brcmfmac: define and use platform specific data for SDIO.

This patch adds support for platform specific data for SDIO
fullmac devices. Currently OOB interrupts are configured by Kconfig
BRCMFMAC_SDIO_OOB but that is now determined dynamically by checking
availibility of platform data.

Cc: Hauke Mehrtens <hauke@hauke-m.de>
Reviewed-by: Arend Van Spriel <arend@broadcom.com>
Reviewed-by: Franky (Zhenhui) Lin <frankyl@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Piotr Haber <phaber@broadcom.com>
Signed-off-by: Hante Meuleman <meuleman@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

5 files changed, 126 insertions, 187 deletions

diff --git a/drivers/net/wireless/brcm80211/Kconfig b/drivers/net/wireless/brcm80211/Kconfig
index 747e9317dabd..fc8a0fa6d3b2 100644
--- a/drivers/net/wireless/brcm80211/Kconfig
+++ b/drivers/net/wireless/brcm80211/Kconfig
@@ -37,15 +37,6 @@ config BRCMFMAC_SDIO
           IEEE802.11n embedded FullMAC WLAN driver. Say Y if you want to
           use the driver for a SDIO wireless card.
 
-config BRCMFMAC_SDIO_OOB
-        bool "Out of band interrupt support for SDIO interface chipset"
-        depends on BRCMFMAC_SDIO
-        ---help---
-          This option enables out-of-band interrupt support for Broadcom
-          SDIO Wifi chipset using fullmac in order to gain better
-          performance and deep sleep wake up capability on certain
-          platforms. Say N if you are unsure.
-
 config BRCMFMAC_USB
         bool "USB bus interface support for FullMAC driver"
         depends on USB
diff --git a/drivers/net/wireless/brcm80211/brcmfmac/bcmsdh.c b/drivers/net/wireless/brcm80211/brcmfmac/bcmsdh.c
index aa51f370be49..4891e3df2058 100644
--- a/drivers/net/wireless/brcm80211/brcmfmac/bcmsdh.c
+++ b/drivers/net/wireless/brcm80211/brcmfmac/bcmsdh.c
@@ -25,6 +25,7 @@
 #include <linux/mmc/sdio.h>
 #include <linux/mmc/sdio_func.h>
 #include <linux/mmc/card.h>
+#include <linux/platform_data/brcmfmac-sdio.h>
 
 #include <defs.h>
 #include <brcm_hw_ids.h>
@@ -37,16 +38,15 @@
 
 #define SDIOH_API_ACCESS_RETRY_LIMIT    2
 
-#ifdef CONFIG_BRCMFMAC_SDIO_OOB
-static irqreturn_t brcmf_sdio_irqhandler(int irq, void *dev_id)
+
+static irqreturn_t brcmf_sdio_oob_irqhandler(int irq, void *dev_id)
 {
         struct brcmf_bus *bus_if = dev_get_drvdata(dev_id);
         struct brcmf_sdio_dev *sdiodev = bus_if->bus_priv.sdio;
 
-        brcmf_dbg(INTR, "oob intr triggered\n");
+        brcmf_dbg(INTR, "OOB intr triggered\n");
 
-        /*
-         * out-of-band interrupt is level-triggered which won't
+        /* out-of-band interrupt is level-triggered which won't
          * be cleared until dpc
          */
         if (sdiodev->irq_en) {
@@ -59,72 +59,12 @@ static irqreturn_t brcmf_sdio_irqhandler(int irq, void *dev_id)
         return IRQ_HANDLED;
 }
 
