/****************************************************************************
 * arch/avr/src/avr/up_romgetc.c
 *
 *   Copyright (C) 2011 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <nuttx/arch.h>
#include <avr/pgmspace.h>

#ifdef CONFIG_ARCH_ROMGETC

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/****************************************************************************
 * Private Data
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: up_romgetc
 *
 * Description:
 *   In Harvard architectures, data accesses and instruction accesses occur
 *   on different busses, perhaps concurrently.  All data accesses are
 *   performed on the data bus unless special  machine instructions are
 *   used to read data from the instruction address space.  Also, in the
 *   typical MCU, the available SRAM data memory is much smaller that the
 *   non-volatile FLASH instruction memory.  So if the application requires
 *   many constant strings, the only practical solution may be to store
 *   those constant strings in FLASH memory where they can only be accessed
 *   using architecture-specific machine instructions.
 *
 *   A similar case is where strings are retained in "external" memory such
 *   as EEPROM or serial FLASH.  This case is similar only in that again
 *   special operations are required to obtain the string data; it cannot
 *   be accessed directly from a string pointer.
 *
 *   If CONFIG_ARCH_ROMGETC is defined, then the architecture logic must
 *   export the function up_romgetc().  up_romgetc() will simply read one
 *   byte of data from the instruction space.
 *
 *   If CONFIG_ARCH_ROMGETC, certain C stdio functions are effected: (1)
 *   All format strings in printf, fprintf, sprintf, etc. are assumed to
 *   lie in FLASH (string arguments for %s are still assumed to reside in
 *   SRAM). And (2), the string argument to puts and fputs is assumed to
 *   reside in FLASH.  Clearly, these assumptions may have to modified for
 *   the particular needs of your environment.  There is no "one-size-fits-all"
 *   solution for this problem.
 *
 * Additional AVR Assumptions:
 *
 * - This version of up_romgetc obtains string data from FLASH memory.
 * - Since the passed pointer is 16-bits, the strings must lie in the first
 *   64Kb of FLASH.
 *
 ****************************************************************************/

char up_romgetc(FAR const char *ptr)
{
  return pgm_read_byte_near(ptr);
}
#endif
