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decompressors: add XZ decompressor module In userspace, the .lzma format has become mostly a legacy file format that got superseded by the .xz format. Similarly, LZMA Utils was superseded by XZ Utils. These patches add support for XZ decompression into the kernel. Most of the code is as is from XZ Embedded <http://tukaani.org/xz/embedded.html>. It was written for the Linux kernel but is usable in other projects too. Advantages of XZ over the current LZMA code in the kernel: - Nice API that can be used by other kernel modules; it's not limited to kernel, initramfs, and initrd decompression. - Integrity check support (CRC32) - BCJ filters improve compression of executable code on certain architectures. These together with LZMA2 can produce a few percent smaller kernel or Squashfs images than plain LZMA without making the decompression slower. This patch: Add the main decompression code (xz_dec), testing module (xz_dec_test), wrapper script (xz_wrap.sh) for the xz command line tool, and documentation. The xz_dec module is enough to have a usable XZ decompressor e.g. for Squashfs. Signed-off-by: Lasse Collin <lasse.collin@tukaani.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Alain Knaff <alain@knaff.lu> Cc: Albin Tonnerre <albin.tonnerre@free-electrons.com> Cc: Phillip Lougher <phillip@lougher.demon.co.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-01-13 09:01:22 +08:00
config XZ_DEC
tristate "XZ decompression support"
select CRC32
help
LZMA2 compression algorithm and BCJ filters are supported using
the .xz file format as the container. For integrity checking,
CRC32 is supported. See Documentation/xz.txt for more information.
config XZ_DEC_X86
bool "x86 BCJ filter decoder" if EMBEDDED
default y
depends on XZ_DEC
select XZ_DEC_BCJ
config XZ_DEC_POWERPC
bool "PowerPC BCJ filter decoder" if EMBEDDED
default y
depends on XZ_DEC
select XZ_DEC_BCJ
config XZ_DEC_IA64
bool "IA-64 BCJ filter decoder" if EMBEDDED
default y
depends on XZ_DEC
select XZ_DEC_BCJ
config XZ_DEC_ARM
bool "ARM BCJ filter decoder" if EMBEDDED
default y
depends on XZ_DEC
select XZ_DEC_BCJ
config XZ_DEC_ARMTHUMB
bool "ARM-Thumb BCJ filter decoder" if EMBEDDED
default y
depends on XZ_DEC
select XZ_DEC_BCJ
config XZ_DEC_SPARC
bool "SPARC BCJ filter decoder" if EMBEDDED
default y
depends on XZ_DEC
select XZ_DEC_BCJ
config XZ_DEC_BCJ
bool
default n
config XZ_DEC_TEST
tristate "XZ decompressor tester"
default n
depends on XZ_DEC
help
This allows passing .xz files to the in-kernel XZ decoder via
a character special file. It calculates CRC32 of the decompressed
data and writes diagnostics to the system log.
Unless you are developing the XZ decoder, you don't need this
and should say N.