64 lines
2.3 KiB
C
64 lines
2.3 KiB
C
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// Copyright (c) 2014 Adafruit Industries
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// Author: Tony DiCola
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// Based on code from Gert van Loo & Dom: http://elinux.org/RPi_Low-level_peripherals#GPIO_Code_examples
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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// The above copyright notice and this permission notice shall be included in all
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// copies or substantial portions of the Software.
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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// SOFTWARE.
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#include <fcntl.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/mman.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include "pi_mmio.h"
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#define BASE 0x20000000
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#define GPIO_BASE (BASE + 0x200000)
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#define GPIO_LENGTH 4096
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volatile uint32_t* pi_mmio_gpio = NULL;
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int pi_mmio_init(void) {
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if (pi_mmio_gpio == NULL) {
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int fd;
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// On older kernels user readable /dev/gpiomem might not exists.
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// Falls back to root-only /dev/mem.
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if( access( "/dev/gpiomem", F_OK ) != -1 ) {
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fd = open("/dev/gpiomem", O_RDWR | O_SYNC);
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} else {
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fd = open("/dev/mem", O_RDWR | O_SYNC);
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}
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if (fd == -1) {
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// Error opening /dev/gpiomem.
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return MMIO_ERROR_DEVMEM;
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}
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// Map GPIO memory to location in process space.
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pi_mmio_gpio = (uint32_t*)mmap(NULL, GPIO_LENGTH, PROT_READ | PROT_WRITE, MAP_SHARED, fd, GPIO_BASE);
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close(fd);
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if (pi_mmio_gpio == MAP_FAILED) {
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// Don't save the result if the memory mapping failed.
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pi_mmio_gpio = NULL;
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return MMIO_ERROR_MMAP;
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}
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}
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return MMIO_SUCCESS;
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}
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