of: Add helpers to get one string in multiple strings property

Add of_property_read_string_index and of_property_count_strings
to retrieve one string inside a property that will contains
severals strings.

Signed-off-by: Benoit Cousson <b-cousson@ti.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Kevin Hilman <khilman@ti.com>

1 files changed, 84 insertions, 0 deletions

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 3ff22e32b602..f7239b33d762 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -662,6 +662,90 @@ int of_property_read_string(struct device_node *np, const char *propname,
 EXPORT_SYMBOL_GPL(of_property_read_string);
 
 /**
+ * of_property_read_string_index - Find and read a string from a multiple
+ * strings 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 string in the list of strings
+ * @out_string: pointer to null terminated return string, modified only if
+ *              return value is 0.
+ *
+ * Search for a property in a device tree node and retrieve a null
+ * terminated string value (pointer to data, not a copy) in the list of strings
+ * contained in that property.
+ * Returns 0 on success, -EINVAL if the property does not exist, -ENODATA if
+ * property does not have a value, and -EILSEQ if the string is not
+ * null-terminated within the length of the property data.
+ *
+ * The out_string pointer is modified only if a valid string can be decoded.
+ */
+int of_property_read_string_index(struct device_node *np, const char *propname,
+                                  int index, const char **output)
+{
+        struct property *prop = of_find_property(np, propname, NULL);
+        int i = 0;
+        size_t l = 0, total = 0;
+        const char *p;
+
+        if (!prop)
+                return -EINVAL;
+        if (!prop->value)
+                return -ENODATA;
+        if (strnlen(prop->value, prop->length) >= prop->length)
+                return -EILSEQ;
+
+        p = prop->value;
+
+        for (i = 0; total < prop->length; total += l, p += l) {
+                l = strlen(p) + 1;
+                if ((*p != 0) && (i++ == index)) {
+                        *output = p;
+                        return 0;
+                }
+        }
+        return -ENODATA;
+}
+EXPORT_SYMBOL_GPL(of_property_read_string_index);
+
+
+/**
+ * of_property_count_strings - Find and return the number of strings from a
+ * multiple strings 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 tree node and retrieve the number of null
+ * terminated string contain in it. Returns the number of strings on
+ * success, -EINVAL if the property does not exist, -ENODATA if property
+ * does not have a value, and -EILSEQ if the string is not null-terminated
+ * within the length of the property data.
+ */
+int of_property_count_strings(struct device_node *np, const char *propname)
+{
+        struct property *prop = of_find_property(np, propname, NULL);
+        int i = 0;
+        size_t l = 0, total = 0;
+        const char *p;
+
+        if (!prop)
+                return -EINVAL;
+        if (!prop->value)
+                return -ENODATA;
+        if (strnlen(prop->value, prop->length) >= prop->length)
+                return -EILSEQ;
+
+        p = prop->value;
+
+        for (i = 0; total < prop->length; total += l, p += l) {
+                l = strlen(p) + 1;
+                if (*p != 0)
+                        i++;
+        }
+        return i;
+}
+EXPORT_SYMBOL_GPL(of_property_count_strings);
+
+/**
  * of_parse_phandle - Resolve a phandle property to a device_node pointer
  * @np: Pointer to device node holding phandle property
  * @phandle_name: Name of property holding a phandle value