Re: Dynamic Pci configuration devices

[Guy Raviv <guyraviv8@gmail.com>]

Thanks for the detailed answer.

if i choose the 2nd approach would it be possible to modify the structrue
itself of the pci tree,
and not only a specific device number?
example: if i add a pci bridge between my board and a graphic card.

Thanks,

On Tue, May 8, 2018 at 5:47 PM, Laszlo Ersek <lersek@redhat.com> wrote:

> On 05/08/18 16:16, Guy Raviv wrote:
> > Hi all,
> >
> > currently in
> >
> > \Vlv2DeviceRefCodePkg\AcpiTablesPCAT\HOST_BUS.ASL
> >
> > The PCI devices are declared statically.
> >
> > i want to make this declaration dynamic - so that the device number can
> change
> >
> > according according to my hardware setup. Is it possible?
>
> There are generally two ways for this.
>
> One is to write the bulk of the ASL like seen here, statically, but all
> the customizable values are referenced as external objects / fields.
> Then, a platform ACPI DXE driver in the firmware computes those values,
> and installs a small SSDT with just those objects. The AML is generated
> manually by the firmware, which is super awkward, but due to the small
> size of the integer objects etc, it is tolerable.
>
> A similar approach can be seen e.g. in "OvmfPkg/AcpiPlatformDxe/Qemu.c",
> function QemuInstallAcpiSsdtTable(). And the referring ASL code is in
> "OvmfPkg/AcpiTables/Dsdt.asl". (Search both for "FWDT".)
>
> (Note however that said function is not used nowadays on QEMU, because
> now QEMU generates *all* of the AML dynamically.)
>
> The other approach is to process the (static) AML before installing it
> with EFI_ACPI_TABLE_PROTOCOL.InstallAcpiTable(). If you know the exact
> path to / structure of the AML node that you want to modify, the
> EFI_ACPI_SDT_PROTOCOL lets you navigate to the node, and patch it
> in-place, in a memory array. Then you can install the modified table
> blob with EFI_ACPI_TABLE_PROTOCOL. (Important: do not modify a table
> *after* it is installed.)
>
> One example for the 2nd approach should be
> "QuarkPlatformPkg/Acpi/Dxe/AcpiPlatform/AcpiPciUpdate.c".
>
> Thanks
> Laszlo
>