uboot/u-boot-stm32mp-2020.01/doc/README.JFFS2

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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 do now need the commands, you can enable the filesystem separately
with CONFIG_FS_JFFS2 and call the jffs2 functions yourself.
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).