Re: [PATCH 1/1] tools/libacpi: clear ASL warning about PCI0

["Ariel Otilibili-Anieli" <Ariel.Otilibili-Anieli@xxxxxxxxxx>]

On Monday, December 16, 2024 12:01 CET, Jan Beulich <jbeulich@xxxxxxxx> wrote:

> On 16.12.2024 11:36, Ariel Otilibili-Anieli wrote:
> > On Monday, December 16, 2024 10:53 CET, Jan Beulich <jbeulich@xxxxxxxx> 
> > wrote:
> > 
> >> On 15.12.2024 16:40, Ariel Otilibili wrote:
> >>> * iasl complains _HID and _ADR cannot be used at the same time
> >>>
> >>> ```
> >>> /usr/bin/iasl -vs -p tools/firmware/hvmloader/dsdt_anycpu.tmp -tc 
> >>> tools/firmware/hvmloader/dsdt_anycpu.asl 2>&1 | grep -B10 HID
> >>> tools/firmware/hvmloader/dsdt_anycpu.asl     40:        Device (PCI0)
> >>> Warning  3073 -                                    Multiple types ^  
> >>> (Device object requires either a _HID or _ADR, but not both)
> >>> ```
> >>>
> >>> * generally _HID devices are enumerated and have their drivers loaded by 
> >>> ACPI
> >>> * this is from "ASL 2.0 Introduction and Overview" (page 4).
> >>> * removing _ADR, the warning is cleared out.
> >>
> >> Okay, that's the positive aspect. Yet what about the potential fallout 
> >> thereof?
> >> Can you confirm that there's no risk of regressions with older guest OSes, 
> >> for
> >> example?
> > 
> > OSes that were released after ACPI 2.0 should work [1]; including WinXP: 
> > The 2.0 specs says either _HID or _ADR should be included [2], not both 
> > (Section 6.1, page 146).
> 
> We must be looking at two different variants of the spec then. My copy says
> "device object must contain either an _HID object or an _ADR object, but can
> contain both." Also still in 2.0c. I agree that in e.g. 6.5 the wording has
> changed. I also agree that the use of "either" doesn't help clarity.

I looked up 2.0 (July 2000); indeed, it said "can contain both". My bad.
> 
> > I chose WinXP because, on another patch, it came up in the discussion [3].

The change should work down to WinXP: the name _HID is kept.

```
$ git grep -B2 -A2 -n PNP0A03
tools/libacpi/dsdt.asl-40-       Device (PCI0)
tools/libacpi/dsdt.asl-41-       {
tools/libacpi/dsdt.asl:42:           Name (_HID, EisaId ("PNP0A03"))
tools/libacpi/dsdt.asl-43-           Name (_UID, 0x00)
tools/libacpi/dsdt.asl-44-           Name (_ADR, 0x00)
```

Its EISA ID is "PNP0A03"; the namespace is reserved for Microsoft. Microsoft 
identifies "PNP0A03" as PCI devices [1].

```
$ curl -k -s 
https://download.microsoft.com/download/1/6/1/161ba512-40e2-4cc9-843a-923143f3456c/devids.txt
 | grep PNP0A03
PNP0A03         PCI Bus
```
Linux displays PCI devices with _HID and no _HID [2].

[1] 
https://download.microsoft.com/download/1/6/1/161ba512-40e2-4cc9-843a-923143f3456c/devids.txt
[2] 
https://www.infradead.org/~mchehab/kernel_docs/firmware-guide/acpi/namespace.html
> 
> And indeed appropriately so.
> 
> Jan