Linux驱动使用GPIO

GPIO引脚控制是嵌入式开发的基础知识。在Linux驱动中控制GPIO也是很方便的。下面的例子就演示了如何初始化GPIO引脚，并获取和设置GPIO引脚电位？

实验环境

raspberry pi3b

Linux raspberrypi 6.1.21-v8+ #1642 SMP PREEMPT Mon Apr  3 17:24:16 BST 2023 aarch64 GNU/Linux

驱动代码

// simple.c

#include <linux/gpio/consumer.h>
#include <linux/init.h>
#include <linux/module.h>

#define IO_OFFSET 0
#define IO_BUTTON 20
#define IO_LED 21

static struct gpio_desc *led = NULL, *button = NULL;

static int __init simple_init(void) {
    int status = 0;

    pr_info("simple_init\n");

    button = gpio_to_desc(IO_BUTTON + IO_OFFSET);
    if (!button) {
        pr_err("gpiod_desc 20 error\n");
        return -ENODEV;
    }

    led = gpio_to_desc(IO_LED + IO_OFFSET);
    if (!led) {
        pr_err("gpiod_desc 21 error\n");
        return -ENODEV;
    }

    status = gpiod_direction_output(led, 0);
    if (status) {
        pr_err("gpiod_desc 20 error\n");
        return status;
    }

    status = gpiod_direction_input(button);
    if (status) {
        pr_err("gpiod_desc 21 error\n");
        return status;
    }

    gpiod_set_value(led, 1);

    pr_info("button is %spressed\n", gpiod_get_value(button) ? "" : "not ");

    return 0;
}

static void __exit simple_exit(void) {
    pr_info("simple_exit\n");
    gpiod_set_value(led, 0);
}

module_init(simple_init);
module_exit(simple_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("heng30");
MODULE_VERSION("v0.0.1");
MODULE_DESCRIPTION("A simple kernel module");

Makefile编译脚本

#!/bin/sh

top-dir = $(shell pwd)
kernel-version = $(shell uname -r)
kernel-dir ?= /lib/modules/$(kernel-version)/build

obj-m += simple.o

all:
        make -C $(kernel-dir) modules M=$(top-dir)

clean:
        rm -f *.o *.ko *.mod *.mod.c *.order *.symvers *.dtbo
        make -C $(kernel-dir) clean m=$(top-dir)

测试

• 安装gpio工具：sudo apt install gpiod

• 查看gpio设备：gpiodetect

gpiochip0 [pinctrl-bcm2835] (54 lines)
gpiochip1 [raspberrypi-exp-gpio] (8 lines)

• 查看gpio 20引脚状态：gpioget 0 20

0

• 查看gpio 21引脚状态：gpioget 0 21

0

• 设置gpio 20引脚为高电平: gpioset 0 20=1

• 编译程序：make

• 安装驱动：insmod simple.ko

• 查看gpio 21引脚：gpioget 0 21

1

• 移除驱动：rmmod simple.ko

• 查看输出：dmesg

[75536.557115] simple_init
[75536.557561] button is pressed
[75566.364839] simple_exit

• 查看gpio 21引脚状态：gpioget 0 21

0

参考

• 树莓派引脚图