/*
 * Brontes PCI frame grabber driver
 *
 * Copyright (C) 2008 3M Company
 * Contact: Justin Bronder <jsbronder@brontes3d.com>
 * Original Authors: Daniel Drake <ddrake@brontes3d.com>
 *                   Duane Griffin <duaneg@dghda.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#include <linux/device.h>
#include <linux/fs.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/ioctl.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/types.h>
#include <linux/cdev.h>
#include <linux/list.h>
#include <linux/poll.h>
#include <linux/wait.h>
#include <linux/mm.h>
#include <linux/uaccess.h>
#include <linux/sched.h>

static unsigned int b3dfg_nbuf = 2;

module_param_named(buffer_count, b3dfg_nbuf, uint, 0444);

MODULE_PARM_DESC(buffer_count, "Number of buffers (min 2, default 2)");

MODULE_AUTHOR("Daniel Drake <ddrake@brontes3d.com>");
MODULE_DESCRIPTION("Brontes frame grabber driver");
MODULE_LICENSE("GPL");

#define DRIVER_NAME "b3dfg"
#define B3DFG_MAX_DEVS 4
#define B3DFG_FRAMES_PER_BUFFER 3

#define B3DFG_BAR_REGS  0
#define B3DFG_REGS_LENGTH 0x10000

#define B3DFG_IOC_MAGIC         0xb3 /* dfg :-) */
#define B3DFG_IOCGFRMSZ         _IOR(B3DFG_IOC_MAGIC, 1, int)
#define B3DFG_IOCTNUMBUFS       _IO(B3DFG_IOC_MAGIC, 2)
#define B3DFG_IOCTTRANS         _IO(B3DFG_IOC_MAGIC, 3)
#define B3DFG_IOCTQUEUEBUF      _IO(B3DFG_IOC_MAGIC, 4)
#define B3DFG_IOCTPOLLBUF       _IOWR(B3DFG_IOC_MAGIC, 5, struct b3dfg_poll)
#define B3DFG_IOCTWAITBUF       _IOWR(B3DFG_IOC_MAGIC, 6, struct b3dfg_wait)
#define B3DFG_IOCGWANDSTAT      _IOR(B3DFG_IOC_MAGIC, 7, int)

enum {
        /* number of 4kb pages per frame */
        B3D_REG_FRM_SIZE = 0x0,

        /* bit 0: set to enable interrupts
         * bit 1: set to enable cable status change interrupts */
        B3D_REG_HW_CTRL = 0x4,

        /* bit 0-1 - 1-based ID of next pending frame transfer (0 = none)
         * bit 2 indicates the previous DMA transfer has completed
         * bit 3 indicates wand cable status change
         * bit 8:15 - counter of number of discarded triplets */
        B3D_REG_DMA_STS = 0x8,

        /* bit 0: wand status (1 = present, 0 = disconnected) */
        B3D_REG_WAND_STS = 0xc,

        /* bus address for DMA transfers. lower 2 bits must be zero because DMA
         * works with 32 bit word size. */
        B3D_REG_EC220_DMA_ADDR = 0x8000,

        /* bit 20:0 - number of 32 bit words to be transferred
         * bit 21:31 - reserved */
        B3D_REG_EC220_TRF_SIZE = 0x8004,

        /* bit 0 - error bit
         * bit 1 - interrupt bit (set to generate interrupt at end of transfer)
         * bit 2 - start bit (set to start transfer)
         * bit 3 - direction (0 = DMA_TO_DEVICE, 1 = DMA_FROM_DEVICE
         * bit 4:31 - reserved */
        B3D_REG_EC220_DMA_STS = 0x8008,
};

enum b3dfg_buffer_state {
        B3DFG_BUFFER_POLLED = 0,
        B3DFG_BUFFER_PENDING,
        B3DFG_BUFFER_POPULATED,
};

struct b3dfg_buffer {
        unsigned char *frame[B3DFG_FRAMES_PER_BUFFER];
        struct list_head list;
        u8 state;
};

struct b3dfg_dev {

        /* no protection needed: all finalized at initialization time */
        struct pci_dev *pdev;
        struct cdev chardev;
        struct device *dev;
        void __iomem *regs;
        unsigned int frame_size;

        /*
         * Protects buffer state, including buffer_queue, triplet_ready,
         * cur_dma_frame_idx & cur_dma_frame_addr.
         */
        spinlock_t buffer_lock;
        struct b3dfg_buffer *buffers;
        struct list_head buffer_queue;

        /* Last frame in triplet transferred (-1 if none). */
        int cur_dma_frame_idx;

        /* Current frame's address for DMA. */
        dma_addr_t cur_dma_frame_addr;

