Re: [edk2-devel] [edk2-platforms][PATCH v1 1/1] IntelSiliconPkg: Add BaseSmmAccessLibNull

["Michael Kubacki" <mikuback@linux.microsoft.com>]

I don't understand your argument.

The library class (SmmAccessLib) that already exists is the abstraction 
layer. This is not introducing a new layer of abstraction. It is using 
the current layer of abstraction.

Thanks,
Michael

On 8/19/2021 5:49 AM, Ni, Ray wrote:
> Michael,
> 
> I don’t think scenario #1 is a good reason for NULL instance of 
> SmmAccessLib. The root cause is BoardInitLib lib class supports pre-mem 
> and post-mem board init.
> 
> Below solution can avoid NULL SmmAccessLib:
> 
> Create two instances of BoardInitLib for pre-mem and post-mem. Pre-mem 
> one doesn’t link to SmmAccessLib.
> 
> For scenario #2, if a particular platform doesn’t support S3, why does 
> this platform include the PEIM?
> 
> Please understand that I want to avoid introducing more abstraction layers.
> 
> Thanks,
> 
> Ray
> 
> *From:* Michael Kubacki <mikuback@linux.microsoft.com>
> *Sent:* Friday, August 13, 2021 10:16 AM
> *To:* Ni; Ni, Ray <ray.ni@intel.com>; devel@edk2.groups.io
> *Subject:* Re: [edk2-devel] [edk2-platforms][PATCH v1 1/1] 
> IntelSiliconPkg: Add BaseSmmAccessLibNull
> 
> Sure.
> 
> Scenario #1:
> 
> MinPlatformPkg/PlatformInit/PlatformInitPei/PlatformInitPreMem.inf and 
> MinPlatormPkg/PlatformInit/PlatformInitPei/PlatformInitPostMem.inf both 
> link against an instance of BoardInitLib.
> 
> Many boards link against a single BoardInitLib instance. See example - 
> https://github.com/tianocore/edk2-platforms/blob/cd4e6b716c7d1bcde94035e7dce14b53a553e103/Platform/Intel/KabylakeOpenBoardPkg/KabylakeRvp3/OpenBoardPkg.dsc#L203 
> <https://github.com/tianocore/edk2-platforms/blob/cd4e6b716c7d1bcde94035e7dce14b53a553e103/Platform/Intel/KabylakeOpenBoardPkg/KabylakeRvp3/OpenBoardPkg.dsc#L203>
> 
> That BoardInitLib instance may link against SmmAccessLib. 
> PlatformInitPreMem may wish to library class override the SmmAccessLib 
> to the NULL instance while keeping it to non-NULL instance in 
> PlatformInitPostMem.
> 
> Scenario #2:
> 
> A PEIM is built that checks whether the boot mode is S3. If so, it calls 
> PeiInstallSmmAccessPpi(). A particular platform does not support S3, 
> therefore, it links BaseSmmAccessLibNull as its library instance for 
> SmmAccessLib.
> 
>