binman: Support updating the dtb in an ELF file
WIth EFI we must embed the devicetree in an ELF image so that it is loaded
as part of the executable file. We want it to include the binman
definition in there also, which in some cases cannot be created until the
ELF (u-boot) is built. Add an option to binman to support writing the
updated dtb to the ELF file u-boot.out
This is useful with the EFI app, which is always packaged as an ELF file.
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/binman.rst b/tools/binman/binman.rst
index 614df54..35de93b 100644
--- a/tools/binman/binman.rst
+++ b/tools/binman/binman.rst
@@ -818,6 +818,42 @@
# u_boot_dtsi_options_debug = $(u_boot_dtsi_options_raw)
+Updating an ELF file
+====================
+
+For the EFI app, where U-Boot is loaded from UEFI and runs as an app, there is
+no way to update the devicetree after U-Boot is built. Normally this works by
+creating a new u-boot.dtb.out with he updated devicetree, which is automatically
+built into the output image. With ELF this is not possible since the ELF is
+not part of an image, just a stand-along file. We must create an updated ELF
+file with the new devicetree.
+
+This is handled by the --update-fdt-in-elf option. It takes four arguments,
+separated by comma:
+
+ infile - filename of input ELF file, e.g. 'u-boot's
+ outfile - filename of output ELF file, e.g. 'u-boot.out'
+ begin_sym - symbol at the start of the embedded devicetree, e.g.
+ '__dtb_dt_begin'
+ end_sym - symbol at the start of the embedded devicetree, e.g.
+ '__dtb_dt_end'
+
+When this flag is used, U-Boot does all the normal packaging, but as an
+additional step, it creates a new ELF file with the new devicetree embedded in
+it.
+
+If logging is enabled you will see a message like this::
+
+ Updating file 'u-boot' with data length 0x400a (16394) between symbols
+ '__dtb_dt_begin' and '__dtb_dt_end'
+
+There must be enough space for the updated devicetree. If not, an error like
+the following is produced::
+
+ ValueError: Not enough space in 'u-boot' for data length 0x400a (16394);
+ size is 0x1744 (5956)
+
+
Entry Documentation
===================