Why this interrupt handler does not work?
 

The main idea is that each time that the Real time Clock (RTC) enables, my_handler print the message.


#include <stdio.h>
#include <linux/rtc.h>
#include <sys/ioctl.h>
#include <sys/time.h>
#include <sys/types.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>

#include <linux/sched.h>

void my_handler(int irq, void *dev_id, struct pt_regs *regs)
{
printk("working");

}

void main(void) {

int i, fd, retval, irqcount = 0;
unsigned long tmp, data;
struct rtc_time;

free_irq(8,NULL);
request_irq(8,my_handler,SA_INTERRUPT,"test",NULL);

fd = open ("/dev/rtc", O_RDONLY);

if (fd == -1) {
perror("/dev/rtc");
exit(errno);
}

fprintf(stderr, "\n\t\t\tRTC \n\n");


fprintf(stderr, "Counting 20 interrupts at:");
fflush(stderr);


for (tmp=2; tmp<=8192; tmp*=2) {

retval = ioctl(fd, RTC_IRQP_SET, tmp);
if (retval == -1) {
perror("ioctl");
exit(errno);
}

fprintf(stderr, "\n%ldHz:\t", tmp);
fflush(stderr);

/* Enable periodic interrupts */
retval = ioctl(fd, RTC_PIE_ON, 0);
if (retval == -1) {
perror("ioctl");
exit(errno);
}

for (i=1; i<21; i++) {
/* This blocks */
retval = read(fd, &data, sizeof(unsigned long));
if (retval == -1) {
perror("read");
exit(errno);
}
fprintf(stderr, " %d",i);
fflush(stderr);
irqcount++;
}

/* Disable periodic interrupts */
retval = ioctl(fd, RTC_PIE_OFF, 0);
if (retval == -1) {
perror("ioctl");
exit(errno);
}
}

close(fd);

free_irq(8,NULL);

}

i was under the impression that installing/freeing interrupt handlers could only be done in kernel space?