Booting directly to JFFS2 question

[James Ewing]

Hi David,

The partitions are setup dynalically, yes.

It looks like JFFS2 uses a 2 byte magic number with a varying 2 byte block
type. My guess is that I need to look for any of the permutations and return
a pointer if found.

My next question is how to add the boot/startup code to do_mounts.c.
Currently it finds the super_block and returns it to the routines for ext2,
cramfs, etc.

What would the return to JFFS2 look like?

Thanks for the help.

James


----- Original Message ----- 
From: David Woodhouse
To: James Ewing
Cc: linux-mtd at lists.infradead.org
Sent: Thursday, January 15, 2004 2:51 AM
Subject: Re: Booting directly to JFFS2 question


On Thu, 2004-01-15 at 11:45 -0800, James Ewing wrote:
> After creating the partitions the system looks for the file system image
by
> checking 64K boundaries of the 2nd flash partition looking for cramfs or
> squashfs magic numbers. The routine then returns a pointer to the fs
system
> start byte and the init/do_mount.c code takes over.

This works by setting up the partitions dynamically according to what's
found in the image, right?

> This pointer was to the super_block for the filesystem. Apparently jffs2
> doesn't have a super_block in the traditional sense so I am a bit stumped.

It should still be possible -- look for a JFFS2 node (0x1985 etc..)
starting at the beginning of an eraseblock.

See struct jffs2_unknown_node in include/linux/jffs2.h

-- 
dwmw2