[people/ms/u-boot.git] / doc / README.JFFS2

JFFS2 options and usage.
-----------------------

JFFS2 in U-Boot is a read only implementation of the file system in
Linux with the same name. To use JFFS2 define CONFIG_CMD_JFFS2.

The module adds three new commands.
fsload  - load binary file from a file system image
fsinfo  - print information about file systems
ls      - list files in a directory
chpart  - change active partition

If you boot from a partition which is mounted writable, and you
update your boot environment by replacing single files on that
partition, you should also define CONFIG_SYS_JFFS2_SORT_FRAGMENTS. Scanning
the JFFS2 filesystem takes *much* longer with this feature, though.
Sorting is done while inserting into the fragment list, which is
more or less a bubble sort. That algorithm is known to be O(n^2),
thus you should really consider if you can avoid it!


There only one way for JFFS2 to find the disk. It uses the flash_info
structure to find the start of a JFFS2 disk (called partition in the code)
and you can change where the partition is with two defines.

CONFIG_SYS_JFFS2_FIRST_BANK
	defined the first flash bank to use

CONFIG_SYS_JFFS2_FIRST_SECTOR
	defines the first sector to use
---

TODO.

	Remove the assumption that JFFS can dereference a pointer
	into the disk. The current code do not work with memory holes
	or hardware with a sliding window (PCMCIA).
Commit	Line	Data
c609719b WD	1	JFFS2 options and usage.
	2	-----------------------
	3
	4	JFFS2 in U-Boot is a read only implementation of the file system in
b3aff0cb	5	Linux with the same name. To use JFFS2 define CONFIG_CMD_JFFS2.
c609719b WD	6
	7	The module adds three new commands.
	8	fsload - load binary file from a file system image
	9	fsinfo - print information about file systems
	10	ls - list files in a directory
f39748ae	11	chpart - change active partition
c609719b	12
06d01dbe WD	13	If you boot from a partition which is mounted writable, and you
06d01dbe WD	14	update your boot environment by replacing single files on that
6d0f6bcf	15	partition, you should also define CONFIG_SYS_JFFS2_SORT_FRAGMENTS. Scanning
06d01dbe WD	16	the JFFS2 filesystem takes much longer with this feature, though.
	17	Sorting is done while inserting into the fragment list, which is
	18	more or less a bubble sort. That algorithm is known to be O(n^2),
	19	thus you should really consider if you can avoid it!
	20
c609719b	21
b2482dff SG	22	There only one way for JFFS2 to find the disk. It uses the flash_info
	23	structure to find the start of a JFFS2 disk (called partition in the code)
	24	and you can change where the partition is with two defines.
c609719b	25
6d0f6bcf	26	CONFIG_SYS_JFFS2_FIRST_BANK
c609719b WD	27	defined the first flash bank to use
c609719b WD	28
6d0f6bcf	29	CONFIG_SYS_JFFS2_FIRST_SECTOR
c609719b	30	defines the first sector to use
c609719b WD	31	---
	32
	33	TODO.
	34
8bde7f77 WD	35	Remove the assumption that JFFS can dereference a pointer
	36	into the disk. The current code do not work with memory holes
	37	or hardware with a sliding window (PCMCIA).