Re: [edk2-devel] [edk2-rfc] MdeModulePkg/StatusCodeHandler: Separate NULL class libraries for Memory and serial handlers from MdeModulePkg/Universal/StatusCodeHandler modules

["Dong, Eric" <eric.dong@intel.com>]

[-- Attachment #1: Type: text/plain, Size: 10243 bytes --]

Hi Brian,

In this new design, we still use register status code handler Protocol/Ppi to register the handler logic. We just want to change the StatusCodeHandler driver. We try to split the register logic to NULL library to make the code more modularity. We already created sample library in Edk2-Platforms repo  https://github.com/tianocore/edk2-platforms/tree/master/Features/Intel/Debugging/PostCodeDebugFeaturePkg/Library/PostCodeStatusCodeHandlerLib.  You can check this code to understand more about what we want to do.

Thanks,
Eric
From: Brian J. Johnson <brian.johnson@hpe.com>
Sent: Thursday, June 25, 2020 4:25 AM
To: Bi, Dandan <dandan.bi@intel.com>; Andrew Fish <afish@apple.com>; edk2-devel-groups-io <devel@edk2.groups.io>
Cc: rfc@edk2.groups.io; Dong, Eric <eric.dong@intel.com>; Ni, Ray <ray.ni@intel.com>; Wang, Jian J <jian.j.wang@intel.com>; Wu, Hao A <hao.a.wu@intel.com>; Tan, Ming <ming.tan@intel.com>; Laszlo Ersek <lersek@redhat.com>
Subject: Re: [edk2-devel] [edk2-rfc] MdeModulePkg/StatusCodeHandler: Separate NULL class libraries for Memory and serial handlers from MdeModulePkg/Universal/StatusCodeHandler modules

Dandan,

The Status Code Protocol/PPI is the high-level interface which is being implemented.  The ReportStatusCodeRouter module implements this in terms of the ReportStatusCodeHandler Protocol/PPI.  That allows multiple ReportStatusCodeHandler modules to be used at once, so they can each react to different types of status codes, or report them through multiple channels.  That sort of multiplexing seems like a useful feature.

Now we're considering adding a mechanism which allows registering status code handlers via NULL libraries, rather than via the protocol/PPI.  That sounds like exactly what ReportStatusCodeRouter is intended for.  It wouldn't really change its scope, it would just make it more flexible.  Adding this feature via a StatusCodeHandler module wouldn't improve modularity, it would just add complexity.  As an OEM, adding a custom handler would look the same to me either way:  I would have to add the NULL class library to a MdeModulePkg driver's entry in my .dsc file.  It doesn't matter to me whether it's the ReportStatusCodeRouter or StatusCodeHandler module.  And if I can do it in ReportStatusCodeRouter, then I don't need to include any StatusCodeHandler modules in the build at all.  That saves code space and reduces the number of modules in the APRIORI list, which are both good things.

ReportStatusCodeRouterPei already has to track registered handlers in PEI when running from ROM (it uses a HOB.)  Tracking handlers from NULL libraries wouldn't be any harder.  In fact, it looks like it could just export the Register() function to the NULL libraries, and they could call it in their constructors.

I think using NULL libraries for status code handlers is a great idea.  I'd just like to take that opportunity to reduce the complexity of the overall status code stack while we're at it.

