core/fdt: Introduce opal_get_device_tree()

This introduces OPAL API opal_get_device_tree() to get the device
sub-tree. It's going to be used in PCI hot add path.

Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/doc/opal-api/opal-get-device-tree-118.txt b/doc/opal-api/opal-get-device-tree-118.txt
new file mode 100644
index 0000000..235a321
--- /dev/null
+++ b/doc/opal-api/opal-get-device-tree-118.txt
@@ -0,0 +1,24 @@
+OPAL_GET_DEVICE_TREE
+--------------------
+
+Get device sub-tree
+
+Parameters:
+	uint32_t phandle: root device node phandle of the device sub-tree
+	uint64_t buf: FDT blob buffer or NULL
+	uint64_t len: length of the FDT blob buffer
+
+Calling:
+
+Retrieve device sub-tree. The root node's phandle is identified by @phandle.
+The typical use is for the kernel to update its device tree following a change
+in hardware (e.g. PCI hotplug).
+
+Return Codes:
+
+FDT blob size - returned FDT blob buffer size when @buf is NULL
+OPAL_SUCCESS - FDT blob is created successfully
+OPAL_PARAMETER - invalid argument @phandle or @len
+OPAL_INTERNAL_ERROR - failure creating FDT blob when calculating its size
+OPAL_NO_MEM - not enough room in buffer for device sub-tree
+OPAL_EMPTY - failure creating FDT blob