Merge commit 'crater/master'

[dragonfly.git] / sys / dev / video / bktr / bktr_os.c

/*-
 * 1. Redistributions of source code must retain the 
 * Copyright (c) 1997 Amancio Hasty, 1999 Roger Hardiman
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by Amancio Hasty and
 *      Roger Hardiman
 * 4. The name of the author may not be used to endorse or promote products 
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 * $FreeBSD: src/sys/dev/bktr/bktr_os.c,v 1.54 2007/02/23 12:18:34 piso Exp $
 * $DragonFly: src/sys/dev/video/bktr/bktr_os.c,v 1.21 2008/05/18 03:02:53 pavalos Exp $
 */

/*
 * This is part of the Driver for Video Capture Cards (Frame grabbers)
 * and TV Tuner cards using the Brooktree Bt848, Bt848A, Bt849A, Bt878, Bt879
 * chipset.
 * Copyright Roger Hardiman and Amancio Hasty.
 *
 * bktr_os : This has all the Operating System dependant code,
 *             probe/attach and open/close/ioctl/read/mmap
 *             memory allocation
 *             PCI bus interfacing
 */

#include "opt_bktr.h"           /* include any kernel config options */

#define FIFO_RISC_DISABLED      0
#define ALL_INTS_DISABLED       0

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/conf.h>
#include <sys/device.h>
#include <sys/uio.h>
#include <sys/kernel.h>
#include <sys/signalvar.h>
#include <sys/malloc.h>
#include <sys/mman.h>
#include <sys/poll.h>
#include <sys/select.h>
#include <sys/bus.h>
#include <sys/rman.h>
#include <sys/thread2.h>
#include <sys/selinfo.h>

#include <vm/vm.h>
#include <vm/vm_kern.h>
#include <vm/pmap.h>
#include <vm/vm_extern.h>

#include <bus/pci/pcivar.h>
#include <bus/pci/pcireg.h>
#include <bus/pci/pcidevs.h>

#include <sys/sysctl.h>
int bt848_card = -1; 
int bt848_tuner = -1;
int bt848_reverse_mute = -1; 
int bt848_format = -1;
int bt848_slow_msp_audio = -1;
#ifdef BKTR_NEW_MSP34XX_DRIVER
int bt848_stereo_once = 0;      /* no continuous stereo monitoring */
int bt848_amsound = 0;          /* hard-wire AM sound at 6.5 Hz (france),
                                   the autoscan seems work well only with FM... */
int bt848_dolby = 0;
#endif

SYSCTL_NODE(_hw, OID_AUTO, bt848, CTLFLAG_RW, 0, "Bt848 Driver mgmt");
SYSCTL_INT(_hw_bt848, OID_AUTO, card, CTLFLAG_RW, &bt848_card, -1, "");
SYSCTL_INT(_hw_bt848, OID_AUTO, tuner, CTLFLAG_RW, &bt848_tuner, -1, "");
SYSCTL_INT(_hw_bt848, OID_AUTO, reverse_mute, CTLFLAG_RW, &bt848_reverse_mute, -1, "");
SYSCTL_INT(_hw_bt848, OID_AUTO, format, CTLFLAG_RW, &bt848_format, -1, "");
SYSCTL_INT(_hw_bt848, OID_AUTO, slow_msp_audio, CTLFLAG_RW, &bt848_slow_msp_audio, -1, "");
#ifdef BKTR_NEW_MSP34XX_DRIVER
SYSCTL_INT(_hw_bt848, OID_AUTO, stereo_once, CTLFLAG_RW, &bt848_stereo_once, 0, "");
SYSCTL_INT(_hw_bt848, OID_AUTO, amsound, CTLFLAG_RW, &bt848_amsound, 0, "");
SYSCTL_INT(_hw_bt848, OID_AUTO, dolby, CTLFLAG_RW, &bt848_dolby, 0, "");
#endif

#include <dev/video/meteor/ioctl_meteor.h>
#include <dev/video/bktr/ioctl_bt848.h> /* extensions to ioctl_meteor.h */
#include <dev/video/bktr/bktr_reg.h>
#include <dev/video/bktr/bktr_tuner.h>
#include <dev/video/bktr/bktr_card.h>
#include <dev/video/bktr/bktr_audio.h>
#include <dev/video/bktr/bktr_core.h>
#include <dev/video/bktr/bktr_os.h>

