1 // Copyright (c) 2014 Adafruit Industries

     2 // Author: Tony DiCola

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

     4 

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

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

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

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

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

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

    11 

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

    13 // copies or substantial portions of the Software.

    14 

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

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

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

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

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

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

    21 // SOFTWARE.

    22 #include <fcntl.h>

    23 #include <stdlib.h>

    24 #include <stdio.h>

    25 #include <string.h>

    26 #include <sys/mman.h>

    27 #include <sys/stat.h>

    28 #include <sys/types.h>

    29 #include <unistd.h>

    30 

    31 #include "pi_2_mmio.h"

    32 

    33 #define GPIO_BASE_OFFSET 0x200000

    34 #define GPIO_LENGTH 4096

    35 

    36 volatile uint32_t* pi_2_mmio_gpio = NULL;

    37 

    38 int pi_2_mmio_init(void) {

    39   if (pi_2_mmio_gpio == NULL) {

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

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

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

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

    44     if (fp == NULL) {

    45       return MMIO_ERROR_OFFSET;

    46     }

    47     fseek(fp, 4, SEEK_SET);

    48     unsigned char buf[4];

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

    50       return MMIO_ERROR_OFFSET;

    51     }

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

    53     uint32_t gpio_base = peri_base + GPIO_BASE_OFFSET;

    54     fclose(fp);

    55 

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

    57     if (fd == -1) {

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

    59       return MMIO_ERROR_DEVMEM;

    60     }

    61     // Map GPIO memory to location in process space.

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

    63     close(fd);

    64     if (pi_2_mmio_gpio == MAP_FAILED) {

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

    66       pi_2_mmio_gpio = NULL;

    67       return MMIO_ERROR_MMAP;

    68     }

    69   }

    70   return MMIO_SUCCESS;

    71 }