本程序是基于三星s3c2410ARM平台下的按键驱动例程,程序中两个按键分别占用了ARM芯片上的外部中断16和17,程序中设定外部中断为下降沿响应中断.本程序是在2.6.16内核版本下编译测试通过,交叉编译器采用3.4.1版本的arm-linux-gcc.
1.驱动程序文件名为button.c,其源码如下示:
/**********************start*******************************/
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#define BUTTON_IRQ1 IRQ_EINT16
#define BUTTON_IRQ2 IRQ_EINT17
#define DEVICE_NAME "button"
static int buttonMajor=0;
#define BUTTONMINOR 0
#define MAX_BUTTON_BUF 16
#define BUTTONSTATUS_1 16
#define BUTTONSTATUS_2 17
static unsigned char buttonRead(void);
static int flag=0;
typedef struct {
unsigned int buttonStatus; //按键状态
unsigned char buf[MAX_BUTTON_BUF]; //按键缓冲区
unsigned int head,tail; //按键缓冲区头和尾
wait_queue_head_t wq; //等待队列
} BUTTON_DEV;
static BUTTON_DEV buttondev;
#define BUF_HEAD (buttondev.buf[buttondev.head]) //缓冲区头
#define BUF_TAIL (buttondev.buf[buttondev.tail]) //缓冲区尾
#define INCBUF(x,mod) ((++(x)) & ((mod)-1)) //移动缓冲区指针
static void (*buttonEvent)(void);
static void buttonEvent_dummy(void) {}
static void buttonEvent_1(void)
{
if(buttondev.buttonStatus==BUTTONSTATUS_2) {
BUF_HEAD=BUTTONSTATUS_2;
}
else {
BUF_HEAD=BUTTONSTATUS_1;
}
buttondev.head=INCBUF(buttondev.head,MAX_BUTTON_BUF);
flag=1;
wake_up_interruptible(&(buttondev.wq));
printk("buttonEvent_1\n");
}
static irqreturn_t isr_button(int irq,void *dev_id,struct pt_regs *regs)
{
printk("Occured key board Inetrrupt,irq=%d\n",irq-44);
switch (irq) {
case BUTTON_IRQ1:buttondev.buttonStatus=BUTTONSTATUS_1;
break;
case BUTTON_IRQ2:buttondev.buttonStatus=BUTTONSTATUS_2;
break;
default:break;
}
buttonEvent();
return 0;
}
static int button_open(struct inode *inode,struct file *filp)
{
int ret;
buttondev.head=buttondev.tail=0;
buttonEvent=buttonEvent_1;
ret=request_irq(BUTTON_IRQ1,isr_button,SA_INTERRUPT,DEVICE_NAME,NULL);
if(ret) {
printk("BUTTON_IRQ1: could not register interrupt\n");
return ret;
}
ret=request_irq(BUTTON_IRQ2,isr_button,SA_INTERRUPT,DEVICE_NAME,NULL);
if(ret) {
printk("BUTTON_IRQ2: could not register interrupt\n");
return ret;
}
return 0;
}
static int button_release(struct inode *inode,struct file *filp)
{
buttonEvent=buttonEvent_dummy;
free_irq(BUTTON_IRQ1,NULL);
free_irq(BUTTON_IRQ2,NULL);
return 0;
}
static ssize_t button_read(struct file *filp,char *buffer,size_t count,loff_t *ppos)
{
static unsigned char button_ret;
retry:
printk("retry start\n");
if(buttondev.head!=buttondev.tail) {
button_ret=buttonRead();
copy_to_user(buffer,(char *)&button_ret,sizeof(unsigned char));
printk("the button_ret is 0x%x\n",button_ret);
return sizeof(unsigned char);
}
else {
if(filp->f_flags & O_NONBLOCK)
return -EAGAIN;
printk("sleep\n");
//interruptible_sleep_on(&(buttondev.wq));//为安全起见,最好不要调用该睡眠函数
wait_event_interruptible(buttondev.wq,flag);
flag=0;
