[U-Boot] booting from half of NAND, and mounting jffs on other half of NAND

[John Stile <john@stilen.com>]

Using uboot 2013.01, booting from NAND, I am having difficulty
understanding how partitions (areas of NAND) work.

I have written to NAND in the following layout:
0x0000000 at91bootstrap1
0x0020000 uboot1
0x0060000 uboot-env1
0x0200000 kernel1
0x0400000 rootfs1
0x8000000 at91bootstrap2
0x8020000 uboot2
0x8060000 uboot-env2
0x8200000 kernel
0x8400000 rootfs2

I hacked at91bootstrap to load into ram a uboot and an environment, and
I can stop uboot and 'env print' to see that the proper environment was
loaded.

While booted into linux on one rootfs I would like to access the other
rootfs. 

I try tried to use the mtdparts parameter that describes the partitions
of NAND, but this isn't working, and I don't think I understand what it
should be.

First problem, or signs that I'm doing something wrong is my mtdparts
parameter.  If I try to edit on the interactive uboot shell, the line is
too long to change, so I have to write flash for each test.  That can't
be correct?  Regardless of which uboot environemnt I use, this is what I
am trying to use to describe my NAND layout:
mtdparts=at91_nand:128k(bootstrap1)ro,256k(uboot1)ro,128k(env1)ro,1536K(unused),2M(linux1),124M(rootfs1),128k(bootstrap2)ro,256k(uboot2)ro,128k(env2)ro,1536k(unused2),2M(linux2),124M(rootfs2)
What should I use here?

Second problem is what to use for root=/dev/mtdblock*.  I have tried
many things, but most lead to an inability to find the file system, and
since each test requires re-writing NAND flash it takes a really long
time to debug.  What should I use here?