Config fragments

[Simon Glass]

Hi,

Up until 2023.04 it has been possible to build all the defconfigs but
with 2023.07 that changed. Tom mentioned this to me recently.

Up until 2023.04 we can enumerate all the board configs that can be
built. We can build any of them using a single name and a single
defconfig. The boards.cfg file which buildman creates contains a full
list of things that can be built.

>From 2023.07 this changes and we now have random .config files
sprinkled about the place. I say random because they are not connected
to anything. For example, here is
board/ti/am62x/MAINTAINERS:

AM62x BOARD
M: Dave Gerlach <d-gerlach at ti.com>
M: Tom Rini <trini at konsulko.com>
S: Maintained
F: board/ti/am62x/
F: include/configs/am62x_evm.h
F: configs/am62x_evm_r5_defconfig
F: configs/am62x_evm_a53_defconfig

BEAGLEPLAY BOARD
M:     Nishanth Menon <nm at ti.com>
M:     Robert Nelson <robertcnelson at gmail.com>
M:     Tom Rini <trini at konsulko.com>
S:     Maintained
N:     beagleplay

In most cases the MAINTAINERS file tells us about each board and until
[1] I had assumed that was the case. With that patch reverted, these
are the only 'orphaned' MAINTAINERS entries (buildman
--maintainer-check):

WARNING: orphaned defconfig in board/armltd/vexpress64/MAINTAINERS
ending at line 8
WARNING: orphaned defconfig in board/google/veyron/MAINTAINERS ending at line 44
WARNING: orphaned defconfig in
board/mikrotik/crs3xx-98dx3236/MAINTAINERS ending at line 7
WARNING: orphaned defconfig in board/st/common/MAINTAINERS ending at line 6
WARNING: orphaned defconfig in board/ti/am62x/MAINTAINERS ending at line 15

But Tom advised me that MAINTAINERS is not intended for this purpose,
so the check has been dropped. I am not suggesting we bring it back,
necessarily, but if we did, we could use it to specify the .config and
defconfig files which are used by each board.

*Failing that*, I suggest a new 'name.brd' file in the board directory
to contain this information, e.g.

# Contents of board/ti/am62x/beagleplay.brd:
beagleplay-r5: am62x_evm_r5_defconfig beagleplay_r5.config
beagleplay-a53: am62x_evm_a53_defconfig beagleplay_a53.config

This could be parsed by buildman and other tools, to produce a list of
available boards and to build each using a single name (e.g. make
beagleplay-r5_defconfig)

What do people think?

Regards,
Simon

[1] https://patchwork.ozlabs.org/project/uboot/patch/20230803185144.1760729-2-sjg@chromium.org/