In the following example, the high-level mutex (xsp->high_mu) is used only to protect data shared between the high-level interrupt handler and the soft interrupt handler. The protected data includes a queue used by both the high-level interrupt handler and the low-level handler, and a flag that indicates that the low-level handler is running. A separate low-level mutex (xsp->low_mu) protects the rest of the driver from the soft interrupt handler.
static int mydevattach(dev_info_t *dip, ddi_attach_cmd_t cmd) { struct mydevstate *xsp; /* ... */ ret = ddi_intr_get_supported_types(dip, &type); if ((ret != DDI_SUCCESS) || (!(type & DDI_INTR_TYPE_FIXED))) { cmn_err(CE_WARN, "ddi_intr_get_supported_types() failed"); return (DDI_FAILURE); } ret = ddi_intr_get_nintrs(dip, DDI_INTR_TYPE_FIXED, &count); /* * Fixed interrupts can only have one interrupt. Check to make * sure that number of supported interrupts and number of * available interrupts are both equal to 1. */ if ((ret != DDI_SUCCESS) || (count != 1)) { cmn_err(CE_WARN, "No fixed interrupts found"); return (DDI_FAILURE); } xsp->xs_htable = kmem_zalloc(count * sizeof (ddi_intr_handle_t), KM_SLEEP); ret = ddi_intr_alloc(dip, xsp->xs_htable, DDI_INTR_TYPE_FIXED, 0, count, &actual, 0); if ((ret != DDI_SUCCESS) || (actual != 1)) { cmn_err(CE_WARN, "ddi_intr_alloc failed 0x%x", ret"); kmem_free(xsp->xs_htable, sizeof (ddi_intr_handle_t)); return (DDI_FAILURE); } ret = ddi_intr_get_pri(xsp->xs_htable[0], &intr_pri); if (ret != DDI_SUCCESS) { cmn_err(CE_WARN, "ddi_intr_get_pri failed 0x%x", ret"); (void) ddi_intr_free(xsp->xs_htable[0]); kmem_free(xsp->xs_htable, sizeof (ddi_intr_handle_t)); return (DDI_FAILURE); } if (intr_pri >= ddi_intr_get_hilevel_pri()) { mutex_init(&xsp->high_mu, NULL, MUTEX_DRIVER, DDI_INTR_PRI(intr_pri)); ret = ddi_intr_add_handler(xsp->xs_htable[0], mydevhigh_intr, (caddr_t)xsp, NULL); if (ret != DDI_SUCCESS) { cmn_err(CE_WARN, "ddi_intr_add_handler failed 0x%x", ret"); mutex_destroy(&xsp>xs_int_mutex); (void) ddi_intr_free(xsp->xs_htable[0]); kmem_free(xsp->xs_htable, sizeof (ddi_intr_handle_t)); return (DDI_FAILURE); } /* add soft interrupt */ if (ddi_intr_add_softint(xsp->xs_dip, &xsp->xs_softint_hdl, DDI_INTR_SOFTPRI_MAX, xs_soft_intr, (caddr_t)xsp) != DDI_SUCCESS) { cmn_err(CE_WARN, "add soft interrupt failed"); mutex_destroy(&xsp->high_mu); (void) ddi_intr_remove_handler(xsp->xs_htable[0]); (void) ddi_intr_free(xsp->xs_htable[0]); kmem_free(xsp->xs_htable, sizeof (ddi_intr_handle_t)); return (DDI_FAILURE); } xsp->low_soft_pri = DDI_INTR_SOFTPRI_MAX; mutex_init(&xsp->low_mu, NULL, MUTEX_DRIVER, DDI_INTR_PRI(xsp->low_soft_pri)); } else { /* * regular interrupt registration continues from here * do not use a soft interrupt */ } return (DDI_SUCCESS); }
The high-level interrupt routine services the device and queues the data. The high-level routine triggers a software interrupt if the low-level routine is not running, as the following example demonstrates.
static uint_t mydevhigh_intr(caddr_t arg1, caddr_t arg2) { struct mydevstate *xsp = (struct mydevstate *)arg1; uint8_t status; volatile uint8_t temp; int need_softint; mutex_enter(&xsp->high_mu); /* read status */ status = ddi_get8(xsp->data_access_handle, &xsp->regp->csr); if (!(status & INTERRUPTING)) { mutex_exit(&xsp->high_mu); return (DDI_INTR_UNCLAIMED); /* dev not interrupting */ } ddi_put8(xsp->data_access_handle,&xsp->regp->csr, CLEAR_INTERRUPT | ENABLE_INTERRUPTS); /* flush store buffers */ temp = ddi_get8(xsp->data_access_handle, &xsp->regp->csr); /* read data from device, queue data for low-level interrupt handler */ if (xsp->softint_running) need_softint = 0; else { xsp->softint_count++; need_softint = 1; } mutex_exit(&xsp->high_mu); /* read-only access to xsp->id, no mutex needed */ if (need_softint) { ret = ddi_intr_trigger_softint(xsp->xs_softint_hdl, NULL); if (ret == DDI_EPENDING) { cmn_err(CE_WARN, "ddi_intr_trigger_softint() soft interrupt " "already pending for this handler"); } else if (ret != DDI_SUCCESS) { cmn_err(CE_WARN, "ddi_intr_trigger_softint() failed"); } } return (DDI_INTR_CLAIMED); }
The low-level interrupt routine is started by the high-level interrupt routine, which triggers a software interrupt. The low-level interrupt routine runs until there is nothing left to process, as the following example shows.
static uint_t mydev_soft_intr(caddr_t arg1, caddr_t arg2) { struct mydevstate *mydevp = (struct mydevstate *)arg1; /* ... */ mutex_enter(&mydevp->low_mu); mutex_enter(&mydevp->high_mu); if (mydevp->softint_count > 1) { mydevp->softint_count--; mutex_exit(&mydevp->high_mu); mutex_exit(&mydevp->low_mu); return (DDI_INTR_CLAIMED); } if ( /* queue empty */ ) { mutex_exit(&mydevp->high_mu); mutex_exit(&mydevp->low_mu); return (DDI_INTR_UNCLAIMED); } mydevp->softint_running = 1; while (EMBEDDED COMMENT:data on queue) { ASSERT(mutex_owned(&mydevp->high_mu); /* Dequeue data from high-level queue. */ mutex_exit(&mydevp->high_mu); /* normal interrupt processing */ mutex_enter(&mydevp->high_mu); } mydevp->softint_running = 0; mydevp->softint_count = 0; mutex_exit(&mydevp->high_mu); mutex_exit(&mydevp->low_mu); return (DDI_INTR_CLAIMED); }