AM335x内核模块驱动之LED

在Ubuntu的任意可操作的文件才建立text目录

在text中建立zyr-hello.c：

#include<linux/kernel.h>
#include<linux/module.h>
#include<linux/init.h>
#include <linux/miscdevice.h>
#include <linux/types.h>
#include <linux/ioctl.h>
#include <linux/cdev.h>
#include <linux/delay.h>
#include <linux/gpio.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/init.h>

#define CORE_LED (1*32 + 7)  //硬件上的一个led灯为goip1_7
#define DEVICE "led_core"
#define MAGIC_NUM 0xDB
#define MAGIC_SET_LOW _IO(MAGIC_NUM,0)
#define MAGIC_SET_HIGH _IO(MAGIC_NUM,1)

int led_open(struct inode *inode, struct file *file)
{
    int ret;
    ret = gpio_request_one(CORE_LED,
            (GPIOF_DIR_OUT|GPIOF_OUT_INIT_HIGH),"core_led");
    if(ret)
    {
        printk("Error: cannot request gpio CORE_LED. 
");
        printk("Error ret = %d but still can be manipulated. 
", ret);
    }            
    
    gpio_set_value(CORE_LED,1);
    return 0;
            
}

int led_release(struct inode *inode, struct file *filp)
{
    gpio_free(CORE_LED);
    printk("GPIO LED dev release. 
");
    return 0;
}

long led_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
    switch(cmd)
    {
        case MAGIC_SET_LOW:
            printk("GPIO LED set low.
");
            gpio_set_value(CORE_LED,0);
            break;
        case MAGIC_SET_HIGH:
            printk("GPIO LED set high.
");
            gpio_set_value(CORE_LED,1);
            break;
        default:
            printk("ERROR unvalid cmd.
");
            break;    
    }
    return 0;
}

struct file_operations led_fops ={
    .owner             = THIS_MODULE,
    .open              = led_open,
    .release         = led_release,
    .unlocked_ioctl = led_ioctl,
};

struct miscdevice led_dev ={
    .minor        = MISC_DYNAMIC_MINOR,
    .name        = DEVICE,
    .fops        = &led_fops,
};

static int led_init(void)
{
    int ret;
    ret = misc_register(&led_dev);
    if (ret)
    {
        printk("Error: cannot register misc. 
");
        return ret;
    }
    printk("misc-register %s
",DEVICE);
    return 0;
}

static void led_exit(void)
{
    misc_deregister(&led_dev);
    printk("misc-deregister %s
",DEVICE);
}

module_init(led_init);
module_exit(led_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("zyr<yr736002477@qq.com>");

在该目录下建立Makefile文件：

ifneq ($(KERNELRELEASE),)
obj-m := zyr-hello.o
else
KDIR :=/home/zyr/Source_code/linux-3.14.65/
all:
    make -C $(KDIR) M=$(PWD) modules ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- -j8
clean:
    rm -f *.ko *.o *.mod.o *.mod.c *.symvers *.order
endif

其中KDIR为内核的路径，要想编译arm可运行的驱动，一定要指定交叉编译器

在该目录下执行make，会编译器出zyr-hello.ko文件，此文件为可加载于内核的.ko模块的文件。

然后编写这个led驱动的的测试文件(运行在文件系统中)：

同样在任意的可执行处建立一个目录放测试文件比如aa：

在该目录下建立led_test.c：

#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<fcntl.h>
#include<errno.h>
#include<string.h>
#include<asm-generic/ioctl.h>

#define DEVICE          "/dev/led_core"
#define MAGIC_NUM       0xDB
#define MAGIC_SET_LOW   _IO(MAGIC_NUM, 0)
#define MAGIC_SET_HIGH  _IO(MAGIC_NUM, 1)

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

        printf("Start led test.
");

        fd = open(DEVICE, O_RDWR);
        if (fd < 2) {
                printf("Cannot open device %s
", DEVICE);
                return -EFAULT;
        }       
        while (1) {
                ioctl(fd, MAGIC_SET_LOW, 0);
                sleep(1);
                ioctl(fd, MAGIC_SET_HIGH, 0);
                sleep(1);
        }
        return 0;       
}

在该目录下建立Makefile文件：

#----------------------------
CC    = arm-linux-gnueabihf-gcc 
CFLAGS    =         
main : led_test.c 
    $(CC) $(CFLAGS) led_test.c -o led_test

在该目录下执行make：生成led_test可执行文件。

将led_test可执行文件和zyr-hello.ko模块文件copy到建立好的NFS共享文件夹下敲击命令（在arm板的终端中）：

[root@zyr-am335x ]#mount -t nfs -o nolock 192.168.200.123:/home/zyr/Source_code/text/nfs /mnt
[root@zyr-am335x ]#cd /mnt
[root@zyr-am335x mnt]#ls
led_test      zyr-hello.ko
[root@zyr-am335x mnt]#insmod zyr-hello.ko
[ 5299.759382] misc-register led_core
[root@zyr-am335x mnt]#./led_test
Start led test.
[ 5309.324907] GPIO LED set low.
[ 5310.338522] GPIO LED set high.
[ 5311.342169] GPIO LED set low.
[ 5312.345413] GPIO LED set high.

参考博客：

http://www.eefocus.com/marianna/blog/15-02/310302_72e75.html