kbuild: document recursive dependency limitation / resolution

Recursive dependency issues with kconfig are unavoidable due to
some limitations with kconfig, since these issues are recurring
provide a hint to the user how they can resolve these dependency
issues and also document why such limitation exists.

While at it also document a bit of future prospects of ways to
enhance Kconfig, including providing formal semantics and evaluation
of use of a SAT solver. If you're interested in this work or prospects
of it check out the kconfig-sat project wiki [0] and mailing list [1].

[0] http://kernelnewbies.org/KernelProjects/kconfig-sat
[1] https://groups.google.com/d/forum/kconfig-sat

Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: James Bottomley <jbottomley@odin.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Paul Bolle <pebolle@tiscali.nl>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Takashi Iwai <tiwai@suse.de>
Cc: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mate Soos <soos.mate@gmail.com>
Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
Signed-off-by: Michal Marek <mmarek@suse.com>
Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>

diff --git a/config/symbol.c b/config/symbol.c
index 50878dc025a5746d51316c6f1bd4c1e1b8a41707..25cf0c2c0c795ac36658a2bfa061c9f3383630a1 100644 (file)
--- a/config/symbol.c
+++ b/config/symbol.c
@@ -1116,6 +1116,8 @@ static void sym_check_print_recursive(struct symbol *last_sym)
                if (stack->sym == last_sym)
                        fprintf(stderr, "%s:%d:error: recursive dependency detected!\n",
                                prop->file->name, prop->lineno);
+                       fprintf(stderr, "For a resolution refer to Documentation/kbuild/kconfig-language.txt\n");
+                       fprintf(stderr, "subsection \"Kconfig recursive dependency limitations\"\n");
                if (stack->expr) {
                        fprintf(stderr, "%s:%d:\tsymbol %s %s value contains %s\n",
                                prop->file->name, prop->lineno,