reading u-boot wiki page on image formats:
http://www.denx.de/wiki/view/DULG/UBootImages
wherein one reads:
"Compression Type (Provisions for uncompressed, gzip, bzip2, lzo; Currently supported: uncompressed, gzip, bzip2, lzo)."
clearly, that wiki page list is incomplete, but there's more here.
first, the full list appears to live in include/image.h:
/* * Compression Types */ enum { IH_COMP_NONE = 0, /* No Compression Used */ IH_COMP_GZIP, /* gzip Compression Used */ IH_COMP_BZIP2, /* bzip2 Compression Used */ IH_COMP_LZMA, /* lzma Compression Used */ IH_COMP_LZO, /* lzo Compression Used */ IH_COMP_LZ4, /* lz4 Compression Used */
IH_COMP_COUNT, };
but how those types are selected seems a bit inconsistent.
first, gzip appears to be automatic(?) for everyone, from include/config_defaults.h:
#define CONFIG_GZIP 1
however, of all 5 types of compression, only one has a Kconfig file entry, LZ4, in lib/Kconfig:
menu "Compression Support"
config LZ4 bool "Enable LZ4 decompression support" help If this option is set, support for LZ4 compressed images is included. The LZ4 algorithm can run in-place as long as the compressed image is loaded to the end of the output buffer, and trades lower compression ratios for much faster decompression.
NOTE: This implements the release version of the LZ4 frame format as generated by default by the 'lz4' command line tool. This is not the same as the outdated, less efficient legacy frame format currently (2015) implemented in the Linux kernel (generated by 'lz4 -l'). The two formats are incompatible.
endmenu
for consistency, isn't it standard for any CONFIG_* settings to be defined in Kconfig files? the other compression types seem to be selectable simply by manually setting them in config files, as in:
$ grep -r "define CONFIG_LZMA" * include/configs/bfin_adi_common.h:#define CONFIG_LZMA include/configs/VCMA9.h:#define CONFIG_LZMA include/configs/ap143.h:#define CONFIG_LZMA include/configs/qemu-mips.h:#define CONFIG_LZMA include/configs/iconnect.h:#define CONFIG_LZMA include/configs/ap121.h:#define CONFIG_LZMA include/configs/nsa310s.h:#define CONFIG_LZMA include/configs/mv-plug-common.h:#define CONFIG_LZMA include/configs/ib62x0.h:#define CONFIG_LZMA include/configs/qemu-mips64.h:#define CONFIG_LZMA include/configs/tplink_wdr4300.h:#define CONFIG_LZMA include/configs/sandbox.h:#define CONFIG_LZMA include/configs/smdk2410.h:#define CONFIG_LZMA $
should not all compression types get their own entries in lib/Kconfig? anyway, i'll at least update the wiki page.
movin' on ...
rday