xref: /OK3568_Linux_fs/u-boot/doc/README.JFFS2 (revision 4882a59341e53eb6f0b4789bf948001014eff981)
1*4882a593SmuzhiyunJFFS2 options and usage.
2*4882a593Smuzhiyun-----------------------
3*4882a593Smuzhiyun
4*4882a593SmuzhiyunJFFS2 in U-Boot is a read only implementation of the file system in
5*4882a593SmuzhiyunLinux with the same name. To use JFFS2 define CONFIG_CMD_JFFS2.
6*4882a593Smuzhiyun
7*4882a593SmuzhiyunThe module adds three new commands.
8*4882a593Smuzhiyunfsload  - load binary file from a file system image
9*4882a593Smuzhiyunfsinfo  - print information about file systems
10*4882a593Smuzhiyunls      - list files in a directory
11*4882a593Smuzhiyunchpart  - change active partition
12*4882a593Smuzhiyun
13*4882a593SmuzhiyunIf you do now need the commands, you can enable the filesystem separately
14*4882a593Smuzhiyunwith CONFIG_FS_JFFS2 and call the jffs2 functions yourself.
15*4882a593Smuzhiyun
16*4882a593SmuzhiyunIf you boot from a partition which is mounted writable, and you
17*4882a593Smuzhiyunupdate your boot environment by replacing single files on that
18*4882a593Smuzhiyunpartition, you should also define CONFIG_SYS_JFFS2_SORT_FRAGMENTS. Scanning
19*4882a593Smuzhiyunthe JFFS2 filesystem takes *much* longer with this feature, though.
20*4882a593SmuzhiyunSorting is done while inserting into the fragment list, which is
21*4882a593Smuzhiyunmore or less a bubble sort. That algorithm is known to be O(n^2),
22*4882a593Smuzhiyunthus you should really consider if you can avoid it!
23*4882a593Smuzhiyun
24*4882a593Smuzhiyun
25*4882a593SmuzhiyunThere only one way for JFFS2 to find the disk. It uses the flash_info
26*4882a593Smuzhiyunstructure to find the start of a JFFS2 disk (called partition in the code)
27*4882a593Smuzhiyunand you can change where the partition is with two defines.
28*4882a593Smuzhiyun
29*4882a593SmuzhiyunCONFIG_SYS_JFFS2_FIRST_BANK
30*4882a593Smuzhiyun	defined the first flash bank to use
31*4882a593Smuzhiyun
32*4882a593SmuzhiyunCONFIG_SYS_JFFS2_FIRST_SECTOR
33*4882a593Smuzhiyun	defines the first sector to use
34*4882a593Smuzhiyun---
35*4882a593Smuzhiyun
36*4882a593SmuzhiyunTODO.
37*4882a593Smuzhiyun
38*4882a593Smuzhiyun	Remove the assumption that JFFS can dereference a pointer
39*4882a593Smuzhiyun	into the disk. The current code do not work with memory holes
40*4882a593Smuzhiyun	or hardware with a sliding window (PCMCIA).
41