        /*
         * Protects cstate_tstamp.
         * Nests inside buffer_lock.
         */
        spinlock_t cstate_lock;
        unsigned long cstate_tstamp;

        /*
         * Protects triplets_dropped.
         * Nests inside buffers_lock.
         */
        spinlock_t triplets_dropped_lock;
        unsigned int triplets_dropped;

        wait_queue_head_t buffer_waitqueue;

        unsigned int transmission_enabled:1;
        unsigned int triplet_ready:1;
};

static u8 b3dfg_devices[B3DFG_MAX_DEVS];

static struct class *b3dfg_class;
static dev_t b3dfg_devt;

static const struct pci_device_id b3dfg_ids[] __devinitdata = {
        { PCI_DEVICE(0x0b3d, 0x0001) },
        { },
};

MODULE_DEVICE_TABLE(pci, b3dfg_ids);

/***** user-visible types *****/

struct b3dfg_poll {
        int buffer_idx;
        unsigned int triplets_dropped;
};

struct b3dfg_wait {
        int buffer_idx;
        unsigned int timeout;
        unsigned int triplets_dropped;
};

/**** register I/O ****/

static u32 b3dfg_read32(struct b3dfg_dev *fgdev, u16 reg)
{
        return ioread32(fgdev->regs + reg);
}

static void b3dfg_write32(struct b3dfg_dev *fgdev, u16 reg, u32 value)
{
        iowrite32(value, fgdev->regs + reg);
}

/**** buffer management ****/

/*
 * Program EC220 for transfer of a specific frame.
 * Called with buffer_lock held.
 */
static int setup_frame_transfer(struct b3dfg_dev *fgdev,
        struct b3dfg_buffer *buf, int frame)
{
        unsigned char *frm_addr;
        dma_addr_t frm_addr_dma;
        unsigned int frm_size = fgdev->frame_size;

        frm_addr = buf->frame[frame];
        frm_addr_dma = pci_map_single(fgdev->pdev, frm_addr,
                                          frm_size, PCI_DMA_FROMDEVICE);
        if (pci_dma_mapping_error(fgdev->pdev, frm_addr_dma))
                return -ENOMEM;

        fgdev->cur_dma_frame_addr = frm_addr_dma;
        fgdev->cur_dma_frame_idx = frame;

        b3dfg_write32(fgdev, B3D_REG_EC220_DMA_ADDR,
                                        cpu_to_le32(frm_addr_dma));
        b3dfg_write32(fgdev, B3D_REG_EC220_TRF_SIZE,
                                        cpu_to_le32(frm_size >> 2));
        b3dfg_write32(fgdev, B3D_REG_EC220_DMA_STS, 0xf);

        return 0;
}

/* Caller should hold buffer lock */
static void dequeue_all_buffers(struct b3dfg_dev *fgdev)
{
        int i;
        for (i = 0; i < b3dfg_nbuf; i++) {
                struct b3dfg_buffer *buf = &fgdev->buffers[i];
                buf->state = B3DFG_BUFFER_POLLED;
                list_del_init(&buf->list);
        }
}

/* queue a buffer to receive data */
static int queue_buffer(struct b3dfg_dev *fgdev, int bufidx)
{
        struct device *dev = &fgdev->pdev->dev;
        struct b3dfg_buffer *buf;
        unsigned long flags;
        int r = 0;

        spin_lock_irqsave(&fgdev->buffer_lock, flags);
        if (bufidx < 0 || bufidx >= b3dfg_nbuf) {
                dev_dbg(dev, "Invalid buffer index, %d\n", bufidx);
                r = -ENOENT;
                goto out;
        }
        buf = &fgdev->buffers[bufidx];

        if (unlikely(buf->state == B3DFG_BUFFER_PENDING)) {
                dev_dbg(dev, "buffer %d is already queued\n", bufidx);
                r = -EINVAL;
                goto out;
        }

        buf->state = B3DFG_BUFFER_PENDING;
        list_add_tail(&buf->list, &fgdev->buffer_queue);

        if (fgdev->transmission_enabled && fgdev->triplet_ready) {
                dev_dbg(dev, "triplet is ready, pushing immediately\n");
                fgdev->triplet_ready = 0;
                r = setup_frame_transfer(fgdev, buf, 0);
                if (r)
                        dev_err(dev, "unable to map DMA buffer\n");
        }

out:
        spin_unlock_irqrestore(&fgdev->buffer_lock, flags);
        return r;
}

