Tim, All good ideas to evaluate.
We did design in the Dynamic PCDs with generated local tokens to minimize the size overhead of the PCD database for source builds. We can do some size impact analysis of these ideas to see which one makes the most sense. The database is currently optimized for Dynamic PCDs. When a DynamicEx PCD is used it is internally translated to a Dynamic request. I think all of the ideas here require this concept to be reversed. We need to optimized the database for DynamicEx and never reference Dynamic part of database to process a DynamicEx request. If Dynamic is used, it can either be internally translated to a DynamicEx request with a fixed token space guid or be processed as a local token. In mixed Dynamic/DynamicEx environments, the same PCD may be accessed using both methods. Current design supports this mixed env, so we need to make sure that aspect is not broken if we change internal code/database. Best regards, Mike > -----Original Message----- > From: Tim Lewis [mailto:[email protected]] > Sent: Wednesday, February 10, 2016 9:50 AM > To: Kinney, Michael D <[email protected]>; [email protected] > Subject: RE: PCD Local Token Numbers in PEI/DXE > > Mike -- > > Yes, we use all DynamicEx PCDs because we use a large number of binary > deliverables in > certain segments. > > It would be a much simpler database design if the look up was purely a > GUID/token > number/SkuId look-up (no local token numbers at all). The existing Dynamic > PCDs could > be supported by assigning them a single GUID. That is, Dynamic PCDs would be > translated > up to DynamicEx by using gEfiDynamicPcdGuid. Or we could deprecate Dynamic. > Or make it > auto-translate to DynamicEx. > > Tim > > > -----Original Message----- > From: edk2-devel [mailto:[email protected]] On Behalf Of > Kinney, Michael > D > Sent: Wednesday, February 10, 2016 9:41 AM > To: Tim Lewis <[email protected]>; [email protected]; Kinney, > Michael D > <[email protected]> > Subject: Re: [edk2] PCD Local Token Numbers in PEI/DXE > > Hi Tim, > > Your description looks correct to me. The current design does have an > assumption that > the PCD database used in PEI is aligned with the PCD database used in DXE. > > If the number of Dynamic/DynamicEx PCDs used in a platform changes, then the > PCD > database associated with the PCD PEIM and PCD DXE Driver both need to be > updated. > > I think it would be good to work on a method that allows the PEI Database and > DXE > Database to be updated independently. > > In general, if binary modules are used, then Dynamic PCDs can not be used. > Instead all > Dynamic PCDs must be updated to by DynamicEx PCDs. That is for binary > modules that > performs PCD Get/Set operations through the PCD PPI/Protocol. > > I think the gap here is that the PCD database does not have a build mode that > forces > use of only DynamicEx (TokenSpaceGuid, TokenNumber) for the entire database > contents. > If we added that build mode (so there are no "local token numbers") then the > PEI > database and DXE database could be updated independently. > > This build mode could only be enabled if there are no Dynamic PCDs. In fact, > this > build mode could be automatic if there are no Dynamic PCDs in DSC file. > > Mike > > > -----Original Message----- > > From: edk2-devel [mailto:[email protected]] On Behalf Of > > Tim Lewis > > Sent: Tuesday, February 9, 2016 10:24 AM > > To: [email protected] > > Subject: [edk2] PCD Local Token Numbers in PEI/DXE > > > > We have run into an interesting problem with the PCD database when the > > PEI and DXE databases were not built at the same time. This happens > > with boot-block type arrangements. This is not a Dynamic vs. DynamicEx > > issue. > > > > Short form: > > > > > > 1) The standard PCD database for Dynamic/DynamicEx PCDs is broken into > > two > pieces, > > based on whether the PCD is access by a PEIM, a DXE driver, or both. > > The pieces are embedded directly into the PCD PEIM and PCD DXE driver that > > produces > the PCD services. > > > > 2) Each Dynamic/DynamicEx PCD is assigned a unique "local token > > number" This > > number is different than the token number which is in the PCD > > declaration in the .dec file. This number is assigned at build time. > > > > 3) If a later version of the DXE PCD driver is a) built in a later > > codebase > where > > there are more or less PEI-access PCDs, but later b) executed with a > > version of the PEI PCD database from the earlier codebase where there > > were fewer, it causes a problem. For example, if the new PEI PCD > > database has 4 more, the new DXE PCD database will start its numbering > > at +4. But when it is executed with the old PEI PCD database, it will > > end up looking up the wrong PCD > > > > We're not sure what the best course is to solve this. Frankly, the PCD > > database format is a muddle. We have a temporary work-around, but > > we're wondering if anyone has thoughts on a good solution. > > > > Thanks, > > > > Tim > > _______________________________________________ > > edk2-devel mailing list > > [email protected] > > https://lists.01.org/mailman/listinfo/edk2-devel > _______________________________________________ > edk2-devel mailing list > [email protected] > https://lists.01.org/mailman/listinfo/edk2-devel _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
