dt: add helper for empty dt creation

We want to get rid of the concept of loading an external device tree and instead
generate our own. However, to do this we need to also create a device tree
template programatically.

This patch adds a helper to create an empty device tree in memory.

Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Peter Crosthwaite <peter.crosthwaite@petalogix.com>

2 files changed, 38 insertions, 0 deletions

diff --git a/device_tree.c b/device_tree.c
index 2f127b71b0..d0378961f0 100644
--- a/device_tree.c
+++ b/device_tree.c
@@ -25,6 +25,43 @@
 
 #include <libfdt.h>
 
+#define FDT_MAX_SIZE  0x10000
+
+void *create_device_tree(int *sizep)
+{
+    void *fdt;
+    int ret;
+
+    *sizep = FDT_MAX_SIZE;
+    fdt = g_malloc0(FDT_MAX_SIZE);
+    ret = fdt_create(fdt, FDT_MAX_SIZE);
+    if (ret < 0) {
+        goto fail;
+    }
+    ret = fdt_begin_node(fdt, "");
+    if (ret < 0) {
+        goto fail;
+    }
+    ret = fdt_end_node(fdt);
+    if (ret < 0) {
+        goto fail;
+    }
+    ret = fdt_finish(fdt);
+    if (ret < 0) {
+        goto fail;
+    }
+    ret = fdt_open_into(fdt, fdt, *sizep);
+    if (ret) {
+        fprintf(stderr, "Unable to copy device tree in memory\n");
+        exit(1);
+    }
+
+    return fdt;
+fail:
+    fprintf(stderr, "%s Couldn't create dt: %s\n", __func__, fdt_strerror(ret));
+    exit(1);
+}
+
 void *load_device_tree(const char *filename_path, int *sizep)
 {
     int dt_size;
diff --git a/device_tree.h b/device_tree.h
index 36fc9dbede..5f76f40eeb 100644
--- a/device_tree.h
+++ b/device_tree.h
@@ -14,6 +14,7 @@
 #ifndef __DEVICE_TREE_H__
 #define __DEVICE_TREE_H__
 
+void *create_device_tree(int *sizep);
 void *load_device_tree(const char *filename_path, int *sizep);
 
 int qemu_devtree_setprop(void *fdt, const char *node_path,