Re: PCI Hotplug ACPI device names only 3 characters long

[Marcello Sylverster Bauer]

Hi Philippe,

On 9/5/23 17:09, Philippe Mathieu-Daudé wrote:
> Hi Marcello,
>
> On 5/9/23 17:05, Marcello Sylverster Bauer wrote:
> > Greetings,
> >
> > I'm currently working on a project to support Intel IPU6 in QEMU via 
> > VFIO so that the guest system can access the camera. This requires 
> > extending the ACPI device definition so that the guest knows how to 
> > access the camera.
> >
> > However, I cannot extend the PCI devices because their names are not 4 
> > characters long and therefore do not follow the ACPI specification.
> >
> > When I use '-acpitable' to include my own SSDT for the IPU6 PCI 
> > device, it does not allow me to declare the device as an External 
> > Object because it automatically adds padding underscores.
> >
> > e.g.
> > Before:
> > ```
> > External(_SB.PCI0.S18.SA0, DeviceObj)
> > ```
> > After:
> > ```
> > External(_SB.PCI0.S18_.SA0_, DeviceObj)
> > ```
>
> What do you mean by "before" / "after"?

Before is what is written in my SSDT ASL source file that is provided to 
QEMU via the "-acpitable" flag. After is what is actually written to the 
SSDT inside the VM.

If you compile and decompile the source file with iasl, you will get the 
same result.

> > Adding the underscore padding is hard coded in iASL and also in QEMU 
> > when parsing an ASL file. (see: build_append_nameseg())
> >
> > So here are my questions:
> > 1. Is there a solution to extend the ACPI PCI device using 
> > '-acpitable' without having to patch iASL or QEMU?
> > 2. Are there any plans to change the names to comply with the ACPI 
> > spec? (e.g. use "S%.03X" format string instead)
> >
> > Thanks
> > Marcello