On Wed, Jul 04, 2018 at 10:57:16AM +0100, Grant Likely wrote: > > It would be reasonable for one or more LUNs to be dedicated to firmware > > which gets us out of the shared ESP scenario and the OS can do what it > > wants with the GPT in the 'general-purpose' LUN. > > Actually reading the UFS spec helps a lot! :-) > > https://www.jedec.org/system/files/docs/JESD220D.pdf > > Right, so UFS seems to support up to 128 partitions, or LUNs. It appears > that each LUN can be treated as an separate block device. Up to 2 can be > configured as boot LUNs (boot A and B), and one can be an RPMB. Size of > the boot and RPMB regions is not fixed, so as much space as needed for > firmware could be allocated. > > I'm going to rework the text to talk about shared storage in terms of a > single device or LUN. If firmware is contained in a separate LUN (one of > the boot partitions), then it is outside the scope of EBBR.
Thanks for summary! > > It would be possible for separate LUNs to be allocated for each OS > partition, but I don't think EBBR needs to tackle that. In that scenario > each LUN would probably still need to have a GPT partition table, (or at > the very least the LUN containing the ESP would). Each LUN would show up > as a separate block device in Linux (I think). Given the "I think" here is a quick grep over the Dragonboard 820C boot logs to confirm that... you will see most of the LUNs (those that aren't special) being allocated their own block device: https://gist.github.com/daniel-thompson/45275d0667bf93581703ad0dbc867a29 > I've also learned that removable UFS cards exist. If the platform > strictly requires a UFS boot partition on the removable media, then that > could be an issue for the firmware for multiple platforms on a single > card use case. We could mitigate this by recommending a filesystem be > used on the boot partition. I'm concerned about overreaching though. We are certainly approaching aspirational with things like that ;-) . No objections on my side but I'd like it to be very clearly separated from level 0 requirements. Daniel. _______________________________________________ boot-architecture mailing list boot-architecture@lists.linaro.org https://lists.linaro.org/mailman/listinfo/boot-architecture