Thanks,

Brian J. Johnson
Enterprise X86 Lab

Hewlett Packard Enterprise

________________________________
From: Bi, Dandan [mailto:dandan.bi@intel.com]
Sent: Monday, June 22, 2020, 2:27 AM
To: Andrew Fish <afish@apple.com><mailto:afish@apple.com>, edk2-devel-groups-io <devel@edk2.groups.io><mailto:devel@edk2.groups.io>, brian.johnson@hpe.com<mailto:brian.johnson@hpe.com> <brian.johnson@hpe.com><mailto:brian.johnson@hpe.com>
Cc: rfc@edk2.groups.io<mailto:rfc@edk2.groups.io> <rfc@edk2.groups.io><mailto:rfc@edk2.groups.io>, Dong, Eric <eric.dong@intel.com><mailto:eric.dong@intel.com>, Ni, Ray <ray.ni@intel.com><mailto:ray.ni@intel.com>, Wang, Jian J <jian.j.wang@intel.com><mailto:jian.j.wang@intel.com>, Wu, Hao A <hao.a.wu@intel.com><mailto:hao.a.wu@intel.com>, Tan, Ming <ming.tan@intel.com><mailto:ming.tan@intel.com>, Laszlo Ersek <lersek@redhat.com><mailto:lersek@redhat.com>, Bi, Dandan <dandan.bi@intel.com><mailto:dandan.bi@intel.com>
Subject: [edk2-devel] [edk2-rfc] MdeModulePkg/StatusCodeHandler: Separate NULL class libraries for Memory and serial handlers from MdeModulePkg/Universal/StatusCodeHandler modules

Hi Brian,

Personally, I prefer to add the NULL class Library to StatusCodeHandler modules.

  1.  I think we should make the functionality of each module clear and separated. It may also be why we added ReportStatusCodeRouter and StatusCodeHandler modules in edk2 repo before.

ReportStatusCodeRouter modules are responsible for producing Status Code Protocol/PPI and Report Status Code Handler Protocol/PPI, and StatusCodeHandler modules are responsible for producing handlers (Handlers can be provided by NULL class Libraries in this RFC).

 So, that’s why I don’t want to add the NULL class Library to ReportStatusCodeRouter modules directly, which change the functionality scope of existing modules.



  1.  I agree that we have a lot of layers of indirection now, but what we may gain is the good modularity. And you also mentioned that one or more StatusCodeHandler Modules may be used. We also want to achieve that only the StatusCodeHandler modules in MdeModulePkg can be used after this separation, platform can only add its own handler Libs to meet its requirement.



  1.  As Andrew mentioned below, if add the libraries to ReportStatusCodeRouter, there will be some issue we need to fix, which seems also make the code logic a little tricky to me.



Thanks,
Dandan
From: Andrew Fish <afish@apple.com><mailto:afish@apple.com>
Sent: Saturday, June 20, 2020 2:04 AM
To: edk2-devel-groups-io <devel@edk2.groups.io><mailto:devel@edk2.groups.io>; brian.johnson@hpe.com<mailto:brian.johnson@hpe.com>
Cc: Bi, Dandan <dandan.bi@intel.com><mailto:dandan.bi@intel.com>; rfc@edk2.groups.io<mailto:rfc@edk2.groups.io>; Dong, Eric <eric.dong@intel.com><mailto:eric.dong@intel.com>; Ni, Ray <ray.ni@intel.com><mailto:ray.ni@intel.com>; Wang, Jian J <jian.j.wang@intel.com><mailto:jian.j.wang@intel.com>; Wu, Hao A <hao.a.wu@intel.com><mailto:hao.a.wu@intel.com>; Tan, Ming <ming.tan@intel.com><mailto:ming.tan@intel.com>
Subject: Re: [edk2-devel] [edk2-rfc] MdeModulePkg/StatusCodeHandler: Separate NULL class libraries for Memory and serial handlers from MdeModulePkg/Universal/StatusCodeHandler modules





On Jun 19, 2020, at 10:29 AM, Brian J. Johnson <brian.johnson@hpe.com<mailto:brian.johnson@hpe.com>wrote:

On 6/18/20 2:01 AM, Dandan Bi wrote:
Hi All,

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2816

We plan to separate two kinds of NULL class libraries for Memory and serial handlers fromMdeModulePkg/Universal/StatusCodeHandler/…/ StatusCodeHandlerPei/RuntimeDxe/Smm modules.
The benefit we want to gain from this separation is to 1) make the code clear and easy to maintain, 2) make platform flexible to choose any handler library they need, and it also can reduce image size since the unused handlers can be excluded.
If you have any concern or comments for this separation, please let me know.

