[PATCHv2 1/7] of: Add support for reading a u32 from a multi-value property.

[Tony Prisk]

This patch adds an of_property_read_u32_index() function to allow
reading a single indexed u32 value from a property containing multiple
u32 values.

Signed-off-by: Tony Prisk <linux at prisktech.co.nz>
---
cc: Grant Likely <grant.likely at secretlab.ca>
cc: Rob Herring <rob.herring at calxeda.com>
cc: devicetree-discuss at lists.ozlabs.org

Hi Rob/Grant,
After a review of my pinctrl driver, it was suggested that one of the helper
functions be moved into the OF subsystem. Could you review and ack this patch
if you're happy with it.
Regards
Tony P

 drivers/of/base.c  |   33 +++++++++++++++++++++++++++++++++
 include/linux/of.h |    9 +++++++++
 2 files changed, 42 insertions(+)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 321d3ef..7dc001e 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -746,6 +746,39 @@ struct device_node *of_find_node_by_phandle(phandle handle)
 EXPORT_SYMBOL(of_find_node_by_phandle);
 
 /**
+ * of_property_read_u32_index - Find and read a u32 from a multi-value property.
+ *
+ * @np:		device node from which the property value is to be read.
+ * @propname:	name of the property to be searched.
+ * @index:	index of the u32 in the list of values
+ * @out_value:	pointer to return value, modified only if no error.
+ *
+ * Search for a property in a device node and read nth 32-bit value from
+ * it. Returns 0 on success, -EINVAL if the property does not exist,
+ * -ENODATA if property does not have a value, and -EOVERFLOW if the
+ * property data isn't large enough.
+ *
+ * The out_value is modified only if a valid u32 value can be decoded.
+ */
+int of_property_read_u32_index(const struct device_node *np,
+				       const char *propname,
+				       u32 index, u32 *out_value)
+{
+	struct property *prop = of_find_property(np, propname, NULL);
+
+	if (!prop)
+		return -EINVAL;
+	if (!prop->value)
+		return -ENODATA;
+	if ((index * sizeof(*out_value)) > prop->length)
+		return -EOVERFLOW;
+
+	*out_value = be32_to_cpup(((__be32 *)prop->value) + index);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(of_property_read_u32_index);
+
+/**
  * of_property_read_u8_array - Find and read an array of u8 from a property.
  *
  * @np:		device node from which the property value is to be read.
diff --git a/include/linux/of.h b/include/linux/of.h
index a0f1292..c0747a4 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -235,6 +235,9 @@ extern struct device_node *of_find_node_with_property(
 extern struct property *of_find_property(const struct device_node *np,
 					 const char *name,
 					 int *lenp);
+extern int of_property_read_u32_index(const struct device_node *np,
+				       const char *propname,
+				       u32 index, u32 *out_value);
 extern int of_property_read_u8_array(const struct device_node *np,
 			const char *propname, u8 *out_values, size_t sz);
 extern int of_property_read_u16_array(const struct device_node *np,
@@ -394,6 +397,12 @@ static inline struct device_node *of_find_compatible_node(
 	return NULL;
 }
 
+static inline int of_property_read_u32_index(const struct device_node *np,
+			const char *propname, u32 index, u32 *out_value)
+{
+	return -ENOSYS;
+}
+
 static inline int of_property_read_u8_array(const struct device_node *np,
 			const char *propname, u8 *out_values, size_t sz)
 {
-- 
1.7.9.5