[OE-core] trying to summarize the flexibility in bbappend'ing to kernel recipes

[Christopher Larson]

A bbappend basically concatenates to the recipe in bitgbake, so it can do
anything the recipe can do, within reason, so yes, use of filespath and
overrides works the way it's always worked with recipes.

On Wed, Feb 24, 2016 at 3:00 PM Robert P. J. Day <rpjday at crashcourse.ca>
wrote:

>    let's see if i can explain this properly -- i want to enumerate all
> possible ways to .bbappend to a kernel recipe if i have multiple
> target machines and multiple kernel recipes. so let's imagine the
> following scenario -- i grab a layer that has two recipe files for
> two versions of the kernel, *and* i have two target boards. so ...
>
>   * linux-4.0.bb
>   * linux-4.1.bb
>
> and i have two target machines, "mach1" and "mach2", and the combination
> of all of these involves various patches. so what are my possibilities?
>
>    first (as long as i understood chris larson properly), i can define
> two separate .bbappend files:
>
>   * linux-4.0.bbappend
>   * linux-4.1.bbappend
>
> or i can define a single wildcard .bbappend file that covers both:
>
>   * linux-4.%.bbappend
>
> so far, so good.
>
>    next, in these .bbappend files, SRC_URI can refer to any of:
>
>   * .scc files
>   * .patch/.diff files
>   * .cfg files
>
> so each of my two .bbappend files can enumerate a different set
> of files to be applied to that version of the kernel. but wait ...
> there's more.
>
>    in each .bbappend file, i can conditionally include files in the
> SRC_URI, as in:
>
>   * SRC_URI_mach1 += mach1.patch
>
> so depending on the target machine, i can conditionally include
> any of patch files, cfg files or scc files.
>
>    in addition, i can take advantage of FILESEXTRAPATHS, that i once
> wrote up here:
>
>    http://www.crashcourse.ca/wiki/index.php/Poky_bbappend_FILESEXTRAPATHS
>
> so that i have a ridiculous set of possibilities as to which patch
> files will be applied depending on the:
>
>   * architecture
>   * distro
>   * target machine
>
> am i making sense so far? because there will be more coming shortly.
>
> rday
>
>
>
> --
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