[PATCH 1/2] kconfig: Print reverse dependencies on new line consistently

[Eugeniu Rosca <roscaeugeniu@gmail.com>]

From: Eugeniu Rosca <erosca@de.adit-jv.com>

Commit 1ccb27143360 ("kconfig: make "Selected by:" and "Implied by:"
readable") made an incredible improvement in how reverse dependencies
are perceived by the user, by breaking down the single (often
interminable) expression string into small readable chunks, each of
them displayed on a separate line:

Selected by:
- A & B
- C & (D || E)

Unfortunately, what happens with the non-OR (either E_SYMBOL or E_AND)
expressions is that they don't get a dedicated line:

Selected by: F & G

That's arguably a bug/misbehavior, but it makes the implementation of
something like below more complicated:

Selected by:
- [m] F & G /* where (F & G) evaluates to '=m' */

Adding '[m]', '[y]' or '[ ]' to the left side of each reverse dependency
is subject of a different commit. The purpose of current commit is to
print the 'Selected by:' and 'Implied by:' expressions on a separate
line _consistently_.

An example of change contributed by this commit is seen below.

│ Symbol: NEED_SG_DMA_LENGTH [=y]
│ ...
│   Selected by: IOMMU_DMA [=y] && IOMMU_SUPPORT [=y]

becomes:

│ Symbol: NEED_SG_DMA_LENGTH [=y]
│ ...
│   Selected by:
│   - IOMMU_DMA [=y] && IOMMU_SUPPORT [=y]

This patch has been tested using a custom variant of zconfdump which
prints the reverse dependencies for each config symbol.

Suggested-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Suggested-by: Ulf Magnusson <ulfalizer@gmail.com>
Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
---
 scripts/kconfig/expr.c | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/scripts/kconfig/expr.c b/scripts/kconfig/expr.c
index d45381986ac7..0704bcdf4c78 100644
--- a/scripts/kconfig/expr.c
+++ b/scripts/kconfig/expr.c
@@ -1179,6 +1179,16 @@ struct expr *expr_simplify_unmet_dep(struct expr *e1, struct expr *e2)
 	return expr_get_leftmost_symbol(ret);
 }
 
+static void
+expr_print_newline(struct expr *e,
+		   void (*fn)(void *, struct symbol *, const char *),
+		   void *data,
+		   int prevtoken)
+{
+	fn(data, NULL, "\n  - ");
+	expr_print(e, fn, data, prevtoken);
+}
+
 static void __expr_print(struct expr *e, void (*fn)(void *, struct symbol *, const char *), void *data, int prevtoken, bool revdep)
 {
 	if (!e) {
@@ -1191,7 +1201,10 @@ static void __expr_print(struct expr *e, void (*fn)(void *, struct symbol *, con
 	switch (e->type) {
 	case E_SYMBOL:
 		if (e->left.sym->name)
-			fn(data, e->left.sym, e->left.sym->name);
+			if (revdep)
+				expr_print_newline(e, fn, data, E_OR);
+			else
+				fn(data, e->left.sym, e->left.sym->name);
 		else
 			fn(data, NULL, "<choice>");
 		break;
@@ -1234,19 +1247,19 @@ static void __expr_print(struct expr *e, void (*fn)(void *, struct symbol *, con
 		fn(data, e->right.sym, e->right.sym->name);
 		break;
 	case E_OR:
-		if (revdep && e->left.expr->type != E_OR)
-			fn(data, NULL, "\n  - ");
 		__expr_print(e->left.expr, fn, data, E_OR, revdep);
-		if (revdep)
-			fn(data, NULL, "\n  - ");
-		else
+		if (!revdep)
 			fn(data, NULL, " || ");
 		__expr_print(e->right.expr, fn, data, E_OR, revdep);
 		break;
 	case E_AND:
-		expr_print(e->left.expr, fn, data, E_AND);
-		fn(data, NULL, " && ");
-		expr_print(e->right.expr, fn, data, E_AND);
+		if (revdep) {
+			expr_print_newline(e, fn, data, E_OR);
+		} else {
+			expr_print(e->left.expr, fn, data, E_AND);
+			fn(data, NULL, " && ");
+			expr_print(e->right.expr, fn, data, E_AND);
+		}
 		break;
 	case E_LIST:
 		fn(data, e->right.sym, e->right.sym->name);
-- 
2.16.1