linux/lib/xz/Kconfig
Lasse Collin aaa2975f2b lib/xz: Add MicroLZMA decoder
MicroLZMA is a yet another header format variant where the first
byte of a raw LZMA stream (without the end of stream marker) has
been replaced with a bitwise-negation of the lc/lp/pb properties
byte. MicroLZMA was created to be used in EROFS but can be used
by other things too where wasting minimal amount of space for
headers is important.

This is implemented using most of the LZMA2 code as is so the
amount of new code is small. The API has a few extra features
compared to the XZ decoder. On the other hand, the API lacks
XZ_BUF_ERROR support which is important to take into account
when using this API.

MicroLZMA doesn't support BCJ filters. In theory they could be
added later as there are many unused/reserved values for the
first byte of the compressed stream but in practice it is
somewhat unlikely to happen due to a few implementation reasons.

Link: https://lore.kernel.org/r/20211010213145.17462-5-xiang@kernel.org
Signed-off-by: Lasse Collin <lasse.collin@tukaani.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
2021-10-19 23:44:30 +08:00

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# SPDX-License-Identifier: GPL-2.0-only
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/staging/xz.rst for more information.
if XZ_DEC
config XZ_DEC_X86
bool "x86 BCJ filter decoder" if EXPERT
default y
select XZ_DEC_BCJ
config XZ_DEC_POWERPC
bool "PowerPC BCJ filter decoder" if EXPERT
default y
select XZ_DEC_BCJ
config XZ_DEC_IA64
bool "IA-64 BCJ filter decoder" if EXPERT
default y
select XZ_DEC_BCJ
config XZ_DEC_ARM
bool "ARM BCJ filter decoder" if EXPERT
default y
select XZ_DEC_BCJ
config XZ_DEC_ARMTHUMB
bool "ARM-Thumb BCJ filter decoder" if EXPERT
default y
select XZ_DEC_BCJ
config XZ_DEC_SPARC
bool "SPARC BCJ filter decoder" if EXPERT
default y
select XZ_DEC_BCJ
config XZ_DEC_MICROLZMA
bool "MicroLZMA decoder"
default n
help
MicroLZMA is a header format variant where the first byte
of a raw LZMA stream (without the end of stream marker) has
been replaced with a bitwise-negation of the lc/lp/pb
properties byte. MicroLZMA was created to be used in EROFS
but can be used by other things too where wasting minimal
amount of space for headers is important.
Unless you know that you need this, say N.
endif
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.