8e35bb07eb mkimage: Support automatic creating of a FIT without a .its

[Wolfgang Denk]

Hi Simon,

your commit 8e35bb07eb (2016-03-14) "mkimage: Support automatic
creating of a FIT without a .its" added the "-f auto" option to
mkimage.  While convenient in many situation, I had to notice that
with "-f auto" there is no checksum information included with any of
the blobs stored in the FIT image.

I guess the rationale was that the primary use case for this was to
generate combinations of a U-Boot image with several device tree
blobs to be used / selected by the SPL, as one can see for example
in scripts/Makefile.spl :

MKIMAGEFLAGS_$(SPL_BIN).multidtb.fit = -f auto -A $(ARCH) -T firmware -C none -O u-boot \
        -n "Multi DTB fit image for $(SPL_BIN)" -E \
        $(patsubst %,-b %,$(SHRUNK_ARCH_DTB))

And - at least at that time - most implementations of the SPL did
not need/want checksum verification.


However I'm asking myself if this is not an unfortunate choice.
It is trivial for a not-checksum-enabled SPL to ignore any checksum
in the image, but not the other way round: if there is no checksum
in the images, the SPL will never be able to verify one.


Would it not be a more reasonable default for operation unter the
"-f auto" flag to enable at least simple checksumming, say by
auto-adding something like

	hash-1 {
		algo = "crc32";
	};

to the generated descriptions?

Best regards,

Wolfgang Denk

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