On Jul 23, 2014, at 5:36 AM, Laszlo Ersek <ler...@redhat.com> wrote:
> On 07/23/14 13:34, Varad Gautam wrote:
>> Hi, I am working on the BeagleBoneBlack port for EDK2 and am facing an
>> issue with
>> PcdGet(): it always returns `0` no matter what the PCD is set to. However,
>> FixedPcdGet() works fine (I've had to patch edk2 to replace all PcdGet
>> calls with
>> FixedPcdGet to get PrePi working which is a bad idea).
>>
What form do get for _PCD_GET_MODE_*_PcdFvBaseAddress in the AutoGen.h? That is
the real issue.
https://svn.code.sf.net/p/edk2/code/trunk/edk2/MdePkg/Include/Library/PcdLib.h
#define PcdGet8(TokenName) _PCD_GET_MODE_8_##TokenName
The behavior of libraries (try to inherit things from drivers) and drivers is
different. Where is the PCD in question?
>> The build report too shows the PCDs being set to their proper values,
>> and so do the
>> AutoGen.i file macros like `const UINT32 _gPcd_FixedAtBuild_PcdFvBaseAddress
>> = 0x80008000U;`
>>
>> I've come up with two reasons to this,
>> * Is there a build flag I'm missing to enable PcdGet support?
>> * `_gPcd_FixedAtBuild_PcdFvBaseAddress` is declared with
>> `GLOBAL_REMOVE_IF_UNREFERENCED` in AutoGen.c and gets removed before
>> I can use it. This also explains why FixedPcdGet would work, since
>> `_PCD_VALUE_PcdFvBaseAddress` is correctly #defined to be 0x80008000U.
>>
>> This happens for all fixed-at-build type PCDs. Also, I'm linked to
>> PcdLib|MdePkg/Library/BasePcdLibNull/BasePcdLibNull.inf for the buid. What
>> could
>> I try to fix it?
>
> You're getting this result because you're combining incorrect library
> class resolution with RELEASE builds.
Yes it is good to debug with DEBUG builds.
Thanks,
Andrew Fish
> (I cannot condemn RELEASE builds
> enough.) Namely, you call
>
> UINT32
> EFIAPI
> LibPcdGet32 (
> IN UINTN TokenNumber
> )
> {
> ASSERT (FALSE);
>
> return 0;
> }
>
> from "MdePkg/Library/BasePcdLibNull/PcdLib.c", and since you build for
> RELEASE, the ASSERT() is a no-op. In a DEBUG build you'd have caught
> this immediately with a failed assertion: the Null implementation of
> PcdLib doesn't allow you to actually access PCDs.
>
> Library instances that usably resolve the PcdLib library class are:
>
> $ git grep -l 'LIBRARY_CLASS *= *PcdLib' -- '*.inf'
>
> EmulatorPkg/Library/SmbiosLib/SmbiosLib.inf
> MdePkg/Library/BasePcdLibNull/BasePcdLibNull.inf
> MdePkg/Library/DxePcdLib/DxePcdLib.inf
> MdePkg/Library/PeiPcdLib/PeiPcdLib.inf
>
> In PEIMs, you need the fourth; in DXE & UEFI drivers, you need the third.
>
> However, this is not the entire picture yet, because these libraries
> delegate the work to a PPI (in PEI) and to a protocol (in DXE) that are
> provided by dedicated drivers, respectively:
> - MdeModulePkg/Universal/PCD/Pei/Pcd.inf
> - MdeModulePkg/Universal/PCD/Dxe/Pcd.inf
>
> You should add these drivers to the corresponding (ie. PEI vs. DXE)
> APRIORI files of the firmware volumes that your FDF file defines, so
> that any driver loaded / dispatched later can use their PCD services
> (through the above-mentioned library instances). Refer to
> OvmfPkg/OvmfPkgX64.fdf for examples.
>
> Thanks
> Laszlo
>
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