/*
    ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010 Giovanni Di Sirio.

    This file is part of ChibiOS/RT.

    ChibiOS/RT is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    ChibiOS/RT is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/**
 * @page article_portguide Porting ChibiOS/RT for Dummies
 * Porting the operating system on a new platform is one of the most common
 * tasks. The difficulty can range from easy to very difficult depending
 * on several factors.<br>
 * We can divide in problem in several classes of progressively increasing
 * difficulty:
 * - @ref port_board
 * - @ref port_family
 * - @ref port_chip
 * - @ref port_core
 * .
 * Another kind of port type is porting to another compiler and this is an
 * added complexity level on the above classes. The kernel itself is portable
 * but the port-specific code usually contains compiler specific extensions to
 * the C language and the asm files syntax is almost never compatible.
 *
 * @section port_board Porting the OS to a new board
 * This is the easiest port type, the scenario is that the specific
 * microcontroller is already supported and a demo exists. This scenario also
 * applies when porting the OS on a custom hardware using a supported
 * microcontroller. This task can be easily performed with the following
 * steps:
 * -# Create a new directory under ./boards and copy inside the board files
 *    from another board using the same microcontroller.
 * -# Customize the board files:
 *   - @p board.h This file contains the I/O pins setup for the uC, it
 *     may also contain other board-dependent settings, as example, the clock
 *     frequency. Customize this file depending on your target hardware.
 *   - @p board.c This file contains the initialization code, it is possible
 *     you just need to customize @p board.h and not this file. If you have
 *     some hardware specific initialization code then put it here.
 *   .
 * -# Create a new directory under the ChibiOS/RT installation directory:
 *    <tt>./projects/<i>@<my_app_name@></i></tt>
 * -# Copy an existing demo code under the newly created directory.
 * -# Customize the demo:
 *   - @p Makefile You may edit this file in order to remove the test related
 *     sources and/or add you application source files.
 *   - @p main.c It contains the demo simple code, clean it and write your
 *     own @p main() function here, use this file just as a template.
 * -# Compile your application and debug.
 * .
 * @section port_family Porting the OS to a closely related microcontroller
 * In this scenario all the above steps are required but an analysis must
 * be performed to evaluate the differences between from the supported micro
 * and the target micro. Often the micros just differ for the memory area
 * sizes and a change to the linker script is enough (the file is usually
 * named @p ch.ld). Chips having more or less peripherals, everything else
 * being the same or compatible are not a problem also as long the timer and
 * the serial peripherals used by the port do not change.<br>
 * If there are differences in the internal peripherals, as example non
 * compatible interrupt controllers (this happens in the LPC2000 family)
 * or differences in UARTS, timers etc then the port falls in the following
 * category.
 *
 * @section port_chip Porting the OS to another microcontroller using the same core
 * This kind of port is required when a target microcontroller has the same
 * core (a common example: ARM7) of a supported microcontroller but has
 * differences in the internal peripherals.<br>
 * If this is your case proceed as follow:
 * -# Create a new directory under @p <tt>./os/io/platforms</tt> and
 *    name it with the microcontroller name (or family name).<br>
 *    In case of the ARM-based microcontroller you also need to create a
 *    equally named directory under
 *    @p <tt>./os/ports/<i>@<compiler@></i>/<i>@<arch@></i></tt> and
 *    put there the microcontroller related files such as the vectors table,
 *    see the existing ports as example.
 * -# Copy into the newly created directory the most closely related existing
 *    chip port or the naked template files from
 *    @p <tt>./os/io/templates</tt>.
 * -# Work out the differences in the drivers or implement them if you started
 *    from the templates.
 * -# Edit/create the documentation file @p <tt>platform.dox</tt>, this
 *    is required if you want to regenerate this documentation including
 *    your work.
 * .
 * Usually this kind of port just requires a serial driver (and those are very
 * similar each other) and some code for the interrupt controller (this one
 * can be part of the core port, as example the Cortex-M3 has this as standard
 * part of the core).<br>
 * When the chip port is completed created your application as seen in the
 * previous sections.
 *
 * @section port_core Porting the OS to a whole new architecture
 * This is the hardest scenario, the time required by core ports depends
 * strongly by the target architecture complexity and the level of support you
 * need for the architecture specific features.<br>
 * As a reference, the MSP430 port took me 2 hours and it worked at the first
 * run, it can be a reference for simple architectures, the ARM Cortex-M3 was
 * painful instead, the architecture enforces you to implement things in a very
 * specific way and I spent 2 week to go through all the documentation and
 * figure out the correct way to implement the port (you can see that the
 * preemption context switch is done in a very peculiar way because the
 * exceptions architecture).<br>
 * One thing is sure, port an OS to a new architecture is not an easy task and
 * if you have the required experience for such an effort then probably you
 * don't need any advice from me. Just follow the directory patterns and fill
 * the OS template files, the hardest part is decide the correct and efficient
 * way to implement the context switching.
 */