Up until now, Zephyr has patched Kconfig to use the last 'default' with
a satisfied condition, instead of the first one. I'm not sure why the
patch was added (it predates Kconfiglib), but I suspect it's related to
Kconfig.defconfig files.
There are at least three problems with the patch:
1. It's inconsistent with how Kconfig works in other projects, which
might confuse newcomers.
2. Due to oversights, earlier 'range' properties are still preferred,
as well as earlier 'default' properties on choices.
In addition to being inconsistent, this makes it impossible to
override 'range' properties and choice 'default' properties if the
base definition of the symbol/choice already has 'range'/'default'
properties.
I've seen errors caused by the inconsistency, and I suspect there
are more.
3. A fork of Kconfiglib that adds the patch needs to be maintained.
Get rid of the patch and go back to standard Kconfig behavior, as
follows:
1. Include the Kconfig.defconfig files first instead of last in
Kconfig.zephyr.
2. Include boards/Kconfig and arch/<arch>/Kconfig first instead of
last in arch/Kconfig.
3. Include arch/<arch>/soc/*/Kconfig first instead of last in
arch/<arch>/Kconfig.
4. Swap a few other 'source's to preserve behavior for some scattered
symbols with multiple definitions.
Swap 'source's in some no-op cases too, where it might match the
intent.
5. Reverse the defaults on symbol definitions that have more than one
default.
Skip defaults that are mutually exclusive, e.g. where each default
has an 'if <some board>' condition. They are already safe.
6. Remove the prefer-later-defaults patch from Kconfiglib.
Testing was done with a Python script that lists all Kconfig
symbols/choices with multiple defaults, along with a whitelist of fixed
symbols. The script also verifies that there are no "unreachable"
defaults hidden by defaults without conditions
As an additional test, zephyr/.config was generated before and after the
change for several samples and checked to be identical (after sorting).
This commit includes some default-related cleanups as well:
- Simplify some symbol definitions, e.g. where a default has 'if FOO'
when the symbol already has 'depends on FOO'.
- Remove some redundant 'default ""' for string symbols. This is the
implicit default.
Piggyback fixes for swapped ranges on BT_L2CAP_RX_MTU and
BT_L2CAP_TX_MTU (caused by confusing inconsistency).
Piggyback some fixes for style nits too, e.g. unindented help texts.
Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>
ec3eff57e0