目標：按下按鍵時，驅動程序通知應用程序，而不是應用程序自己查詢
步驟：
1.應用程序註冊信號處理函數；
2.誰發？驅動程序發；
3.發給誰？應用程序要告訴驅動它的pid號；
4.怎麼發？驅動程序調用某個函數，kill_fasync函數。
驅動程序：
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <linux/irqreturn.h>
#include <mach/irqs.h>
#include <linux/irq.h>
#include <linux/gpio.h>
#include <mach/gpio-davinci.h>
#include <linux/interrupt.h>
#include <linux/wait.h>
#include <linux/sched.h>
#include <linux/poll.h>
#include <asm/atomic.h>
#include <linux/semaphore.h>
static struct class *fifthdrv_class;
static struct device *fifthdrv_class_dev;
volatile unsigned long *gpfcon;
volatile unsigned long *gpgcon;
volatile unsigned long *gpfdat;
volatile unsigned long *gpgdat;
static DECLARE_WAIT_QUEUE_HEAD(button_waitq);
static volatile int ev_press=0;
static struct fasync_struct *button_async;
struct pin_desc{
unsigned int pin;
unsigned char key_val;
};
static unsigned char key_val;
struct pin_desc pins_desc[2]={
{GPIO_TO_PIN(6, 1),0x01},
{GPIO_TO_PIN(0, 6),0x02},
};
#if 0
static atomic_t canopen=ATOMIC_INIT(1);
#endif
static DEFINE_SEMAPHORE(button_lock);
static irqreturn_t buttons_irq(int irq,void *dev_id)
{
struct pin_desc *pindesc=(struct pin_desc*)dev_id;
unsigned int pinval;
pinval=gpio_get_value(pindesc->pin);
if(pinval)
{
key_val=0x80|pindesc->key_val;
}
else
{
key_val=pindesc->key_val;
}
ev_press=1;
wake_up_interruptible(&button_waitq);
kill_fasync(&button_async,SIGIO,POLL_IN);//在驅動程序中發
return IRQ_RETVAL(IRQ_HANDLED);
}
struct gpio_irq_desc {
int irq;
unsigned long flags;
char *name;
};
struct gpio_irq_desc press_dev_desc0 = {
IRQ_DA8XX_GPIO6,
IRQ_TYPE_EDGE_BOTH,
"sw9_push_button"
};
struct gpio_irq_desc press_dev_desc1 = {
IRQ_DA8XX_GPIO0,
IRQ_TYPE_EDGE_BOTH,
"sw8_push_button"
};
static int fifth_drv_open(struct inode *inode,struct file *file)
{
#if 0
if(!atomic_dec_and_test(&canopen))
{
atomic_inc(&canopen);
return -EBUSY;
}
#endif
down(&button_lock);
press_dev_desc0.irq=gpio_to_irq(GPIO_TO_PIN(6, 1));
request_irq(press_dev_desc0.irq,buttons_irq,press_dev_desc0.flags,press_dev_desc0.name,&pins_desc[0]);
press_dev_desc1.irq=gpio_to_irq(GPIO_TO_PIN(0, 6));
request_irq(press_dev_desc1.irq,buttons_irq,press_dev_desc1.flags,press_dev_desc1.name,&pins_desc[1]);
return 0;
}
static int fifth_drv_read(struct file *file, char __user *buf, size_t size, loff_t *ppos )
{
if(size!=1)
return -EINVAL;
wait_event_interruptible(button_waitq, ev_press);
copy_to_user(buf, &key_val, 1);
ev_press=0;
return 0;
}
int fifth_drv_close(struct inode *inode,struct file *file)
{
//atomic_inc(&canopen);
up(&button_lock);
free_irq(press_dev_desc0.irq,&pins_desc[0]);
free_irq(press_dev_desc1.irq,&pins_desc[1]);
return 0;
}
static unsigned fifth_drv_poll(struct file *file,poll_table *wait)
{
unsigned int mask=0;
poll_wait(file,&button_waitq,wait);
if(ev_press)
mask|=POLLIN | POLLRDNORM;
return mask;
}
/*初始化button_async結構體*/
static int fifth_drv_fasync(int fd, struct file *filp,int on)
{
printk("driver: fifth_drv_fasync\n");
return fasync_helper( fd, filp, on, &button_async);
}
static struct file_operations fifth_drv_fops={
.owner = THIS_MODULE,
.open =fifth_drv_open,
.read = fifth_drv_read,
.release=fifth_drv_close,
.poll=fifth_drv_poll,
.fasync=fifth_drv_fasync,
};
int major=0;
static int fifth_drv_init(void)
{
major=register_chrdev(0,"fifth_drv",&fifth_drv_fops);
fifthdrv_class=class_create(THIS_MODULE,"fifth_drv");
fifthdrv_class_dev=device_create(fifthdrv_class,NULL,MKDEV(major, 0),NULL,"buttons");
return 0;
}
static int fifth_drv_exit(void)
{
unregister_chrdev(major,"fifth_drv");
device_destroy(fifthdrv_class,MKDEV(major, 0));
class_destroy(fifthdrv_class);
return 0;
}
module_init(fifth_drv_init);
module_exit(fifth_drv_exit);
MODULE_LICENSE("GPL");
測試程序：
#include <fcntl.h>
#include <stdio.h>
#include <poll.h>
#include <signal.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
int fd;
void my_signal_fun(int signum)
{
unsigned char key_val;
read(fd,&key_val,1);
printf("key_val: 0x%x\n",key_val);
}
int main(int argc,char **argv)
{
unsigned char key_val;
int ret;
int oflags;
signal(SIGIO,my_signal_fun);
fd=open("/dev/buttons",O_RDWR);
if(fd<0)
{
printf("can't open !\n");
return -1;
}
/*F_SETOWN (long)
Set the process ID or process group ID that will receive SIGIO
and SIGURG signals for events on file descriptor fd to the ID
given in arg. A process ID is specified as a positive value; a
process group ID is specified as a negative value. */
fcntl(fd,F_SETOWN,getpid());
oflags=fcntl(fd,F_GETFL);
fcntl(fd,F_SETFL,oflags|FASYNC);
while(1)
{
sleep(1000);
}
return 0;
}