Error in Common Ubiquiti Procedures for XM AirMax devices?

[Russell Senior]

On Sun, Nov 7, 2021 at 5:07 PM Joe Ayers <joe at ayerscasa.com> wrote:
>
> Openwrt Github commit notes, Forum posts, and Documentation, refer to:
>
> "The mtd partitions layout for XM-type devices changed from AirOS v5.5
> to AirOS v5.6. Before installing OpenWrt, downgrade first to AirOS
> 5.5."
>
> reference:  https://openwrt.org/toh/ubiquiti/common
>
> While the documentation is a path to succeed loading openwrt firmware,
> this commit fixed the soft-brick issue (soft-brick meaning tftp
> recovery with serial cable is possible):
> https://github.com/openwrt/openwrt/commit/076d58d3440f382c536ea8874f58b0df23c263bc

I went looking and found that this commit is in all releases starting
with 17.01.x, but not in v15.05.1

>
> It is a key message, that openwrt firmware after this commit, will no
> longer soft-brick the device, not communicated.
>
> The key misunderstanding is around the root cause due to Ubiquiti
> tightening up uboot to further check partition sizes.   The root cause
> was identified as a bad openwrt size definition that older versions of
> uboot accepted, without end user awareness.
>
> The reason I raise this issue is due to users in the
> https//www.arednmesh.org community struggling to downgrade to AirOX
> v5.5, and we spend time working with them only to do tftp
> "hold-reset-button" firmware loads to succeed as quickest path.
>
> Note, however, there are still issues where newer Uboot versions
> expect images to have particular naming conventions, which are also
> addressed in later fixes:
>
> https://github.com/openwrt/openwrt/commit/6009b3fd586a1fd91400074080afb9545c6cf7e2

This one is in releases starting with v19.07.x, but not in v18.06.x and earlier.