/* non-blocking buffer poll. returns 1 if data is present in the buffer,
 * 0 otherwise */
static int poll_buffer(struct b3dfg_dev *fgdev, void __user *arg)
{
        struct device *dev = &fgdev->pdev->dev;
        struct b3dfg_poll p;
        struct b3dfg_buffer *buf;
        unsigned long flags;
        int r = 1;
        int arg_out = 0;

        if (copy_from_user(&p, arg, sizeof(p)))
                return -EFAULT;

        if (unlikely(!fgdev->transmission_enabled)) {
                dev_dbg(dev, "cannot poll, transmission disabled\n");
                return -EINVAL;
        }

        if (p.buffer_idx < 0 || p.buffer_idx >= b3dfg_nbuf)
                return -ENOENT;

        buf = &fgdev->buffers[p.buffer_idx];

        spin_lock_irqsave(&fgdev->buffer_lock, flags);

        if (likely(buf->state == B3DFG_BUFFER_POPULATED)) {
                arg_out = 1;
                buf->state = B3DFG_BUFFER_POLLED;

                /* IRQs already disabled by spin_lock_irqsave above. */
                spin_lock(&fgdev->triplets_dropped_lock);
                p.triplets_dropped = fgdev->triplets_dropped;
                fgdev->triplets_dropped = 0;
                spin_unlock(&fgdev->triplets_dropped_lock);
        } else {
                r = 0;
        }

        spin_unlock_irqrestore(&fgdev->buffer_lock, flags);

        if (arg_out && copy_to_user(arg, &p, sizeof(p)))
                r = -EFAULT;

        return r;
}

static unsigned long get_cstate_change(struct b3dfg_dev *fgdev)
{
        unsigned long flags, when;

        spin_lock_irqsave(&fgdev->cstate_lock, flags);
        when = fgdev->cstate_tstamp;
        spin_unlock_irqrestore(&fgdev->cstate_lock, flags);
        return when;
}

static int is_event_ready(struct b3dfg_dev *fgdev, struct b3dfg_buffer *buf,
                          unsigned long when)
{
        int result;
        unsigned long flags;

        spin_lock_irqsave(&fgdev->buffer_lock, flags);
        spin_lock(&fgdev->cstate_lock);
        result = (!fgdev->transmission_enabled ||
                  buf->state == B3DFG_BUFFER_POPULATED ||
                  when != fgdev->cstate_tstamp);
        spin_unlock(&fgdev->cstate_lock);
        spin_unlock_irqrestore(&fgdev->buffer_lock, flags);

        return result;
}

/* sleep until a specific buffer becomes populated */
static int wait_buffer(struct b3dfg_dev *fgdev, void __user *arg)
{
        struct device *dev = &fgdev->pdev->dev;
        struct b3dfg_wait w;
        struct b3dfg_buffer *buf;
        unsigned long flags, when;
        int r;

        if (copy_from_user(&w, arg, sizeof(w)))
                return -EFAULT;

        if (!fgdev->transmission_enabled) {
                dev_dbg(dev, "cannot wait, transmission disabled\n");
                return -EINVAL;
        }

        if (w.buffer_idx < 0 || w.buffer_idx >= b3dfg_nbuf)
                return -ENOENT;

        buf = &fgdev->buffers[w.buffer_idx];

        spin_lock_irqsave(&fgdev->buffer_lock, flags);

        if (buf->state == B3DFG_BUFFER_POPULATED) {
                r = w.timeout;
                goto out_triplets_dropped;
        }

        spin_unlock_irqrestore(&fgdev->buffer_lock, flags);

        when = get_cstate_change(fgdev);
        if (w.timeout > 0) {
                r = wait_event_interruptible_timeout(fgdev->buffer_waitqueue,
                        is_event_ready(fgdev, buf, when),
                        (w.timeout * HZ) / 1000);

                if (unlikely(r < 0))
                        goto out;

                w.timeout = r * 1000 / HZ;
        } else {
                r = wait_event_interruptible(fgdev->buffer_waitqueue,
                        is_event_ready(fgdev, buf, when));

                if (unlikely(r)) {
                        r = -ERESTARTSYS;
                        goto out;
                }
        }

        /* TODO: Inform the user via field(s) in w? */
        if (!fgdev->transmission_enabled || when != get_cstate_change(fgdev)) {
                r = -EINVAL;
                goto out;
        }

        spin_lock_irqsave(&fgdev->buffer_lock, flags);

        if (buf->state != B3DFG_BUFFER_POPULATED) {
                r = -ETIMEDOUT;
                goto out_unlock;
        }

        buf->state = B3DFG_BUFFER_POLLED;

out_triplets_dropped:

        /* IRQs already disabled by spin_lock_irqsave above. */
        spin_lock(&fgdev->triplets_dropped_lock);
        w.triplets_dropped = fgdev->triplets_dropped;
        fgdev->triplets_dropped = 0;
        spin_unlock(&fgdev->triplets_dropped_lock);

out_unlock:
        spin_unlock_irqrestore(&fgdev->buffer_lock, flags);
        if (copy_to_user(arg, &w, sizeof(w)))
                r = -EFAULT;
out:
        return r;
}

