Chromium CL:1365116

My proposal is to re-purpose partition #8 to be the diagnostics partition. In the base Disk Format (http://www.chromium.org/chromium-os/chromiumos-design-docs/disk-format) layout, it is designated as "16MiB for OEM customization". As far as I can tell, it is currently not used in Wilco.

Wilco partitions would be:

11  RWFW (firmware)
6   KERN-C
7   ROOTC
9   reserved
10  reserved
2   KERN-A
4   KERN-B

8   DIAGNOSTICS fat32 16MiB 
    (instead of: 16MiB for OEM customization ext4)

12  EFI-SYSTEM legacy BIOSes
5   4096 Mib rootf for Wilco
3   2300 Mib rootfs for Wilco


Does that seem reasonable?

How do we know that OEM customization is not used? I suppose the people on this bug might know?

Not sure about user land program. but at least in factory process, this partition is empty and we never write anything to it.

Project: chromiumos/overlays/board-overlays
Branch: master

commit 411c409f29e9b7c9774b21c1137c0a22f2c2abf9
Author: Georges Winkenbach <gwink@chromium.org>
Date:   Thu Dec 06 09:25:32 2018

    Add a diagnostics partition
    
    For Wilco: repurposed partition #9 (reserved) to be a 1 Mib vfat
    data partition labeled DIAGNOSTICS.
    
    BUG=b:120548896
    TEST=Build a new image, flash sarien board via USB flash, verified that
         1 Mib DIAGNOSTICS partition is present.
    
    Change-Id: Ifa8d7335c0393612ece545398b4f76f02d09ee20
    Reviewed-on: https://chromium-review.googlesource.com/1365116
    Commit-Ready: Georges Winkenbach <gwink@chromium.org>
    Tested-by: Georges Winkenbach <gwink@chromium.org>
    Reviewed-by: Simon Glass <sjg@chromium.org>

M       overlay-sarien/scripts/disk_layout.json

https://chromium-review.googlesource.com/1365116