Hi François, On Thu, 15 Jul 2021 at 08:25, François Ozog <francois.o...@linaro.org> wrote:
> > > On Sat, 10 Jul 2021 at 01:07, Julius Werner <jwer...@chromium.org> wrote: > >> > - "bloblist" is a general term for concept of linked list and it's not >> exactly U-boot implementation. The proposed solution will cause some degree >> of changes in all the participating projects. For backward compatibility >> issue, we have already though about it and proposed to have build configs >> which will be enabled by platform integrators. >> >> Okay, let's gather the requirements and then decide how the existing >> system needs to be expanded to meet them. Please keep me in the loop >> on those discussions. >> >> > > U-Boot has an established mechanism which is used in particular on >> all chrome >> > > books in both x86 and Arm environments. I have the impression that >> > > U-Boot is the typical BL33 so I would import the mechanism into TFA, >> > > not the other way round. >> >> There has been no Chromebook (x86 or Arm) shipping with U-Boot since >> 2013 (before TF-A existed). In fact, Chromebooks are all running >> coreboot today and using the bl_aux_params mechanism (it's 3 SoC >> vendors, more than 3 SoCs, but the parameter code is shared at the >> vendor level), and one of my concerns here is trying to limit >> disruption to those existing setups. I don't have enough data to say >> what the "typical" boot flow among all TF-A devices in existence is, >> but at least for the millions of Chromebooks out there it is coreboot >> + TF-A, not U-Boot. >> > My bad! I candidly inferred from Chromebook reference in U-Boot and > Simon's VBE proposal that U-Boot was used. > This is a bit off-topic, but it is somewhat in the reverse. U-Boot's verified boot (2014 I think) uses the crypto from Chromium OS (which I think came from Android at some point). VBE is an attempt to provide a standard boot flow for U-Boot devices and is again heavily influenced by Chromium OS. U-Boot does ship on most Chromebooks (oddly enough, not the ARM ones!) but just as an alternate bootloader and is not used in the verified-boot flow. I won't get into the details of how the Chroimum OS replacement came about, as that is way off topic! To me, bl_aux_params is a pretty limited. I am looking here: https://github.com/ARM-software/arm-trusted-firmware/blob/master/include/export/lib/bl_aux_params/bl_aux_params_exp.h Is that the right place? There is not a huge amount of code in TF-A that uses it (mediatek and rockchip?) so I don't see a problem with updating it, given the benefits of interoperability. In fact, having taken a bit of a look, my view is that U-Boot's bloblist is a much better starting point for this effort: - fuller implementation with more features - has comments / more documentation - easily supports everything in one block instead of a linked list (easier to allocate) - avoids 64-bit tags/size which seem quite unnecessary - has unit tests plus some minor points I won't mention. So I think it is worth the pain to switch TF-A over. Perhaps we can gather the requirements that are needed for this? So far I am aware of: - devicetree bob tag - vendor-private tag area - ability to link to another bloblist (do we really need this?) Regards, Simon _______________________________________________ boot-architecture mailing list boot-architecture@lists.linaro.org https://lists.linaro.org/mailman/listinfo/boot-architecture
