On Wed, Apr 30, 2025 at 08:51:53AM -0600, Simon Glass wrote: > Hi Tom, > > On Wed, 30 Apr 2025 at 08:29, Tom Rini <tr...@konsulko.com> wrote: > > > > On Wed, Apr 30, 2025 at 07:55:01AM -0600, Simon Glass wrote: > > > Hi Tom, > > > > > > On Tue, 29 Apr 2025 at 11:11, Tom Rini <tr...@konsulko.com> wrote: > > > > > > > > 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. > > > > > > I want to use OF_BLOBLIST as it clearly indicates that the devicetree > > > comes from a bloblist. The BLOBLIST_PASSAGE_MANDATORY thing is a > > > work-around to try to avoid having OF_BLOBLIST. > > > > Or: > > Other people want to use BLOBLIST_PASSAGE_MANDATORY as it clearly > > indicates that the standard passage will be present and so include the > > devicetree and any other required logs/blobs/content. The OF_BLOBLIST > > thing is a work-around to try and avoid having > > BLOBLIST_PASSAGE_MANDATORY. > > > > It's a naming problem and I don't care as long as we end up with an > > implementation that's useful. And *that* is where my list of what > > bloblist needs to have, in the end, comes from. > > My approach does the same thing, but allows my x86 boards to work > without all the confusion. It shows fdt coming from 'standard passage' > when it is.
It does not matter. Really. Whatever you're doing with OF_BLOBLIST can also be done with BLOBLIST_PASSAGE_MANDATORY as it's just a naming thing. There's nothing confusing here unless you insist on confusing it. Which gets back to what I was saying before about what changes need to happen to bloblist. > > > > > 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. > > > > > > In this case I disagree and if you look at the x86 code, this kind of > > > approach is just not sensible. Please take a look at the contortions > > > of xferlist_from_boot_arg(). It was written for one architecture only, > > > yet purports to be a general API. My approach is simpler. Also, if > > > save_boot_args() is implemented by the board, then standard passage > > > will be broken for that board. It's a weak function! > > > > I don't see why this has to be in assembly and not C, no. And it's a > > weak function because it doesn't yet exist on other architectures and > > everyone hates #if. > > We just don't need it, though. If you would like this to work on x86, > it needs to go. > > > > > > More generally, please decide if you are willing to let me maintain > > > bloblist. > > > > Can you be given substantive feedback? Or is only trivial feedback > > allowed? > > I'm happy to discuss it on a call, but if you insist on > BLOBLIST_PASSAGE_MANDATORY, then it is going to be tricky. The > OF_BLOBLIST thing has consumed far too much time. If you want Linaro > to maintain bloblist, please just say so. I had thought you were OK > with my taking that on again. As I've said numerous times now, BLOBLIST_PASSAGE_MANDATORY and OF_BLOBLIS are just names. Names are one of the hardest problems in computer science. As I've also said numerous times now, you need to show ME that you have a good design. That means you need to implement register passing rather than BLOBLIST_FIXED. You then also likely need to untie "Is there a bloblist?" from "Make a bloblist" as that's what complicates things. -- Tom
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