Userspace IRQ: Difference between revisions
From embeddedTS Manuals
No edit summary |
No edit summary |
||
Line 1: | Line 1: | ||
We include a userspace IRQ patch in our 2.6 based 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 irq file | We include a userspace IRQ patch in our 2.6 based 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 [http://lwn.net/Articles/127293/ here]. | The original patch is documented [http://lwn.net/Articles/127293/ here]. |
Revision as of 16:43, 9 January 2012
We include a userspace IRQ patch in our 2.6 based 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 boards. 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;
}