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of: Add support for linking device tree blobs into vmlinux

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This patch adds support for linking device tree blob(s) into
vmlinux. Modifies asm-generic/vmlinux.lds.h to add linking
.dtb sections into vmlinux. To maintain compatiblity with the of/fdt
driver code platforms MUST copy the blob to a non-init memory location
before the kernel frees the .init.* sections in the image.

Modifies scripts/Makefile.lib to add a kbuild command to
compile DTS files to device tree blobs and a rule to create objects to
wrap the blobs for linking.

STRUCT_ALIGNMENT is defined in vmlinux.lds.h for use in the rule to
create wrapper objects for the dtb in Makefile.lib.  The
STRUCT_ALIGN() macro in vmlinux.lds.h is modified to use the
STRUCT_ALIGNMENT definition.

The DTB's are placed on 32 byte boundries to allow parsing the blob
with driver/of/fdt.c during early boot without having to copy the blob
to get the structure alignment GCC expects.

A DTB is linked in by adding the DTB object to the list of objects to
be linked into vmlinux in the archtecture specific Makefile using
   obj-y += foo.dtb.o

Signed-off-by: Dirk Brandewie <dirk.brandewie@gmail.com>
Acked-by: Michal Marek <mmarek@suse.cz>
[grant.likely@secretlab.ca: cleaned up whitespace inconsistencies]
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
This commit is contained in:
Dirk Brandewie
2010-12-22 11:57:26 -08:00
committed by Grant Likely
parent cfb13c5db0
commit aab94339cd
3 changed files with 49 additions and 2 deletions
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15
Documentation/kbuild/makefiles.txt
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@@ -1136,6 +1136,21 @@ When kbuild executes, the following steps are followed (roughly):
resulting in the target file being recompiled for no
obvious reason.
dtc
Create flattend device tree blob object suitable for linking
into vmlinux. Device tree blobs linked into vmlinux are placed
in an init section in the image. Platform code *must* copy the
blob to non-init memory prior to calling unflatten_device_tree().
Example:
#arch/x86/platform/ce4100/Makefile
clean-files := *dtb.S
DTC_FLAGS := -p 1024
obj-y += foo.dtb.o
$(obj)/%.dtb: $(src)/%.dts
$(call cmd,dtc)
--- 6.7 Custom kbuild commands