[RFC 08/19] xen/dts: Provide an helper to get a DT node from a path provided by a guest

[Julien Grall <julien.grall@linaro.org>]

Signed-off-by: Julien Grall <julien.grall@linaro.org>
---
 xen/common/device_tree.c      |   19 +++++++++++++++++++
 xen/include/xen/device_tree.h |   17 +++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
index 4736e0d..fd95307 100644
--- a/xen/common/device_tree.c
+++ b/xen/common/device_tree.c
@@ -13,6 +13,7 @@
 #include <xen/config.h>
 #include <xen/types.h>
 #include <xen/init.h>
+#include <xen/guest_access.h>
 #include <xen/device_tree.h>
 #include <xen/kernel.h>
 #include <xen/lib.h>
@@ -661,6 +662,24 @@ struct dt_device_node *dt_find_node_by_path(const char *path)
     return np;
 }
 
+int dt_find_node_by_gpath(XEN_GUEST_HANDLE(char) u_path, uint32_t u_plen,
+                          struct dt_device_node **node)
+{
+    char *path;
+    int ret;
+
+    ret = copy_string_from_guest(u_path, &path, u_plen,
+                                 DEVICE_TREE_MAX_PATHLEN);
+    if ( ret )
+        return ret;
+
+    *node = dt_find_node_by_path(path);
+
+    xfree(path);
+
+    return (*node == NULL) ? -ESRCH : 0;
+}
+
 struct dt_device_node *dt_find_node_by_alias(const char *alias)
 {
     const struct dt_alias_prop *app;
diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
index e413447..bb33e54 100644
--- a/xen/include/xen/device_tree.h
+++ b/xen/include/xen/device_tree.h
@@ -20,6 +20,9 @@
 
 #define DEVICE_TREE_MAX_DEPTH 16
 
+/* This limit is used by the hypercalls to restrict the size of the path */
+#define DEVICE_TREE_MAX_PATHLEN 1024
+
 #define NR_MEM_BANKS 8
 
 #define MOD_XEN    0
@@ -484,6 +487,20 @@ struct dt_device_node *dt_find_node_by_alias(const char *alias);
  */
 struct dt_device_node *dt_find_node_by_path(const char *path);
 
+
+/**
+ * dt_find_node_by_gpath - Same as dt_find_node_by_path but retrieve the
+ * path from the guest
+ *
+ * @u_path: Xen Guest handle to the buffer containing the path
+ * @u_plen: Length of the buffer
+ * @node: TODO
+ *
+ * Return 0 if succeed otherwise -errno
+ */
+int dt_find_node_by_gpath(XEN_GUEST_HANDLE(char) u_path, uint32_t u_plen,
+                          struct dt_device_node **node);
+
 /**
  * dt_get_parent - Get a node's parent if any
  * @node: Node to get parent
-- 
1.7.10.4