an EndTag (most of the time).
> This function finds the EndTag (if present) in a list of Resource Data
> elements and sets the checksum.
>
> ACPI 6.4, s6.4.2.9 "End Tag":
> "This checksum is generated such that adding it to the sum of all the data
> bytes will produce a zero sum."
> "If the checksum field is zero, the resource data is treated as if the
> checksum operation succeeded. Configuration proceeds normally."
>
> Signed-off-by: Pierre Gondois <Pierre.Gondois@arm.com>
> ---
>   .../Library/Common/AmlLib/Utils/AmlUtility.c  | 76 +++++++++++++++++++
>   .../Library/Common/AmlLib/Utils/AmlUtility.h  | 32 ++++++++
>   2 files changed, 108 insertions(+)
>
> diff --git a/DynamicTablesPkg/Library/Common/AmlLib/Utils/AmlUtility.c b/DynamicTablesPkg/Library/Common/AmlLib/Utils/AmlUtility.c
> index 7ebd08f945c0..ef159e3b831e 100644
> --- a/DynamicTablesPkg/Library/Common/AmlLib/Utils/AmlUtility.c
> +++ b/DynamicTablesPkg/Library/Common/AmlLib/Utils/AmlUtility.c
> @@ -904,3 +904,79 @@ AmlPropagateInformation (
>
>     return EFI_SUCCESS;
>   }
> +
> +/** Find and set the EndTag's Checksum of a list of Resource Data elements.
> +
> +  Lists of Resource Data elements end with an EndTag (most of the time). This
> +  function finds the EndTag (if present) in a list of Resource Data elements
> +  and sets the checksum.
> +
> +  ACPI 6.4, s6.4.2.9 "End Tag":
> +  "This checksum is generated such that adding it to the sum of all the data
> +  bytes will produce a zero sum."
> +  "If the checksum field is zero, the resource data is treated as if the
> +  checksum operation succeeded. Configuration proceeds normally."
> +
> +  To avoid re-computing checksums, if a new resource data elements is
> +  added/removed/modified in a list of resource data elements, the AmlLib
> +  resets the checksum to 0.
> +
> +  @param [in]  BufferOpNode   Node having a list of Resource Data elements.
> +  @param [in]  CheckSum       CheckSum to store in the EndTag.
> +                              To ignore/avoid computing the checksum,
> +                              give 0.
> +
> +  @retval EFI_SUCCESS             The function completed successfully.
> +  @retval EFI_INVALID_PARAMETER   Invalid parameter.
> +  @retval EFI_NOT_FOUND           No EndTag found.
> +**/
> +EFI_STATUS
> +EFIAPI
> +AmlSetRdListCheckSum (
> +  IN  AML_OBJECT_NODE   * BufferOpNode,
> +  IN  UINT8               CheckSum
> +  )
> +{
> +  EFI_STATUS        Status;
> +  AML_DATA_NODE   * LastRdNode;
> +  AML_RD_HEADER     RdDataType;
> +
> +  if (!AmlNodeCompareOpCode (BufferOpNode, AML_BUFFER_OP, 0)) {
> +    ASSERT (0);
> +    return EFI_INVALID_PARAMETER;
> +  }
> +
> +  // Get the last Resource data node in the variable list of
> +  // argument of the BufferOp node.
> +  LastRdNode = (AML_DATA_NODE*)AmlGetPreviousVariableArgument (
> +                                 (AML_NODE_HEADER*)BufferOpNode,
> +                                 NULL
> +                                 );
> +  if ((LastRdNode == NULL)             ||
> +      !IS_AML_DATA_NODE (LastRdNode)   ||
> +      (LastRdNode->DataType != EAmlNodeDataTypeResourceData)) {
> +    ASSERT (0);
> +    return EFI_INVALID_PARAMETER;
> +  }
> +
> +  Status = AmlGetResourceDataType (LastRdNode, &RdDataType);
> +  if (EFI_ERROR (Status)) {
> +    ASSERT (0);
> +    return Status;
> +  }
> +
> +  // Check the LastRdNode is an EndTag.
> +  // It is possible to have only one Resource Data in a BufferOp with
> +  // no EndTag. Return EFI_NOT_FOUND is such case.
> +  if (!AmlRdCompareDescId (
> +        &RdDataType,
> +        AML_RD_BUILD_SMALL_DESC_ID (ACPI_SMALL_END_TAG_DESCRIPTOR_NAME))) {
> +    ASSERT (0);
> +    return EFI_NOT_FOUND;
> +  }
> +
> +  Status = AmlRdSetEndTagChecksum (LastRdNode->Buffer, CheckSum);
> +  ASSERT_EFI_ERROR (Status);
> +
> +  return Status;
> +}
> diff --git a/DynamicTablesPkg/Library/Common/AmlLib/Utils/AmlUtility.h b/DynamicTablesPkg/Library/Common/AmlLib/Utils/AmlUtility.h
> index c57d780140d4..4667f57d7f08 100644
> --- a/DynamicTablesPkg/Library/Common/AmlLib/Utils/AmlUtility.h
> +++ b/DynamicTablesPkg/Library/Common/AmlLib/Utils/AmlUtility.h
> @@ -91,5 +91,37 @@ AmlPropagateInformation (
>     IN  UINT8               NodeCount
>     );
>
> +/** Find and set the EndTag's Checksum of a list of Resource Data elements.
> +
> +  Lists of Resource Data elements end with an EndTag (most of the time). This
> +  function finds the EndTag (if present) in a list of Resource Data elements
> +  and sets the checksum.
> +
> +  ACPI 6.4, s6.4.2.9 "End Tag":
> +  "This checksum is generated such that adding it to the sum of all the data
> +  bytes will produce a zero sum."
> +  "If the checksum field is zero, the resource data is treated as if the
> +  checksum operation succeeded. Configuration proceeds normally."
> +
> +  To avoid re-computing checksums, if a new resource data elements is
> +  added/removed/modified in a list of resource data elements, the AmlLib
> +  resets the checksum to 0.
> +
> +  @param [in]  BufferOpNode   Node having a list of Resource Data elements.
> +  @param [in]  CheckSum       CheckSum to store in the EndTag.
> +                              To ignore/avoid computing the checksum,
> +                              give 0.
> +
> +  @retval EFI_SUCCESS             The function completed successfully.
> +  @retval EFI_INVALID_PARAMETER   Invalid parameter.
> +  @retval EFI_NOT_FOUND           No EndTag found.
> +**/
> +EFI_STATUS
> +EFIAPI
> +AmlSetRdListCheckSum (
> +  IN  AML_OBJECT_NODE   * BufferOpNode,
> +  IN  UINT8               CheckSum
> +  );
> +
>   #endif // AML_UTILITY_H_
>

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