上篇文章中断按键的驱动跨度有点大,这里面揉合了太多的东西,所以特地再重新写以下,以加强理解:
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/sched.h>
#include <linux/poll.h>
#include <linux/irq.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <linux/interrupt.h>
#include <asm/uaccess.h>
#include <mach/hardware.h>
#include <linux/platform_device.h>
#include <linux/cdev.h>
#include <linux/miscdevice.h>
#include <linux/gpio.h>
#include <mach/map.h>
#include <mach/gpio.h>
#include <mach/regs-clock.h>
#include <mach/regs-gpio.h>
#define DEVICE_NAME "buttons"
#define BUTTON_MAJOR 254
#define KEY_STATUS_DOWN '0'
#define KEY_STATUS_UP '1'
struct button_desc {
int gpio;
int number;
char *name;
};
static struct button_desc buttons[] = {
{ S5PV210_GPH2(0), 0, "KEY0" },
{ S5PV210_GPH2(1), 1, "KEY1" },
{ S5PV210_GPH2(2), 2, "KEY2" },
{ S5PV210_GPH2(3), 3, "KEY3" },
{ S5PV210_GPH3(0), 4, "KEY4" },
{ S5PV210_GPH3(1), 5, "KEY5" },
{ S5PV210_GPH3(2), 6, "KEY6" },
{ S5PV210_GPH3(3), 7, "KEY7" },
};
static volatile char key_states[] = {
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP
};
static DECLARE_WAIT_QUEUE_HEAD(button_waitq);
static volatile int ev_press = 0;
static irqreturn_t button_interrupt(int irq, void *dev_id)
{
struct button_desc *bdata = (struct button_desc *)dev_id;
if(gpio_get_value(bdata->gpio) == 0)//when press down
{
key_states[bdata->number]=KEY_STATUS_DOWN;
ev_press = 1;
wake_up_interruptible(&button_waitq);
}
else
{
key_states[bdata->number]=KEY_STATUS_UP;
}
return IRQ_HANDLED;
}
static ssize_t smart210_buttons_read(struct file *filp, char __user *buff, size_t count, loff_t *offp){
unsigned long err;
wait_event_interruptible(button_waitq, ev_press);
ev_press = 0;
err = copy_to_user((void *)buff, (const void *)(&key_states),
min(sizeof(key_states), count));
return err ? -EFAULT : min(sizeof(key_states), count);
};
static int smart210_buttons_open(struct inode *inode, struct file *file){
int i;
int err;
int irq;
for(i=0;i< ARRAY_SIZE(buttons);i++){
//注册中断函数
irq = gpio_to_irq(buttons[i].gpio);
err = request_irq(irq, button_interrupt, IRQ_TYPE_EDGE_BOTH,
buttons[i].name, (void *)&buttons[i]);
if (err)
break;
}
if(err)
{
i--;
for (; i >= 0; i--) {
if (!buttons[i].gpio)
continue;
irq = gpio_to_irq(buttons[i].gpio);
disable_irq(irq);
free_irq(irq, (void *)&buttons[i]);
}
return -EBUSY;
}
return 0;
};
static int smart210_buttons_close(struct inode *inode, struct file *file){
int irq, i;
for (i = 0; i < ARRAY_SIZE(buttons); i++) {
if (!buttons[i].gpio)
continue;
irq = gpio_to_irq(buttons[i].gpio);
free_irq(irq, (void *)&buttons[i]);
}
return 0;
};
static struct file_operations smart210_buttons_dev_fops = {
.owner = THIS_MODULE,
.open =smart210_buttons_open,
.release =smart210_buttons_close,
.read =smart210_buttons_read,
};
static int __init smart210_buttons_dev_init(void) {
int ret;
//字符设备
ret=register_chrdev(BUTTON_MAJOR,DEVICE_NAME,&smart210_buttons_dev_fops);
if (ret < 0) {
printk("request char device failed\n");
return ret;
}
printk(DEVICE_NAME"\tinitialized\n");
return ret;
}
static void __exit smart210_buttons_dev_exit(void) {
//注销字符设备
unregister_chrdev(BUTTON_MAJOR,DEVICE_NAME);
}
module_init(smart210_buttons_dev_init);
module_exit(smart210_buttons_dev_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("FriendlyARM Inc.");
这里少了定时器中断的内容。原先我一直不理解为什么在按键中断里面又要加入定时器。等到我把定时器拿掉后,才发现。好像是为了按键消抖。如果不消抖,有时候会出现按下去一下,实际驱动中会get 到按下去多次。
将设备注册为字符设备,而非混杂设备,这里只是试试看两者会有什么差异。
实际上字符设备需要手动在dev目录下创建设备文件,如果没有特殊处理的话,这样的话会非常麻烦。
首先先cat /proc/devices
由于我们是静态分配,所以知道主设备号为254,如果是动态分配主设备号,则安上面操作查询主设备号!
