/*
    ChibiOS - Copyright (C) 2006,2007,2008,2009,2010,
              2011,2012,2013,2014 Giovanni Di Sirio.

    This file is part of ChibiOS/HAL 

    ChibiOS/HAL 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/>.
*/

/**
 * @defgroup SPI SPI Driver
 * @brief   Generic SPI Driver.
 * @details This module implements a generic SPI (Serial Peripheral Interface)
 *          driver allowing bidirectional and monodirectional transfers,
 *          complex atomic transactions are supported as well.
 * @pre     In order to use the SPI driver the @p HAL_USE_SPI option
 *          must be enabled in @p halconf.h.
 *
 * @section spi_1 Driver State Machine
 * The driver implements a state machine internally, not all the driver
 * functionalities can be used in any moment, any transition not explicitly
 * shown in the following diagram has to be considered an error and shall
 * be captured by an assertion (if enabled).
 * @if LATEX_PDF
 * @dot
  digraph example {
    size="5, 7";
    rankdir="LR";
    node [shape=circle, fontname=Helvetica, fontsize=8, fixedsize="true",
          width="0.9", height="0.9"];
    edge [fontname=Helvetica, fontsize=8];

    stop  [label="SPI_STOP\nLow Power"];
    uninit [label="SPI_UNINIT", style="bold"];
    ready [label="SPI_READY\nClock Enabled"];
    active [label="SPI_ACTIVE\nBus Active"];
    complete [label="SPI_COMPLETE\nComplete"];

    uninit -> stop [label="\n spiInit()", constraint=false];
    stop -> ready [label="\nspiStart()"];
    ready -> ready [label="\nspiSelect()\nspiUnselect()\nspiStart()"];
    ready -> stop [label="\nspiStop()"];
    stop -> stop [label="\nspiStop()"];
    ready -> active [label="\nspiStartXXXI() (async)\nspiXXX() (sync)"];
    active -> ready [label="\nsync return"];
    active -> complete [label="\nasync callback\n>spc_endcb<"];
    complete -> active [label="\nspiStartXXXI() (async)\nthen\ncallback return"];
    complete -> ready [label="\ncallback return"];
  }
 * @enddot
 * @else
 * @dot
  digraph example {
    rankdir="LR";
    node [shape=circle, fontname=Helvetica, fontsize=8, fixedsize="true", width="0.9", height="0.9"];
    edge [fontname=Helvetica, fontsize=8];

    stop  [label="SPI_STOP\nLow Power"];
    uninit [label="SPI_UNINIT", style="bold"];
    ready [label="SPI_READY\nClock Enabled"];
    active [label="SPI_ACTIVE\nBus Active"];
    complete [label="SPI_COMPLETE\nComplete"];

    uninit -> stop [label="\n spiInit()", constraint=false];
    stop -> ready [label="\nspiStart()"];
    ready -> ready [label="\nspiSelect()\nspiUnselect()\nspiStart()"];
    ready -> stop [label="\nspiStop()"];
    stop -> stop [label="\nspiStop()"];
    ready -> active [label="\nspiStartXXX() (async)\nspiXXX() (sync)"];
    active -> ready [label="\nsync return"];
    active -> complete [label="\nasync callback\n>spc_endcb<"];
    complete -> active [label="\nspiStartXXXI() (async)\nthen\ncallback return"];
    complete -> ready [label="\ncallback return"];
  }
 * @enddot
 * @endif
 *
 * The driver is not thread safe for performance reasons, if you need to access
 * the SPI bus from multiple threads then use the @p spiAcquireBus() and
 * @p spiReleaseBus() APIs in order to gain exclusive access.
 *
 * @ingroup IO
 */