/* mmap page fault handler */
static int b3dfg_vma_fault(struct vm_area_struct *vma,
        struct vm_fault *vmf)
{
        struct b3dfg_dev *fgdev = vma->vm_file->private_data;
        unsigned long off = vmf->pgoff << PAGE_SHIFT;
        unsigned int frame_size = fgdev->frame_size;
        unsigned int buf_size = frame_size * B3DFG_FRAMES_PER_BUFFER;
        unsigned char *addr;

        /* determine which buffer the offset lies within */
        unsigned int buf_idx = off / buf_size;
        /* and the offset into the buffer */
        unsigned int buf_off = off % buf_size;

        /* determine which frame inside the buffer the offset lies in */
        unsigned int frm_idx = buf_off / frame_size;
        /* and the offset into the frame */
        unsigned int frm_off = buf_off % frame_size;

        if (unlikely(buf_idx >= b3dfg_nbuf))
                return VM_FAULT_SIGBUS;

        addr = fgdev->buffers[buf_idx].frame[frm_idx] + frm_off;
        vm_insert_pfn(vma, (unsigned long)vmf->virtual_address,
                          virt_to_phys(addr) >> PAGE_SHIFT);

        return VM_FAULT_NOPAGE;
}

static struct vm_operations_struct b3dfg_vm_ops = {
        .fault = b3dfg_vma_fault,
};

static int get_wand_status(struct b3dfg_dev *fgdev, int __user *arg)
{
        u32 wndstat = b3dfg_read32(fgdev, B3D_REG_WAND_STS);
        dev_dbg(&fgdev->pdev->dev, "wand status %x\n", wndstat);
        return __put_user(wndstat & 0x1, arg);
}

static int enable_transmission(struct b3dfg_dev *fgdev)
{
        u16 command;
        unsigned long flags;
        struct device *dev = &fgdev->pdev->dev;

        dev_dbg(dev, "enable transmission\n");

        /* check the cable is plugged in. */
        if (!b3dfg_read32(fgdev, B3D_REG_WAND_STS)) {
                dev_dbg(dev, "cannot start transmission without wand\n");
                return -EINVAL;
        }

        /*
         * Check we're a bus master.
         * TODO: I think we can remove this having added the pci_set_master call
         */
        pci_read_config_word(fgdev->pdev, PCI_COMMAND, &command);
        if (!(command & PCI_COMMAND_MASTER)) {
                dev_err(dev, "not a bus master, force-enabling\n");
                pci_write_config_word(fgdev->pdev, PCI_COMMAND,
                        command | PCI_COMMAND_MASTER);
        }

        spin_lock_irqsave(&fgdev->buffer_lock, flags);

        /* Handle racing enable_transmission calls. */
        if (fgdev->transmission_enabled) {
                spin_unlock_irqrestore(&fgdev->buffer_lock, flags);
                goto out;
        }

        spin_lock(&fgdev->triplets_dropped_lock);
        fgdev->triplets_dropped = 0;
        spin_unlock(&fgdev->triplets_dropped_lock);

        fgdev->triplet_ready = 0;
        fgdev->cur_dma_frame_idx = -1;
        fgdev->transmission_enabled = 1;

        spin_unlock_irqrestore(&fgdev->buffer_lock, flags);

        /* Enable DMA and cable status interrupts. */
        b3dfg_write32(fgdev, B3D_REG_HW_CTRL, 0x03);

out:
        return 0;
}

static void disable_transmission(struct b3dfg_dev *fgdev)
{
        struct device *dev = &fgdev->pdev->dev;
        unsigned long flags;
        u32 tmp;

        dev_dbg(dev, "disable transmission\n");

        /* guarantee that no more interrupts will be serviced */
        spin_lock_irqsave(&fgdev->buffer_lock, flags);
        fgdev->transmission_enabled = 0;

        b3dfg_write32(fgdev, B3D_REG_HW_CTRL, 0);

        /* FIXME: temporary debugging only. if the board stops transmitting,
         * hitting ctrl+c and seeing this message is useful for determining
         * the state of the board. */
        tmp = b3dfg_read32(fgdev, B3D_REG_DMA_STS);
        dev_dbg(dev, "DMA_STS reads %x after TX stopped\n", tmp);

        dequeue_all_buffers(fgdev);
        spin_unlock_irqrestore(&fgdev->buffer_lock, flags);

        wake_up_interruptible(&fgdev->buffer_waitqueue);
}

static int set_transmission(struct b3dfg_dev *fgdev, int enabled)
{
        int res = 0;

        if (enabled && !fgdev->transmission_enabled)
                res = enable_transmission(fgdev);
        else if (!enabled && fgdev->transmission_enabled)
                disable_transmission(fgdev);

        return res;
}

/* Called in interrupt context. */
static void handle_cstate_unplug(struct b3dfg_dev *fgdev)
{
        /* Disable all interrupts. */
        b3dfg_write32(fgdev, B3D_REG_HW_CTRL, 0);

