[U-Boot] [PATCH v2 2/2] cmd: Add 'bcb' command to read/modify/write BCB fields

[Eugeniu Rosca]

Hi Simon
cc: Sam, Igor, feel free to correct/augment anything of below

On Sat, May 18, 2019 at 10:33:02AM -0600, Simon Glass wrote:
> Hi Eugeniu,
> 
> On Fri, 17 May 2019 at 08:46, Eugeniu Rosca <erosca at de.adit-jv.com> wrote:
> >
> > 'Bootloader Control Block' (BCB) is a well established term/acronym in
> > the Android namespace which refers to a location in a dedicated raw
> > (i.e. FS-unaware) flash (e.g. eMMC) partition, usually called "misc",
> > which is used as media for exchanging messages between Android userspace
> > (particularly recovery [1]) and an Android-capable bootloader.
> >
[..]
> 
> Where is this documented? Perhaps it should go in README.avb2?

README.avb2 is solely about the "verified/secure" booting of Android,
while the 'bcb' command proposed in this patch can be useful both in
verified boot scenarios (e.g. full-featured U-Boot builds), as well
as in non-avb ones (e.g. development, PoC, demos, custom
configurations). Thus, I think that README.avb2 is not the best
place for 'bcb'.

More generally, as somebody who uses git as an extension of himself, I
am quite happy with commit-only documentation. OTOH, for those who
receive U-Boot in tarballs or expect source-level docs/tutorials, I
agree that having the 'bcb' described in a README might be helpful.

I can identify two Android-dedicated README files, but none of them
seems to be suitable for the new command:
 - doc/README.android-fastboot
 - doc/README.avb2

Igor, Sam, what's your view on the above? Would you suggest creating
a doc/README.android-bcb or there is a more elegant solution to it?

> 
> Should it default to enabled if avb is used?

I think at this specific moment in time, 'bcb' is orthogonal (meaning it
is neither a direct, nor a reverse dependency) to any other Android
feature in U-Boot. This could be re-assessed, if platform maintainers
start to rely on 'bcb' in their U-Boot environments on regular basis.

-- 
Best Regards,
Eugeniu.