I am trying to determine how it may be possible to find documentation for namespaces that are not documented in the ACPI spec. I have an Asus uEFI BIOS v(3202) and I'm receiving kernel messages stating AE Namespace lookup failures for DSSP. This is referring to a namespace that is not in the ACPI spec. I'm presuming that this is vendor specific and refers to a Digital Sensor Signal Processor. That is only a presumption.

In an effort to correct ACPI errors I have dumped my DSDT using acpidump and then decompiled it using iASL. Yet to fix the error I need to know the spec on the namespace.

How can I get access to the BIOS documentation that isn't part of the ACPI spec?

  • If it's proprietary, then you can't.
    – psusi
    Jun 13, 2012 at 18:01

1 Answer 1


As psusi said, the BIOS is proprietary. Vendors are free to give whatever meaning they would like to names. You should look at the context to make sense of it.

I guess you are trying to fix errors like this one:

ACPI Error: [DSSP] Namespace lookup failure, AE_NOT_FOUND (20120320/psargs-359)
ACPI Error: Method parse/execution failed [\_SB_.PCI0.SAT0.SPT1._GTF] (Node ffff8805fd4b8b90), AE_NOT_FOUND (20120320/psparse-536)

The related ACPI source is:

Scope (\_SB.PCI0.SAT0)
    // <snip>
    Device (SPT1)
        Name (_ADR, 0x0001FFFF)  // _ADR: Address
        Method (_GTF, 0, NotSerialized)  // _GTF: Get Task File
            Store (Zero, CMDC)
            If (LOr (DSSP, FHPP))
                GTFB (STFD, 0x06)
                GTFB (STFE, 0x06)

            GTFB (FZTF, Zero)
            GTFB (DCFL, Zero)
            Return (SCBF)

\_SB.PCI0.SAT0.SPT1 looks like a SATA controller with its _GTF (Get Task File) method (see ACPI spec v5, section, page 442). Therefore, the names are likely related to (S)ATA-related terminology.

CMDC is initialised to zero ands gets incremented after each GTFB call. SCBF is a buffer of length 3 × 7 (=21). GTFB sets the 7-byte field at index CMDC to its first argument and sets byte CMDC + 1 of SCBF to the second argument.

  • SCBF is probably "SATA Command Buffer".
  • CMDC is probably "Command Counter".
  • STFD, STFE is STF enabled/disabled where STF is an SATA feature/commands.
  • DSSP and FHPP look like some flags that control whether STF is enabled or disabled.
  • FZTF and DCFL are probably some SATA features/commands.

Those features/commands can be looked up in the SATA specification I guess (exercise for the reader).

One final note, where do you usually get documentation from? From the creators, right? Perhaps source code of some BIOSes are available... ;)

  • +1 for a great explanation ... I've not been able to retrieve APCI lookup data for ASUS or any of the support boards ... TY Lekensteyn for the helpful answer ... Jun 27, 2013 at 9:26

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