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+# SPDX-License-Identifier: GPL-2.0
+#
+# Configuration for initramfs
+#
+
+config INITRAMFS_SOURCE
+ string "Initramfs source file(s)"
+ default ""
+ help
+ This can be either a single cpio archive with a .cpio suffix or a
+ space-separated list of directories and files for building the
+ initramfs image. A cpio archive should contain a filesystem archive
+ to be used as an initramfs image. Directories should contain a
+ filesystem layout to be included in the initramfs image. Files
+ should contain entries according to the format described by the
+ "usr/gen_init_cpio" program in the kernel tree.
+
+ When multiple directories and files are specified then the
+ initramfs image will be the aggregate of all of them.
+
+ See <file:Documentation/driver-api/early-userspace/early_userspace_support.rst> for more details.
+
+ If you are not sure, leave it blank.
+
+config INITRAMFS_FORCE
+ bool "Ignore the initramfs passed by the bootloader"
+ depends on CMDLINE_EXTEND || CMDLINE_FORCE
+ help
+ This option causes the kernel to ignore the initramfs image
+ (or initrd image) passed to it by the bootloader. This is
+ analogous to CMDLINE_FORCE, which is found on some architectures,
+ and is useful if you cannot or don't want to change the image
+ your bootloader passes to the kernel.
+
+config INITRAMFS_ROOT_UID
+ int "User ID to map to 0 (user root)"
+ depends on INITRAMFS_SOURCE!=""
+ default "0"
+ help
+ If INITRAMFS_SOURCE points to a directory, files owned by this UID
+ (-1 = current user) will be owned by root in the resulting image.
+
+ If you are not sure, leave it set to "0".
+
+config INITRAMFS_ROOT_GID
+ int "Group ID to map to 0 (group root)"
+ depends on INITRAMFS_SOURCE!=""
+ default "0"
+ help
+ If INITRAMFS_SOURCE points to a directory, files owned by this GID
+ (-1 = current group) will be owned by root in the resulting image.
+
+ If you are not sure, leave it set to "0".
+
+config RD_GZIP
+ bool "Support initial ramdisk/ramfs compressed using gzip"
+ default y
+ select DECOMPRESS_GZIP
+ help
+ Support loading of a gzip encoded initial ramdisk or cpio buffer.
+ If unsure, say Y.
+
+config RD_BZIP2
+ bool "Support initial ramdisk/ramfs compressed using bzip2"
+ default y
+ select DECOMPRESS_BZIP2
+ help
+ Support loading of a bzip2 encoded initial ramdisk or cpio buffer
+ If unsure, say N.
+
+config RD_LZMA
+ bool "Support initial ramdisk/ramfs compressed using LZMA"
+ default y
+ select DECOMPRESS_LZMA
+ help
+ Support loading of a LZMA encoded initial ramdisk or cpio buffer
+ If unsure, say N.
+
+config RD_XZ
+ bool "Support initial ramdisk/ramfs compressed using XZ"
+ default y
+ select DECOMPRESS_XZ
+ help
+ Support loading of a XZ encoded initial ramdisk or cpio buffer.
+ If unsure, say N.
+
+config RD_LZO
+ bool "Support initial ramdisk/ramfs compressed using LZO"
+ default y
+ select DECOMPRESS_LZO
+ help
+ Support loading of a LZO encoded initial ramdisk or cpio buffer
+ If unsure, say N.
+
+config RD_LZ4
+ bool "Support initial ramdisk/ramfs compressed using LZ4"
+ default y
+ select DECOMPRESS_LZ4
+ help
+ Support loading of a LZ4 encoded initial ramdisk or cpio buffer
+ If unsure, say N.
+
+config RD_ZSTD
+ bool "Support initial ramdisk/ramfs compressed using ZSTD"
+ default y
+ depends on BLK_DEV_INITRD
+ select DECOMPRESS_ZSTD
+ help
+ Support loading of a ZSTD encoded initial ramdisk or cpio buffer.
+ If unsure, say N.
