bootconfig: Add append value operator support

Add append value operator "+=" support to bootconfig syntax.
With this operator, user can add new value to the key as
an entry of array instead of overwriting.
For example,

  foo = bar
  ...
  foo += baz

Then the key "foo" has "bar" and "baz" values as an array.

Link: http://lkml.kernel.org/r/158227283195.12842.8310503105963275584.stgit@devnote2

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

Author: mhiramat

Documentation/admin-guide/bootconfig.rst

@@ -71,7 +71,15 @@ For example,::
  foo = bar, baz
  foo = qux  # !ERROR! we can not re-define same key
 
-Also, a sub-key and a value can not co-exist under a parent key.
+If you want to append the value to existing key as an array member,
+you can use ``+=`` operator. For example::
+
+ foo = bar, baz
+ foo += qux
+
+In this case, the key ``foo`` has ``bar``, ``baz`` and ``qux``.
+
+However, a sub-key and a value can not co-exist under a parent key.
 For example, following config is NOT allowed.::
 
  foo = value1

lib/bootconfig.c

@@ -578,7 +578,7 @@ static int __init __xbc_parse_keys(char *k)
 	return __xbc_add_key(k);
 }
 
-static int __init xbc_parse_kv(char **k, char *v)
+static int __init xbc_parse_kv(char **k, char *v, int op)
 {
 	struct xbc_node *prev_parent = last_parent;
 	struct xbc_node *child;
@@ -593,7 +593,7 @@ static int __init xbc_parse_kv(char **k, char *v)
 	if (child) {
 		if (xbc_node_is_key(child))
 			return xbc_parse_error("Value is mixed with subkey", v);
-		else
+		else if (op == '=')
 			return xbc_parse_error("Value is redefined", v);
 	}
 
@@ -774,7 +774,7 @@ int __init xbc_init(char *buf)
 
 	p = buf;
 	do {
-		q = strpbrk(p, "{}=;\n#");
+		q = strpbrk(p, "{}=+;\n#");
 		if (!q) {
 			p = skip_spaces(p);
 			if (*p != '\0')
@@ -785,8 +785,15 @@ int __init xbc_init(char *buf)
 		c = *q;
 		*q++ = '\0';
 		switch (c) {
+		case '+':
+			if (*q++ != '=') {
+				ret = xbc_parse_error("Wrong '+' operator",
+							q - 2);
+				break;
+			}
+			/* Fall through */
 		case '=':
-			ret = xbc_parse_kv(&p, q);
+			ret = xbc_parse_kv(&p, q, c);
 			break;
 		case '{':
 			ret = xbc_open_brace(&p, q);

tools/bootconfig/test-bootconfig.sh

@@ -9,7 +9,7 @@ TEMPCONF=`mktemp temp-XXXX.bconf`
 NG=0
 
 cleanup() {
-  rm -f $INITRD $TEMPCONF
+  rm -f $INITRD $TEMPCONF $OUTFILE
   exit $NG
 }
 
@@ -71,7 +71,6 @@ printf " \0\0\0 \0\0\0" >> $INITRD
 $BOOTCONF -a $TEMPCONF $INITRD > $OUTFILE 2>&1
 xfail grep -i "failed" $OUTFILE
 xfail grep -i "error" $OUTFILE
-rm $OUTFILE
 
 echo "Max node number check"
 
@@ -96,6 +95,19 @@ truncate -s 32764 $TEMPCONF
 echo "\"" >> $TEMPCONF	# add 2 bytes + terminal ('\"\n\0')
 xpass $BOOTCONF -a $TEMPCONF $INITRD
 
+echo "Adding same-key values"
+cat > $TEMPCONF << EOF
+key = bar, baz
+key += qux
+EOF
+echo > $INITRD
+
+xpass $BOOTCONF -a $TEMPCONF $INITRD
+$BOOTCONF $INITRD > $OUTFILE
+xpass grep -q "bar" $OUTFILE
+xpass grep -q "baz" $OUTFILE
+xpass grep -q "qux" $OUTFILE
+
 echo "=== expected failure cases ==="
 for i in samples/bad-* ; do
   xfail $BOOTCONF -a $i $INITRD