We plan to add new separated NULL class library MemoryStausCodeHandlerLib and SerialStatusCodeHandlerLib with different phase implementation into MdeModulePkg\Library\ directory.
The main tree structure may like below:
MdeModulePkg\Library
|------MemoryStausCodeHandlerLib
|------|------ PeiMemoryStausCodeHandlerLib.inf
|------|------ RuntimeDxeMemoryStatusCodeHandlerLib.inf
|------|------ SmmMemoryStausCodeHandlerLib.inf
|------SerialStatusCodeHandlerLib
|------|------ PeiSerialStatusCodeHandlerLib.inf
|------|------ RuntimeDxeSerialStatusCodeHandlerLib.inf
|------|------ SmmSerialStatusCodeHandlerLib.inf


We will update existing platform use cases in edk2 and edk2-platform repo to cover the new NULL class library to make sure this change doesn’t impact any platform.
After this separation, StatusCodeHandler module usage will like below, and it’s also very flexible for platform to cover more handler libraries to meet their requirements.
MdeModulePkg/Universal/StatusCodeHandler/Pei/StatusCodeHandlerPei.inf {
  <LibraryClasses>
NULL|MdeModulePkg/Library/MemoryStausCodeHandlerLib/PeiMemoryStausCodeHandlerLib.inf
NULL|MdeModulePkg/Library/SerialStatusCodeHandlerLib/PeiSerialStatusCodeHandlerLib.inf
    …
}

MdeModulePkg/Universal/StatusCodeHandler/RuntimeDxe/StatusCodeHandlerRuntimeDxe.inf  {
  <LibraryClasses>
NULL|MdeModulePkg/Library/MemoryStausCodeHandlerLib/RuntimeDxeMemoryStausCodeHandlerLib.inf
NULL|MdeModulePkg/Library/SerialStatusCodeHandlerLib/RuntimeDxeSerialStatusCodeHandlerLib.inf
    …
}

MdeModulePkg/Universal/StatusCodeHandler/Smm/StatusCodeHandlerSmm.inf {
  <LibraryClasses>
    NULL|MdeModulePkg/Library/MemoryStausCodeHandlerLib/SmmMemoryStausCodeHandlerLib.inf
NULL|MdeModulePkg/Library/SerialStatusCodeHandlerLib/SmmSerialStatusCodeHandlerLib.inf
    …
}


Thanks,
Dandan

Dandan,
We'll have a lot of layers of indirection....  The ReportStatusCodeRouter modules will call one or more StatusCodeHandlerModules, and the standard StatusCodeHandler modules will call multiple StatusCodeHandlerLib libraries.
How about adding StatusCodeHandlerLib support directly to the ReportStatusCodeRouter modules?  Then platforms could omit the StatusCodeHandler modules if they're only using the open-source code.  That sounds like less overhead since fewer modules would be needed.


I think the need to execute from ROM makes this tricky.

It looks to me that it is easy to move from PCD to libs for the StatusCodeHandler since registration is basically `RscHandlerPpi->Register (SerialStatusCodeReportWorker);`. The issue I see is the ReportStatusCodeRouter publishes RscHandlerPpi after the PEIMs constructor has been called and if the PEIM. Given globals don’t work when running from ROM you would have to do something like publish a HOB in the library constructor and then have the GenericStatusCodePeiEntry() walk the HOBs and install the handlers. So I guess it is a little easier than I 1st thought when I started writing this mail, but it would require a new public API.

Thanks,

Andrew Fish


Thanks,
--

Brian J. Johnson
Enterprise X86 Lab

Hewlett Packard Enterprise

hpe.com<x-msg://64/3D%22hpe.com%22>



-

[-- Attachment #2: Type: text/html, Size: 27302 bytes --]