common: move remove_newline to common.c, add some documentation, minor change to isdigits

common.c

@@ -127,10 +127,10 @@ fail_doc_ptr:
 
 }
 
-int isdigits(const char *pin)
+int isdigits(const char *str)
 {
-	while (*pin) {
-		if (isdigit(*pin++) == 0)
+	while (*str) {
+		if (isdigit(*str++) == 0)
 			return false;
 	}
 
@@ -220,3 +220,14 @@ int check_response(struct json_object *response)
 fail:
 	return -1;
 }
+
+void remove_newline(char *input)
+{
+	char *pos;
+
+	pos = strchr(input, '\n');
+	if (!pos)
+		return;
+
+	*pos = '\0';
+}

common.h

@@ -75,8 +75,34 @@ void json_to_blob(struct json_object *response, struct blob_buf *bb);
 
 char *xml_parser(struct write_result *result, char *tag);
 struct json_object *xml_to_json_converter(struct write_result *result);
-int isdigits(const char *pin);
+
+/**
+ * Function: isdigits
+ *
+ * Checks if a string is made up entirely out of digits.
+ *
+ * Parameters:
+ * 		str - the string to check for digits.
+ *
+ * Returns:
+ * 		true if the string is made up entirely out of digits.
+ * 		false if the string contains any non-digit character.
+ */
+int isdigits(const char *str);
 int validate_puk_format(char *puk);
+
+/**
+ * Function: validate_pin_format
+ *
+ * Checks whether a given PIN code is of valid format or not.
+ *
+ * Parameters:
+ * 		pin - the string to check for structure validity
+ *
+ * Returns:
+ * 		0 if the string is of valid format.
+ * 		-1 on invalid format.
+ */
 int validate_pin_format(char *pin);
 int pin_status(struct blob_buf *bb, struct device *dev);
 int check_response(struct json_object *response);