RFC: README.hardware: Intel Atom device documentation

[Darren Hart <dvhart@linux.intel.com>]

I ran across some issues working with USB keys while booting a couple
different Intel Atom based devices. I drafted the following documenting
what I learned from the process. I'd like to add this (or something
similar) to README.hardware.

Thoughts/Comments?


Intel Atom based PCs and devices (atom-pc)
==========================================

The atom-pc MACHINE is tested on the following platforms:

  o Asus eee901
  o Acer Aspire One
  o Toshiba NB305
  o Intel BlackSand development board (FIXME: correct name)

and is likely to work on many unlisted atom based devices. The MACHINE
type supports ethernet, wifi, sound, and i915 graphics by default in
addition to common PC input devices, busses, and so on.

Depending on the device, it can boot from a traditional hard-disk, a USB
device, or over the network. Writing poky generated images to physical
is straightforward with a caveat for USB devices. The following examples
assume the target boot device is /dev/sdb, be sure to verify this and
use the correct device as the following commands are run as root and are
not reversable.

Hard Disk:
  1. Build a directdisk image format. This will generate proper
     partition tables that will in turn be written to the physical media.
  
  2. Use the "dd" utility to write the image to the raw block device.
     For example:

     $ dd if=poky-image-minimal-live-atom-pc-20101214120906.ddimg of=/dev/sdb
     FIXME: verify image name and extension

USB Device:
  1. Build an hddimg image format. This is a simple filesystem without
     partition tables and is suitable for USB keys.

  2. Use the "dd" utility to write the image to the raw block device.
     For example:

     $ dd if=poky-image-minimal-live-atom-pc-20101214120906.hddimg of=/dev/sdb

  If the device fails to boot with "Boot error" displayed, it is likely
  the BIOS cannot understand the physical layout of the disk (or rather
  it expects it to be a particular layout and can't handle anything
  else). There are two possible solutions to this problem:

  1. Change the BIOS USB Device setting to HDD mode. The label will vary
     my device, but the idea is to force BIOS to read the
     Cylinder/Head/Sector geometry from the device.

  2. Without such an option, the BIOS generally boots the device in
     USB-ZIP mode.

     a. Configure the USB device for USB-ZIP mode:
     
     # mkdiskimage -4 /dev/sdb 0 63 62

     Where 63 and 62 are the cylinder and head count as reported by
     fdisk.  Remove and reinsert the device to allow the kernel to
     detect the new partition layout.

     b. Copy the contents of the poky image to the USB-ZIP mode device:

     # mount -o loop poky-image-minimal-live-atom-pc-20101214120906.hddimg  /tmp/image
     # mount /dev/sdb4 /tmp/usbkey
     # cp -rf /tmp/image/* /tmp/usbkey

     c. Install the syslinux boot loader:

     # syslinux /dev/sdb4

  Install the boot device in the target board and configure the BIOS to
  boot from it.

  For more details on the USB-ZIP scenario, see the syslinux documentation:
  http://git.kernel.org/?p=boot/syslinux/syslinux.git;a=blob_plain;f=doc/usbkey.txt;hb=HEAD

-- 
Darren Hart
Yocto Linux Kernel