Userspace IRQ
From embeddedTS Manuals
We include a userspace IRQ patch in our kernels. This allows you to receive interrupts from your applications where you would normally have to write a kernel driver. This works by creating a file for each interrupt in '/proc/irq/<irqnum>/irq'. The new irq file allows you to block on a read on the file until an interrupt fires.
The original patch is documented here.
This example below will work with any of our TS-Socket boards running Linux. This opens the IRQ number specified in the first argument and prints when it detects an IRQ.
#include <stdio.h>
#include <fcntl.h>
#include <sys/select.h>
#include <sys/stat.h>
#include <unistd.h>
int main(int argc, char **argv)
{
char proc_irq[32];
int ret, irqfd = 0;
int buf; // Holds irq junk data
fd_set fds;
if(argc < 2) {
printf("Usage: %s <irq number>\n", argv[0]);
return 1;
}
snprintf(proc_irq, sizeof(proc_irq), "/proc/irq/%d/irq", atoi(argv[1]));
irqfd = open(proc_irq, O_RDONLY| O_NONBLOCK, S_IREAD);
if(irqfd == -1) {
printf("Could not open IRQ %s\n", argv[1]);
return 1;
}
while(1) {
FD_SET(irqfd, &fds); //add the fd to the set
// See if the IRQ has any data available to read
ret = select(irqfd + 1, &fds, NULL, NULL, NULL);
if(FD_ISSET(irqfd, &fds))
{
FD_CLR(irqfd, &fds); //Remove the filedes from set
printf("IRQ detected\n");
// Clear the junk data in the IRQ file
read(irqfd, &buf, sizeof(buf));
}
//Sleep, or do any other processing here
usleep(10000);
}
return 0;
}