dtc: Sort unit addresses by number

The sort option in dtc treats unit addresses as strings. This causes cpu nodes to end up out of order:

# dtc -s -I fs -O dts /proc/device-tree | grep PowerPC,POWER7

		PowerPC,POWER7@30 {
		PowerPC,POWER7@68 {
		PowerPC,POWER7@70 {
		PowerPC,POWER7@828 {
		PowerPC,POWER7@860 {
		PowerPC,POWER7@868 {
		PowerPC,POWER7@8a0 {
		PowerPC,POWER7@8b0 {
		PowerPC,POWER7@8f0 {
		PowerPC,POWER7@a0 {
		PowerPC,POWER7@a8 {
		PowerPC,POWER7@e0 {

If we use this device tree for a kexec boot we end up with a confusing layout of logical CPUs:

node 0 cpus: 0-23 72-95
node 0 size: 32633 MB

node 1 cpus: 24-71
node 1 size: 32631 MB

The reason for this is that we allocate logical CPU ids as we walk through the device tree.

In cmp_subnode, if both nodes have a hex unit address and the basenames match, then compare by number.

This fixes the issue:

# dtc -s -I fs -O dts /proc/device-tree | grep PowerPC,POWER7
		PowerPC,POWER7@30 {
		PowerPC,POWER7@68 {
		PowerPC,POWER7@70 {
		PowerPC,POWER7@a0 {
		PowerPC,POWER7@a8 {
		PowerPC,POWER7@e0 {
		PowerPC,POWER7@828 {
		PowerPC,POWER7@860 {
		PowerPC,POWER7@868 {
		PowerPC,POWER7@8a0 {
		PowerPC,POWER7@8b0 {
		PowerPC,POWER7@8f0 {

And the CPU layout is as expected:

node 0 cpus: 0-47
node 0 size: 32633 MB

node 1 cpus: 48-95
node 1 size: 32631 MB

Signed-off-by Anton Blanchard <[email protected]>

--

Index: b/livetree.c
===================================================================

livetree.c +25 -1

@@ -656,12 +656,38 @@ static void sort_properties(struct node
 	free(tbl);
 }
 
+static bool is_hex(const char *str)
+{
+	while (*str) {
+		if (!isxdigit(*str++))
+			return false;
+	}
+
+	return true;
+}
+
 static int cmp_subnode(const void *ax, const void *bx)
 {
-	const struct node *a, *b;
+	struct node *a, *b;
+	const char *a_unit, *b_unit;
+
+	a = *((struct node * const *)ax);
+	b = *((struct node * const *)bx);
+
+	a_unit = get_unitname(a);
+	b_unit = get_unitname(b);
+
+	/* Sort hex unit addresses by number */
+	if (a_unit && b_unit && (a->basenamelen == b->basenamelen) &&
+	    !strncmp(a->name, b->name, a->basenamelen) &&
+	    is_hex(a_unit) && is_hex(b_unit)) {
+		unsigned long long a_num, b_num;
+

Minor issue, but when #address-cells == 2, some unit addresses are split in the middle by a ',' to separate the value of each cell, e.g. "flash@2,0". For those, is_hex will return false and we'll compare unit-addresses as strings.

I took a quick look over the dts in the Linux kernel tree (with git grep "@.\+," -- arch/*/boot/dts and I think every instance there would sort correctly as a string, but it would be nice to fix the issue regardless of how large the unit-address is.

Perhaps we could have a helper function for reading the unit-address that would take this into account?