// Copyright (c) 2014 Adafruit Industries

// Author: Tony DiCola

// Based on code from Gert van Loo & Dom: http://elinux.org/RPi_Low-level_peripherals#GPIO_Code_examples

// Permission is hereby granted, free of charge, to any person obtaining a copy

// of this software and associated documentation files (the "Software"), to deal

// in the Software without restriction, including without limitation the rights

// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

// copies of the Software, and to permit persons to whom the Software is

// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all

// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE

// SOFTWARE.

#include <fcntl.h>

#include <stdlib.h>

#include <stdio.h>

#include <string.h>

#include <sys/mman.h>

#include <sys/stat.h>

#include <sys/types.h>

#include <unistd.h>

#include "pi_2_mmio.h"

#define GPIO_BASE_OFFSET 0x200000

#define GPIO_LENGTH 4096

volatile uint32_t* pi_2_mmio_gpio = NULL;

int pi_2_mmio_init(void) {

  if (pi_2_mmio_gpio == NULL) {

    // Check for GPIO and peripheral addresses from device tree.

    // Adapted from code in the RPi.GPIO library at:

    //   http://sourceforge.net/p/raspberry-gpio-python/

    FILE *fp = fopen("/proc/device-tree/soc/ranges", "rb");

    if (fp == NULL) {

      return MMIO_ERROR_OFFSET;

    }

    fseek(fp, 4, SEEK_SET);

    unsigned char buf[4];

    if (fread(buf, 1, sizeof(buf), fp) != sizeof(buf)) {

      return MMIO_ERROR_OFFSET;

    }

    uint32_t peri_base = buf[0] << 24 | buf[1] << 16 | buf[2] << 8 | buf[3] << 0;

    uint32_t gpio_base = peri_base + GPIO_BASE_OFFSET;

    fclose(fp);

    int fd = open("/dev/mem", O_RDWR | O_SYNC);

    if (fd == -1) {

      // Error opening /dev/mem.  Probably not running as root.

      return MMIO_ERROR_DEVMEM;

    }

    // Map GPIO memory to location in process space.

    pi_2_mmio_gpio = (uint32_t*)mmap(NULL, GPIO_LENGTH, PROT_READ | PROT_WRITE, MAP_SHARED, fd, gpio_base);

    close(fd);

    if (pi_2_mmio_gpio == MAP_FAILED) {

      // Don't save the result if the memory mapping failed.

      pi_2_mmio_gpio = NULL;

      return MMIO_ERROR_MMAP;

    }

  }

  return MMIO_SUCCESS;

}