        /* Stop transmission. */
        spin_lock(&fgdev->buffer_lock);
        fgdev->transmission_enabled = 0;

        fgdev->cur_dma_frame_idx = -1;
        fgdev->triplet_ready = 0;
        if (fgdev->cur_dma_frame_addr) {
                pci_unmap_single(fgdev->pdev, fgdev->cur_dma_frame_addr,
                                 fgdev->frame_size, PCI_DMA_FROMDEVICE);
                fgdev->cur_dma_frame_addr = 0;
        }
        dequeue_all_buffers(fgdev);
        spin_unlock(&fgdev->buffer_lock);
}

/* Called in interrupt context. */
static void handle_cstate_change(struct b3dfg_dev *fgdev)
{
        u32 cstate = b3dfg_read32(fgdev, B3D_REG_WAND_STS);
        unsigned long when;
        struct device *dev = &fgdev->pdev->dev;

        dev_dbg(dev, "cable state change: %u\n", cstate);

        /*
         * When the wand is unplugged we reset our state. The hardware will
         * have done the same internally.
         *
         * Note we should never see a cable *plugged* event, as interrupts
         * should only be enabled when transmitting, which requires the cable
         * to be plugged. If we do see one it probably means the cable has been
         * unplugged and re-plugged very rapidly. Possibly because it has a
         * broken wire and is momentarily losing contact.
         *
         * TODO: At the moment if you plug in the cable then enable transmission
         * the hardware will raise a couple of spurious interrupts, so
         * just ignore them for now.
         *
         * Once the hardware is fixed we should complain and treat it as an
         * unplug. Or at least track how frequently it is happening and do
         * so if too many come in.
         */
        if (cstate) {
                dev_warn(dev, "ignoring unexpected plug event\n");
                return;
        }
        handle_cstate_unplug(fgdev);

        /*
         * Record cable state change timestamp & wake anyone waiting
         * on a cable state change. Be paranoid about ensuring events
         * are not missed if we somehow get two interrupts in a jiffy.
         */
        spin_lock(&fgdev->cstate_lock);
        when = jiffies_64;
        if (when <= fgdev->cstate_tstamp)
                when = fgdev->cstate_tstamp + 1;
        fgdev->cstate_tstamp = when;
        wake_up_interruptible(&fgdev->buffer_waitqueue);
        spin_unlock(&fgdev->cstate_lock);
}

/* Called with buffer_lock held. */
static void transfer_complete(struct b3dfg_dev *fgdev)
{
        struct b3dfg_buffer *buf;
        struct device *dev = &fgdev->pdev->dev;

        pci_unmap_single(fgdev->pdev, fgdev->cur_dma_frame_addr,
                         fgdev->frame_size, PCI_DMA_FROMDEVICE);
        fgdev->cur_dma_frame_addr = 0;

        buf = list_entry(fgdev->buffer_queue.next, struct b3dfg_buffer, list);

        dev_dbg(dev, "handle frame completion\n");
        if (fgdev->cur_dma_frame_idx == B3DFG_FRAMES_PER_BUFFER - 1) {

                /* last frame of that triplet completed */
                dev_dbg(dev, "triplet completed\n");
                buf->state = B3DFG_BUFFER_POPULATED;
                list_del_init(&buf->list);
                wake_up_interruptible(&fgdev->buffer_waitqueue);
        }
}

/*
 * Called with buffer_lock held.
 *
 * Note that idx is the (1-based) *next* frame to be transferred, while
 * cur_dma_frame_idx is the (0-based) *last* frame to have been transferred (or
 * -1 if none). Thus there should be a difference of 2 between them.
 */
static bool setup_next_frame_transfer(struct b3dfg_dev *fgdev, int idx)
{
        struct b3dfg_buffer *buf;
        struct device *dev = &fgdev->pdev->dev;
        bool need_ack = 1;

        dev_dbg(dev, "program DMA transfer for next frame: %d\n", idx);

        buf = list_entry(fgdev->buffer_queue.next, struct b3dfg_buffer, list);
        if (idx == fgdev->cur_dma_frame_idx + 2) {
                if (setup_frame_transfer(fgdev, buf, idx - 1))
                        dev_err(dev, "unable to map DMA buffer\n");
                need_ack = 0;
        } else {
                dev_err(dev, "frame mismatch, got %d, expected %d\n",
                        idx, fgdev->cur_dma_frame_idx + 2);

