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# SPDX-License-Identifier: GPL-2.0-only
config CRAMFS
tristate "Compressed ROM file system support (cramfs)"
Saying Y here includes support for CramFs (Compressed ROM File
System). CramFs is designed to be a simple, small, and compressed
file system for ROM based embedded systems. CramFs is read-only,
limited to 256MB file systems (with 16MB files), and doesn't support
16/32 bits uid/gid, hard links and timestamps.
See <file:Documentation/filesystems/cramfs.rst> and
<file:fs/cramfs/README> for further information.
To compile this as a module, choose M here: the module will be called
cramfs. Note that the root file system (the one containing the
directory /) cannot be compiled as a module.
This filesystem is limited in capabilities and performance on
purpose to remain small and low on RAM usage. It is most suitable
for small embedded systems. If you have ample RAM to spare, you may
consider a more capable compressed filesystem such as SquashFS
which is much better in terms of performance and features.
If unsure, say N.
bool "Support CramFs image over a regular block device" if EXPERT
depends on CRAMFS && BLOCK
default y
This option allows the CramFs driver to load data from a regular
block device such a disk partition or a ramdisk.
bool "Support CramFs image directly mapped in physical memory"
depends on CRAMFS && CRAMFS <= MTD
default y if !CRAMFS_BLOCKDEV
This option allows the CramFs driver to load data directly from
a linear adressed memory range (usually non volatile memory
like flash) instead of going through the block device layer.
This saves some memory since no intermediate buffering is
The location of the CramFs image is determined by a
MTD device capable of direct memory mapping e.g. from
the 'physmap' map driver or a resulting MTD partition.
For example, this would mount the cramfs image stored in
the MTD partition named "xip_fs" on the /mnt mountpoint:
mount -t cramfs mtd:xip_fs /mnt
If unsure, say N.