u-boot/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 CFG_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 CFG_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 is two ways for JFFS2 to find the disk. The default way 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.

CFG_JFFS2_FIRST_BANK
	defined the first flash bank to use

CFG_JFFS2_FIRST_SECTOR
	defines the first sector to use


The second way is to define CFG_JFFS_CUSTOM_PART and implement the
jffs2_part_info(int part_num) function in your board specific files.
In this mode CFG_JFFS2_FIRST_BANK and CFG_JFFS2_FIRST_SECTOR is not
used.

The input is a partition number starting with 0.
Return a pointer to struct part_info or NULL for error;

Ex jffs2_part_info() for one partition.
---
#if defined CFG_JFFS_CUSTOM_PART
#include <jffs2/jffs2.h>

static struct part_info part;

struct part_info*
jffs2_part_info(int part_num)
{
	if(part_num==0){
		if(part.usr_priv==(void*)1)
			return &part;

		memset(&part, 0, sizeof(part));
		part.offset=(char*)0xFF800000;
		part.size=1024*1024*8;

		/* Mark the struct as ready */
		part.usr_priv=(void*)1;

		return &part;
	}
	return 0;
}
#endif
---

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).