然后在dev目录下 mknod buttons c 254 1 创建设备文件
可见手动创建设备节点还是比较繁琐的,misc混杂设备是可以自动生成的,很实用!
使字符设备可以自动创建设备节点:
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/sched.h>
#include <linux/poll.h>
#include <linux/irq.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <linux/interrupt.h>
#include <asm/uaccess.h>
#include <mach/hardware.h>
#include <linux/platform_device.h>
#include <linux/cdev.h>
#include <linux/miscdevice.h>
#include <linux/gpio.h>
#include <mach/map.h>
#include <mach/gpio.h>
#include <mach/regs-clock.h>
#include <mach/regs-gpio.h>
#define DEVICE_NAME "buttons"
/*set to 0 自动分配主设备号,否则手动分配,但是如果已经被占用,便会分配失败*/
#define BUTTON_MAJOR 0
#define KEY_STATUS_DOWN '0'
#define KEY_STATUS_UP '1'
struct button_desc {
int gpio;
int number;
char *name;
};
static struct button_desc buttons[] = {
{ S5PV210_GPH2(0), 0, "KEY0" },
{ S5PV210_GPH2(1), 1, "KEY1" },
{ S5PV210_GPH2(2), 2, "KEY2" },
{ S5PV210_GPH2(3), 3, "KEY3" },
{ S5PV210_GPH3(0), 4, "KEY4" },
{ S5PV210_GPH3(1), 5, "KEY5" },
{ S5PV210_GPH3(2), 6, "KEY6" },
{ S5PV210_GPH3(3), 7, "KEY7" },
};
static volatile char key_states[] = {
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP
};
static DECLARE_WAIT_QUEUE_HEAD(button_waitq);
static volatile int ev_press = 0;
/*当用户空间已经移植了udev/mdev,使用下列方式可以在dev目录下自动创建字符设备*/
static struct class* buttons_class;
static dev_t dev;
static irqreturn_t button_interrupt(int irq, void *dev_id)
{
struct button_desc *bdata = (struct button_desc *)dev_id;
if(gpio_get_value(bdata->gpio) == 0)//when press down
{
key_states[bdata->number]=KEY_STATUS_DOWN;
ev_press = 1;
wake_up_interruptible(&button_waitq);
}
else
{
key_states[bdata->number]=KEY_STATUS_UP;
}
return IRQ_HANDLED;
}
static ssize_t smart210_buttons_read(struct file *filp, char __user *buff, size_t count, loff_t *offp){
unsigned long err;
//等待 wait队列被唤醒,获取值,阻塞模式访问,没有数据一直等待
wait_event_interruptible(button_waitq, ev_press);
ev_press = 0;
err = copy_to_user((void *)buff, (const void *)(&key_states),
min(sizeof(key_states), count));
return err ? -EFAULT : min(sizeof(key_states), count);
};
static int smart210_buttons_open(struct inode *inode, struct file *file){
int i;
int err;
int irq;
for(i=0;i< ARRAY_SIZE(buttons);i++){
//注册中断函数
irq = gpio_to_irq(buttons[i].gpio);
err = request_irq(irq, button_interrupt, IRQ_TYPE_EDGE_BOTH,
buttons[i].name, (void *)&buttons[i]);
if (err)
break;
}
if(err)
{
i--;
for (; i >= 0; i--) {
if (!buttons[i].gpio)
continue;
irq = gpio_to_irq(buttons[i].gpio);
disable_irq(irq);
free_irq(irq, (void *)&buttons[i]);
}
return -EBUSY;
}
return 0;
};
static int smart210_buttons_close(struct inode *inode, struct file *file){
int irq, i;
for (i = 0; i < ARRAY_SIZE(buttons); i++) {
if (!buttons[i].gpio)
continue;
irq = gpio_to_irq(buttons[i].gpio);
free_irq(irq, (void *)&buttons[i]);
}
return 0;
};
static struct file_operations smart210_buttons_dev_fops = {
.owner = THIS_MODULE,
.open =smart210_buttons_open,
.release =smart210_buttons_close,
.read =smart210_buttons_read,
};
static int __init smart210_buttons_dev_init(void) {
int major;
//字符设备
major=register_chrdev(BUTTON_MAJOR,DEVICE_NAME,&smart210_buttons_dev_fops);
if (major < 0) {
printk("request char device failed\n");
return major;
}
buttons_class=class_create(THIS_MODULE,DEVICE_NAME);
dev = MKDEV(major, 1);
device_create(buttons_class,NULL,dev,NULL,"%s",buttons_class->name);
printk(DEVICE_NAME"\tinitialized\n");
return major;
}
static void __exit smart210_buttons_dev_exit(void) {
//注销字符设备
unregister_chrdev(BUTTON_MAJOR,DEVICE_NAME);
device_destroy(buttons_class, dev);
class_destroy(buttons_class);
}
module_init(smart210_buttons_dev_init);
module_exit(smart210_buttons_dev_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("FriendlyARM Inc.");
另外还有一种方式,因为以上驱动读设备时阻塞访问,一直停留在那里等待,有点浪费资源!
