AT91SAM9X25字符驱动实例

AT91SAM9X25字符驱动实例

概述

Linux下的字符驱动写法有固定的模式，不同的芯片有略微的差别，可以参照之前在TiAM1808的实验板上完成的字符驱动写法，本实例是以Led闪烁为例来实现简单的字符驱动过程。

从CM板的原理图中（CM_EMBEST_RevB）可以看到：CM板上有一蓝一红两个LED，因为蓝灯还起到别的指示作用，我们就以红色led为实验对象，其控制管脚为CPU的PD21，将其置低电平时led为亮。

经过之前对内核打上atmel的补丁以后，内核的相应文件会增加芯片的管脚定义以及操作函数实现，相对TI的驱动简单一点。

驱动代码led.c

#include

#include

#include

#include

#include

#include

#include

#include

#define MY_LED_MAJOR 203 //定义主设备号

#define MY_LED_MINOR 0 //定义从设备号

#define LED_ON 0

#define LED_OFF 1

#define PIN AT91_PIN_PD21 //PD21为要Led的pin

#define DEVICE_NAME "my_led" //设备名

struct global_dev{

struct cdev cdev;

}; //定义设备结构体

struct global_dev *global_devp; //定义一个指向设备结构体的指针

static int my_led_open(struct inode *inode, struct file *filp) {

filp->private_data = global_devp;

printk("AT91-LED Driver Open Called!\n");

return 0;

}

static int my_led_release(struct inode *inode, struct file *file) {

printk("AT91-LED Driver Release Called!\n");

return 0;

}

static int my_led_ioctl(struct file *filp, unsigned int cmd)

{

switch(cmd)

{

case LED_ON:

at91_set_gpio_value(PIN, 0); //pin on

break;

case LED_OFF:

at91_set_gpio_value(PIN, 1); //pin off

break;

default:

printk("no valid cmd input!\n");

break;

}

return 0;

}

/*初始化设备结构体*/

struct file_operations my_led_ctl_ops ={

.owner = THIS_MODULE,

.open = my_led_open,

.release = my_led_release,

.unlocked_ioctl = my_led_ioctl,

};

static int my_led_init(void)

{

int result;

dev_t devno = MKDEV(MY_LED_MAJOR, MY_LED_MINOR);//通过主次设备号得到设备号at91_set_GPIO_periph(PIN, 1);

at91_set_gpio_output(PIN, 1); //对Pin引脚的初始化

result = register_chrdev_region(devno, 1, DEVICE_NAME);//注册静态设备号，与设备名相关联

if(result < 0)

printk(KERN_ERR "can't get device number \n");

else

printk("get device number\n");

global_devp = kmalloc(sizeof(struct global_dev), GFP_KERNEL); //申请设备内存

memset(global_devp, 0, sizeof(struct global_dev));

cdev_init(&global_devp->cdev, &my_led_ctl_ops); //初始化cdev，与fop相关联

global_devp->cdev.owner = THIS_MODULE;

global_devp->cdev.ops = &my_led_ctl_ops;

result = cdev_add(&global_devp->cdev, devno, 1); //注册设备，设备号与设备结构体相关联

if (result < 0)

printk(KERN_ERR "can't add led device");

return 0;

}

static void my_led_cleanup(void)

{