Hacking Linux for chumby

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Existing Software

See existing Chumby Software Applications, Scripts and Tools already on your Chumby stock linux distro.

Alpha Prototype

The Alpha Prototype chumby runs a modified linux 2.4.20 kernel.

Compiling the Kernel

First, install the GCC Toolchain (gcc 3.3.2)

In order to build the chumby kernel, you can download the kernel source from chumby_kernel.tgz and build by doing the following:

# mkdir kernel
# cd kernel
# tar zxvf chumby_kernel.tgz
# make menuconfig
(then immediately exit and save the config)
# make dep
# make Image

If all goes well, you should end up with an uncompressed kernel image at arch/arm/boot/Image.

Ironforge

The "Ironforge" production chumby runs Linux 2.6.16 kernel.

First install the GNU Toolchain (gcc 4.1.2)

In order to build the chumby kernel, you can download the kernel source from linux-2.6.16-chumby-1.0.tar.gz and build by doing the following, NOT as root, but as a normal user.

$ mkdir kernel
$ cd kernel
$ tar zxvf linux-2.6.16-chumby-1.0.tar.gz
$ cd linux-2.6.16
$ cp arch/arm/configs/mx21ads_defconfig .config
$ ARCH=arm BOARD=mx21ads CROSS_COMPILE=arm-linux- make oldconfig
  (select 'Y' when asked if you wish to build in the 224 color Turbochef logo)
$ ARCH=arm BOARD=mx21ads CROSS_COMPILE=arm-linux- make


If all goes well, you should end up with a compressed kernel image at arch/arm/boot/zImage and all of loadable kernel modules under the drivers directory.

By default, there are only 3 drivers built with this configuration:

$ find drivers -name *.ko

Which should return:

drivers/char/chumby_accel.ko
drivers/char/chumby_sense1.ko
drivers/char/chumby_timer.ko
drivers/mfd/chumby-tsc2100.ko

Warning, this configuration will not get you a working kernel! Do not use just yet...

You might want to enable more modules to get the recommended:

# find drivers -name *.ko

Which should return:

drivers/media/video/cpia.ko
drivers/media/video/compat_ioctl32.ko
drivers/media/video/cpia_usb.ko
drivers/media/video/v4l1-compat.ko
drivers/media/video/v4l2-common.ko
drivers/media/video/videodev.ko
drivers/bluetooth/hci_usb.ko
drivers/bluetooth/hci_vhci.ko
drivers/video/console/bitblit.ko
drivers/video/console/fbcon.ko
drivers/video/console/fbcon_ccw.ko
drivers/video/console/fbcon_cw.ko
drivers/video/console/fbcon_rotate.ko
drivers/video/console/fbcon_ud.ko
drivers/video/console/font.ko
drivers/video/console/softcursor.ko
drivers/char/chumby_accel.ko
drivers/char/chumby_sense1.ko
drivers/char/chumby_timer.ko
drivers/usb/media/dsbr100.ko
drivers/usb/net/asix.ko
drivers/usb/net/cdc_ether.ko
drivers/usb/net/pegasus.ko
drivers/usb/net/usbnet.ko
drivers/usb/input/usbhid.ko
drivers/mfd/chumby-tsc2100.ko


Flashing the Kernel

Directions provided by Bunnie in the forum: [1]

If you want to reflash the kernel image, the quickest way to do it is to take the zImage file,
zip it, and copy it to a VFAT formatted USB disk, and put it in a directory called "update2" by
the name of k1.bin.zip. Even though zImage is already compressed, you need to zip it again because
of the way the firmware updater works.

Then, power on the chumby while pressing the touchscreen, and continue pressing it until you get
into special options. Select the menu option to update the chumby, and then select update via USB. 
This will take the kernel image on the USB disk and flash it into the device.

You can completely destroy the k1.bin.zip image and recover from this, because this update mechanism
uses its own copy of the kernel that is unaffected by the update to k1.bin.zip.

If you want to add more apps, you need to build a cramfs filesystem, and use a similar procedure
but name the resulting cramfs binary image rfs1.bin.zip, also stuck in the update2/ directory on
the USB drive.

Building and Installing a new chumby v1.2 kernel

Building the kernel

The following instructions will compile the Linux 2.6.16 kernel shipped with chumby firmware version 1.2:

mkdir kernel
cd kernel
wget http://files.chumby.com/source/ironforge/build396/align.pl
wget http://files.chumby.com/source/ironforge/build396/linux-2.6.16-chumby-1.2.tar.gz
tar zxvf linux-2.6.16-chumby-1.2.tar.gz
cd linux-2.6.16
ARCH=arm BOARD=mx21ads CROSS_COMPILE=arm-linux- make
perl ../align.pl arch/arm/boot/zImage 
zip k1.bin.zip arch/arm/boot/zImage 

Installing the kernel image

  • create an update2 directory on the root of a USB storage drive
  • copy k1.bin.zip to the update2 directory on the USB storage drive
  • insert the USB storage drive into chumby
  • hold the touch screen down and power on the chumby (keep holding the screen for 5 seconds)
  • once the device has booted into special options mode, click Install updates
  • click Install from USB flash drive