+
+choice
+ prompt "Built-in initramfs compression mode"
+ depends on INITRAMFS_SOURCE != ""
+ help
+ This option allows you to decide by which algorithm the builtin
+ initramfs will be compressed. Several compression algorithms are
+ available, which differ in efficiency, compression and
+ decompression speed. Compression speed is only relevant
+ when building a kernel. Decompression speed is relevant at
+ each boot. Also the memory usage during decompression may become
+ relevant on memory constrained systems. This is usually based on the
+ dictionary size of the algorithm with algorithms like XZ and LZMA
+ featuring large dictionary sizes.
+
+ High compression options are mostly useful for users who are
+ low on RAM, since it reduces the memory consumption during
+ boot.
+
+ Keep in mind that your build system needs to provide the appropriate
+ compression tool to compress the generated initram cpio file for
+ embedding.
+
+ If in doubt, select 'None'
+
+config INITRAMFS_COMPRESSION_GZIP
+ bool "Gzip"
+ depends on RD_GZIP
+ help
+ Use the old and well tested gzip compression algorithm. Gzip provides
+ a good balance between compression ratio and decompression speed and
+ has a reasonable compression speed. It is also more likely to be
+ supported by your build system as the gzip tool is present by default
+ on most distros.
+
+config INITRAMFS_COMPRESSION_BZIP2
+ bool "Bzip2"
+ depends on RD_BZIP2
+ help
+ It's compression ratio and speed is intermediate. Decompression speed
+ is slowest among the choices. The initramfs size is about 10% smaller
+ with bzip2, in comparison to gzip. Bzip2 uses a large amount of
+ memory. For modern kernels you will need at least 8MB RAM or more for
+ booting.
+
+ If you choose this, keep in mind that you need to have the bzip2 tool
+ available to be able to compress the initram.
+
+config INITRAMFS_COMPRESSION_LZMA
+ bool "LZMA"
+ depends on RD_LZMA
+ help
+ This algorithm's compression ratio is best but has a large dictionary
+ size which might cause issues in memory constrained systems.
+ Decompression speed is between the other choices. Compression is
+ slowest. The initramfs size is about 33% smaller with LZMA in
+ comparison to gzip.
+
+ If you choose this, keep in mind that you may need to install the xz
+ or lzma tools to be able to compress the initram.
+
+config INITRAMFS_COMPRESSION_XZ
+ bool "XZ"
+ depends on RD_XZ
+ help
+ XZ uses the LZMA2 algorithm and has a large dictionary which may cause
+ problems on memory constrained systems. The initramfs size is about
+ 30% smaller with XZ in comparison to gzip. Decompression speed is
+ better than that of bzip2 but worse than gzip and LZO. Compression is
+ slow.
+
+ If you choose this, keep in mind that you may need to install the xz
+ tool to be able to compress the initram.
+
+config INITRAMFS_COMPRESSION_LZO
+ bool "LZO"
+ depends on RD_LZO
+ help
+ It's compression ratio is the second poorest amongst the choices. The
+ kernel size is about 10% bigger than gzip. Despite that, it's
+ decompression speed is the second fastest and it's compression speed
+ is quite fast too.
+
+ If you choose this, keep in mind that you may need to install the lzop
+ tool to be able to compress the initram.
+
+config INITRAMFS_COMPRESSION_LZ4
+ bool "LZ4"
+ depends on RD_LZ4
+ help
+ It's compression ratio is the poorest amongst the choices. The kernel
+ size is about 15% bigger than gzip; however its decompression speed
+ is the fastest.
+
+ If you choose this, keep in mind that most distros don't provide lz4
+ by default which could cause a build failure.
+
+config INITRAMFS_COMPRESSION_ZSTD
+ bool "ZSTD"
+ depends on RD_ZSTD
+ help
+ ZSTD is a compression algorithm targeting intermediate compression
+ with fast decompression speed. It will compress better than GZIP and
+ decompress around the same speed as LZO, but slower than LZ4.
+
+ If you choose this, keep in mind that you may need to install the zstd
+ tool to be able to compress the initram.
+
+config INITRAMFS_COMPRESSION_NONE
+ bool "None"
+ help
+ Do not compress the built-in initramfs at all. This may sound wasteful
+ in space, but, you should be aware that the built-in initramfs will be
+ compressed at a later stage anyways along with the rest of the kernel,
+ on those architectures that support this. However, not compressing the
+ initramfs may lead to slightly higher memory consumption during a
+ short time at boot, while both the cpio image and the unpacked
+ filesystem image will be present in memory simultaneously
+
+endchoice