Re: How to look up ACPI device node from DXE driver

[Laszlo Ersek <lersek@redhat.com>]

On 05/16/17 14:55, Evgeny Yakovlev wrote:
> I am writing a DXE driver for a paravirtualized HyperV storage device for
> OvmfPkg. Host hypervisor exposes the presence of this device through ACPI
> device node in DSDT. Specific AML path itself may be different from host to
> host but device UID is always a string: "VMBus".
> 
> I was hoping to be able to walk DSDT table in my DXE driver to locate this
> device node and start publishing necessary protocols, but I am having
> trouble figuring out how to do this, i.e. are there any support libraries
> or protocols to traverse ACPI tables or how do I have to do that manually.
> Will be glad for any advice, thanks.

This is one of the goals that EFI_ACPI_SDT_PROTOCOL serves.

The protocol is specified in Volume 5 of the PI spec.

In edk2, the protocol is produced by

  MdeModulePkg/Universal/Acpi/AcpiTableDxe

when the

  gEfiMdeModulePkgTokenSpaceGuid.PcdInstallAcpiSdtProtocol

Feature PCD is set to TRUE.

I think there are a handful (?) of protocol consumers in edk2 as well,
for example in

  QuarkPlatformPkg/Acpi/Dxe/AcpiPlatform/

Thanks,
Laszlo