Hi Simon, We did discuss this in OSFC but perhaps you forgot. The discussion was based on the mail here [0].
On Tue, 5 Dec 2023 at 02:52, Simon Glass <s...@chromium.org> wrote: > > Hi Raymond, > > On Mon, 4 Dec 2023 at 12:25, Raymond Mao <raymond....@linaro.org> wrote: > > > > Hi Simon, > > > > When `OF_BOARD` is defined, the FDT should be from one of the > > board-specific mechanisms: > > 1. FDT from a bloblist via boot args > > 2. FDT in memory > > I don't think we need a new build option to distinguish these two, since it > > can be done in runtime by checking whether the boot args follow the FW > > Handoff spec conventions and the FDT exists in the bloblist. > > No, I would really like this to be deterministic, so we can fail if > something goes wrong. The bloblist should be 'declared' as the way to > boot, for a board. We *are* deterministic. I am just going to repeat what we discussed in OSFC for completeness. OF_BLOBLIST makes little sense because we are not going to add a Kconfig per blolblist entry. I haven't looked at what the patch does yet but the idea was really simple. - Under OF_BOARD (which can arguably be renamed to OF_PREVIOUS_STAGE or something like that) if CONFIG_BLOB is enabled we scan for a bloblist - If CONFIG_BLOB is enabled but no bloblist is provided we fail the boot - If CONFIG_BLOB is not enabled we do what we did up to now, maybe with a message that this is going to be obsoleted once enough boards migrate to a bloblist IOW if support for a bloblist is enabled we expect to find one from the previous bootloader. I've lost count of how many times I repeated this, but here it goes again The device tree can come - From u-boot - From a previous stage loader *somehow* (eg. passed on a bloblist, passed on a register, read from an EEPROM etc) We should keep that distinction and create subcategories for the 'comes from a previous stage loader', rather than adding arbitrary config options which only confuse people Regards /Ilias > > If in the future all boards a reusing bloblist for this feature, then > sure, we can drop it. But we have things like rpi which do their own > thing. > > > If it fulfills the above conditions, we can take the FDT from bloblist, > > otherwise from the predefined memory address. > > This is fully backward compatible without adding a new build option. > > Again, we need to obtain the FDT from the bloblist if and only if the > board requires it. It creates a lot of confusion to have it as an > optional feature, when we know which way it should be. > > Ultimately OF_BOARD should go away. We just need to push bloblist to > other projects and closed-source firmware as the correct way to pass a > DT. > > Regards, > Simon > [.] [0] https://lore.kernel.org/u-boot/capnjgz0sqvyj_drleqrp21zpycco3hop-ryd+nkjma0bvyp...@mail.gmail.com/
