Re: [docs] [PATCH] ref-manual/variables.rst: document KERNEL_EXTRA_FEATURES

["Antonin Godard" <antonin.godard@bootlin.com>]

Hi,

On Mon Jun 2, 2025 at 5:41 PM CEST, Alper Ak via lists.yoctoproject.org wrote:
> Since the KERNEL_FEATURES variable is handled in kernel-yocto.bbclass
> and KERNEL_EXTRA_FEATURES is usually appended to it, I wanted to
> emphasize that this class should be used.
> That's why I made a connection between them and assumed that they were
> complementary. Apparently I misinterpreted it.  As you said, it always
> in final/leaf recipes and not .inc files or classes.
>
>> > +      such as Poky may set a default value using a soft assignment (``?=``).
>> Does it? I don't see it, only an :append is used.
>
> "bitbake-getvar KERNEL_EXTRA_FEATURES" shows that it is
> appended(:append) in poky.conf but somehow I missed it and wrote soft

I don't think we should document variable default values based on poky.conf, as
Poky is only a reference distro after all.

What bothers me is that KERNEL_EXTRA_FEATURES does not have any default value in
the kernel-yocto class. And I don't see the added value compared to
KERNEL_FEATURES, since what happens in the end is always:

  KERNEL_FEATURES:append = " ${KERNEL_EXTRA_FEATURES}"

Meaning users are fine modifying the KERNEL_FEATURES variable directly, I
believe. What do you think?

Antonin

-- 
Antonin Godard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com