From 91ef8da010fb8edf25b66d89994c0889ca15fb47 Mon Sep 17 00:00:00 2001
From: Adrian Chadd <adrian@FreeBSD.org>
Date: Tue, 9 Feb 2016 03:35:40 +0000
Subject: [PATCH] Teach ofw_bus_parse_xref_list_alloc to be able to return the
 length of the parsed list.

Currently, there is no easy way to know in advance how many entries a list parsed by
ofw_bus_parse_xref_list_alloc() in sys/dev/ofw/ofw_bus_subr.c has.

This patch:

* teaches the existing function about handling idx == -1 and returning how big
  the set is; then renames it as _internal;
* create a new function that asserts idx != -1, so the old API is maintained;
* add a new function that returns just the list length.

Submitted by:	Stanislav Galabov <sgalabov@gmail.com>
Differential Revision:	https://reviews.freebsd.org/D5043
---
 sys/dev/ofw/ofw_bus_subr.c | 59 +++++++++++++++++++++++++++++++++++---
 sys/dev/ofw/ofw_bus_subr.h |  2 ++
 2 files changed, 57 insertions(+), 4 deletions(-)

diff --git a/sys/dev/ofw/ofw_bus_subr.c b/sys/dev/ofw/ofw_bus_subr.c
index dafaaedb8ae..653f04c8c8b 100644
--- a/sys/dev/ofw/ofw_bus_subr.c
+++ b/sys/dev/ofw/ofw_bus_subr.c
@@ -629,13 +629,16 @@ ofw_bus_find_child_device_by_phandle(device_t bus, phandle_t node)
  *  node - consumers device node
  *  list_name  - name of parsed list - "clocks"
  *  cells_name - name of size property - "#clock-cells"
+ *  idx - the index of the requested list entry, or, if -1, an indication
+ *        to return the number of entries in the parsed list.
  * Output arguments:
  *  producer - handle of producer
- *  ncells   - number of cells in result
+ *  ncells   - number of cells in result or the number of items in the list when
+ *             idx == -1.
  *  cells    - array of decoded cells
  */
-int
-ofw_bus_parse_xref_list_alloc(phandle_t node, const char *list_name,
+static int
+ofw_bus_parse_xref_list_internal(phandle_t node, const char *list_name,
     const char *cells_name, int idx, phandle_t *producer, int *ncells,
     pcell_t **cells)
 {
@@ -649,7 +652,7 @@ ofw_bus_parse_xref_list_alloc(phandle_t node, const char *list_name,
 	    (void **)&elems);
 	if (nelems <= 0)
 		return (ENOENT);
-	rv = ENOENT;
+	rv = (idx == -1) ? 0 : ENOENT;
 	for (i = 0, cnt = 0; i < nelems; i += pcells, cnt++) {
 		pnode = elems[i++];
 		if (OF_getencprop(OF_node_from_xref(pnode),
@@ -678,9 +681,57 @@ ofw_bus_parse_xref_list_alloc(phandle_t node, const char *list_name,
 	}
 	if (elems != NULL)
 		free(elems, M_OFWPROP);
+	if (idx == -1 && rv == 0)
+		*ncells = cnt;
 	return (rv);
 }
 
+/*
+ * Parse property that contain list of xrefs and values
+ * (like standard "clocks" and "resets" properties)
+ * Input arguments:
+ *  node - consumers device node
+ *  list_name  - name of parsed list - "clocks"
+ *  cells_name - name of size property - "#clock-cells"
+ *  idx - the index of the requested list entry (>= 0)
+ * Output arguments:
+ *  producer - handle of producer
+ *  ncells   - number of cells in result
+ *  cells    - array of decoded cells
+ */
+int
+ofw_bus_parse_xref_list_alloc(phandle_t node, const char *list_name,
+    const char *cells_name, int idx, phandle_t *producer, int *ncells,
+    pcell_t **cells)
+{
+
+	KASSERT(idx >= 0,
+	    ("ofw_bus_parse_xref_list_alloc: negative index supplied"));
+
+	return (ofw_bus_parse_xref_list_internal(node, list_name, cells_name,
+		    idx, producer, ncells, cells));
+}
+
+/*
+ * Parse property that contain list of xrefs and values
+ * (like standard "clocks" and "resets" properties)
+ * and determine the number of items in the list
+ * Input arguments:
+ *  node - consumers device node
+ *  list_name  - name of parsed list - "clocks"
+ *  cells_name - name of size property - "#clock-cells"
+ * Output arguments:
+ *  count - number of items in list
+ */
+int
+ofw_bus_parse_xref_list_get_length(phandle_t node, const char *list_name,
+    const char *cells_name, int *count)
+{
+
+	return (ofw_bus_parse_xref_list_internal(node, list_name, cells_name,
+		    -1, NULL, count, NULL));
+}
+
 /*
  * Find index of string in string list property (case sensitive).
  */
diff --git a/sys/dev/ofw/ofw_bus_subr.h b/sys/dev/ofw/ofw_bus_subr.h
index 7c4df337776..b7953970128 100644
--- a/sys/dev/ofw/ofw_bus_subr.h
+++ b/sys/dev/ofw/ofw_bus_subr.h
@@ -118,6 +118,8 @@ device_t ofw_bus_find_child_device_by_phandle(device_t bus, phandle_t node);
 int ofw_bus_parse_xref_list_alloc(phandle_t node, const char *list_name,
     const char *cells_name, int idx, phandle_t *producer, int *ncells,
     pcell_t **cells);
+int ofw_bus_parse_xref_list_get_length(phandle_t node, const char *list_name,
+    const char *cells_name, int *count);
 int ofw_bus_find_string_index(phandle_t node, const char *list_name,
     const char *name, int *idx);
 int ofw_bus_string_list_to_array(phandle_t node, const char *list_name,