-int brcmf_sdio_intr_register(struct brcmf_sdio_dev *sdiodev)
-{
-        int ret = 0;
-        u8 data;
-        unsigned long flags;
-
-        brcmf_dbg(SDIO, "Entering: irq %d\n", sdiodev->irq);
-
-        ret = request_irq(sdiodev->irq, brcmf_sdio_irqhandler,
-                          sdiodev->irq_flags, "brcmf_oob_intr",
-                          &sdiodev->func[1]->dev);
-        if (ret != 0)
-                return ret;
-        spin_lock_init(&sdiodev->irq_en_lock);
-        spin_lock_irqsave(&sdiodev->irq_en_lock, flags);
-        sdiodev->irq_en = true;
-        spin_unlock_irqrestore(&sdiodev->irq_en_lock, flags);
-
-        ret = enable_irq_wake(sdiodev->irq);
-        if (ret != 0)
-                return ret;
-        sdiodev->irq_wake = true;
-
-        sdio_claim_host(sdiodev->func[1]);
-
-        /* must configure SDIO_CCCR_IENx to enable irq */
-        data = brcmf_sdio_regrb(sdiodev, SDIO_CCCR_IENx, &ret);
-        data |= 1 << SDIO_FUNC_1 | 1 << SDIO_FUNC_2 | 1;
-        brcmf_sdio_regwb(sdiodev, SDIO_CCCR_IENx, data, &ret);
-
-        /* redirect, configure and enable io for interrupt signal */
-        data = SDIO_SEPINT_MASK | SDIO_SEPINT_OE;
-        if (sdiodev->irq_flags & IRQF_TRIGGER_HIGH)
-                data |= SDIO_SEPINT_ACT_HI;
-        brcmf_sdio_regwb(sdiodev, SDIO_CCCR_BRCM_SEPINT, data, &ret);
-
-        sdio_release_host(sdiodev->func[1]);
-
-        return 0;
-}
-
-int brcmf_sdio_intr_unregister(struct brcmf_sdio_dev *sdiodev)
-{
-        brcmf_dbg(SDIO, "Entering\n");
-
-        sdio_claim_host(sdiodev->func[1]);
-        brcmf_sdio_regwb(sdiodev, SDIO_CCCR_BRCM_SEPINT, 0, NULL);
-        brcmf_sdio_regwb(sdiodev, SDIO_CCCR_IENx, 0, NULL);
-        sdio_release_host(sdiodev->func[1]);
-
-        if (sdiodev->irq_wake) {
-                disable_irq_wake(sdiodev->irq);
-                sdiodev->irq_wake = false;
-        }
-        free_irq(sdiodev->irq, &sdiodev->func[1]->dev);
-        sdiodev->irq_en = false;
-
-        return 0;
-}
-#else           /* CONFIG_BRCMFMAC_SDIO_OOB */
-static void brcmf_sdio_irqhandler(struct sdio_func *func)
+static void brcmf_sdio_ib_irqhandler(struct sdio_func *func)
 {
         struct brcmf_bus *bus_if = dev_get_drvdata(&func->dev);
         struct brcmf_sdio_dev *sdiodev = bus_if->bus_priv.sdio;
 
-        brcmf_dbg(INTR, "ib intr triggered\n");
+        brcmf_dbg(INTR, "IB intr triggered\n");
 
         brcmf_sdbrcm_isr(sdiodev->bus);
 }
@@ -136,12 +76,56 @@ static void brcmf_sdio_dummy_irqhandler(struct sdio_func *func)
 
 int brcmf_sdio_intr_register(struct brcmf_sdio_dev *sdiodev)
 {
-        brcmf_dbg(SDIO, "Entering\n");
+        int ret = 0;
+        u8 data;
+        unsigned long flags;
 
