of: add functions to count number of elements in a property
The need to know the number of array elements in a property is
a common pattern. To prevent duplication of open-coded implementations
add a helper static function that also centralises strict sanity
checking and DTB format details, as well as a set of wrapper functions
for u8, u16, u32 and u64.
Suggested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Heiko Stuebner <heiko.stuebner@bqreaders.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Grant Likely <grant.likely@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
diff --git a/drivers/of/base.c b/drivers/of/base.c
index ff85450..8a2a55c 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -886,6 +886,38 @@
EXPORT_SYMBOL(of_find_node_by_phandle);
/**
+ * of_property_count_elems_of_size - Count the number of elements in a property
+ *
+ * @np: device node from which the property value is to be read.
+ * @propname: name of the property to be searched.
+ * @elem_size: size of the individual element
+ *
+ * Search for a property in a device node and count the number of elements of
+ * size elem_size in it. Returns number of elements on sucess, -EINVAL if the
+ * property does not exist or its length does not match a multiple of elem_size
+ * and -ENODATA if the property does not have a value.
+ */
+int of_property_count_elems_of_size(const struct device_node *np,
+ const char *propname, int elem_size)
+{
+ struct property *prop = of_find_property(np, propname, NULL);
+
+ if (!prop)
+ return -EINVAL;
+ if (!prop->value)
+ return -ENODATA;
+
+ if (prop->length % elem_size != 0) {
+ pr_err("size of %s in node %s is not a multiple of %d\n",
+ propname, np->full_name, elem_size);
+ return -EINVAL;
+ }
+
+ return prop->length / elem_size;
+}
+EXPORT_SYMBOL_GPL(of_property_count_elems_of_size);
+
+/**
* of_find_property_value_of_size
*
* @np: device node from which the property value is to be read.