#if defined(BKTR_USE_FREEBSD_SMBUS)
#include <dev/video/bktr/bktr_i2c.h>

#include "iicbb_if.h"
#include "smbus_if.h"
#endif

static int      bktr_probe( device_t dev );
static int      bktr_attach( device_t dev );
static int      bktr_detach( device_t dev );
static int      bktr_shutdown( device_t dev );
static void     bktr_intr(void *arg) { common_bktr_intr(arg); }

static device_method_t bktr_methods[] = {
        /* Device interface */
        DEVMETHOD(device_probe,         bktr_probe),
        DEVMETHOD(device_attach,        bktr_attach),
        DEVMETHOD(device_detach,        bktr_detach),
        DEVMETHOD(device_shutdown,      bktr_shutdown),

#if defined(BKTR_USE_FREEBSD_SMBUS)
        /* iicbb interface */
        DEVMETHOD(iicbb_callback,       bti2c_iic_callback),
        DEVMETHOD(iicbb_setsda,         bti2c_iic_setsda),
        DEVMETHOD(iicbb_setscl,         bti2c_iic_setscl),
        DEVMETHOD(iicbb_getsda,         bti2c_iic_getsda),
        DEVMETHOD(iicbb_getscl,         bti2c_iic_getscl),
        DEVMETHOD(iicbb_reset,          bti2c_iic_reset),
        
        /* smbus interface */
        DEVMETHOD(smbus_callback,       bti2c_smb_callback),
        DEVMETHOD(smbus_writeb,         bti2c_smb_writeb),
        DEVMETHOD(smbus_writew,         bti2c_smb_writew),
        DEVMETHOD(smbus_readb,          bti2c_smb_readb),
#endif

        { 0, 0 }
};

static driver_t bktr_driver = {
        "bktr",
        bktr_methods,
        sizeof(struct bktr_softc),
};

static devclass_t bktr_devclass;

static  d_open_t        bktr_open;
static  d_close_t       bktr_close;
static  d_read_t        bktr_read;
static  d_write_t       bktr_write;
static  d_ioctl_t       bktr_ioctl;
static  d_mmap_t        bktr_mmap;
static  d_poll_t        bktr_poll;

#define CDEV_MAJOR 92 
static struct dev_ops bktr_ops = {
        { "bktr", CDEV_MAJOR, 0 },
        .d_open =       bktr_open,
        .d_close =      bktr_close,
        .d_read =       bktr_read,
        .d_write =      bktr_write,
        .d_ioctl =      bktr_ioctl,
        .d_poll =       bktr_poll,
        .d_mmap =       bktr_mmap,
};

DRIVER_MODULE(bktr, pci, bktr_driver, bktr_devclass, 0, 0);
MODULE_DEPEND(bktr, bktr_mem, 1,1,1);
MODULE_VERSION(bktr, 1);

/*
 * the boot time probe routine.
 */
static int
bktr_probe( device_t dev )
{
        unsigned int type = pci_get_devid(dev);
        unsigned int rev  = pci_get_revid(dev);

        if (PCI_VENDOR(type) == PCI_VENDOR_BROOKTREE)
        {
                switch (PCI_PRODUCT(type)) {
                case PCI_PRODUCT_BROOKTREE_BT848:
                        if (rev == 0x12)
                                device_set_desc(dev, "BrookTree 848A");
                        else
                                device_set_desc(dev, "BrookTree 848");
                        return BUS_PROBE_DEFAULT;
                case PCI_PRODUCT_BROOKTREE_BT849:
                        device_set_desc(dev, "BrookTree 849A");
                        return BUS_PROBE_DEFAULT;
                case PCI_PRODUCT_BROOKTREE_BT878:
                        device_set_desc(dev, "BrookTree 878");
                        return BUS_PROBE_DEFAULT;
                case PCI_PRODUCT_BROOKTREE_BT879:
                        device_set_desc(dev, "BrookTree 879");
                        return BUS_PROBE_DEFAULT;
                }
        };

        return ENXIO;
}


/*
 * the attach routine.
 */
static int
bktr_attach( device_t dev )
{
        u_long          latency;
        u_long          fun;
        u_long          val;
        unsigned int    rev;
        unsigned int    unit;
        int             error = 0;
#ifdef BROOKTREE_IRQ
        u_long          old_irq, new_irq;
#endif 

        struct bktr_softc *bktr = device_get_softc(dev);

        unit = device_get_unit(dev);

