[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 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.

CONFIG_SYS_JFFS2_FIRST_BANK
	defined the first flash bank to use

CONFIG_SYS_JFFS2_FIRST_SECTOR
	defines the first sector to use


The second way is to define CONFIG_SYS_JFFS_CUSTOM_PART and implement the
jffs2_part_info(int part_num) function in your board specific files.
In this mode CONFIG_SYS_JFFS2_FIRST_BANK and CONFIG_SYS_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 CONFIG_SYS_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).
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 WD	21
	22	There is two ways for JFFS2 to find the disk. The default way uses
	23	the flash_info structure to find the start of a JFFS2 disk (called
	24	partition in the code) and you can change where the partition is with
	25	two defines.
	26
6d0f6bcf	27	CONFIG_SYS_JFFS2_FIRST_BANK
c609719b WD	28	defined the first flash bank to use
c609719b WD	29
6d0f6bcf	30	CONFIG_SYS_JFFS2_FIRST_SECTOR
c609719b WD	31	defines the first sector to use
	32
	33
6d0f6bcf	34	The second way is to define CONFIG_SYS_JFFS_CUSTOM_PART and implement the
c609719b	35	jffs2_part_info(int part_num) function in your board specific files.
6d0f6bcf	36	In this mode CONFIG_SYS_JFFS2_FIRST_BANK and CONFIG_SYS_JFFS2_FIRST_SECTOR is not
c609719b WD	37	used.
	38
	39	The input is a partition number starting with 0.
	40	Return a pointer to struct part_info or NULL for error;
	41
	42	Ex jffs2_part_info() for one partition.
	43	---
6d0f6bcf	44	#if defined CONFIG_SYS_JFFS_CUSTOM_PART
c609719b WD	45	#include <jffs2/jffs2.h>
	46
	47	static struct part_info part;
	48
	49	struct part_info*
	50	jffs2_part_info(int part_num)
	51	{
	52	if(part_num==0){
	53	if(part.usr_priv==(void*)1)
	54	return ∂
	55
	56	memset(&part, 0, sizeof(part));
	57	part.offset=(char*)0xFF800000;
	58	part.size=102410248;
	59
	60	/* Mark the struct as ready */
	61	part.usr_priv=(void*)1;
	62
	63	return ∂
	64	}
	65	return 0;
	66	}
	67	#endif
	68	---
	69
	70	TODO.
	71
8bde7f77 WD	72	Remove the assumption that JFFS can dereference a pointer
	73	into the disk. The current code do not work with memory holes
	74	or hardware with a sliding window (PCMCIA).