Unified multi-platform USB/SD imaging support

[greenfeld]

It would be nice if we could use the same USB stick or SD card to support XO-1.5 & 1.75 (and maybe even XO-1) reimaging via the four-button approach. The XO should be able to see that more than one image type is available on the storage media and automatically select the one appropriate to it.

That way, Teachers and support personnel would not have to find the correct USB stick out of several when dealing with a deployment with multiple models of XOs.

The approach used should be backward compatible with older firmware for currently deployed laptop types. Only having one image type on the USB stick or the wrong type should be handled gracefully. If this can be done in a manner which allows older firmware to auto-detect which image to use, that's even better.

[wmb@…]

Implemented by svn 2270. If fs.zip is not found, OFW tries fsN.zip, where N=0 for XO-1, N=1 for XO-1.5, N=2 for XO-1.75. This fallback strategy also applies to all other signed .zip bundles, such as bootfw, ecfw, os, and rd.

[Quozl]

OpenFirmware implementation complete, and tested. What remains is for build files to be unique across platforms, so that the .zsp in the .zip file can specify a unique zblock file. Currently, olpc-os-builder is generating os5.zd4 for both XO-1.5 and XO-1.75. This needs to change.

[Quozl]

An interim action might be to add Forth code to the start of a .zd file that aborts the fs-update if an incorrect model is detected:

3 value required-model : model@ ofw-model$ drop d# 14 + c@ h# 30 - ; model@ required-model <> abort" incorrect model"

Where the required-model would be set to 3 for XO-1.5, 4 for XO-1.75, and 5 for XO-3, corresponding to the digit after the firmware version.