Add support for user-defined Python preprocessor functions

Allow preprocessor functions to be defined in Python by putting a module
called 'kconfigfunctions' into sys.path. Internally, this simply adds
the functions to the predefined functions in Kconfig._functions.

User-defined Python functions make it simple to integrate information
from existing Python tools into Kconfig, e.g. to have Kconfig symbols
depend on hardware information stored in some other format. This might
be used to get device tree information into Kconfig in Zephyr.

Piggyback module docstring documentation for some extensions that were
previously only mentioned in the README.

2 files changed, 25 insertions, 0 deletions

diff --git a/tests/Kuserfunctions b/tests/Kuserfunctions
new file mode 100644
index 0000000..99ef23a
--- /dev/null
+++ b/tests/Kuserfunctions
@@ -0,0 +1,11 @@
+add-zero  = $(add)
+add-one   = $(add,1)
+add-three = $(add,1,-1,2,1)
+
+one-zero = $(one)
+one-one = $(one,foo bar)
+one-two = $(one,foo bar,baz)
+
+one-or-more-zero = $(one-or-more)
+one-or-more-one = $(one-or-more,foo)
+one-or-more-three = $(one-or-more,foo,bar,baz)
diff --git a/tests/kconfigfunctions.py b/tests/kconfigfunctions.py
new file mode 100644
index 0000000..e760468
--- /dev/null
+++ b/tests/kconfigfunctions.py
@@ -0,0 +1,14 @@
+def add(kconf, name, *args):
+    return str(sum(map(int, args)))
+
+def one(kconf, name, s):
+    return name + 2*s
+
+def one_or_more(kconf, name, arg, *args):
+    return arg + " + " + ",".join(args)
+
+functions = {
+    "add":         (add,         0, None),
+    "one":         (one,         1,    1),
+    "one-or-more": (one_or_more, 1, None),
+}