[PATCH] lib: Extend kstrtobool() to accept "true"/"false"

[Peter Zijlstra <peterz@infradead.org>]

On Fri, Jun 26, 2020 at 12:22:55PM +0200, Peter Zijlstra wrote:

> > This is too lax - it will be enabled for any !0 value. Please accept
> > only 0 and 1.
> 
> kstrtobool() ftw

And looking at that, I find it really strange it does not in fact accept
"true" / "false", so how about this?

---
Subject: lib: Extend kstrtobool() to accept "true"/"false"

Extend the strings recognised by kstrtobool() to cover:

  - 1/0
  - y/n
  - yes/no	(new)
  - t/f		(new)
  - true/false  (new)
  - on/off

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 lib/kstrtox.c | 60 ++++++++++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 45 insertions(+), 15 deletions(-)

diff --git a/lib/kstrtox.c b/lib/kstrtox.c
index 1006bf70bf74..b8b950325097 100644
--- a/lib/kstrtox.c
+++ b/lib/kstrtox.c
@@ -325,9 +325,17 @@ EXPORT_SYMBOL(kstrtos8);
  * @s: input string
  * @res: result
  *
- * This routine returns 0 iff the first character is one of 'Yy1Nn0', or
- * [oO][NnFf] for "on" and "off". Otherwise it will return -EINVAL.  Value
- * pointed to by res is updated upon finding a match.
+ * This return return 0 on success, otherwise it will return -EINVAL.
+ * It will accept (case invariant):
+ *
+ *  - 1/0
+ *  - y/n
+ *  - yes/no
+ *  - t/f
+ *  - true/false
+ *  - on/off
+ *
+ * and set @*res to either true/false respectively.
  */
 int kstrtobool(const char *s, bool *res)
 {
@@ -335,30 +343,52 @@ int kstrtobool(const char *s, bool *res)
 		return -EINVAL;
 
 	switch (s[0]) {
+	case 't':
+	case 'T':
+		if (!s[1] || !strcasecmp(s, "true"))
+			goto have_true;
+
+		break;
+
 	case 'y':
 	case 'Y':
+		if (!s[1] || !strcasecmp(s, "yes"))
+			goto have_true;
+
+		break;
+
 	case '1':
+have_true:
 		*res = true;
 		return 0;
+
+	case 'f':
+	case 'F':
+		if (!s[1] || !strcasecmp(s, "false"))
+			goto have_false;
+
+		break;
 	case 'n':
 	case 'N':
+		if (!s[1] || !strcasecmp(s, "no"))
+			goto have_false;
+
+		break;
 	case '0':
+have_false:
 		*res = false;
 		return 0;
+
 	case 'o':
 	case 'O':
-		switch (s[1]) {
-		case 'n':
-		case 'N':
-			*res = true;
-			return 0;
-		case 'f':
-		case 'F':
-			*res = false;
-			return 0;
-		default:
-			break;
-		}
+		if (!strcasecmp(s, "on"))
+			goto have_true;
+
+		if (!strcasecmp(s, "off"))
+			goto have_false;
+
+		break;
+
 	default:
 		break;
 	}