kconfig: simplify select-with-unmet-direct-dependency warning

This is an attempt to simplify the expressing printed by kconfig when a
symbol is selected but still has direct unmet dependency.

First, the symbol reverse dependency is split in sub-expression. Then,
each sub-expression is checked to ensure that it does not contains the
unmet dependency. This removes the false-positive symbols and fixed symbol
which already have the correct dependency. Finally, only the symbol
responsible of the "select" is printed, instead of its full dependency tree.

CC: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Arnaud Lacombe <lacombar@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>

2 files changed, 47 insertions, 1 deletions

diff --git a/scripts/kconfig/expr.c b/scripts/kconfig/expr.c
index 330e7c0048a8..65531a7f28a8 100644
--- a/scripts/kconfig/expr.c
+++ b/scripts/kconfig/expr.c
@@ -1013,6 +1013,48 @@ int expr_compare_type(enum expr_type t1, enum expr_type t2)
 #endif
 }
 
+static inline struct expr *
+expr_get_leftmost_symbol(const struct expr *e)
+{
+
+        if (e == NULL)
+                return NULL;
+
+        while (e->type != E_SYMBOL)
+                e = e->left.expr;
+
+        return expr_copy(e);
+}
+
+/*
+ * Given expression `e1' and `e2', returns the leaf of the longest
+ * sub-expression of `e1' not containing 'e2.
+ */
+struct expr *expr_simplify_unmet_dep(struct expr *e1, struct expr *e2)
+{
+        struct expr *ret;
+
+        switch (e1->type) {
+        case E_OR:
+                return expr_alloc_and(
+                    expr_simplify_unmet_dep(e1->left.expr, e2),
+                    expr_simplify_unmet_dep(e1->right.expr, e2));
+        case E_AND: {
+                struct expr *e;
+                e = expr_alloc_and(expr_copy(e1), expr_copy(e2));
+                e = expr_eliminate_dups(e);
+                ret = (!expr_eq(e, e1)) ? e1 : NULL;
+                expr_free(e);
+                break;
+                }
+        default:
+                ret = e1;
+                break;
+        }
+
+        return expr_get_leftmost_symbol(ret);
+}
+
 void expr_print(struct expr *e, void (*fn)(void *, struct symbol *, const char *), void *data, int prevtoken)
 {
         if (!e) {
diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
index 60830ce4a0a9..fa52e6f44ac4 100644
--- a/scripts/kconfig/symbol.c
+++ b/scripts/kconfig/symbol.c
@@ -351,12 +351,16 @@ void sym_calc_value(struct symbol *sym)
                         }
                 calc_newval:
                         if (sym->dir_dep.tri == no && sym->rev_dep.tri != no) {
+                                struct expr *e;
+                                e = expr_simplify_unmet_dep(sym->rev_dep.expr,
+                                    sym->dir_dep.expr);
                                 fprintf(stderr, "warning: (");
-                                expr_fprint(sym->rev_dep.expr, stderr);
+                                expr_fprint(e, stderr);
                                 fprintf(stderr, ") selects %s which has unmet direct dependencies (",
                                         sym->name);
                                 expr_fprint(sym->dir_dep.expr, stderr);
                                 fprintf(stderr, ")\n");
+                                expr_free(e);
                         }
                         newval.tri = EXPR_OR(newval.tri, sym->rev_dep.tri);
                 }