linux-kernel - [PATCH v3 4/9] device property: add fwnode_property_read_string

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Message-Id: <20220325113148.588163-5-clement.leger@bootlin.com>
Date:   Fri, 25 Mar 2022 12:31:43 +0100
From:   Clément Léger <clement.leger@...tlin.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Daniel Scally <djrscally@...il.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Wolfram Sang <wsa@...nel.org>, Peter Rosin <peda@...ntia.se>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Len Brown <lenb@...nel.org>
Cc:     Hans de Goede <hdegoede@...hat.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Allan Nielsen <allan.nielsen@...rochip.com>,
        linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
        Clément Léger <clement.leger@...tlin.com>
Subject: [PATCH v3 4/9] device property: add fwnode_property_read_string_index()

Add fwnode_property_read_string_index() function which allows to
retrieve a single string from an array by its index. This function is
the equivalent of of_property_read_string_index() but for fwnode
support.

Signed-off-by: Clément Léger <clement.leger@...tlin.com>
---
 drivers/base/property.c  | 33 +++++++++++++++++++++++++++++++++
 include/linux/property.h |  3 +++
 2 files changed, 36 insertions(+)

diff --git a/drivers/base/property.c b/drivers/base/property.c
index d95c949e0a79..a2cfdf57b847 100644
--- a/drivers/base/property.c
+++ b/drivers/base/property.c
@@ -406,6 +406,39 @@ int fwnode_property_read_string(const struct fwnode_handle *fwnode,
 }
 EXPORT_SYMBOL_GPL(fwnode_property_read_string);
 
+/**
+ * fwnode_property_read_string_index - read a string in an array using an index
+ * @fwnode: Firmware node to get the property of
+ * @propname: Name of the property holding the array
+ * @index: Index of the string to look for
+ * @string: Pointer to the string if found
+ *
+ * Find a string by a given index in a string array and if it is found return
+ * the string value in @string.
+ *
+ * Return: %0 if the string was found (success),
+ *	   %-EINVAL if given arguments are not valid,
+ *	   %-ENODATA if the property does not have a value,
+ *	   %-EPROTO if the property is not an array of strings,
+ *	   %-ENXIO if no suitable firmware interface is present.
+ */
+int fwnode_property_read_string_index(const struct fwnode_handle *fwnode,
+				      const char *propname, int index,
+				      const char **string)
+{
+	int ret;
+
+	ret = fwnode_call_int_op(fwnode, property_read_string_array, propname,
+				 string, 1, index);
+	if (ret == -EINVAL && !IS_ERR_OR_NULL(fwnode) &&
+	    !IS_ERR_OR_NULL(fwnode->secondary))
+		ret = fwnode_call_int_op(fwnode->secondary,
+					 property_read_string_array, propname,
+					 string, 1, index);
+	return ret == 1 ? 0 : ret;
+}
+EXPORT_SYMBOL_GPL(fwnode_property_read_string_index);
+
 /**
  * fwnode_property_match_string - find a string in an array and return index
  * @fwnode: Firmware node to get the property of
diff --git a/include/linux/property.h b/include/linux/property.h
index 7399a0b45f98..a033920eb10a 100644
--- a/include/linux/property.h
+++ b/include/linux/property.h
@@ -70,6 +70,9 @@ int fwnode_property_read_string_array(const struct fwnode_handle *fwnode,
 				      size_t nval);
 int fwnode_property_read_string(const struct fwnode_handle *fwnode,
 				const char *propname, const char **val);
+int fwnode_property_read_string_index(const struct fwnode_handle *fwnode,
+				      const char *propname, int index,
+				      const char **string);
 int fwnode_property_match_string(const struct fwnode_handle *fwnode,
 				 const char *propname, const char *string);
 int fwnode_property_get_reference_args(const struct fwnode_handle *fwnode,
-- 
2.34.1