[maemo-developers] Debian on the n900 / Configuring NOLO

[From: Frantisek Dufka]

Carsten Valdemar Munk wrote:
> . Or allow for flashing  
> the NAND/eMMC through USB.

Oh, right,  if it can flash eMMC then the mmc code is in, so loading 
kernel from mmc is one NOLO bugzilla enhancement away ;-)

> In this case, noone says you cannot include  
> a bootmenu in that zImage that selects a new root.

Since I posted previous mail I have checked this and it looks like 
attaching some sort of initrd/initramfs is not available for arm 
architecture. It is very platform and bootloader dependent.
https://linuxlink.timesys.com/forum/1021
http://www.denx.de/wiki/view/DULG/CombiningKernelAndRamdisk

Also It is nontrivial to unzip kernel, modify command line and zip it 
again. It is implement at linker level
piggy.S:
-----
         .section .piggydata,#alloc 

         .globl  input_data 

input_data: 

         .incbin "arch/arm/boot/compressed/piggy.gz" 

         .globl  input_data_end 

input_data_end: 


-----

The input_data_end label is used in decompressor code 
(size=input_data_end-input_data) and whole image is zipped so different 
text yields different length.

For out tablets it is still of course doable to modify decompressor code 
directly and change the size there. It is not very clean, though.

Again, having kernel commandline stored inside config partition and NOLO 
using it instead of builtin command line would be ideal situation.

> I doubt u-boot will be ported due to the lack of JTAG and that it's a  
> bit of risky business in terms of bricking your device trying to port  
> it. :)

It should be possible to modify any current free bootloader to appear as 
zImage becoming 3rd stage bootloader. zImage is run with basic hardware 
already initialized and MMU still off so any bootloader code should be 
happy with this.

Also there is this old LAB idea
http://handhelds.org/moin/moin.cgi/HpIpaqH2200LAB

Also kexec is another option.

So basically we either need free bootloader that can show on-screen menu 
and load kernel etc. or use linux kernel and userspace code to do this 
(kexec, pivot_root).

Frantisek