Allow accessing supported timer frequencies with a dedicated API.
This API needs to be implemented per platform and is available with
the feature periph_timer_query_freqs.
Whenever the module of a peripheral driver, i.e., periph_* should be used, the corresponding entry in the
FEATURES_REQUIRED should be added. Conflicts between these modules are
only checked when this entry is present.
Some DEFAULT_MODULEs in tree have dependencies of their own. This is
usually done for aliases of init modules, and do not have dependencies
themselves.
This adds the final stage to dependency resolutions where DEFAULT_MODULEs
dependencies MAY be included. These included modules MUST NOT have
dependencies themselves.
This allows for modules to disable DEFAULT_MODULEs during dependencies
resolution independent of the inclusion order.
auto_init and periph_init modules are moved to this outer-loop, allowing
therefore for modules to disable them during the dependency resolution
Goals:
- Untangle dependency resolution and feature checking for better maintainability
- Improve performance of "make info-boards-supported"
Changes:
- Makefile.dep
- Dropped handling of default modules and recursion
- Now only dependencies of the current set of used modules and pkgs are
added
==> External recursion is needed to catch transient dependencies
- Changed Makefile.features:
- Dropped checking of provided features
- Dropped populating FEATURES_USED with provided features that are required
or optional
- Dropped populating FEATURES_MISSING with required but not provided
features
- Dropped adding modules implementing used features to USE_MODULE
==> This now only populates FEATURES_PROVIDED, nothing more
- Added makefiles/features_check.inc.mk:
- This performs the population of FEATURES_USED and FEATURES_MISSING now
- Added makefiles/features_modules.inc.mk:
- This performs now the addition of modules implementing used features
- Added makefiles/dependency_resolution.inc.mk:
- This now performs the recursion required to catch transient dependencies
- Also the feature check is performed recursively to handle also required
and optional features of the transient dependencies
- DEFAULT_MODULES are added repeatedly to allow it to be extended based on
used features and modules
==> This allows modules to have optional dependencies, as these
dependencies can be blacklisted
- Use simply expanded variables instead of recursively expended variables
(`foo := $(bar)` instead `foo = $(bar)`) for internal variables during feature
resolution. This improves performance significantly for
`make info-boards-supported`.
- Reduce dependency resolution steps in `make info-boards-supported`
- Globally resolve dependencies without any features (including arch)
provided
==> This results in the common subset of feature requirements and modules
used
- But for individual boards additional modules might be used on top due
to architecture specific dependencies or optional features
- Boards not supporting this subset of commonly required features are not
supported, so no additional dependency resolution is needed for them
- For each board supporting the common set of requirements a complete
dependency resolution is still needed to also catch architecture specific
hacks
- But this resolution is seeded with the common set of dependencies to
speed this up
