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diff --git a/lib/lufa/LUFA/Build/DMBS/DMBS/WritingYourOwnModules.md b/lib/lufa/LUFA/Build/DMBS/DMBS/WritingYourOwnModules.md new file mode 100644 index 0000000000..16df7a53bb --- /dev/null +++ b/lib/lufa/LUFA/Build/DMBS/DMBS/WritingYourOwnModules.md @@ -0,0 +1,95 @@ +DMBS - Dean's Makefile Build System +=================================== + + +Writing Your Own Modules +------------------------ + +A DMBS module consists of the several boilerplate sections, explained below. + +## The DMBS module hooks + +Your module needs to advertise to DMBS its name, its makefile targets, the +required and optional variables, and the variables and macros the module +provides for use elsewhere. This is achieved with the following section: + + DMBS_BUILD_MODULES += EXAMPLE + DMBS_BUILD_TARGETS += example-target another-target + DMBS_BUILD_MANDATORY_VARS += MANDATORY_NAME ALSO_MANDATORY + DMBS_BUILD_OPTIONAL_VARS += OPTIONAL_NAME ALSO_OPTIONAL + DMBS_BUILD_PROVIDED_VARS += MEANING_OF_LIFE + DMBS_BUILD_PROVIDED_MACROS += STRIP_WHITESPACE + +The example above declares that this module is called `EXAMPLE`, and exposes the +listed targets, variable requirements and provides variables and macros. + +Your module name and provided variable/macro names must be unique, however you +can (and should) re-use variable names where appropriate if they apply to +several modules (such as `ARCH` to specify the project's microcontroller +architecture). Re-using targets is not recommended, but can be used to extend +the dependencies of another module's targets. + +## Importing the CORE module + +Next, your module should always import the DMBS `CORE` module, via the +following: + + # Conditionally import the CORE module of DMBS if it is not already imported + DMBS_MODULE_PATH := $(patsubst %/,%,$(dir $(lastword $(MAKEFILE_LIST)))) + ifeq ($(findstring CORE, $(DMBS_BUILD_MODULES)),) + include $(DMBS_MODULE_PATH)/core.mk + endif + +This ensures that the `make help` target is always available. In addition, the +`CORE` module exposes some [commonly used macros and variables](core.md) to +your module. + +## Setting optional variable's defaults + +If a variable is optional, you should provide a default value. Do this via the +`?=` operator of `make`, which sets a variable's value if it has not yet been +set: + + MY_OPTIONAL_VARIABLE ?= some_default_value + +## Sanity checking user input + +Sanity checks are what make DMBS useful. Where possible, validate user input and +convert generated errors to human-friendly messages. This can be achieved by +enforcing that all the declared module mandatory variables have been set by the +user: + + # Sanity-check values of mandatory user-supplied variables + $(foreach MANDATORY_VAR, $(DMBS_BUILD_MANDATORY_VARS), $(call ERROR_IF_UNSET, $(MANDATORY_VAR))) + +As well as complaining if they are set, but currently empty: + + $(call ERROR_IF_EMPTY, SOME_MANDATORY_VARIABLE) + $(call ERROR_IF_EMPTY, SOME_OPTIONAL_BUT_NON_EMPTY_VARIABLE) + +Or even if they are boolean (`Y` or `N`) variables that have an invalid value: + + $(call ERROR_IF_NONBOOL, SOME_BOOL_VARIABLE) + +## Adding targets + +The meat of a DMBS module is the targets, which are run when the user types +`make {target name}` from the command line. These can be as complex or simple +as you like. See the GNU make manual for information on writing make targets. + + example-target: + echo "Your DMBS module works!" + +## And finally, list the PHONYs + +Important in GNU Make is the concept of phony targets; this special directive +tells make that a given target should never be considered a valid file. Listing +phonies ensures that, for example, if your module had a target called `build`, +it would always run when the user types `make build` from the command line, even +if a file called `build` existed in the user project folder. + +You can list module-internal targets here, as well as mark all public targets +via the module header's `DMBS_BUILD_TARGETS` variable. + + # Phony build targets for this module + .PHONY: $(DMBS_BUILD_TARGETS) some-module-internal-target another-internal-target |