[RFC PATCH 12/31] xen/device-tree: Add dt_property_read_string_helper and friends

[Oleksandr Tyshchenko <olekstysh@gmail.com>]

From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>

This is a port from Linux.

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
CC: Stefano Stabellini <sstabellini@kernel.org>
CC: Julien Grall <julien.grall@linaro.org>
---
 xen/common/device_tree.c      | 27 +++++++++++++++
 xen/include/xen/device_tree.h | 81 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 108 insertions(+)

diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
index 7b4cad3..827eadd 100644
--- a/xen/common/device_tree.c
+++ b/xen/common/device_tree.c
@@ -260,6 +260,33 @@ int dt_property_read_string(const struct dt_device_node *np,
     return 0;
 }
 
+int dt_property_read_string_helper(const struct dt_device_node *np,
+                                   const char *propname, const char **out_strs,
+                                   size_t sz, int skip)
+{
+    const struct dt_property *prop = dt_find_property(np, propname, NULL);
+    int l = 0, i = 0;
+    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 && (!out_strs || i < skip + sz); i++, p += l )
+    {
+        l = strnlen(p, end - p) + 1;
+        if ( p + l > end )
+            return -EILSEQ;
+        if ( out_strs && i >= skip )
+            *out_strs++ = p;
+    }
+    i -= skip;
+    return i <= 0 ? -ENODATA : i;
+}
+
 const char *dt_property_next_string(const struct dt_property *prop,
                                     const char *cur)
 {
diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
index e2d7346..7e51a7a 100644
--- a/xen/include/xen/device_tree.h
+++ b/xen/include/xen/device_tree.h
@@ -440,6 +440,87 @@ int dt_property_read_string(const struct dt_device_node *np,
                             const char *propname, const char **out_string);
 
 /**
+ * dt_property_read_string_helper() - Utility helper for parsing string properties
+ * @np:       device node from which the property value is to be read.
+ * @propname: name of the property to be searched.
+ * @out_strs: output array of string pointers.
+ * @sz:       number of array elements to read.
+ * @skip:     Number of strings to skip over at beginning of list.
+ *
+ * Don't call this function directly. It is a utility helper for the
+ * dt_property_read_string*() family of functions.
+ */
+int dt_property_read_string_helper(const struct dt_device_node *np,
+                                   const char *propname, const char **out_strs,
+                                   size_t sz, int skip);
+
+/**
+ * dt_property_read_string_array() - Read an array 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.
+ * @out_strs: output array of string pointers.
+ * @sz:       number of array elements to read.
+ *
+ * Search for a property in a device tree node and retrieve a list of
+ * terminated string values (pointer to data, not a copy) in that property.
+ *
+ * If @out_strs is NULL, the number of strings in the property is returned.
+ */
+static inline int dt_property_read_string_array(const struct dt_device_node *np,
+                                                const char *propname,
+                                                const char **out_strs,
+                                                size_t sz)
+{
+	return dt_property_read_string_helper(np, propname, out_strs, sz, 0);
+}
+
+/**
+ * dt_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.
+ */
+static inline int dt_property_count_strings(const struct dt_device_node *np,
+                                            const char *propname)
+{
+	return dt_property_read_string_helper(np, propname, NULL, 0, 0);
+}
+
+/**
+ * dt_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.
+ */
+static inline int dt_property_read_string_index(const struct dt_device_node *np,
+                                                const char *propname,
+                                                int index, const char **output)
+{
+	int rc = dt_property_read_string_helper(np, propname, output, 1, index);
+
+	return rc < 0 ? rc : 0;
+}
+
+/**
  * dt_property_for_each_string - Iterate over an array of strings within
  * a property with a given name for a given node.
  *
-- 
2.7.4


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