printk("sleep_after\n");
if(signal_pending(current))
{
printk("rturn -ERESTARTSYS\n");
return -ERESTARTSYS;
}
goto retry;
}
return sizeof(unsigned char);
}
static struct file_operations button_fops= {
.owner = THIS_MODULE,
.open = button_open,
.read = button_read,
.release = button_release,
};
static int __init s3c2410_button_init(void)
{
int ret;
set_irq_type(BUTTON_IRQ1,IRQT_FALLING);
set_irq_type(BUTTON_IRQ2,IRQT_FALLING);
buttonEvent=buttonEvent_dummy;
ret=register_chrdev(0,DEVICE_NAME,&button_fops);
if(ret<0) {
printk("button: can't get major number\n");
return ret;
}
buttonMajor=ret;
#ifdef CONFIG_DEVFS_FS
devfs_mk_cdev(MKDEV(buttonMajor,BUTTONMINOR),S_IFCHR | S_IRUSR | S_IWUSR | S_IRGRP,DEVICE_NAME);
#endif
//buttondev.head=buttondev.tail=0;
buttondev.buttonStatus=BUTTONSTATUS_1;
init_waitqueue_head(&(buttondev.wq));
printk(DEVICE_NAME"initialized\n");
return 0;
}
static unsigned char buttonRead(void)
{
unsigned char button_ret;
button_ret=BUF_TAIL;
buttondev.tail=INCBUF(buttondev.tail,MAX_BUTTON_BUF);
return button_ret;
}
static void __exit s3c2410_button_eixt(void)
{
#ifdef CONFIG_DEVFS_FS
devfs_remove(DEVICE_NAME);
#endif
unregister_chrdev(buttonMajor,DEVICE_NAME);
}
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Kision");
MODULE_DEscrīptION ("the first char device driver");
module_init(s3c2410_button_init);
module_exit(s3c2410_button_eixt);
/*************************end***************************/
2. 当然在编写2.6内核驱动程序之前应该已经自己建立好一个2.6的内核源码树(我这里是基于s3c2410移植的源码树,本处该源码是放在宿主机的/home/src/linux-2.6.16目录下的),如果没有的话,那么需要自己去建立好这个源码树.自己编写的模块化驱动程序可以不放在内核源码之内,但是此外还需要一个自己编写一个Makefile文件(该文件和上面的button.c文件应放在同一个目录下),其内容如下示:
ifneq ($(KERNELRELEASE),)
obj-m :=button.o
else
KERNELDIR ?= /home/src/linux-2.6.16
PWD := $(shell pwd)
default:
$(MAKE) -C $(KERNELDIR) M=$(PWD) modules
clean:
rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions
endif
3.在宿主机的终端下,进入驱动程序目录内,敲入命令:
#make
就会在该目录下生成button.ko文件,这就是2.6内核下生成的驱动加载模块,注意是.ko文件,不同于2.4内核下的.o文件.
把该button.ko文件拷贝到目标板上,在minicom终端下进入该文件目录,敲入:
#insmod button.ko
如果终端显示有buttoninitialized则表示加载成功.
这时可以用命令lsmod查看动态加载模块:
#lsmod
当然,可以用如下命令查看devfs文件系统信息:
#cat /proc/devices
如果用卸载该模块,敲入命令:
#rmmod button
4.加载驱动程序后,可以自己再编写一个简单的测试程序,如下:
/**************************start***********************/
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main()
{
int retval;
int fileno;
int ts, maxfd;
int ret= 0,i,j;
int number;
fileno = open("/dev/button",O_RDWR);
if (fileno == -1) {
printf("open device led errr!\n");
return 0;
}
while(1) {
read(fileno,&number,1);
printf("key=0x%x\n",number);
}
close(fileno);
return 0;
}
/**************************end***********************/
命名为test.c,并交叉编译该文件:
#arm-linux-gcc test.c -o test
将二进制文件同样拷贝到目标板上,运行:
#./test &
即可看到实验效果
