On Mon, Apr 28, 2025 at 10:41:25AM -0400, Raymond Mao wrote: > Hi Simon, > > On Thu, 17 Apr 2025 at 14:16, Simon Glass <s...@chromium.org> wrote: > > > > > > This series adds a standard way of passing information between different > > firmware phases. This already exists in U-Boot at a very basic level, in > > the form of a bloblist containing an spl_handoff structure, but the intent > > here is to define something useful across projects. > > > > The need for this is growing as firmware fragments into multiple binaries > > each with its own purpose. Without any run-time connection, we must rely > > on build-time settings which are brittle and painful to keep in sync. > > > > This feature is named 'standard passage' since the name is more unique > > than many others that could be chosen, it is a passage in the sense that > > information is flowing from one place to another and it is standard, > > because that is what we want to create. > > > > The implementation is mostly a pointer to a bloblist in a register, with > > an extra register to point to a devicetree, for more complex data. This > > should cover all cases (small memory footprint as well as complex data > > flow) and be easy enough to implement on all architectures. > > > > The emphasis is on enabling open communcation between binaries, not > > enabling passage of secret, undocumented data, although this is possible > > in a private environment. > > > > This series is available at u-boot-dm/pass-working > > > > First of all, can you group those patches which are necessary for > refactoring the "passage" concept into a smaller series for an easy > review? > > Actually as I mentioned in our previous discussions, I don't agree to > add a OF_BLOBLIST as this is duplicated with "BLOBLIST + > BLOBLIST_PASSAGE_MANDATORY (aka PASSAGE_IN in the context of your > patch - I am not sure the reason you prefer to rename it - do we have > any other passage approaches other than using bloblist? And do you > have any considerations to allow a fallback or not in case passage > failures?)"
As preamble, I am actively working to push the changes for vexpress_fvp_bloblist to be available in CI and so provide an easier testing path. At the high level, I don't see what the difference is between "BLOBLIST + BLOBLIST_PASSAGE_MANDATORY" and "BLOBLIST + OF_BLOBLIST" or "BLOBLIST + whatever v4 of this series ends up showing". Everyone seems wildly in agreement that if the prior stage is supposed to give us information then it must have done so. One of the long running "jokes" in computer science about naming being one of the hardest problems applies here, too. > Secondly I prefer to keep the register convention code as a xferlist > library that can be used for arm arches other than split them into > different low level assemblies. In case of any firmware handoff > specification update, we just need to maintain this library. Yes, if things can be written in a C file, they should be in a C file, not assembler. -- Tom
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