Toolchain and Embedded Distributions
For many embedded applications, the requirements for the processor deviate from those in development workstations. The chosen processor architecture, therefore, usually differs and requires cross development tools to compile the target applications on the workstation. Generating the cross development tools and a suitable environment is certainly not an easy venture. Several projects have, therefore, materialized over time to alleviate the process.
Note that most embedded distributions listed below don't currently support the Xtensa architecture and require modifications. Patches for various versions of the toolchain sources can be found under http://www.linux-xtensa.org/pub/patches/.
Start from scratch with FSF/OSS sources
Starting from sources is certainly the most challenging approach. It usually requires additional patches and sometimes matching versions of sources.
This project is docomprises several projects intended to help building a Linux system from sources. The main project resembles a book that describes the build-process in great detail.
The Xtensa Linux Development Environment (XLIDE) is a very simple perl script to build the cross development tools specific for Xtensa.
CrossTool (http://kegel.com/crosstool/") was developed by Dan Kegel originally to test different versions of the toolchain in various combinations for cross-compilation. It consists of a set of scripts and configuration files.
Buildroot is a set of Makefiles and patches that makes it easy generate a cross-compilation toolchain and root filesystem for your target Linux system using the uClibc C library.
OpenEmbedded (http://openembedded.org) provided a development environment for embedded systems.