        /* build the device name for bktr_name() */
        ksnprintf(bktr->bktr_xname, sizeof(bktr->bktr_xname), "bktr%d",unit);

        /*
         * Enable bus mastering and Memory Mapped device
         */
        val = pci_read_config(dev, PCIR_COMMAND, 4);
        val |= (PCIM_CMD_MEMEN|PCIM_CMD_BUSMASTEREN);
        pci_write_config(dev, PCIR_COMMAND, val, 4);

        /*
         * Map control/status registers.
         */
        bktr->mem_rid = PCIR_BAR(0);
        bktr->res_mem = bus_alloc_resource_any(dev, SYS_RES_MEMORY, 
                                        &bktr->mem_rid, RF_ACTIVE);

        if (!bktr->res_mem) {
                device_printf(dev, "could not map memory\n");
                error = ENXIO;
                goto fail;
        }
        bktr->memt = rman_get_bustag(bktr->res_mem);
        bktr->memh = rman_get_bushandle(bktr->res_mem);


        /*
         * Disable the brooktree device
         */
        OUTL(bktr, BKTR_INT_MASK, ALL_INTS_DISABLED);
        OUTW(bktr, BKTR_GPIO_DMA_CTL, FIFO_RISC_DISABLED);


#ifdef BROOKTREE_IRQ            /* from the configuration file */
        old_irq = pci_conf_read(tag, PCI_INTERRUPT_REG);
        pci_conf_write(tag, PCI_INTERRUPT_REG, BROOKTREE_IRQ);
        new_irq = pci_conf_read(tag, PCI_INTERRUPT_REG);
        kprintf("bktr%d: attach: irq changed from %d to %d\n",
                unit, (old_irq & 0xff), (new_irq & 0xff));
#endif 

        /*
         * Allocate our interrupt.
         */
        bktr->irq_rid = 0;
        bktr->res_irq = bus_alloc_resource_any(dev, SYS_RES_IRQ, 
                                &bktr->irq_rid, RF_SHAREABLE | RF_ACTIVE);
        if (bktr->res_irq == NULL) {
                device_printf(dev, "could not map interrupt\n");
                error = ENXIO;
                goto fail;
        }

        error = bus_setup_intr(dev, bktr->res_irq, 0,
                               bktr_intr, bktr, &bktr->res_ih, NULL);
        if (error) {
                device_printf(dev, "could not setup irq\n");
                goto fail;

        }


        /* Update the Device Control Register */
        /* on Bt878 and Bt879 cards           */
        fun = pci_read_config( dev, 0x40, 2);
        fun = fun | 1;  /* Enable writes to the sub-system vendor ID */

#if defined( BKTR_430_FX_MODE )
        if (bootverbose) kprintf("Using 430 FX chipset compatibilty mode\n");
        fun = fun | 2;  /* Enable Intel 430 FX compatibility mode */
#endif

#if defined( BKTR_SIS_VIA_MODE )
        if (bootverbose) kprintf("Using SiS/VIA chipset compatibilty mode\n");
        fun = fun | 4;  /* Enable SiS/VIA compatibility mode (useful for
                           OPTi chipset motherboards too */
#endif
        pci_write_config(dev, 0x40, fun, 2);

#if defined(BKTR_USE_FREEBSD_SMBUS)
        if (bt848_i2c_attach(dev))
                kprintf("bktr%d: i2c_attach: can't attach\n", unit);
#endif

