Re: type mismatch in SSDT

[Igor Mammedov <imammedo@redhat.com>]

On Thu, 27 Oct 2022 01:59:22 -0400
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> Just noticed this when disassembling:
> 
> Parsing completed
> ACPI Warning: NsLookup: Type mismatch on ODAT (RegionField), searching for (Buffer) (20210604/nsaccess-760)
> Disassembly completed
> ASL Output:    /tmp/old-asl2/tests/data/acpi/virt/SSDT.memhp.dsl - 14945 bytes
> 
> Did not look into this yet but it seems new.
It was there practically 'forever'.

ODAT should be treated as Buffer according to implicit Field/data conversion rules,
that's probably the reason why it works. So warning looks a bit bogus to me.

however:
  DefCreateByteField := CreateByteFieldOp SourceBuff ByteIndex NameString
  SourceBuff := TermArg => Buffer
  TermArg := ExpressionOpcode | DataObject | ArgObj | LocalObj

and none of that explicitly leads to 

  TermObj := Object | StatementOpcode | ExpressionOpcode
  Object := NameSpaceModifierObj | NamedObj

So if we are to be as pedantic as IASL, we need to supply
field to CreateByteField not by name but via one of TermArg.
We could copy/assign whole buffer to a LocalObj
or summarily use ExpressionOpcode => ToBuffer() // this one has a bit controversial definition in 6.4 spec
or to avoid any copying add 'useless' DerefOf(RefOf())
wrapper around name to make argument of ExpressionOpcode kind.

following should silence warning.

diff --git a/hw/acpi/nvdimm.c b/hw/acpi/nvdimm.c
index 31e46df0bd..7488007540 100644
--- a/hw/acpi/nvdimm.c
+++ b/hw/acpi/nvdimm.c
@@ -1127,7 +1127,7 @@ static void nvdimm_build_common_dsm(Aml *dev,
     /* If RLEN >= Integer size, just use CreateField() operator */
     aml_append(method, aml_store(aml_shiftleft(dsm_out_buf_size, aml_int(3)),
                                  dsm_out_buf_size));
-    aml_append(method, aml_create_field(aml_name(NVDIMM_DSM_OUT_BUF),
+    aml_append(method, aml_create_field(aml_derefof(aml_refof(aml_name(NVDIMM_DSM_OUT_BUF))),
                aml_int(0), dsm_out_buf_size, "OBUF"));
     aml_append(method, aml_return(aml_name("OBUF")));