[Arm-netbook] First stab at a custom kernel

[Frans Pop]

On Wednesday 03 March 2010, JLB wrote:
> How would one install such a thing? I can't make heads or tails of
> /dev/mmcblk0p1, which I presume is where the kernel is stashed.

The idea is to use the firmware tarball that Luke has uploaded and then 
replace the zImage_dt file from that with the custom zImage.
Then copy the whole lot to an SD card and use the "update firmware from SD 
card" boot option to let u-boot install everything into mmcblk0p1.

Preparation before that:
- copy modules from the custom deb into place in the root FS
- ensure a 'depmod -a' gets run before udev in /etc/rc.S [1]

I'm not sure if the update will overwrite the whole root FS. If that's the 
case these preparations should not be made on the netbook, but by creating 
a custom datang-epc.tar.gz.
But maybe a partial firmware update is possible: with u-boot and kernel 
included, but without the datang-epc tarball.

Luke: have you perhaps checked if the root FS gets erased before installing 
a new tarball or if partial firmware updates are possible?

I think this method should be safe enough as one could still revert to the 
standard installation by doing a firmware update with the standard kernel 
etc. As long as u-boot is not corrupted at least.

The main question is whether or not u-boot will have problems with the 
changed size of the kernel image, but I think not.

Alternatively it should I think in theory also be possible to just dd the 
custom zImage to mmcblk0p1 with an offset of 90971136...

See also my mail "Disecting mmcblk0p1 and the boot process" from yesterday.

Cheers,
FJP

[1] Something like this in e.g. /etc/rcS.d/S02depmod -> /etc/init.d/depmod:
#! /bin/sh

case "$1" in
    start)
	# Avoid messing with the default kernel
        if [ "$(uname -r)" != "2.6.24.2" ]; then
                depmod -a
        fi
        ;;
esac