kconfig: fix submenu rendering of negative dependencies

The Kconfig frontend should render options that depend on a
previous option in the submenu of that previous option. But
currently, this breaks for negative dependencies. For example,
option FOO may be rendered in the submenu of option BAR, despite
FOO actually depending on !BAR.

Let's fix this ironic rendering by modifying Kconfig to explicitly
check negative dependencies.

I've only tested locally on x86, but as far as I can tell, this only
changes how 2 options are rendered in the menu:
1. NTFS3_FS, no longer in the NTFS_FS submenu, and
2. MTD_BLOCK_RO, no longer in the MTD_BLOCK submenu.

Tested-by: Nathan Chancellor <nathan@kernel.org>
Reported-by: Xi Ruoyao <xry111@xry111.site>
Closes: https://lore.kernel.org/all/cbe95c15d2760f6fce8eaf207c969ce8fd3703aa.camel@xry111.site/
Assisted-by: Claude:claude-4.8-opus
Signed-off-by: Julian Braha <julianbraha@gmail.com>
Link: https://patch.msgid.link/20260801145238.2140291-1-julianbraha@gmail.com
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Tested-by: Nicolas Schier <nsc@kernel.org>
Signed-off-by: Nicolas Schier <nsc@kernel.org>

1 files changed, 33 insertions, 0 deletions

diff --git a/scripts/kconfig/expr.c b/scripts/kconfig/expr.c
index 16f92c4a775a..2b91d16bf14f 100644
--- a/scripts/kconfig/expr.c
+++ b/scripts/kconfig/expr.c
@@ -738,6 +738,39 @@ bool expr_contains_symbol(struct expr *dep, struct symbol *sym)
 	return false;
 }
 
+/*
+ * Check if the expression references 'sym' in a way that is satisfiable
+ * with 'sym' disabled, e.g.'sym!=y'.
+ *
+ * Expects that expr_transform() was already called on 'expr'.
+ */
+bool expr_contains_symbol_negated(struct expr *dep, struct symbol *sym)
+{
+	if (!dep)
+		return false;
+
+	switch (dep->type) {
+	case E_AND:
+	case E_OR:
+		return expr_contains_symbol_negated(dep->left.expr, sym) ||
+		       expr_contains_symbol_negated(dep->right.expr, sym);
+	case E_NOT:
+		return dep->left.expr->type == E_SYMBOL &&
+		       dep->left.expr->left.sym == sym;
+	case E_EQUAL:
+		/* sym=n */
+		return dep->left.sym == sym && dep->right.sym == &symbol_no;
+	case E_UNEQUAL:
+		/* sym!=y, sym!=m */
+		return dep->left.sym == sym &&
+		       (dep->right.sym == &symbol_yes ||
+			dep->right.sym == &symbol_mod);
+	default:
+		break;
+	}
+	return false;
+}
+
 bool expr_depends_symbol(struct expr *dep, struct symbol *sym)
 {
 	if (!dep)