[PATCH v3] of: add functions to count number of elements in a property

Heiko Stübner
2014-01-17T17:27:53Z

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@sntech.de>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
---
changes since v2:
address more comments from Mark Rutland
- switch to of_property_count_elems_of_size
- use full_name instead of name in error message
changes since v1:
address comments from Rob Herring and Mark Rutland:
- provide a helper and a set of wrappers for u8-u64
- get rid of extra len variable, prop->length is enough
- include node name in error message

Posted for completenes sake. If nobody complains,
I'll simply make it part of my Rockchip-SMP series.

drivers/of/base.c | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/of.h | 32 +++++++++++++++++
2 files changed, 131 insertions(+)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index f807d0e..1cd6dc9 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -862,6 +862,105 @@ struct device_node *of_find_node_by_phandle(phandle handle)
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
+ */
+static 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;
+
+pr_err("size of %s in node %s is not a multiple of %d\n", propname, np->full_name, elem_size);
+ 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;
+}
+
+/**
+ * of_property_count_u8_elems - Count the number of u8 elements in a property
+ *
+ * @np: device node from which the property value is to be read.
+ * @propname: name of the property to be searched.
+ *
+ * Search for a property in a device node and count the number of u8 elements
+ * in it. Returns number of elements on sucess, -EINVAL if the property does
+ * not exist or its length does not match a multiple of u8 and -ENODATA if the
+ * property does not have a value.
+ */
+int of_property_count_u8_elems(const struct device_node *np,
+ const char *propname)
+{
+ return of_property_count_elems_of_size(np, propname, sizeof(u8));
+}
+EXPORT_SYMBOL_GPL(of_property_count_u8_elems);
+
+/**
+ * of_property_count_u16_elems - Count the number of u16 elements in a property
+ *
+ * @np: device node from which the property value is to be read.
+ * @propname: name of the property to be searched.
+ *
+ * Search for a property in a device node and count the number of u16 elements
+ * in it. Returns number of elements on sucess, -EINVAL if the property does
+ * not exist or its length does not match a multiple of u16 and -ENODATA if the
+ * property does not have a value.
+ */
+int of_property_count_u16_elems(const struct device_node *np,
+ const char *propname)
+{
+ return of_property_count_elems_of_size(np, propname, sizeof(u16));
+}
+EXPORT_SYMBOL_GPL(of_property_count_u16_elems);
+
+/**
+ * of_property_count_u32_elems - Count the number of u32 elements in a property
+ *
+ * @np: device node from which the property value is to be read.
+ * @propname: name of the property to be searched.
+ *
+ * Search for a property in a device node and count the number of u32 elements
+ * in it. Returns number of elements on sucess, -EINVAL if the property does
+ * not exist or its length does not match a multiple of u32 and -ENODATA if the
+ * property does not have a value.
+ */
+int of_property_count_u32_elems(const struct device_node *np,
+ const char *propname)
+{
+ return of_property_count_elems_of_size(np, propname, sizeof(u32));
+}
+EXPORT_SYMBOL_GPL(of_property_count_u32_elems);
+
+/**
+ * of_property_count_u64_elems - Count the number of u64 elements in a property
+ *
+ * @np: device node from which the property value is to be read.
+ * @propname: name of the property to be searched.
+ *
+ * Search for a property in a device node and count the number of u64 elements
+ * in it. Returns number of elements on sucess, -EINVAL if the property does
+ * not exist or its length does not match a multiple of u64 and -ENODATA if the
+ * property does not have a value.
+ */
+int of_property_count_u64_elems(const struct device_node *np,
+ const char *propname)
+{
+ return of_property_count_elems_of_size(np, propname, sizeof(u64));
+}
+EXPORT_SYMBOL_GPL(of_property_count_u64_elems);
+
+/**
* of_find_property_value_of_size
*
* @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 276c546..06fe898 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -250,6 +250,14 @@ 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_count_u8_elems(const struct device_node *np,
+ const char *propname);
+extern int of_property_count_u16_elems(const struct device_node *np,
+ const char *propname);
+extern int of_property_count_u32_elems(const struct device_node *np,
+ const char *propname);
+extern int of_property_count_u64_elems(const struct device_node *np,
+ const char *propname);
extern int of_property_read_u32_index(const struct device_node *np,
const char *propname,
u32 index, u32 *out_value);
@@ -426,6 +434,30 @@ static inline struct device_node *of_find_compatible_node(
return NULL;
}

+static inline int of_property_count_u8_elems(const struct device_node *np,
+ const char *propname)
+{
+ return -ENOSYS;
+}
+
+static inline int of_property_count_u16_elems(const struct device_node *np,
+ const char *propname)
+{
+ return -ENOSYS;
+}
+
+static inline int of_property_count_u32_elems(const struct device_node *np,
+ const char *propname)
+{
+ return -ENOSYS;
+}
+
+static inline int of_property_count_u64_elems(const struct device_node *np,
+ const char *propname)
+{
+ return -ENOSYS;
+}
+
static inline int of_property_read_u32_index(const struct device_node *np,
const char *propname, u32 index, u32 *out_value)
{
--
1.7.10.4