kconfig: menuconfig make "Selected by:" readable

Quoted 70 lines

rev_dep expressions can get rather unwieldy, especially if a symbol is selected by more than a handful of other symbols. Ie, it's possible to have near endless expressions like:

   A && B && !C || D || F && (G || H) || [...]

Chop these expressions into actually readable chunks:
- A && B && !C
- D
- F && (G || H)
- [...]

Ie, transform the top level "||" tokens into newlines and prepend each line with a minus. This makes the "Selected by:" blurb much easier to read.

Not-yet-signed-off-by Paul Bolle <pebolle@xxxxxxxxxx>

---
Today I found myself wondering why a certain Kconfig was selected. Currently menuconfig's help is of no use in complicated cases. Please look at the help of USB or CRYPTO to see what I mean.

This is a _hack_ to show what might be a better way to do this. It parses a stringified version of the reverse dependency, and not the actual reverse dependecy expression. But that was easier to cobble together.

One cool improvement would be to change to minus in front of the subexpressions to Y or M for those that actually set the symbol. Anyhow, other suggestions and feedback is welcome.

 scripts/kconfig/menu.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 81 insertions(+), 2 deletions(-)

scripts/kconfig/menu.c +29 -0

index 72c9dba84c5d..eb73fe77513e 100644
@@ -613,6 +613,86 @@ static struct property *get_symbol_prop(struct symbol *sym)
 }
 
 /*
+ * Assuming we're just past an opening parenthesis in a NUL terminated string,
+ * find it's closing parenthesis and return its postion. Die otherwise.
+ */
+static const char *matching_paren(const char *s)
+{
+	int lvl = 1;
+
+	while (1) {
+		if (*s == '(')
+			lvl++;
+		else if (*s == ')')
+			lvl--;
+		if (lvl == 0)
+			break;
+		if (*s == '\0')
+			/* huh? */
+			exit(1);
+		s++;
+	}
+
+	return s;
+}
+
+/*
+ * rev_dep expressions can get rather unwieldy, especially if a symbol is
+ * selected by more than a handful of other symbols. Ie, it's possible to
+ * have near endless expressions like:
+ *    A && B && !C || D || F && (G || H) || [...]
+ *

scripts/kconfig/menu.c static struct property *get_symbol_prop(struct symbol *sym) · line 654

Quoted 10 lines

scripts/kconfig/menu.c +10 -0

+ * Chop these expressions into actually readable chunks:
+ *    - A && B && !C
+ *    - D
+ *    - F && (G || H)
+ *    - [...]
+ *
+ * Ie, transform the top level "||" tokens into newlines and prepend each line
+ * with a minus. This makes the "Selected by:" blurb much easier to read.
+ */
+static void rev_dep_gstr_print(struct gstr *gs, struct expr *e)

Charge: posting just before suspending machine and self. Verdict:
guilty.

That should have been
static void rev_dep_gstr_print(struct expr *e, struct gstr *gs)

Quoted 49 lines

scripts/kconfig/menu.c +41 -1

+{
+	struct gstr tmp = str_new();
+	const char *prev, *start;
+	char *beam;
+
+	expr_gstr_print(e, &tmp);
+	prev = start = str_get(&tmp);
+
+	str_append(gs, "\n  - ");
+
+	while ((beam = index(start, '|'))) {
+		char *lparen = index(start, '(');
+
+		/* don't split "(I || J)" */
+		if (lparen && (lparen < beam)) {
+			const char *rparen = matching_paren(++lparen);
+
+			/* skip the expression inside parentheses */
+			start = ++rparen;
+			continue;
+		}
+
+		/* we can assume we're fed a sane string, so the space before
+		 * the beam gets turned into a NUL */
+		*(beam - 1) = '\0';
+		str_append(gs, prev);
+		str_append(gs, "\n  - ");
+		/* assume sane string, so skip the second beam */
+		beam++;
+		/* trim */
+		while (*++beam == ' ')
+			;
+		prev = start = beam;
+	}
+
+	str_append(gs, prev);
+
+	str_free(&tmp);
+}
+
+/*
  * head is optional and may be NULL
  */
 void get_symbol_str(struct gstr *r, struct symbol *sym,

@@ -661,8 +741,7 @@ void get_symbol_str(struct gstr *r, struct symbol *sym,
 		str_append(r, "\n");
 	if (sym->rev_dep.expr) {
 		str_append(r, _("  Selected by: "));
-		expr_gstr_print(sym->rev_dep.expr, r);

scripts/kconfig/menu.c void get_symbol_str(struct gstr *r, struct symbol *sym, · line 747

Quoted 5 lines

scripts/kconfig/menu.c +1 -1

-		str_append(r, "\n");
+		rev_dep_gstr_print(sym->rev_dep.expr, r);
 	}
 	str_append(r, "\n\n");
 }

Paul Bolle

This is very nice improvement, thanks for that :-). I use it happily on some old kernel. Although it's just a draft, it would be nice to have it in mainline.

There are quite a few Kconfig related things that I should put more effort into. Let's call the sum of those my "social debt". I'm not sure how I'll handle that debt, but feel free to prod me in a few weeks about the status of this idea. Perhaps that will help me at least handle this part.