[RFC PATCH 10/31] xen/device-tree: Add dt_property_read_u32_index helper

[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      | 52 +++++++++++++++++++++++++++++++++++++++++++
 xen/include/xen/device_tree.h | 20 +++++++++++++++++
 2 files changed, 72 insertions(+)

diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
index 08f8072..0fa654e 100644
--- a/xen/common/device_tree.c
+++ b/xen/common/device_tree.c
@@ -176,6 +176,58 @@ bool_t dt_property_read_u32(const struct dt_device_node *np,
     return 1;
 }
 
+/**
+ * dt_find_property_value_of_size
+ *
+ * @np:       device node from which the property value is to be read.
+ * @propname: name of the property to be searched.
+ * @min:      minimum allowed length of property value
+ * @max:      maximum allowed length of property value (0 means unlimited)
+ * @len:      if !=NULL, actual length is written to here
+ *
+ * Search for a property in a device node and valid the requested size.
+ * Returns the property value on success, -EINVAL if the property does not
+ * exist, -ENODATA if property does not have a value, and -EOVERFLOW if the
+ * property data is too small or too large.
+ */
+static void *dt_find_property_value_of_size(const struct dt_device_node *np,
+                                            const char *propname,
+                                            u32 min, u32 max, size_t *len)
+{
+    const struct dt_property *prop = dt_find_property(np, propname, NULL);
+
+    if ( !prop )
+        return ERR_PTR(-EINVAL);
+    if ( !prop->value )
+        return ERR_PTR(-ENODATA);
+    if ( prop->length < min )
+        return ERR_PTR(-EOVERFLOW);
+    if ( max && prop->length > max )
+        return ERR_PTR(-EOVERFLOW);
+
+    if ( len )
+        *len = prop->length;
+
+    return prop->value;
+}
+
+int dt_property_read_u32_index(const struct dt_device_node *np,
+                               const char *propname,
+                               u32 index, u32 *out_value)
+{
+    const u32 *val =
+        dt_find_property_value_of_size(np, propname,
+                                       ((index + 1) * sizeof(*out_value)),
+                                       0,
+                                       NULL);
+
+    if ( IS_ERR(val) )
+        return PTR_ERR(val);
+
+    *out_value = be32_to_cpup(((__be32 *)val) + index);
+
+    return 0;
+}
 
 bool_t dt_property_read_u64(const struct dt_device_node *np,
                          const char *name, u64 *out_value)
diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
index 9e0931c..87b4b67 100644
--- a/xen/include/xen/device_tree.h
+++ b/xen/include/xen/device_tree.h
@@ -374,6 +374,26 @@ const struct dt_property *dt_find_property(const struct dt_device_node *np,
  */
 bool_t dt_property_read_u32(const struct dt_device_node *np,
                             const char *name, u32 *out_value);
+
+/**
+ * dt_property_read_u32_index - Find and read a u32 from a multi-value 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 u32 in the list of values
+ * @out_value: pointer to return value, modified only if no error.
+ *
+ * Search for a property in a device node and read nth 32-bit value from
+ * it. Returns 0 on success, -EINVAL if the property does not exist,
+ * -ENODATA if property does not have a value, and -EOVERFLOW if the
+ * property data isn't large enough.
+ *
+ * The out_value is modified only if a valid u32 value can be decoded.
+ */
+int dt_property_read_u32_index(const struct dt_device_node *np,
+                               const char *propname,
+                               u32 index, u32 *out_value);
+
 /**
  * dt_property_read_u64 - Helper to read a u64 property.
  * @np: node to get the value
-- 
2.7.4


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