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>

1 files changed, 2 insertions, 0 deletions

diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
index 50878dc025a5..25cf0c2c0c79 100644
--- a/scripts/kconfig/symbol.c
+++ b/scripts/kconfig/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,