of: Create function for counting number of phandles in a property

This patch creates of_count_phandle_with_args(), a new function for
counting the number of phandle+argument tuples in a given property. This
is better than the existing method of parsing each phandle individually
until parsing fails which is a horribly slow way to do the count.

Tested on ARM using the selftest code.

v3: - Rebased on top of selftest code cleanup patch
v2: - fix bug where of_parse_phandle_with_args() could behave like _count_.
    - made of_gpio_named_count() into a static inline regardless of CONFIG_OF_GPIO

Tested-by: Andreas Larsson <andreas@gaisler.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Rob Herring <rob.herring@calxeda.com>

2 files changed, 52 insertions, 4 deletions

diff --git a/drivers/of/base.c b/drivers/of/base.c
index c5572cb87a88..321d3ef05006 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -1091,9 +1091,10 @@ EXPORT_SYMBOL(of_parse_phandle);
  * To get a device_node of the `node2' node you may call this:
  * of_parse_phandle_with_args(node3, "list", "#list-cells", 1, &args);
  */
-int of_parse_phandle_with_args(const struct device_node *np, const char *list_name,
-                                const char *cells_name, int index,
-                                struct of_phandle_args *out_args)
+static int __of_parse_phandle_with_args(const struct device_node *np,
+                                        const char *list_name,
+                                        const char *cells_name, int index,
+                                        struct of_phandle_args *out_args)
 {
         const __be32 *list, *list_end;
         int rc = 0, size, cur_index = 0;
@@ -1183,15 +1184,47 @@ int of_parse_phandle_with_args(const struct device_node *np, const char *list_na
          * Unlock node before returning result; will be one of:
          * -ENOENT : index is for empty phandle
          * -EINVAL : parsing error on data
+         * [1..n]  : Number of phandle (count mode; when index = -1)
          */
-        rc = -ENOENT;
+        rc = index < 0 ? cur_index : -ENOENT;
  err:
         if (node)
                 of_node_put(node);
         return rc;
 }
+
+int of_parse_phandle_with_args(const struct device_node *np, const char *list_name,
+                                const char *cells_name, int index,
+                                struct of_phandle_args *out_args)
+{
+        if (index < 0)
+                return -EINVAL;
+        return __of_parse_phandle_with_args(np, list_name, cells_name, index, out_args);
+}
 EXPORT_SYMBOL(of_parse_phandle_with_args);
 
+/**
+ * of_count_phandle_with_args() - Find the number of phandles references in a property
+ * @np:         pointer to a device tree node containing a list
+ * @list_name:  property name that contains a list
+ * @cells_name: property name that specifies phandles' arguments count
+ *
+ * Returns the number of phandle + argument tuples within a property. It
+ * is a typical pattern to encode a list of phandle and variable
+ * arguments into a single property. The number of arguments is encoded
+ * by a property in the phandle-target node. For example, a gpios
+ * property would contain a list of GPIO specifies consisting of a
+ * phandle and 1 or more arguments. The number of arguments are
+ * determined by the #gpio-cells property in the node pointed to by the
+ * phandle.
+ */
+int of_count_phandle_with_args(const struct device_node *np, const char *list_name,
+                                const char *cells_name)
+{
+        return __of_parse_phandle_with_args(np, list_name, cells_name, -1, NULL);
+}
+EXPORT_SYMBOL(of_count_phandle_with_args);
+
 #if defined(CONFIG_OF_DYNAMIC)
 static int of_property_notify(int action, struct device_node *np,
                               struct property *prop)
diff --git a/drivers/of/selftest.c b/drivers/of/selftest.c
index 01b4174a3b46..0eb5c38b4e07 100644
--- a/drivers/of/selftest.c
+++ b/drivers/of/selftest.c
@@ -36,6 +36,9 @@ static void __init of_selftest_parse_phandle_with_args(void)
                 return;
         }
 
+        rc = of_count_phandle_with_args(np, "phandle-list", "#phandle-cells");
+        selftest(rc == 7, "of_count_phandle_with_args() returned %i, expected 7\n", rc);
+
         for (i = 0; i < 8; i++) {
                 bool passed = true;
                 rc = of_parse_phandle_with_args(np, "phandle-list",
@@ -94,21 +97,33 @@ static void __init of_selftest_parse_phandle_with_args(void)
         rc = of_parse_phandle_with_args(np, "phandle-list-missing",
                                         "#phandle-cells", 0, &args);
         selftest(rc == -ENOENT, "expected:%i got:%i\n", -ENOENT, rc);
+        rc = of_count_phandle_with_args(np, "phandle-list-missing",
+                                        "#phandle-cells");
+        selftest(rc == -ENOENT, "expected:%i got:%i\n", -ENOENT, rc);
 
         /* Check for missing cells property */
         rc = of_parse_phandle_with_args(np, "phandle-list",
                                         "#phandle-cells-missing", 0, &args);
         selftest(rc == -EINVAL, "expected:%i got:%i\n", -EINVAL, rc);
+        rc = of_count_phandle_with_args(np, "phandle-list",
+                                        "#phandle-cells-missing");
+        selftest(rc == -EINVAL, "expected:%i got:%i\n", -EINVAL, rc);
 
         /* Check for bad phandle in list */
         rc = of_parse_phandle_with_args(np, "phandle-list-bad-phandle",
                                         "#phandle-cells", 0, &args);
         selftest(rc == -EINVAL, "expected:%i got:%i\n", -EINVAL, rc);
+        rc = of_count_phandle_with_args(np, "phandle-list-bad-phandle",
+                                        "#phandle-cells");
+        selftest(rc == -EINVAL, "expected:%i got:%i\n", -EINVAL, rc);
 
         /* Check for incorrectly formed argument list */
         rc = of_parse_phandle_with_args(np, "phandle-list-bad-args",
                                         "#phandle-cells", 1, &args);
         selftest(rc == -EINVAL, "expected:%i got:%i\n", -EINVAL, rc);
+        rc = of_count_phandle_with_args(np, "phandle-list-bad-args",
+                                        "#phandle-cells");
+        selftest(rc == -EINVAL, "expected:%i got:%i\n", -EINVAL, rc);
 }
 
 static void __init of_selftest_property_match_string(void)