[coreboot] using overlayfs to have several coreboot dev envs

[ron minnich]

I think the build system could stand some cleanup so that external build
would not be needed and building many mainboards in one tree would be easy.

LinuxBIOS V1 allowed you to build any number of mainboards in one source
tree -- it was initially modeled on the BSD
build system. objects were placed in a tree that followed the mainboard
naming conventions.

We might want to think about getting back to multi-mainboard builds in one
tree. Requiring people to use external build or overlayfs is kind of a
burden.

It might be as simple as rewiring the build/ naming to something like
build/vendor/mainboard

There's also no fundamental reason for using the name .config other than
tradition. We could, for example, create
build/vendor/mainboard/config and use that.

Then it's as simple as saying something like
MAINBOARD=vendor/mainboard make
and letting the build system figure out the rest.

You could also
export MAINBOARD=vendor/mainboard
when you are doing lots of builds for one mainboard.

I personally would find this extremely useful. Having to bounce around
between the various riscv boards has been
inconvenient at best.

I'm willing to do the work if no one objects.





On Sun, Nov 20, 2016 at 10:43 AM Trammell Hudson <hudson at trmm.net> wrote:

> On Sun, Nov 13, 2016 at 03:34:49PM -0500, Charlotte Plusplus wrote:
> > With the cross compiling tool chain, coreboot takes 1G. If you are a bit
> > short on space, or if you want to save writes to your SSD, instead of
> > having multiple copies of the coreboot source folder, I have found out
> > overlayfs is very practical. [...]
>
> An alternative is to use the "external build" option if you're building
> for multiple targets with different .config files for each.  It isn't
> quite as simple as the Linux kernel's kbuild O= syntax, but works
> fairly well.
>
> I have three main builds that I'm alternating between (x230, chell and
> qemu)
> so I've created three directories and have a .config for each stored in
> a top-level config directory.  From the coreboot directory I can modify
> the configs and build them independently:
>
>         make obj=./x230 DOTCONFIG=./config/x230 menuconfig
>         make obj=./x230 DOTCONFIG=./config/x230 -j 8
>
> The builds will share the same cross build tree, so the actual build
> output is only 64M per configuration.
>
> Also note that any paths to external files like bzImage and initrd in
> each buld's .config are relative to the coreboot tree, not the output
> directory.
>
> --
> Trammell
>
> --
> coreboot mailing list: coreboot at coreboot.org
> https://www.coreboot.org/mailman/listinfo/coreboot
>
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