我们可以用poll的方式:poll里面有一个timeout参数,比如poll一个设备50ms,如果在50ms内设备可以进行某些操作,比如
可以被读,或者IO允许被写,此时我们再直接调用read函数或者write函数,便可以直接获得/操作数据.
如果50ms内设备返回 0,即超时。我们此时可以选择继续poll或者做其他事情。
这里主要研究下poll函数的作用!
最后的驱动这样写:
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/sched.h>
#include <linux/poll.h>
#include <linux/irq.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <linux/interrupt.h>
#include <asm/uaccess.h>
#include <mach/hardware.h>
#include <linux/platform_device.h>
#include <linux/cdev.h>
#include <linux/miscdevice.h>
#include <linux/gpio.h>
#include <mach/map.h>
#include <mach/gpio.h>
#include <mach/regs-clock.h>
#include <mach/regs-gpio.h>
#define DEVICE_NAME "buttons"
/*set to 0 自动分配主设备号,否则手动分配,但是如果已经被占用,便会分配失败*/
#define BUTTON_MAJOR 0
#define KEY_STATUS_DOWN '0'
#define KEY_STATUS_UP '1'
struct button_desc {
int gpio;
int number;
char *name;
};
static struct button_desc buttons[] = {
{ S5PV210_GPH2(0), 0, "KEY0" },
{ S5PV210_GPH2(1), 1, "KEY1" },
{ S5PV210_GPH2(2), 2, "KEY2" },
{ S5PV210_GPH2(3), 3, "KEY3" },
{ S5PV210_GPH3(0), 4, "KEY4" },
{ S5PV210_GPH3(1), 5, "KEY5" },
{ S5PV210_GPH3(2), 6, "KEY6" },
{ S5PV210_GPH3(3), 7, "KEY7" },
};
static volatile char key_states[] = {
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP
};
static DECLARE_WAIT_QUEUE_HEAD(button_waitq);
static volatile int ev_press = 0;
/*当用户空间已经移植了udev/mdev,使用下列方式可以在dev目录下自动创建字符设备*/
static struct class* buttons_class;
static dev_t dev;
static irqreturn_t button_interrupt(int irq, void *dev_id)
{
struct button_desc *bdata = (struct button_desc *)dev_id;
if(gpio_get_value(bdata->gpio) == 0)//when press down
{
key_states[bdata->number]=KEY_STATUS_DOWN;
ev_press = 1;
wake_up_interruptible(&button_waitq);
}
else
{
key_states[bdata->number]=KEY_STATUS_UP;
}
return IRQ_HANDLED;
}
static ssize_t smart210_buttons_read(struct file *filp, char __user *buff, size_t count, loff_t *offp){
unsigned long err;
if (!ev_press) {
if (filp->f_flags & O_NONBLOCK){
printk("noneblock return\n");
return -EAGAIN;
}
}
ev_press = 0;
err = copy_to_user((void *)buff, (const void *)(&key_states),
min(sizeof(key_states), count));
return err ? -EFAULT : min(sizeof(key_states), count);
};
static int smart210_buttons_open(struct inode *inode, struct file *file){
int i;
int err;
int irq;
for(i=0;i< ARRAY_SIZE(buttons);i++){
//注册中断函数
irq = gpio_to_irq(buttons[i].gpio);
err = request_irq(irq, button_interrupt, IRQ_TYPE_EDGE_BOTH,
buttons[i].name, (void *)&buttons[i]);
if (err)
break;
}
if(err)
{
i--;
for (; i >= 0; i--) {
if (!buttons[i].gpio)
continue;
irq = gpio_to_irq(buttons[i].gpio);
disable_irq(irq);
free_irq(irq, (void *)&buttons[i]);
}
return -EBUSY;
}
return 0;
};
static int smart210_buttons_close(struct inode *inode, struct file *file){
int irq, i;
for (i = 0; i < ARRAY_SIZE(buttons); i++) {
if (!buttons[i].gpio)
continue;
irq = gpio_to_irq(buttons[i].gpio);
free_irq(irq, (void *)&buttons[i]);
}
return 0;
};
static unsigned int smart210_buttons_poll( struct file *file,
struct poll_table_struct *wait)
{
