Hello, I am trying to correctly register interrupt in kernel for user interface: irq handler ========= static irqreturn_t irq_handler(int irq, void *dev_id) { struct elbit_irq_dev *elbit_irq = &elbit_irq_devices[0]; printk("irq in\n"); <<==== clear interrupt in fpga here or after the call to wake_up, (at the bottom of routine below ) ? atomic_set(&elbit_irq->flag, 1); wake_up_interruptible(&elbit_irq->pollw); return IRQ_HANDLED; } ioctl for waiting on interrupts ====================== static long elbit_device_ioctl( struct file *filp, /* ditto */ unsigned int ioctl_num, /* number and param for ioctl */ unsigned long ioctl_param) { struct elbit_irq_dev *elbit_irq = &elbit_irq_devices[0]; switch (ioctl_num) { case IOCTL_WAIT_IRQ: atomic_set(&elbit_irq->flag, 0); wait_event_interruptible(elbit_irq->pollw, atomic_read(&elbit_irq->flag) != 0) ; break; default: break; } return 0; } my questions: 1. does wake_up and wait_event are countable, i.e. if there are 2 interrupts for example before wait_event is called, does it mean it wake_event will not sleep on 2 consecutive calls ? 2. should we put the clear of interrupts in fpga in the interrupt before or after the wake_up ? can we put them instead in the userspace handler (IOCTL_WAIT_IRQ) instead of clearing the interrupt in the interrupt handler ? Thank you, Ran