of: Add of_property_match_string() to find index into a string list

Add a helper function for finding the index of a string in a string
list property.  This helper is useful for bindings that use a separate
*-name property for attaching names to tuples in another property such
as 'reg' or 'gpios'.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

1 files changed, 36 insertions, 0 deletions

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 133908a6fd8d..13ba72875e25 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -761,6 +761,42 @@ int of_property_read_string_index(struct device_node *np, const char *propname,
 }
 EXPORT_SYMBOL_GPL(of_property_read_string_index);
 
+/**
+ * of_property_match_string() - Find string in a list and return index
+ * @np: pointer to node containing string list property
+ * @propname: string list property name
+ * @string: pointer to string to search for in string list
+ *
+ * This function searches a string list property and returns the index
+ * of a specific string value.
+ */
+int of_property_match_string(struct device_node *np, const char *propname,
+                             const char *string)
+{
+        struct property *prop = of_find_property(np, propname, NULL);
+        size_t l;
+        int i;
+        const char *p, *end;
+
+        if (!prop)
+                return -EINVAL;
+        if (!prop->value)
+                return -ENODATA;
+
+        p = prop->value;
+        end = p + prop->length;
+
+        for (i = 0; p < end; i++, p += l) {
+                l = strlen(p) + 1;
+                if (p + l > end)
+                        return -EILSEQ;
+                pr_debug("comparing %s with %s\n", string, p);
+                if (strcmp(string, p) == 0)
+                        return i; /* Found it; return index */
+        }
+        return -ENODATA;
+}
+EXPORT_SYMBOL_GPL(of_property_match_string);
 
 /**
  * of_property_count_strings - Find and return the number of strings from a