博客

1. ioremap 函数

ioremap 函数用于获取指定物理地址空间对应的虚拟地址空间。

2. iounmap

I/O内存访问函数

1.读操作函数

u8 readb(const volatile void __iomem *addr)
u16 readw(const volatile void __iomem *addr)
u32 readl(const volatile void __iomem *addr)

readb、readw 和 readl 这三个函数分别对应 8bit、16bit 和 32bit 读操作，参数 addr 就是要读取写内存地址，返回值就是读取到的数据。

2. 写操作函数

void writeb(u8 value, volatile void __iomem *addr)
void writew(u16 value, volatile void __iomem *addr)
void writel(u32 value, volatile void __iomem *addr)

writeb、writew 和 writel 这三个函数分别对应 8bit、16bit 和 32bit 写操作，参数 value 是要写入的数值，addr 是要写入的地址

led.c

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/ide.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/gpio.h>
#include <asm/mach/map.h>
#include <asm/uaccess.h>
#include <asm/io.h>

#define LED_MAJOR 200
#define LED_NAME "led"

#define LEDOFF 0
#define LEDON 1

/* 寄存器物理地址 */
#define CCM_CCGR1_BASE (0X020C406C)
#define SW_MUX_GPIO1_IO03_BASE (0X020E0068)
#define SW_PAD_GPIO1_IO03_BASE (0X020E02F4)
#define GPIO1_DR_BASE (0X0209C000)
#define GPIO1_GDIO_BASE (0X0209C004)

// 映射后的寄存器虚拟地址指针
static void __iomem * IMX6U_CCM_CCGR1;
static void __iomem *SW_MUX_GPIO1_IO03;
static void __iomem *SW_PAD_GPIO1_IO03;
static void __iomem *GPIO1_DR;
static void __iomem *GPIO1_GDIR;
void led_switch(u8 sta)
{
    u32 val = 0;
    if (sta == LEDON){
        val = readl(GPIO1_DR);
        val &= ~(1<<3);
        writel(val, GPIO1_DR);
    }else if (sta == LEDOFF){
        val = readl(GPIO1_DR);
        val |= (1<<3);
        writel(val, GPIO1_DR);
    }
}

static int led_open(struct inode *inode, struct file *filp)
{
    return 0;
}

static ssize_t led_read(struct file *filp, char __user *buf,size_t cnt, loff_t *offt)
{
    return 0;
}
static ssize_t led_write(struct file *filp, const char __user *buf,
size_t cnt, loff_t *offt)
{
    int retvalue;
    unsigned char databuf[1];
    unsigned char ledstat;

    retvalue = __copy_from_user(databuf, buf, cnt);
    if (retvalue < 0){
        printk("kernel write failed!\r\n");
        return -EFAULT;
    }

    ledstat = databuf[0];

    if (ledstat == LEDON){
        led_switch(LEDON);
    }else if (ledstat == LEDOFF){
        led_switch(LEDOFF);
    }
    return 0;
}

static int led_release (struct inode *inode, struct file *filp)
{
    return 0;
}

static struct file_operations led_fops = {
    .owner = THIS_MODULE,
    .open = led_open,
    .read = led_read,
    .write = led_write,
    .release = led_release,
};
static int __init led_init(void)
{
    int retvalue = 0;
    u32 val = 0;

    /* 初始化LED */
    // 1 寄存器地址映射
    IMX6U_CCM_CCGR1 = ioremap(CCM_CCGR1_BASE, 4);
    SW_MUX_GPIO1_IO03 = ioremap(SW_MUX_GPIO1_IO03_BASE, 4);
    SW_PAD_GPIO1_IO03 = ioremap(SW_PAD_GPIO1_IO03_BASE, 4);
    GPIO1_DR = ioremap(GPIO1_DR_BASE, 4);
    GPIO1_GDIR = ioremap(GPIO1_DR_BASE, 4);

    //2. 使能gpio1时钟
    val = readl(IMX6U_CCM_CCGR1);
    val &= ~(3 << 26); /* 清除以前的设置 */
    val |= (3 << 26); /* 设置新值 */
    writel(val, IMX6U_CCM_CCGR1);

    // 3 设置gpio1_io03 复用功能。
    writel(5, SW_MUX_GPIO1_IO03);

    writel(0x10b0, SW_PAD_GPIO1_IO03);

    // 4. 设置GPIO1_IO03 为输出功能
    val = readl(GPIO1_GDIR);
    val &= ~(1<<3);
    val |= (1<<3);
    writel(val, GPIO1_GDIR);
        //5 默认关闭
    val = readl(GPIO1_DR);
    val |= (1<<3);
    writel(val, GPIO1_DR);

    // 6 注册字符设备驱动
    retvalue = register_chrdev(LED_MAJOR, LED_NAME, &led_fops);
    if (retvalue < 0){
        printk("registser chrdev faild\n");
        return -EIO;
    }
    return 0;
}

static void __exit led_exit(void)
{
    iounmap(IMX6U_CCM_CCGR1);
    iounmap(SW_MUX_GPIO1_IO03);
    iounmap(SW_PAD_GPIO1_IO03);
    iounmap(GPIO1_DR);
    iounmap(GPIO1_GDIR);

    unregister_chrdev(LED_MAJOR, LED_NAME);
}

module_init(led_init);
module_exit(led_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("zzk");

ledApp.c

#include "stdio.h"
#include "unistd.h"
#include "sys/types.h"
#include "sys/stat.h"
#include "fcntl.h"
#include "stdlib.h"
#include "string.h"

#define LEDOFF 0
#define LEDON 1

int main(int argc, char *argv[])
{
    int fd, retvalue;
    char *filename;

    unsigned char databuf[1];

    if (argc != 3){
        printf("Error Usage!\n");
        return -1;
    }

    filename = argv[1];

    fd = open(filename, O_RDWR);
    if(fd < 0 ){
        printf("file %s open failed!\n", argv[1]);
        return -1;
    }

    databuf[0] = atoi(argv[2]);

    retvalue = write(fd, databuf, sizeof(databuf));
    if (retvalue < 0){
        printf("Led control failed!\n");
        close(fd);
        return -1;
    }

    retvalue = close(fd);
    if (retvalue < 0){
        printf("file %s close failed \r\n", argv[1]);
        return -1;
    }
    return 0;
}

Makefile

KERNELDIR := /home/zzk/linux/IMX6ULL/linux/temp/linux-imx-rel_imx_4.1.15_2.1.0_ga_alientek

CURRENT_PATH := $(shell pwd)
NFS_PATH := /home/zzk/linux/nfs/rootfs/lib/modules/4.1.15
obj-m := led.o
obj-ko := led.ko


build: kernel_modules

kernel_modules:
	$(MAKE) -C $(KERNELDIR) M=$(CURRENT_PATH) modules 
	arm-linux-gnueabihf-gcc ledApp.c -o ledApp

clean:
	$(MAKE) -C $(KERNELDIR) M=$(CURRENT_PATH) clean

install:
	cp $(obj-ko)  ledApp $(NFS_PATH) 

验证

1. depmod
2. modprode led.ko
3. mknod /dev/led c 200 0
4. ./ledApp /dev/led 1 //开 ; ./ledApp /dev/led 0 //关
5. rmmod