/*
 * PCI latency timer.  32 is a good value for 4 bus mastering slots, if
 * you have more than four, then 16 would probably be a better value.
 */
#ifndef BROOKTREE_DEF_LATENCY_VALUE
#define BROOKTREE_DEF_LATENCY_VALUE     10
#endif
        latency = pci_read_config(dev, PCI_LATENCY_TIMER, 4);
        latency = (latency >> 8) & 0xff;
        if ( bootverbose ) {
                if (latency)
                        kprintf("brooktree%d: PCI bus latency is", unit);
                else
                        kprintf("brooktree%d: PCI bus latency was 0 changing to",
                                unit);
        }
        if ( !latency ) {
                latency = BROOKTREE_DEF_LATENCY_VALUE;
                pci_write_config(dev, PCI_LATENCY_TIMER, latency<<8, 4);
        }
        if ( bootverbose ) {
                kprintf(" %d.\n", (int) latency);
        }

        /* read the pci device id and revision id */
        fun = pci_get_devid(dev);
        rev = pci_get_revid(dev);

        /* call the common attach code */
        common_bktr_attach( bktr, unit, fun, rev );

        /* make the device entries */
        make_dev(&bktr_ops, unit,    0, 0, 0444, "bktr%d",  unit);
        make_dev(&bktr_ops, unit+16, 0, 0, 0444, "tuner%d", unit);
        make_dev(&bktr_ops, unit+32, 0, 0, 0444, "vbi%d"  , unit);

        return 0;

fail:
        if (bktr->res_irq)
                bus_release_resource(dev, SYS_RES_IRQ, bktr->irq_rid, bktr->res_irq);
        if (bktr->res_mem)
                bus_release_resource(dev, SYS_RES_IRQ, bktr->mem_rid, bktr->res_mem);
        return error;

}

/*
 * the detach routine.
 */
static int
bktr_detach( device_t dev )
{
        struct bktr_softc *bktr = device_get_softc(dev);

#ifdef BKTR_NEW_MSP34XX_DRIVER
        /* Disable the soundchip and kernel thread */
        if (bktr->msp3400c_info != NULL)
                msp_detach(bktr);
#endif

        /* Disable the brooktree device */
        OUTL(bktr, BKTR_INT_MASK, ALL_INTS_DISABLED);
        OUTW(bktr, BKTR_GPIO_DMA_CTL, FIFO_RISC_DISABLED);

#if defined(BKTR_USE_FREEBSD_SMBUS)
        if (bt848_i2c_detach(dev))
                kprintf("bktr%d: i2c_attach: can't attach\n",
                     device_get_unit(dev));
#endif
#ifdef USE_VBIMUTEX
        mtx_destroy(&bktr->vbimutex);
#endif

        /* Note: We do not free memory for RISC programs, grab buffer, vbi buffers */
        /* The memory is retained by the bktr_mem module so we can unload and */
        /* then reload the main bktr driver module */

        /* removing the ops automatically destroys all related devices */
        dev_ops_remove_minor(&bktr_ops, /*0x0f, */device_get_unit(dev));

        /*
         * Deallocate resources.
         */
        bus_teardown_intr(dev, bktr->res_irq, bktr->res_ih);
        bus_release_resource(dev, SYS_RES_IRQ, bktr->irq_rid, bktr->res_irq);
        bus_release_resource(dev, SYS_RES_MEMORY, bktr->mem_rid, bktr->res_mem);
         
        return 0;
}

/*
 * the shutdown routine.
 */
static int
bktr_shutdown( device_t dev )
{
        struct bktr_softc *bktr = device_get_softc(dev);

        /* Disable the brooktree device */
        OUTL(bktr, BKTR_INT_MASK, ALL_INTS_DISABLED);
        OUTW(bktr, BKTR_GPIO_DMA_CTL, FIFO_RISC_DISABLED);

        return 0;
}


/*
 * Special Memory Allocation
 */
vm_offset_t
get_bktr_mem( int unit, unsigned size )
{
        vm_offset_t     addr = 0;

        addr = (vm_offset_t)contigmalloc(size, M_DEVBUF, M_NOWAIT, 0,
            0xffffffff, 1<<24, 0);
        if (addr == 0)
                addr = (vm_offset_t)contigmalloc(size, M_DEVBUF, M_NOWAIT, 0,
                    0xffffffff, PAGE_SIZE, 0);
        if (addr == 0) {
                kprintf("bktr%d: Unable to allocate %d bytes of memory.\n",
                        unit, size);
        }

        return( addr );
}


/*---------------------------------------------------------
**
**      BrookTree 848 character device driver routines
**
**---------------------------------------------------------
*/