-        sdio_claim_host(sdiodev->func[1]);
-        sdio_claim_irq(sdiodev->func[1], brcmf_sdio_irqhandler);
-        sdio_claim_irq(sdiodev->func[2], brcmf_sdio_dummy_irqhandler);
-        sdio_release_host(sdiodev->func[1]);
+        if ((sdiodev->pdata) && (sdiodev->pdata->oob_irq_supported)) {
+                brcmf_dbg(SDIO, "Enter, register OOB IRQ %d\n",
+                          sdiodev->pdata->oob_irq_nr);
+                ret = request_irq(sdiodev->pdata->oob_irq_nr,
+                                  brcmf_sdio_oob_irqhandler,
+                                  sdiodev->pdata->oob_irq_flags,
+                                  "brcmf_oob_intr",
+                                  &sdiodev->func[1]->dev);
+                if (ret != 0) {
+                        brcmf_err("request_irq failed %d\n", ret);
+                        return ret;
+                }
+                sdiodev->oob_irq_requested = true;
+                spin_lock_init(&sdiodev->irq_en_lock);
+                spin_lock_irqsave(&sdiodev->irq_en_lock, flags);
+                sdiodev->irq_en = true;
+                spin_unlock_irqrestore(&sdiodev->irq_en_lock, flags);
+
+                ret = enable_irq_wake(sdiodev->pdata->oob_irq_nr);
+                if (ret != 0) {
+                        brcmf_err("enable_irq_wake failed %d\n", ret);
+                        return ret;
+                }
+                sdiodev->irq_wake = true;
+
+                sdio_claim_host(sdiodev->func[1]);
+
+                /* must configure SDIO_CCCR_IENx to enable irq */
+                data = brcmf_sdio_regrb(sdiodev, SDIO_CCCR_IENx, &ret);
+                data |= 1 << SDIO_FUNC_1 | 1 << SDIO_FUNC_2 | 1;
+                brcmf_sdio_regwb(sdiodev, SDIO_CCCR_IENx, data, &ret);
+
+                /* redirect, configure and enable io for interrupt signal */
+                data = SDIO_SEPINT_MASK | SDIO_SEPINT_OE;
+                if (sdiodev->pdata->oob_irq_flags & IRQF_TRIGGER_HIGH)
+                        data |= SDIO_SEPINT_ACT_HI;
+                brcmf_sdio_regwb(sdiodev, SDIO_CCCR_BRCM_SEPINT, data, &ret);
+
+                sdio_release_host(sdiodev->func[1]);
+        } else {
+                brcmf_dbg(SDIO, "Entering\n");
+                sdio_claim_host(sdiodev->func[1]);
+                sdio_claim_irq(sdiodev->func[1], brcmf_sdio_ib_irqhandler);
+                sdio_claim_irq(sdiodev->func[2], brcmf_sdio_dummy_irqhandler);
+                sdio_release_host(sdiodev->func[1]);
+        }
 
         return 0;
 }
@@ -150,14 +134,31 @@ int brcmf_sdio_intr_unregister(struct brcmf_sdio_dev *sdiodev)
 {
         brcmf_dbg(SDIO, "Entering\n");
 
-        sdio_claim_host(sdiodev->func[1]);
-        sdio_release_irq(sdiodev->func[2]);
-        sdio_release_irq(sdiodev->func[1]);
-        sdio_release_host(sdiodev->func[1]);
+        if ((sdiodev->pdata) && (sdiodev->pdata->oob_irq_supported)) {
+                sdio_claim_host(sdiodev->func[1]);
+                brcmf_sdio_regwb(sdiodev, SDIO_CCCR_BRCM_SEPINT, 0, NULL);
+                brcmf_sdio_regwb(sdiodev, SDIO_CCCR_IENx, 0, NULL);
+                sdio_release_host(sdiodev->func[1]);
+
+                if (sdiodev->oob_irq_requested) {
+                        sdiodev->oob_irq_requested = false;
+                        if (sdiodev->irq_wake) {
+                                disable_irq_wake(sdiodev->pdata->oob_irq_nr);
+                                sdiodev->irq_wake = false;
+                        }
+                        free_irq(sdiodev->pdata->oob_irq_nr,
+                                 &sdiodev->func[1]->dev);
+                        sdiodev->irq_en = false;
+                }
+        } else {
+                sdio_claim_host(sdiodev->func[1]);
+                sdio_release_irq(sdiodev->func[2]);
+                sdio_release_irq(sdiodev->func[1]);
+                sdio_release_host(sdiodev->func[1]);
+        }
 
         return 0;
 }
-#endif          /* CONFIG_BRCMFMAC_SDIO_OOB */
 
 int
 brcmf_sdcard_set_sbaddr_window(struct brcmf_sdio_dev *sdiodev, u32 address)
diff --git a/drivers/net/wireless/brcm80211/brcmfmac/bcmsdh_sdmmc.c b/drivers/net/wireless/brcm80211/brcmfmac/bcmsdh_sdmmc.c
index b1ea1036e825..44fa0cdbf97b 100644
--- a/drivers/net/wireless/brcm80211/brcmfmac/bcmsdh_sdmmc.c
+++ b/drivers/net/wireless/brcm80211/brcmfmac/bcmsdh_sdmmc.c
@@ -26,6 +26,7 @@
 #include <linux/sched.h>        /* request_irq() */
 #include <linux/module.h>
 #include <linux/platform_device.h>
+#include <linux/platform_data/brcmfmac-sdio.h>
 #include <net/cfg80211.h>
 
