【参考学习用】基于全志芯片的GPIO及底层（C/Python）编程 与 linux下/dev/mem分析

知乎上有一篇带例子的 Linux读写GPIO的几种方法及一些有趣的应用

补一篇 Linux 内核层和 用户层 配置 GPIO 引脚

曾经全志 A20 实现过 Python 操作 GPIO 的接口

http://dl.linux-sunxi.org/users/tom/pySUNXI-0.1.12.tar.gz

基于全志芯片的GPIO及底层（C/Python）编程

操作方法简单粗暴，直接怼到 /dev/mem 设备上用 mmap 映射 SUNXI_PIO_BASE 地址的操作，基于此还实现了 GPIO 模拟 SPI 设备。

gpio.c

/*
 * gpio_lib.c
 *
 * Copyright 2013 Stefan Mavrodiev <support@olimex.com>
 *
 * This program 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 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA 02110-1301, USA.
 */


#include <ctype.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <time.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/select.h>
#include <pthread.h>
#include <unistd.h>
#include <sched.h>

#include "gpio_lib.h"


unsigned int SUNXI_PIO_BASE = 0;
static volatile long int *gpio_map = NULL;

int sunxi_gpio_init(void) {
    int fd;
    unsigned int addr_start, addr_offset;
    unsigned int PageSize, PageMask;


    fd = open("/dev/mem", O_RDWR);
    if(fd < 0) {
        return SETUP_DEVMEM_FAIL;
    }

    PageSize = sysconf(_SC_PAGESIZE);
    PageMask = (~(PageSize-1));

    addr_start = SW_PORTC_IO_BASE & PageMask;
    addr_offset = SW_PORTC_IO_BASE & ~PageMask;

    gpio_map = (void *)mmap(0, PageSize*2, PROT_READ|PROT_WRITE, MAP_SHARED, fd, addr_start);
    if(gpio_map == MAP_FAILED) {
        return SETUP_MMAP_FAIL;
    }

    SUNXI_PIO_BASE = (unsigned int)gpio_map;
    SUNXI_PIO_BASE += addr_offset;

    close(fd);
    return SETUP_OK;
}

int sunxi_gpio_set_cfgpin(unsigned int pin, unsigned int val) {

    unsigned int cfg;
    unsigned int bank = GPIO_BANK(pin);
    unsigned int index = GPIO_CFG_INDEX(pin);
    unsigned int offset = GPIO_CFG_OFFSET(pin);

    if(SUNXI_PIO_BASE == 0) {
        return -1;
    }

    struct sunxi_gpio *pio =
        &((struct sunxi_gpio_reg *)SUNXI_PIO_BASE)->gpio_bank[bank];


    cfg = *(&pio->cfg[0] + index);
    cfg &= ~(0xf << offset);
    cfg |= val << offset;

    *(&pio->cfg[0] + index) = cfg;

    return 0;
}

int sunxi_gpio_get_cfgpin(unsigned int pin) {

    unsigned int cfg;
    unsigned int bank = GPIO_BANK(pin);
    unsigned int index = GPIO_CFG_INDEX(pin);
    unsigned int offset = GPIO_CFG_OFFSET(pin);
    if(SUNXI_PIO_BASE == 0)
    {
        return -1;
    }
    struct sunxi_gpio *pio = &((struct sunxi_gpio_reg *)SUNXI_PIO_BASE)->gpio_bank[bank];
    cfg = *(&pio->cfg[0] + index);
    cfg >>= offset;
    return (cfg & 0xf);
}
int sunxi_gpio_output(unsigned int pin, unsigned int val) {

    unsigned int bank = GPIO_BANK(pin);
    unsigned int num = GPIO_NUM(pin);

    if(SUNXI_PIO_BASE == 0)
    {
        return -1;
    }
    struct sunxi_gpio *pio =&((struct sunxi_gpio_reg *)SUNXI_PIO_BASE)->gpio_bank[bank];

    if(val)
        *(&pio->dat) |= 1 << num;
    else
        *(&pio->dat) &= ~(1 << num);

    return 0;
}

int sunxi_gpio_input(unsigned int pin) {

    unsigned int dat;
    unsigned int bank = GPIO_BANK(pin);
    unsigned int num = GPIO_NUM(pin);

    if(SUNXI_PIO_BASE == 0)
    {
        return -1;
    }

    struct sunxi_gpio *pio =&((struct sunxi_gpio_reg *)SUNXI_PIO_BASE)->gpio_bank[bank];

    dat = *(&pio->dat);
    dat >>= num;

    return (dat & 0x1);
}
void sunxi_gpio_cleanup(void)
{
    unsigned int PageSize;
    if (gpio_map == NULL)
        return;

    PageSize = sysconf(_SC_PAGESIZE);
    munmap((void*)gpio_map, PageSize*2);
}

代码很有参考和学习的价值，看下文加深理解。

• linux下/dev/mem 分析

• /dev/mem可没那么简单