[OE-core] how can i tell which default kernel config OE started with?

[Bruce Ashfield]

On Tue, May 3, 2016 at 11:13 AM, Robert P. J. Day <rpjday at crashcourse.ca>
wrote:

> On Tue, 3 May 2016, Bruce Ashfield wrote:
>
> > If you are not supplying a defconfig, and are inheriting the
> > standard kernel options, then yes, you'd be getting those fragments
> > as well.
>
>   ah, this actually leads me into my next question -- what is magic
> about a "defconfig" file that changes the normal processing?\
>

It's the existing kernel.bbclass mechanism, and a well known convention
used in the kernel. So it is used to trigger the core kernel configuration,
and when I was extending things for kernel fragments it was similarly used
as a sentinel value.


>
>   in the YP kernel dev manual, section 2.2.3, one reads:
>
> "If you have a complete, working Linux kernel .config file you want to
> use for the configuration, as before, copy that file to the
> appropriate ${PN} directory in your layer's recipes-kernel/linux
> directory, and rename the copied file to "defconfig". Then, add the
> following lines to the linux-yocto .bbappend file in your layer:
>
>      FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
>      SRC_URI += "file://defconfig"
>
> so the idea here is that a "defconfig" file is, in some sense, a
> "complete, working" config file that requires no extra processing, is
> that correct? does that mean that if you explicitly use a SRC_URI
> "defconfig" reference, all that extra normal processing won't be done?
>

Nope. Everything is still processed, the kernel version you are using,
patches, etc, all make a difference to what ends up in the .config. The
phrasing there is to point out that it is what the mainline kernel considers
a defconfig, and it is typically a complete configuration of the kernel
(that
is expected to boot your target).


>
>   also, that same section in the YP manual is slightly confusing -- if
> your SRC_URI refers to a defconfig file *and* some .cfg fragment
> files, is it necessarily true that the defconfig file is consulted
> first (no matter where it shows up in SRC_URI), after which all .cfg
> files are applied on top of that in order? it's not entirely clear
> from the manual if that's what happens.
>

Yep. If you mix the two techniques, the defconfig is first (and taken
as the settings), and then fragments are applied on top.

Note: There are some changes in defconfig that are related to features
I'm doing for the fall 2.2 release, but nothing that changes the basic
processing (so compatibility is maintained).

Bruce


>
>   predictably, a couple more kernel config questions coming ...
>
> rday
>
> --
>
> ========================================================================
> Robert P. J. Day                                 Ottawa, Ontario, CANADA
>                         http://crashcourse.ca
>
> Twitter:                                       http://twitter.com/rpjday
> LinkedIn:                               http://ca.linkedin.com/in/rpjday
> ========================================================================
>
>


-- 
"Thou shalt not follow the NULL pointer, for chaos and madness await thee
at its end"
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