#define VIDEO_DEV       0x00
#define TUNER_DEV       0x01
#define VBI_DEV         0x02

#define UNIT(x)         ((x) & 0x0f)
#define FUNCTION(x)     (x >> 4)

/*
 * 
 */
static int
bktr_open(struct dev_open_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        bktr_ptr_t      bktr;
        int             unit;
        int             result;

        unit = UNIT( minor(dev) );

        /* Get the device data */
        bktr = (struct bktr_softc*)devclass_get_softc(bktr_devclass, unit);
        if (bktr == NULL) {
                /* the device is no longer valid/functioning */
                return (ENXIO);
        }

        if (!(bktr->flags & METEOR_INITALIZED)) /* device not found */
                return( ENXIO );        

        /* Record that the device is now busy */
        device_busy(devclass_get_device(bktr_devclass, unit)); 


        if (bt848_card != -1) {
          if ((bt848_card >> 8   == unit ) &&
             ( (bt848_card & 0xff) < Bt848_MAX_CARD )) {
            if ( bktr->bt848_card != (bt848_card & 0xff) ) {
              bktr->bt848_card = (bt848_card & 0xff);
              probeCard(bktr, FALSE, unit);
            }
          }
        }

        if (bt848_tuner != -1) {
          if ((bt848_tuner >> 8   == unit ) &&
             ( (bt848_tuner & 0xff) < Bt848_MAX_TUNER )) {
            if ( bktr->bt848_tuner != (bt848_tuner & 0xff) ) {
              bktr->bt848_tuner = (bt848_tuner & 0xff);
              probeCard(bktr, FALSE, unit);
            }
          }
        }

        if (bt848_reverse_mute != -1) {
          if ((bt848_reverse_mute >> 8)   == unit ) {
            bktr->reverse_mute = bt848_reverse_mute & 0xff;
          }
        }

        if (bt848_slow_msp_audio != -1) {
          if ((bt848_slow_msp_audio >> 8) == unit ) {
              bktr->slow_msp_audio = (bt848_slow_msp_audio & 0xff);
          }
        }

#ifdef BKTR_NEW_MSP34XX_DRIVER
        if (bt848_stereo_once != 0) {
          if ((bt848_stereo_once >> 8) == unit ) {
              bktr->stereo_once = (bt848_stereo_once & 0xff);
          }
        }

        if (bt848_amsound != -1) {
          if ((bt848_amsound >> 8) == unit ) {
              bktr->amsound = (bt848_amsound & 0xff);
          }
        }

        if (bt848_dolby != -1) {
          if ((bt848_dolby >> 8) == unit ) {
              bktr->dolby = (bt848_dolby & 0xff);
          }
        }
#endif

        switch ( FUNCTION( minor(dev) ) ) {
        case VIDEO_DEV:
                result = video_open( bktr );
                break;
        case TUNER_DEV:
                result = tuner_open( bktr );
                break;
        case VBI_DEV:
                result = vbi_open( bktr );
                break;
        default:
                result = ENXIO;
                break;
        }

        /* If there was an error opening the device, undo the busy status */
        if (result != 0)
                device_unbusy(devclass_get_device(bktr_devclass, unit)); 
        return( result );
}


/*
 * 
 */
static int
bktr_close(struct dev_close_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        bktr_ptr_t      bktr;
        int             unit;
        int             result;

        unit = UNIT( minor(dev) );

        /* Get the device data */
        bktr = (struct bktr_softc*)devclass_get_softc(bktr_devclass, unit);
        if (bktr == NULL) {
                /* the device is no longer valid/functioning */
                return (ENXIO);
        }

        switch ( FUNCTION( minor(dev) ) ) {
        case VIDEO_DEV:
                result = video_close( bktr );
                break;
        case TUNER_DEV:
                result = tuner_close( bktr );
                break;
        case VBI_DEV:
                result = vbi_close( bktr );
                break;
        default:
                return (ENXIO);
                break;
        }

        device_unbusy(devclass_get_device(bktr_devclass, unit)); 
        return( result );
}