 #include <defs.h>
@@ -62,14 +63,8 @@ static const struct sdio_device_id brcmf_sdmmc_ids[] = {
 };
 MODULE_DEVICE_TABLE(sdio, brcmf_sdmmc_ids);
 
-#ifdef CONFIG_BRCMFMAC_SDIO_OOB
-static struct list_head oobirq_lh;
-struct brcmf_sdio_oobirq {
-        unsigned int irq;
-        unsigned long flags;
-        struct list_head list;
-};
-#endif          /* CONFIG_BRCMFMAC_SDIO_OOB */
+static struct brcmfmac_sdio_platform_data *brcmfmac_sdio_pdata;
+
 
 static bool
 brcmf_pm_resume_error(struct brcmf_sdio_dev *sdiodev)
@@ -428,33 +423,6 @@ void brcmf_sdioh_detach(struct brcmf_sdio_dev *sdiodev)
 
 }
 
-#ifdef CONFIG_BRCMFMAC_SDIO_OOB
-static int brcmf_sdio_getintrcfg(struct brcmf_sdio_dev *sdiodev)
-{
-        struct brcmf_sdio_oobirq *oobirq_entry;
-
-        if (list_empty(&oobirq_lh)) {
-                brcmf_err("no valid oob irq resource\n");
-                return -ENXIO;
-        }
-
-        oobirq_entry = list_first_entry(&oobirq_lh, struct brcmf_sdio_oobirq,
-                                        list);
-
-        sdiodev->irq = oobirq_entry->irq;
-        sdiodev->irq_flags = oobirq_entry->flags;
-        list_del(&oobirq_entry->list);
-        kfree(oobirq_entry);
-
-        return 0;
-}
-#else
-static inline int brcmf_sdio_getintrcfg(struct brcmf_sdio_dev *sdiodev)
-{
-        return 0;
-}
-#endif          /* CONFIG_BRCMFMAC_SDIO_OOB */
-
 static int brcmf_ops_sdio_probe(struct sdio_func *func,
                                 const struct sdio_device_id *id)
 {
@@ -495,15 +463,13 @@ static int brcmf_ops_sdio_probe(struct sdio_func *func,
         dev_set_drvdata(&func->dev, bus_if);
         dev_set_drvdata(&sdiodev->func[1]->dev, bus_if);
         sdiodev->dev = &sdiodev->func[1]->dev;
+        sdiodev->pdata = brcmfmac_sdio_pdata;
 
         atomic_set(&sdiodev->suspend, false);
         init_waitqueue_head(&sdiodev->request_byte_wait);
         init_waitqueue_head(&sdiodev->request_word_wait);
         init_waitqueue_head(&sdiodev->request_chain_wait);
         init_waitqueue_head(&sdiodev->request_buffer_wait);
-        err = brcmf_sdio_getintrcfg(sdiodev);
-        if (err)
-                goto fail;
 
         brcmf_dbg(SDIO, "F2 found, calling brcmf_sdio_probe...\n");
         err = brcmf_sdio_probe(sdiodev);
@@ -598,7 +564,7 @@ static const struct dev_pm_ops brcmf_sdio_pm_ops = {
 static struct sdio_driver brcmf_sdmmc_driver = {
         .probe = brcmf_ops_sdio_probe,
         .remove = brcmf_ops_sdio_remove,
-        .name = "brcmfmac",
+        .name = BRCMFMAC_SDIO_PDATA_NAME,
         .id_table = brcmf_sdmmc_ids,
 #ifdef CONFIG_PM_SLEEP
         .drv = {
@@ -607,72 +573,51 @@ static struct sdio_driver brcmf_sdmmc_driver = {
 #endif  /* CONFIG_PM_SLEEP */
 };
 
-#ifdef CONFIG_BRCMFMAC_SDIO_OOB
 static int brcmf_sdio_pd_probe(struct platform_device *pdev)
 {
-        struct resource *res;
-        struct brcmf_sdio_oobirq *oobirq_entry;
-        int i, ret;
+        int ret;
 
-        INIT_LIST_HEAD(&oobirq_lh);
+        brcmf_dbg(SDIO, "Enter\n");
 