                /* FIXME: handle dropped triplets here */
        }

        return need_ack;
}

static irqreturn_t b3dfg_intr(int irq, void *dev_id)
{
        struct b3dfg_dev *fgdev = dev_id;
        struct device *dev = &fgdev->pdev->dev;
        u32 sts;
        u8 dropped;
        bool need_ack = 1;
        irqreturn_t res = IRQ_HANDLED;

        sts = b3dfg_read32(fgdev, B3D_REG_DMA_STS);
        if (unlikely(sts == 0)) {
                dev_warn(dev, "ignore interrupt, DMA status is 0\n");
                res = IRQ_NONE;
                goto out;
        }

        if (unlikely(!fgdev->transmission_enabled)) {
                dev_warn(dev, "ignore interrupt, TX disabled\n");
                res = IRQ_HANDLED;
                goto out;
        }

        /* Handle dropped frames, as reported by the hardware. */
        dropped = (sts >> 8) & 0xff;
        dev_dbg(dev, "intr: DMA_STS=%08x (drop=%d comp=%d next=%d)\n",
                sts, dropped, !!(sts & 0x4), sts & 0x3);
        if (unlikely(dropped > 0)) {
                spin_lock(&fgdev->triplets_dropped_lock);
                fgdev->triplets_dropped += dropped;
                spin_unlock(&fgdev->triplets_dropped_lock);
        }

        /* Handle a cable state change (i.e. the wand being unplugged). */
        if (sts & 0x08) {
                handle_cstate_change(fgdev);
                goto out;
        }

        spin_lock(&fgdev->buffer_lock);
        if (unlikely(list_empty(&fgdev->buffer_queue))) {

                /* FIXME need more sanity checking here */
                dev_info(dev, "buffer not ready for next transfer\n");
                fgdev->triplet_ready = 1;
                goto out_unlock;
        }

        /* Has a frame transfer been completed? */
        if (sts & 0x4) {
                u32 dma_status = b3dfg_read32(fgdev, B3D_REG_EC220_DMA_STS);

                /* Check for DMA errors reported by the hardware. */
                if (unlikely(dma_status & 0x1)) {
                        dev_err(dev, "EC220 error: %08x\n", dma_status);

                        /* FIXME flesh out error handling */
                        goto out_unlock;
                }

                /* Sanity check, we should have a frame index at this point. */
                if (unlikely(fgdev->cur_dma_frame_idx == -1)) {
                        dev_err(dev, "completed but no last idx?\n");

                        /* FIXME flesh out error handling */
                        goto out_unlock;
                }

                transfer_complete(fgdev);
        }

        /* Is there another frame transfer pending? */
        if (sts & 0x3)
                need_ack = setup_next_frame_transfer(fgdev, sts & 0x3);
        else
                fgdev->cur_dma_frame_idx = -1;

out_unlock:
        spin_unlock(&fgdev->buffer_lock);
out:
        if (need_ack) {
                dev_dbg(dev, "acknowledging interrupt\n");
                b3dfg_write32(fgdev, B3D_REG_EC220_DMA_STS, 0x0b);
        }
        return res;
}

static int b3dfg_open(struct inode *inode, struct file *filp)
{
        struct b3dfg_dev *fgdev =
                container_of(inode->i_cdev, struct b3dfg_dev, chardev);

        dev_dbg(&fgdev->pdev->dev, "open\n");
        filp->private_data = fgdev;
        return 0;
}

static int b3dfg_release(struct inode *inode, struct file *filp)
{
        struct b3dfg_dev *fgdev = filp->private_data;
        dev_dbg(&fgdev->pdev->dev, "release\n");
        disable_transmission(fgdev);
        return 0;
}

static long b3dfg_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
        struct b3dfg_dev *fgdev = filp->private_data;

        switch (cmd) {
        case B3DFG_IOCGFRMSZ:
                return __put_user(fgdev->frame_size, (int __user *) arg);
        case B3DFG_IOCGWANDSTAT:
                return get_wand_status(fgdev, (int __user *) arg);
        case B3DFG_IOCTTRANS:
                return set_transmission(fgdev, (int) arg);
        case B3DFG_IOCTQUEUEBUF:
                return queue_buffer(fgdev, (int) arg);
        case B3DFG_IOCTPOLLBUF:
                return poll_buffer(fgdev, (void __user *) arg);
        case B3DFG_IOCTWAITBUF:
                return wait_buffer(fgdev, (void __user *) arg);
        default:
                dev_dbg(&fgdev->pdev->dev, "unrecognised ioctl %x\n", cmd);
                return -EINVAL;
        }
}

static unsigned int b3dfg_poll(struct file *filp, poll_table *poll_table)
{
        struct b3dfg_dev *fgdev = filp->private_data;
        unsigned long flags, when;
        int i;
        int r = 0;

        when = get_cstate_change(fgdev);
        poll_wait(filp, &fgdev->buffer_waitqueue, poll_table);

        spin_lock_irqsave(&fgdev->buffer_lock, flags);
        for (i = 0; i < b3dfg_nbuf; i++) {
                if (fgdev->buffers[i].state == B3DFG_BUFFER_POPULATED) {
                        r = POLLIN | POLLRDNORM;
                        break;
                }
        }
        spin_unlock_irqrestore(&fgdev->buffer_lock, flags);