unsigned int mask = 0;
poll_wait(file, &button_waitq, wait);
if (ev_press)
mask |= POLLIN | POLLRDNORM;/*key is press down,IO is readable*/
return mask;
}
static struct file_operations smart210_buttons_dev_fops = {
.owner = THIS_MODULE,
.open =smart210_buttons_open,
.release =smart210_buttons_close,
.read =smart210_buttons_read,
.poll =smart210_buttons_poll,
};
static int __init smart210_buttons_dev_init(void) {
int major;
//字符设备
major=register_chrdev(BUTTON_MAJOR,DEVICE_NAME,&smart210_buttons_dev_fops);
if (major < 0) {
printk("request char device failed\n");
return major;
}
buttons_class=class_create(THIS_MODULE,DEVICE_NAME);
dev = MKDEV(major, 1);
device_create(buttons_class,NULL,dev,NULL,"%s",buttons_class->name);
printk(DEVICE_NAME"\tinitialized\n");
return major;
}
static void __exit smart210_buttons_dev_exit(void) {
//注销字符设备
unregister_chrdev(BUTTON_MAJOR,DEVICE_NAME);
device_destroy(buttons_class, dev);
class_destroy(buttons_class);
}
module_init(smart210_buttons_dev_init);
module_exit(smart210_buttons_dev_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("FriendlyARM Inc.");
这边的差别是:如果打开文件,接下来直接read ,因为没有按键按下时,就直接返回一个负数,而不会等待。
所以测试程序的编写需要改变下:
先打开文件,然后poll ,传给内核驱动中的poll,有一个timeout时间,如果在timeout时间内返回可读,此时调用read函数直接读取,否则,重新poll。
测试程序:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/select.h>
#include <sys/time.h>
#include <errno.h>
#include <termios.h>
#include <sys/poll.h>
#include <string.h>
#define KEY_STATUS_DOWN '0'
#define KEY_STATUS_UP '1'
/*main timeouttime*/
int main(int argc, char **argv)
{
int buttons_fd;
int ret;
int timeoutcount;
char current_buttons[8] = {
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP,
KEY_STATUS_UP
};
struct pollfd event; //创建一个struct pollfd结构体变量,存放文件描述符、要等待发生的事件
if(argc !=2 || sscanf(argv[1], "%d", &timeoutcount) !=1 || timeoutcount <40){
printf("USE like : ./buttons timeout(40-)\n");
exit(1);
}
buttons_fd = open("/dev/buttons", O_NONBLOCK);//非阻塞方式
if (buttons_fd < 0) {
perror("open device buttons");
exit(1);
}
while(timeoutcount--){
int i;
//poll结束后struct pollfd结构体变量的内容被全部清零,需要再次设置
memset(&event,0,sizeof(event)); //memst函数对对象的内容设置为同一值
event.fd=buttons_fd; //存放打开的文件描述符
event.events=POLLIN; //存放要等待发生的事件
ret=poll((struct pollfd *)&event,1,100); //监测event,一个对象,等待100毫秒后超时,-1为无限等待
//判断poll的返回值,负数是出错,0是设定的时间超时,整数表示等待的时间发生
if(ret<0){
printf("poll error!\n");
exit(1);
}
if(ret==0){
//printf("Time out!\n");
continue;
}
if(event.revents&POLLERR){ //revents是由内核记录的实际发生的事件,events是进程等待的事件
printf("Device error!\n");
exit(1);
}
//poll in
if(event.revents&POLLIN){
read(buttons_fd, current_buttons, sizeof(current_buttons));
for (i = 0; i < sizeof(current_buttons) / sizeof(current_buttons[0]); i++) {
if (current_buttons[i] ==KEY_STATUS_DOWN) {
printf("The key %d is pressed down!\n",i);
}
}
}
}
printf("Time out close file\n");
close(buttons_fd);
return 0;
}
大概说明一个;测试程序传入一个参数n,当n*timeout(poll的timeout时间为100ms)后,自动关掉设备文件。
在这段时间之间,如果有某些按键按下,当前被按下的按键都会被打印出来。
这里的驱动程序其实已经和开发板上的按键驱动程序非常相近了。如果我在这里再把定时器消抖的函数拿进来,那么其实就和例程是一样的。
到此,按键驱动开发结束!