1 # SPDX-License-Identifier: GPL-2.0-only 1 # SPDX-License-Identifier: GPL-2.0-only
2 config CRAMFS 2 config CRAMFS
3 tristate "Compressed ROM file system s 3 tristate "Compressed ROM file system support (cramfs)"
4 select ZLIB_INFLATE 4 select ZLIB_INFLATE
5 help 5 help
6 Saying Y here includes support for C 6 Saying Y here includes support for CramFs (Compressed ROM File
7 System). CramFs is designed to be a 7 System). CramFs is designed to be a simple, small, and compressed
8 file system for ROM based embedded s 8 file system for ROM based embedded systems. CramFs is read-only,
9 limited to 256MB file systems (with 9 limited to 256MB file systems (with 16MB files), and doesn't support
10 16/32 bits uid/gid, hard links and t 10 16/32 bits uid/gid, hard links and timestamps.
11 11
12 See <file:Documentation/filesystems/ 12 See <file:Documentation/filesystems/cramfs.rst> and
13 <file:fs/cramfs/README> for further 13 <file:fs/cramfs/README> for further information.
14 14
15 To compile this as a module, choose 15 To compile this as a module, choose M here: the module will be called
16 cramfs. Note that the root file sys 16 cramfs. Note that the root file system (the one containing the
17 directory /) cannot be compiled as a 17 directory /) cannot be compiled as a module.
18 18
19 This filesystem is limited in capabi 19 This filesystem is limited in capabilities and performance on
20 purpose to remain small and low on R 20 purpose to remain small and low on RAM usage. It is most suitable
21 for small embedded systems. If you h 21 for small embedded systems. If you have ample RAM to spare, you may
22 consider a more capable compressed f 22 consider a more capable compressed filesystem such as SquashFS
23 which is much better in terms of per 23 which is much better in terms of performance and features.
24 24
25 If unsure, say N. 25 If unsure, say N.
26 26
27 config CRAMFS_BLOCKDEV 27 config CRAMFS_BLOCKDEV
28 bool "Support CramFs image over a regu 28 bool "Support CramFs image over a regular block device" if EXPERT
29 depends on CRAMFS && BLOCK 29 depends on CRAMFS && BLOCK
30 default y 30 default y
31 help 31 help
32 This option allows the CramFs driver 32 This option allows the CramFs driver to load data from a regular
33 block device such a disk partition o 33 block device such a disk partition or a ramdisk.
34 34
35 config CRAMFS_MTD 35 config CRAMFS_MTD
36 bool "Support CramFs image directly ma 36 bool "Support CramFs image directly mapped in physical memory"
37 depends on CRAMFS && CRAMFS <= MTD 37 depends on CRAMFS && CRAMFS <= MTD
38 default y if !CRAMFS_BLOCKDEV 38 default y if !CRAMFS_BLOCKDEV
39 help 39 help
40 This option allows the CramFs driver 40 This option allows the CramFs driver to load data directly from
41 a linear addressed memory range (usu 41 a linear addressed memory range (usually non-volatile memory
42 like flash) instead of going through 42 like flash) instead of going through the block device layer.
43 This saves some memory since no inte 43 This saves some memory since no intermediate buffering is
44 necessary. 44 necessary.
45 45
46 The location of the CramFs image is 46 The location of the CramFs image is determined by a
47 MTD device capable of direct memory 47 MTD device capable of direct memory mapping e.g. from
48 the 'physmap' map driver or a result 48 the 'physmap' map driver or a resulting MTD partition.
49 For example, this would mount the cr 49 For example, this would mount the cramfs image stored in
50 the MTD partition named "xip_fs" on 50 the MTD partition named "xip_fs" on the /mnt mountpoint:
51 51
52 mount -t cramfs mtd:xip_fs /mnt 52 mount -t cramfs mtd:xip_fs /mnt
53 53
54 If unsure, say N. 54 If unsure, say N.
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