-        for (i = 0; ; i++) {
-                res = platform_get_resource(pdev, IORESOURCE_IRQ, i);
-                if (!res)
-                        break;
+        brcmfmac_sdio_pdata = pdev->dev.platform_data;
 
-                oobirq_entry = kzalloc(sizeof(struct brcmf_sdio_oobirq),
-                                       GFP_KERNEL);
-                if (!oobirq_entry)
-                        return -ENOMEM;
-                oobirq_entry->irq = res->start;
-                oobirq_entry->flags = res->flags & IRQF_TRIGGER_MASK;
-                list_add_tail(&oobirq_entry->list, &oobirq_lh);
-        }
-        if (i == 0)
-                return -ENXIO;
+        if (brcmfmac_sdio_pdata->power_on)
+                brcmfmac_sdio_pdata->power_on();
 
         ret = sdio_register_driver(&brcmf_sdmmc_driver);
-
         if (ret)
                 brcmf_err("sdio_register_driver failed: %d\n", ret);
 
         return ret;
 }
 
-static struct platform_driver brcmf_sdio_pd = {
-        .probe          = brcmf_sdio_pd_probe,
-        .driver         = {
-                .name   = "brcmf_sdio_pd"
-        }
-};
-
-void brcmf_sdio_exit(void)
+static int brcmf_sdio_pd_remove(struct platform_device *pdev)
 {
         brcmf_dbg(SDIO, "Enter\n");
 
+        if (brcmfmac_sdio_pdata->power_off)
+                brcmfmac_sdio_pdata->power_off();
+
         sdio_unregister_driver(&brcmf_sdmmc_driver);
 
-        platform_driver_unregister(&brcmf_sdio_pd);
+        return 0;
 }
 
-void brcmf_sdio_init(void)
-{
-        int ret;
-
-        brcmf_dbg(SDIO, "Enter\n");
-
-        ret = platform_driver_register(&brcmf_sdio_pd);
+static struct platform_driver brcmf_sdio_pd = {
+        .remove         = brcmf_sdio_pd_remove,
+        .driver         = {
+                .name   = BRCMFMAC_SDIO_PDATA_NAME
+        }
+};
 
-        if (ret)
-                brcmf_err("platform_driver_register failed: %d\n", ret);
-}
-#else
 void brcmf_sdio_exit(void)
 {
         brcmf_dbg(SDIO, "Enter\n");
 
-        sdio_unregister_driver(&brcmf_sdmmc_driver);
+        if (brcmfmac_sdio_pdata)
+                platform_driver_unregister(&brcmf_sdio_pd);
+        else
+                sdio_unregister_driver(&brcmf_sdmmc_driver);
 }
 
 void brcmf_sdio_init(void)
@@ -681,9 +626,12 @@ void brcmf_sdio_init(void)
 
         brcmf_dbg(SDIO, "Enter\n");
 
-        ret = sdio_register_driver(&brcmf_sdmmc_driver);
+        ret = platform_driver_probe(&brcmf_sdio_pd, brcmf_sdio_pd_probe);
+        if (ret == -ENODEV) {
+                brcmf_dbg(SDIO, "No platform data available, registering without.\n");
+                ret = sdio_register_driver(&brcmf_sdmmc_driver);
+        }
 
         if (ret)
-                brcmf_err("sdio_register_driver failed: %d\n", ret);
+                brcmf_err("driver registration failed: %d\n", ret);
 }
-#endif          /* CONFIG_BRCMFMAC_SDIO_OOB */
diff --git a/drivers/net/wireless/brcm80211/brcmfmac/dhd_sdio.c b/drivers/net/wireless/brcm80211/brcmfmac/dhd_sdio.c
index fd697ce3683c..d2487518bd2a 100644
--- a/drivers/net/wireless/brcm80211/brcmfmac/dhd_sdio.c
+++ b/drivers/net/wireless/brcm80211/brcmfmac/dhd_sdio.c
@@ -31,6 +31,7 @@
 #include <linux/bcma/bcma.h>
 #include <linux/debugfs.h>
 #include <linux/vmalloc.h>
+#include <linux/platform_data/brcmfmac-sdio.h>
 #include <asm/unaligned.h>
 #include <defs.h>
 #include <brcmu_wifi.h>
@@ -517,7 +518,7 @@ static int qcount[NUMPRIO];
 static int tx_packets[NUMPRIO];
 #endif                          /* DEBUG */
 
