Print Driver Interrupt

Example 9–6 shows the interrupt handling for the printer driver.

lpintr is the driver-interrupt handler registered by the attach routine.

lpout takes a single character from the queue and sends it to the printer. For convenience, the message currently being output is stored in lp->msg in the per-instance structure. This assumes that the message is called with the mutex held.

lpoutchar sends a single character to the printer (in this case the system console using cmn_err(9F)) and interrupts when complete. Of course, hardware would generate a hard interrupt, so the call to ddi_trigger_softintr(9F) would be unnecessary.

Example 9–6 Driver Interrupt Handling

/* Device interrupt routine */static uint
lpintr(caddr_t lp)	 /* minor device number of lp */
{

	struct lp *lpp = (struct lp *)lp;
	
	mutex_enter(&lpp->lp_lock);

	if (!(lpp->flags & BUSY)) {
			mutex_exit(&lpp->lp_lock);
			return (DDI_INTR_UNCLAIMED);
	}

	lpp->flags &= ~BUSY;
	lpout(lpp);
	mutex_exit(&lpp->lp_lock);

	return (DDI_INTR_CLAIMED);
}

/* Start output to device - used by put procedure and driver */

static void
lpout(
	struct lp *lp)
{

	mblk_t *bp;
	queue_t *q;

	q = lp->qptr;

 loop:
	if ((bp = lp->msg) == NULL) { /*no current message*/
			if ((bp = getq(q)) == NULL) {
				lp->flags &= ~BUSY;	
				return;
			}
			if (bp->b_datap->db_type == M_IOCTL) {
				/* lpdoioctl(lp, bp); */
				goto loop;
			}

			lp->msg = bp; /* new message */

		}

	if (bp->b_rptr >= bp->b_wptr) { /* validate message */

			bp = lp->msg->b_cont;
			lp->msg->b_cont = NULL;
			freeb(lp->msg);
			lp->msg = bp;
			goto loop;
	}

	lpoutchar(lp, *bp->b_rptr++); /*output one character*/
	lp->flags |= BUSY;
}

static void
lpoutchar(
	struct lp *lp,
	char c)
{
	cmn_err(CE_CONT, “%c”, c);
	ddi_trigger_softintr(lp->siid);
}