On Sun, Jul 03, 2011 at 11:55:28AM +0800, Shawn Guo wrote:

On Thu, Jun 30, 2011 at 12:13:53PM -0600, Grant Likely wrote:

quoted

On Thu, Jun 30, 2011 at 09:26:10PM +0530, Thomas Abraham wrote:

quoted

Add helper functions to retrive unsigned integer and string property values from
properties of a device node. These helper functions can be used to lookup a
property in a device node, perform error checking and read the property value.

[grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org: Proposal and initial implementation]
Signed-off-by: Thomas Abraham <redacted>

Merged, thanks.  Bonus points to anyone who submits patches converting
existing code to this new api.

g.

quoted

---
 drivers/of/base.c  |   59 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/of.h |    4 +++
 2 files changed, 63 insertions(+), 0 deletions(-)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 632ebae..4823b53 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c

@@ -596,6 +596,65 @@ struct device_node *of_find_node_by_phandle(phandle handle)
 EXPORT_SYMBOL(of_find_node_by_phandle);
 
 /**
+ * of_property_read_u32 - Find a property in a device node and read the
+ *				32-bit property value
+ * @np:		device node from which the property value is to be read.
+ * @propname:	name of the property to be searched.
+ * @out_value:	returned value, valid if return value is 0.
+ *
+ * Search for a property in a device node and read a 32-bit value from a
+ * property. Returns -EINVAL, if the property does not exist, -ENODATA, if
+ * property does not have a value, -EOVERFLOW, if the property data isn't
+ * large enough, and 0 on success.
+ *
+ * The out_value is modified only if a valid u32 value can be decoded.
+ */
+int of_property_read_u32(struct device_node *np, char *propname, u32 *out_value)
+{
+	struct property *prop = of_find_property(np, propname, NULL);
+
+	if (!prop)
+		return -EINVAL;
+	if (!prop->value)
+		return -ENODATA;
+	if (sizeof(*out_value) > prop->length)
+		return -EOVERFLOW;
+	*out_value = be32_to_cpup(prop->value);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(of_property_read_u32);
+
+/**
+ * of_property_read_string - Find a property in a device node and return a
+ *				pointer to the property string value.
+ * @np:		device node from which the property value is to be read.
+ * @propname:	name of the property to be searched.
+ * @out_string:	pointer to a null terminated string, valid only if the return
+ *		value is 0.
+ *
+ * Returns a pointer to a null terminated property value string. Returns
+ * -EINVAL, if the property does not exist, -ENODATA, if property does not have
+ * a value, -EILSEQ, if the string is not null-terminated within the length of
+ * the property value, and 0 on success.
+ *
+ * The out_string value is modified only if a valid string can be decoded.
+ */
+int of_property_read_string(struct device_node *np, char *propname,
+				char **out_string)

When converting my dt code to use this api, the following type
mismatch warning is being seen in a lot of places.

'char **' but argument is of type 'const char **'

This is because the existing codes usually get string from
of_get_property and assign it to a 'const char *'.

I'm wondering if we should drop the const during converting or
change the api with const added to out_string to get converting
a little bit easier.

Add the const to out_string.  It's the right thing to do.  Can you
craft and post a patch doing so?

g.