Re: [RFC] Add Platform Include path in modules

["Gao, Liming" <liming.gao@intel.com>]

Hi, 
  For the first one, the same PCD can be configured to the different value for the different SkuId. 

Here is wiki on structure pcd enable step and examples. 
https://github.com/lgao4/edk2/wiki/StructurePcd-Enable-Steps

TestPkg in https://github.com/lgao4/edk2/tree/UDK2018 has the sample case with structure pcd. 

Thanks
Liming
>-----Original Message-----
>From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of
>Pankaj Bansal
>Sent: Tuesday, February 27, 2018 3:40 PM
>To: Kinney, Michael D <michael.d.kinney@intel.com>; Laszlo Ersek
><lersek@redhat.com>; edk2-devel@lists.01.org
>Cc: Gao, Liming <liming.gao@intel.com>
>Subject: Re: [edk2] [RFC] Add Platform Include path in modules
>
>Hi Laszlo/Michael,
>
>Thanks for your feedback on this proposal.
>I looked at the structured PCDs and UEFI Platform Initialization Distribution
>Packaging Specification.
>Here is my take on these.
>
>1. structured PCDs are good if we want to declare single complex structure.
>    But consider a case where I want to keep device information in structure.
>(e.g. hardware settings, limitations etc)
>    And we may want to tweak this information based on platform revision
>being used.
>    And different platforms can have different number of such devices.
>    In this case, when we want to add a new platform, we might need to
>introduce new PCDs in .dec files, which will not be needed for others.
>    I don't know, will this even increase the PCD database size for existing
>platforms or not ?
>
>2. To mitigate the "hidden" dependency of a module on platform, we can
>explicitly declare this dependency in module inf file.
>     I am thinking something like gEfiCallerIdGuid, i.e. module can declare that
>that platform building(using) the module, supply this information.
>
>3. Using Libraries and Protocols can also solve such use cases. I just felt that it's
>less cumbersome to use include files, and it also avoids code replication.
>    Anyway, this is just my suggestion to have such mechanism in edk2 build
>process. I am more than happy to stick to platform libraries.
>
>Thanks & Regards,
>Pankaj Bansal
>
>> -----Original Message-----
>> From: Kinney, Michael D [mailto:michael.d.kinney@intel.com]
>> Sent: Monday, February 26, 2018 10:56 PM
>> To: Laszlo Ersek <lersek@redhat.com>; Pankaj Bansal
>> <pankaj.bansal@nxp.com>; edk2-devel@lists.01.org; Kinney, Michael D
>> <michael.d.kinney@intel.com>
>> Cc: Gao, Liming <liming.gao@intel.com>
>> Subject: RE: [edk2] [RFC] Add Platform Include path in modules
>>
>> Hi Pankaj,
>>
>> I agree with Laszlo that you should evaluate use of PCDs.  There are a few
>> methods for a driver to use platform specific values/behavior.  These are:
>>
>> * PCDs
>> * Library class/Library Instance
>> * Protocol/PPI
>>
>> One issue with the proposal is that it adds a hidden dependency to modules.
>> An EDK II INF file describes the external interfaces of a module along with
>> produces/consumes usage.  This information is aligned with the XML
>schema
>> that is documented in the UEFI Platform Initialization Distribution Packaging
>> Specification.
>>
>>
>>
>https://emea01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fuefi.
>>
>org%2Fspecifications&data=02%7C01%7Cpankaj.bansal%40nxp.com%7C96c4
>> 2dd7271d449d56e908d57d3df2d4%7C686ea1d3bc2b4c6fa92cd99c5c301635
>> %7C0%7C0%7C636552627376357192&sdata=sS7KT3haANF5TLHSeRGjIQHnLQ
>> BtnTDLIZWntUhsk78%3D&reserved=0
>>
>> If two modules have the same GUID/Version, then the external interfaces
>to
>> those two modules are expected to be identical.
>> With your proposal, two modules built for 2 different platforms would have
>> the same GUID/Version but would not have the same external interfaces
>> because a hidden dependency on a platform package was added.
>>
>> If a module really needs to use content from a platform package, then a
>new
>> copy of the module should be created with a new GUID/Version and the
>> platform package added to the [Packages] section.  The other option is to
>use
>> one of the supported interfaces (PCDs, Lib, Protocol, PPI).
>>
>> Please let us know if any of these exiting methods do not work for your use
>> case.
>>
>> Thanks,
>>
>> Mike
>>
>> > -----Original Message-----
>> > From: Laszlo Ersek [mailto:lersek@redhat.com]
>> > Sent: Monday, February 26, 2018 7:55 AM
>> > To: Pankaj Bansal <pankaj.bansal@nxp.com>; Kinney, Michael D
>> > <michael.d.kinney@intel.com>; edk2- devel@lists.01.org
>> > Cc: Gao, Liming <liming.gao@intel.com>
>> > Subject: Re: [edk2] [RFC] Add Platform Include path in modules
>> >
>> > On 02/26/18 11:55, Pankaj Bansal wrote:
>> > > Hi,
>> > >
>> > > Consider a simple driver which needs that some data
>> > structures be
>> > > filled by the Platform, which is using the driver.
>> > >
>> > > Driver.c #include <Platform.h>
>> > >
>> > > Struct a = platformVal;
>> > >
>> > > We can define platformVal in Platform.h, which would
>> > be unique to the
>> > > platform being built. This Platform.h can be placed in
>> > include
>> > > directories, whose path would be defined in
>> > Platform.dec file.
>> > >
>> > > Now, whenever we build driver for each unique
>> > platform, we need not
>> > > to mention Platform.dec file in driver.inf [packages]
>> > section. We can
>> > > append Platform.dec include paths to each driver. i.e.
>> > look for the
>> > > include files in [packages] section as well as in
>> > Platform include
>> > > directories.
>> > >
>> > > For this, I am looking for Platform.dec file in same
>> > directory as
>> > > Platform.dsc and using same name as Platform.dsc
>> > >
>> > > We can refine this change further. i.e. add Platform
>> > include
>> > > directories to driver's include paths based on some
>> > condition in
>> > > driver.inf file.
>> >
>> > (Apologies in advance if I failed to grasp the use
>> > case.)
>> >
>> > If I understand correctly, you have multiple platforms (defined by DSC
>> > and FDF files), and you build a given driver for several of these
>> > platforms, separately. And, when building the driver for the separate
>> > platforms, you'd like the driver to get different initializers for
>> > various static (global) structure variables.
>> >
>> > Have you tried the structured PCD format? I think that could cover
>> > your use case.
>> >
>> > Unfortunately I couldn't find anything about structured PCDs in the
>> > edk2 specs, but there are several BZ references in the following
>> > mailing list
>> > message:
>> >
>> > [edk2] [Patch 00/14] Enable Structure PCD support in
>> > edk2
>> >
>> >
>>
>https://emea01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fmid.
>> > mail-archive.com%2F1512140335-6932-1-git-send-
>> &data=02%7C01%7Cpankaj.b
>> >
>> ansal%40nxp.com%7C96c42dd7271d449d56e908d57d3df2d4%7C686ea1d3b
>> c2b4c6fa
>> >
>> 92cd99c5c301635%7C0%7C0%7C636552627376357192&sdata=iR50v%2F4Jg%
>> 2BZQh7P
>> > 1LB1bxeCryTangpA1SyVCwCEQW2U%3D&reserved=0
>> > email-liming.gao@intel.com
>> >
>> > Thanks
>> > Laszlo
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