1 # Cumulative Kconfig recursive issue
2 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
3 #
4 # Test with:
5 #
6 # make KBUILD_KCONFIG=Documentation/kbuild/Kco
7 #
8 # The recursive limitations with Kconfig has s
9 # kconfig semantics which are documented here.
10 # of the recursive limitation is that drivers
11 # drivers if they share a common core requirem
12 # annotate those requirements, ie, some driver
13 # use "select". For instance it means if a dri
14 # core requirement, and one uses "select" whil
15 # annotate this, all features that driver A se
16 # driver B.
17 #
18 # A perhaps not so obvious implication of this
19 # core requirements are not carefully synced,
20 # they select or depend on end up becoming sha
21 # negated by other drivers.
22 #
23 # The example provided in Documentation/kbuild
24 # describes a simple driver core layout of exa
25 # have. Let's assume we have some CORE functio
26 # series of bells and whistles it desires to i
27 # it only supports bells at this time: CORE_BE
28 # CORE_BELL_A has some advanced feature CORE_B
29 # CORE_BELL_A then CORE_BELL_A ends up becomin
30 # other bells in the system cannot negate. The
31 # due to the disjoint use of semantics on expr
32 # with CORE, one uses "depends on" while the o
33 # more important reason is that kconfig does n
34 # under 'select' for a symbol, when such symbo
35 # as mandatory required symbols. For more deta
36 # of select refer to Documentation/kbuild/Kcon
37 #
38 # To fix this the "depends on CORE" must be ch
39 # "select CORE" must be changed to "depends on
40 #
41 # For an example real world scenario issue ref
42 # "select FW_LOADER" [0], in the end the simpl
43 # problem consisted on matching semantics with
44 #
45 # [0] https://lore.kernel.org/r/1432241149-876
46
47 mainmenu "Simple example to demo cumulative kc
48
49 config CORE
50 tristate
51
52 config CORE_BELL_A
53 tristate
54 depends on CORE
55
56 config CORE_BELL_A_ADVANCED
57 tristate
58 select CORE_BELL_A
59
60 config CORE_BELL_B
61 tristate
62 depends on !CORE_BELL_A
63 select CORE
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