-#define SDIO_DRIVE_STRENGTH     6       /* in milliamps */
+#define DEFAULT_SDIO_DRIVE_STRENGTH     6       /* in milliamps */
 
 #define RETRYCHAN(chan) ((chan) == SDPCM_EVENT_CHANNEL)
 
@@ -2046,23 +2047,19 @@ static void brcmf_sdbrcm_bus_stop(struct device *dev)
         bus->tx_seq = bus->rx_seq = 0;
 }
 
-#ifdef CONFIG_BRCMFMAC_SDIO_OOB
 static inline void brcmf_sdbrcm_clrintr(struct brcmf_sdio *bus)
 {
         unsigned long flags;
 
-        spin_lock_irqsave(&bus->sdiodev->irq_en_lock, flags);
-        if (!bus->sdiodev->irq_en && !atomic_read(&bus->ipend)) {
-                enable_irq(bus->sdiodev->irq);
-                bus->sdiodev->irq_en = true;
+        if (bus->sdiodev->oob_irq_requested) {
+                spin_lock_irqsave(&bus->sdiodev->irq_en_lock, flags);
+                if (!bus->sdiodev->irq_en && !atomic_read(&bus->ipend)) {
+                        enable_irq(bus->sdiodev->pdata->oob_irq_nr);
+                        bus->sdiodev->irq_en = true;
+                }
+                spin_unlock_irqrestore(&bus->sdiodev->irq_en_lock, flags);
         }
-        spin_unlock_irqrestore(&bus->sdiodev->irq_en_lock, flags);
-}
-#else
-static inline void brcmf_sdbrcm_clrintr(struct brcmf_sdio *bus)
-{
 }
-#endif          /* CONFIG_BRCMFMAC_SDIO_OOB */
 
 static inline void brcmf_sdbrcm_adddpctsk(struct brcmf_sdio *bus)
 {
@@ -3639,6 +3636,7 @@ brcmf_sdbrcm_probe_attach(struct brcmf_sdio *bus, u32 regsva)
         int err = 0;
         int reg_addr;
         u32 reg_val;
+        u32 drivestrength;
 
         bus->alp_only = true;
 
@@ -3679,8 +3677,11 @@ brcmf_sdbrcm_probe_attach(struct brcmf_sdio *bus, u32 regsva)
                 goto fail;
         }
 
-        brcmf_sdio_chip_drivestrengthinit(bus->sdiodev, bus->ci,
-                                          SDIO_DRIVE_STRENGTH);
+        if ((bus->sdiodev->pdata) && (bus->sdiodev->pdata->drive_strength))
+                drivestrength = bus->sdiodev->pdata->drive_strength;
+        else
+                drivestrength = DEFAULT_SDIO_DRIVE_STRENGTH;
+        brcmf_sdio_chip_drivestrengthinit(bus->sdiodev, bus->ci, drivestrength);
 
         /* Get info on the SOCRAM cores... */
         bus->ramsize = bus->ci->ramsize;
diff --git a/drivers/net/wireless/brcm80211/brcmfmac/sdio_host.h b/drivers/net/wireless/brcm80211/brcmfmac/sdio_host.h
index 28ed3cc9f35a..7c1b6332747e 100644
--- a/drivers/net/wireless/brcm80211/brcmfmac/sdio_host.h
+++ b/drivers/net/wireless/brcm80211/brcmfmac/sdio_host.h
@@ -174,13 +174,11 @@ struct brcmf_sdio_dev {
         wait_queue_head_t request_buffer_wait;
         struct device *dev;
         struct brcmf_bus *bus_if;
-#ifdef CONFIG_BRCMFMAC_SDIO_OOB
-        unsigned int irq;               /* oob interrupt number */
-        unsigned long irq_flags;        /* board specific oob flags */
+        struct brcmfmac_sdio_platform_data *pdata;
+        bool oob_irq_requested;
         bool irq_en;                    /* irq enable flags */
         spinlock_t irq_en_lock;
         bool irq_wake;                  /* irq wake enable flags */
-#endif          /* CONFIG_BRCMFMAC_SDIO_OOB */
 };
 
 /* Register/deregister interrupt handler. */