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Subject: Re: [edk2-devel] PCD EX interface.
To: Ken_Taylor@phoenix.com
References: <2fb8e97b19214251bf25f44c7b4149a3@SCL-EXCHMB-13.phoenix.com>
From: "Laszlo Ersek" <lersek@redhat.com>
Cc: devel@edk2.groups.io
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Date: Thu, 23 Jan 2020 12:21:30 +0100
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Hi Ken,

On 01/23/20 02:37, Ken Taylor wrote:

> If I try to get the size of a DynamicEx PCD in the context of a BIOS
> build for which that PCD is undefined, the call locks up.  I expected
> to just get a size of 0, since the PCD is not defined in the build
> context of the PCD DXE service.  Is this a problem that's been fixed
> since my BIOS source code was cut?  What can I do for older builds
> that haven't been fixed (and probably never will)?  Do I have to just
> accept that I'm going to get garbage or lockup if I run my shell
> utility on some builds?  Do I have to write a DXE driver and expose a
> protocol, just so I can know if that PCD exists and is properly
> defined?

I think the ASSERT() that you run into is the one in
GetExPcdTokenNumber(), file "MdeModulePkg/Universal/PCD/Dxe/Service.c":

>   MatchGuid   = ScanGuid (GuidTable, mDxeGuidTableSize, Guid);
>   //
>   // We need to ASSERT here. If GUID can't be found in GuidTable, this is a
>   // error in the BUILD system.
>   //
>   ASSERT (MatchGuid != NULL);

Can you try the following:

- Locate EFI_PCD_PROTOCOL.

- Call EFI_PCD_PROTOCOL.GetNextTokenSpace() in a loop, until you find
  the GUID of your own token space GUID, or the function returns an
  error.

- If your token space GUID has been found, call PcdGetEx8().

Thanks,
Laszlo