        /* TODO: Confirm this is how we want to communicate the change. */
        if (!fgdev->transmission_enabled || when != get_cstate_change(fgdev))
                r = POLLERR;

        return r;
}

static int b3dfg_mmap(struct file *filp, struct vm_area_struct *vma)
{
        struct b3dfg_dev *fgdev = filp->private_data;
        unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
        unsigned long vsize = vma->vm_end - vma->vm_start;
        unsigned long bufdatalen = b3dfg_nbuf * fgdev->frame_size * 3;
        unsigned long psize = bufdatalen - offset;
        int r = 0;

        if (vsize <= psize) {
                vma->vm_flags |= VM_IO | VM_RESERVED | VM_CAN_NONLINEAR |
                                 VM_PFNMAP;
                vma->vm_ops = &b3dfg_vm_ops;
        } else {
                r = -EINVAL;
        }

        return r;
}

static struct file_operations b3dfg_fops = {
        .owner = THIS_MODULE,
        .open = b3dfg_open,
        .release = b3dfg_release,
        .unlocked_ioctl = b3dfg_ioctl,
        .poll = b3dfg_poll,
        .mmap = b3dfg_mmap,
};

static void free_all_frame_buffers(struct b3dfg_dev *fgdev)
{
        int i, j;
        for (i = 0; i < b3dfg_nbuf; i++)
                for (j = 0; j < B3DFG_FRAMES_PER_BUFFER; j++)
                        kfree(fgdev->buffers[i].frame[j]);
        kfree(fgdev->buffers);
}

/* initialize device and any data structures. called before any interrupts
 * are enabled. */
static int b3dfg_init_dev(struct b3dfg_dev *fgdev)
{
        int i, j;
        u32 frm_size = b3dfg_read32(fgdev, B3D_REG_FRM_SIZE);

        /* Disable interrupts. In abnormal circumstances (e.g. after a crash)
         * the board may still be transmitting from the previous session. If we
         * ensure that interrupts are disabled before we later enable them, we
         * are sure to capture a triplet from the start, rather than starting
         * from frame 2 or 3. Disabling interrupts causes the FG to throw away
         * all buffered data and stop buffering more until interrupts are
         * enabled again.
         */
        b3dfg_write32(fgdev, B3D_REG_HW_CTRL, 0);

        fgdev->frame_size = frm_size * 4096;
        fgdev->buffers = kzalloc(sizeof(struct b3dfg_buffer) * b3dfg_nbuf,
                                 GFP_KERNEL);
        if (!fgdev->buffers)
                goto err_no_buf;
        for (i = 0; i < b3dfg_nbuf; i++) {
                struct b3dfg_buffer *buf = &fgdev->buffers[i];
                for (j = 0; j < B3DFG_FRAMES_PER_BUFFER; j++) {
                        buf->frame[j] = kmalloc(fgdev->frame_size, GFP_KERNEL);
                        if (!buf->frame[j])
                                goto err_no_mem;
                }
                INIT_LIST_HEAD(&buf->list);
        }

        INIT_LIST_HEAD(&fgdev->buffer_queue);
        init_waitqueue_head(&fgdev->buffer_waitqueue);
        spin_lock_init(&fgdev->buffer_lock);
        spin_lock_init(&fgdev->cstate_lock);
        spin_lock_init(&fgdev->triplets_dropped_lock);
        return 0;

err_no_mem:
        free_all_frame_buffers(fgdev);
err_no_buf:
        return -ENOMEM;
}

