fdt: Add DEV_TREE_BIN option to specify a device tree binary file
In some cases, an externally-built device tree binary is required to be
attached to U-Boot. An example is when using image signing, since in that
case the .dtb file must include the public keys.
Add a DEV_TREE_BIN option to the Makefile, and update the documentation.
Usage is something like:
make DEV_TREE_BIN=boot/am335x-boneblack-pubkey.dtb
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/README.fdt-control b/doc/README.fdt-control
index 0ceebe7..be92d7a 100644
--- a/doc/README.fdt-control
+++ b/doc/README.fdt-control
@@ -122,7 +122,8 @@
arch/<arch>/dts, and then make any adjustments required.
If CONFIG_OF_EMBED is defined, then it will be picked up and built into
-the U-Boot image (including u-boot.bin).
+the U-Boot image (including u-boot.bin). This is suitable for debugging
+and development only and is not recommended for production devices.
If CONFIG_OF_SEPARATE is defined, then it will be built and placed in
a u-boot.dtb file alongside u-boot.bin. A common approach is then to
@@ -130,7 +131,10 @@
cat u-boot.bin u-boot.dtb >image.bin
-and then flash image.bin onto your board.
+and then flash image.bin onto your board. Note that U-Boot creates
+u-boot-dtb.bin which does the above step for you also. If you are using
+CONFIG_SPL_FRAMEWORK, then u-boot.img will be built to include the device
+tree binary.
If CONFIG_OF_HOSTFILE is defined, then it will be read from a file on
startup. This is only useful for sandbox. Use the -d flag to U-Boot to
@@ -138,6 +142,14 @@
You cannot use more than one of these options at the same time.
+To use a device tree file that you have compiled yourself, pass
+DEV_TREE_BIN=<filename> to 'make', as in:
+
+ make DEV_TREE_BIN=boot/am335x-boneblack-pubkey.dtb
+
+Then U-Boot will copy that file to u-boot.dtb, put it in the .img file
+if used, and u-boot-dtb.bin.
+
If you wish to put the fdt at a different address in memory, you can
define the "fdtcontroladdr" environment variable. This is the hex
address of the fdt binary blob, and will override either of the options.