/*
 * 
 */
static int
bktr_read(struct dev_read_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        bktr_ptr_t      bktr;
        int             unit;
        
        unit = UNIT(minor(dev));

        /* Get the device data */
        bktr = (struct bktr_softc*)devclass_get_softc(bktr_devclass, unit);
        if (bktr == NULL) {
                /* the device is no longer valid/functioning */
                return (ENXIO);
        }

        switch ( FUNCTION( minor(dev) ) ) {
        case VIDEO_DEV:
                return( video_read( bktr, unit, dev, ap->a_uio ) );
        case VBI_DEV:
                return( vbi_read( bktr, ap->a_uio, ap->a_ioflag ) );
        }
        return( ENXIO );
}


/*
 * 
 */
static int
bktr_write(struct dev_write_args *ap)
{
        return( EINVAL ); /* XXX or ENXIO ? */
}


/*
 * 
 */
static int
bktr_ioctl(struct dev_ioctl_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        u_long cmd = ap->a_cmd;
        bktr_ptr_t      bktr;
        int             unit;

        unit = UNIT(minor(dev));

        /* Get the device data */
        bktr = (struct bktr_softc*)devclass_get_softc(bktr_devclass, unit);
        if (bktr == NULL) {
                /* the device is no longer valid/functioning */
                return (ENXIO);
        }

#ifdef BKTR_GPIO_ACCESS
        if (bktr->bigbuf == 0 && cmd != BT848_GPIO_GET_EN &&
            cmd != BT848_GPIO_SET_EN && cmd != BT848_GPIO_GET_DATA &&
            cmd != BT848_GPIO_SET_DATA) /* no frame buffer allocated (ioctl failed) */
                return( ENOMEM );
#else
        if (bktr->bigbuf == 0)  /* no frame buffer allocated (ioctl failed) */
                return( ENOMEM );
#endif

        switch ( FUNCTION( minor(dev) ) ) {
        case VIDEO_DEV:
                return( video_ioctl( bktr, unit, cmd, ap->a_data, curthread ) );
        case TUNER_DEV:
                return( tuner_ioctl( bktr, unit, cmd, ap->a_data, curthread ) );
        }

        return( ENXIO );
}


/*
 * 
 */
static int
bktr_mmap(struct dev_mmap_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        int             unit;
        bktr_ptr_t      bktr;

        unit = UNIT(minor(dev));

        if (FUNCTION(minor(dev)) > 0)   /* only allow mmap on /dev/bktr[n] */
                return(EINVAL);

        /* Get the device data */
        bktr = (struct bktr_softc*)devclass_get_softc(bktr_devclass, unit);
        if (bktr == NULL) {
                /* the device is no longer valid/functioning */
                return (ENXIO);
        }

        if (ap->a_nprot & PROT_EXEC)
                return(EINVAL);

        if (ap->a_offset < 0)
                return(EINVAL);

        if (ap->a_offset >= bktr->alloc_pages * PAGE_SIZE)
                return(EINVAL);

        ap->a_result = atop(vtophys(bktr->bigbuf) + ap->a_offset);
        return(0);
}

static int
bktr_poll(struct dev_poll_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        int             unit;
        bktr_ptr_t      bktr;
        int revents = 0; 

        unit = UNIT(minor(dev));

        /* Get the device data */
        bktr = (struct bktr_softc*)devclass_get_softc(bktr_devclass, unit);
        if (bktr == NULL) {
                /* the device is no longer valid/functioning */
                return (ENXIO);
        }

        LOCK_VBI(bktr);
        crit_enter();

        if (ap->a_events & (POLLIN | POLLRDNORM)) {

                switch ( FUNCTION( minor(dev) ) ) {
                case VBI_DEV:
                        if(bktr->vbisize == 0)
                                selrecord(curthread, &bktr->vbi_select);
                        else
                                revents |= ap->a_events & (POLLIN | POLLRDNORM);
                        break;
                }
        }

        crit_exit();
        UNLOCK_VBI(bktr);

        ap->a_events = revents;
        return (0);
}