/* find next free minor number, returns -1 if none are availabile */
static int get_free_minor(void)
{
        int i;
        for (i = 0; i < B3DFG_MAX_DEVS; i++) {
                if (b3dfg_devices[i] == 0)
                        return i;
        }
        return -1;
}

static int __devinit b3dfg_probe(struct pci_dev *pdev,
        const struct pci_device_id *id)
{
        struct b3dfg_dev *fgdev = kzalloc(sizeof(*fgdev), GFP_KERNEL);
        int r = 0;
        int minor = get_free_minor();
        dev_t devno = MKDEV(MAJOR(b3dfg_devt), minor);
        unsigned long res_len;
        resource_size_t res_base;

        if (fgdev == NULL)
                return -ENOMEM;

        if (minor < 0) {
                dev_err(&pdev->dev, "too many devices found!\n");
                r = -EIO;
                goto err_free;
        }

        b3dfg_devices[minor] = 1;
        dev_info(&pdev->dev, "probe device with IRQ %d\n", pdev->irq);

        cdev_init(&fgdev->chardev, &b3dfg_fops);
        fgdev->chardev.owner = THIS_MODULE;

        r = cdev_add(&fgdev->chardev, devno, 1);
        if (r) {
                dev_err(&pdev->dev, "cannot add char device\n");
                goto err_release_minor;
        }

        fgdev->dev = device_create(
                b3dfg_class,
                &pdev->dev,
                devno,
                dev_get_drvdata(&pdev->dev),
                DRIVER_NAME "%d", minor);

        if (IS_ERR(fgdev->dev)) {
                dev_err(&pdev->dev, "cannot create device\n");
                r = PTR_ERR(fgdev->dev);
                goto err_del_cdev;
        }

        r = pci_enable_device(pdev);
        if (r) {
                dev_err(&pdev->dev, "cannot enable PCI device\n");
                goto err_dev_unreg;
        }

        res_len = pci_resource_len(pdev, B3DFG_BAR_REGS);
        if (res_len != B3DFG_REGS_LENGTH) {
                dev_err(&pdev->dev, "invalid register resource size\n");
                r = -EIO;
                goto err_disable;
        }

        if (pci_resource_flags(pdev, B3DFG_BAR_REGS)
                                != (IORESOURCE_MEM | IORESOURCE_SIZEALIGN)) {
                dev_err(&pdev->dev, "invalid resource flags\n");
                r = -EIO;
                goto err_disable;
        }
        r = pci_request_regions(pdev, DRIVER_NAME);
        if (r) {
                dev_err(&pdev->dev, "cannot obtain PCI resources\n");
                goto err_disable;
        }

        pci_set_master(pdev);

        r = pci_set_dma_mask(pdev, DMA_BIT_MASK(32));
        if (r) {
                dev_err(&pdev->dev, "no usable DMA configuration\n");
                goto err_free_res;
        }

        res_base = pci_resource_start(pdev, B3DFG_BAR_REGS);
        fgdev->regs = ioremap_nocache(res_base, res_len);
        if (!fgdev->regs) {
                dev_err(&pdev->dev, "regs ioremap failed\n");
                r = -EIO;
                goto err_free_res;
        }

        fgdev->pdev = pdev;
        pci_set_drvdata(pdev, fgdev);
        r = b3dfg_init_dev(fgdev);
        if (r < 0) {
                dev_err(&pdev->dev, "failed to initalize device\n");
                goto err_unmap;
        }

        r = request_irq(pdev->irq, b3dfg_intr, IRQF_SHARED, DRIVER_NAME, fgdev);
        if (r) {
                dev_err(&pdev->dev, "couldn't request irq %d\n", pdev->irq);
                goto err_free_bufs;
        }

        return 0;

err_free_bufs:
        free_all_frame_buffers(fgdev);
err_unmap:
        iounmap(fgdev->regs);
err_free_res:
        pci_release_regions(pdev);
err_disable:
        pci_disable_device(pdev);
err_dev_unreg:
        device_destroy(b3dfg_class, devno);
err_del_cdev:
        cdev_del(&fgdev->chardev);
err_release_minor:
        b3dfg_devices[minor] = 0;
err_free:
        kfree(fgdev);
        return r;
}

static void __devexit b3dfg_remove(struct pci_dev *pdev)
{
        struct b3dfg_dev *fgdev = pci_get_drvdata(pdev);
        unsigned int minor = MINOR(fgdev->chardev.dev);

        dev_dbg(&pdev->dev, "remove\n");

        free_irq(pdev->irq, fgdev);
        iounmap(fgdev->regs);
        pci_release_regions(pdev);
        pci_disable_device(pdev);
        device_destroy(b3dfg_class, MKDEV(MAJOR(b3dfg_devt), minor));
        cdev_del(&fgdev->chardev);
        free_all_frame_buffers(fgdev);
        kfree(fgdev);
        b3dfg_devices[minor] = 0;
}

static struct pci_driver b3dfg_driver = {
        .name = DRIVER_NAME,
        .id_table = b3dfg_ids,
        .probe = b3dfg_probe,
        .remove = __devexit_p(b3dfg_remove),
};

static int __init b3dfg_module_init(void)
{
        int r;

        if (b3dfg_nbuf < 2) {
                printk(KERN_ERR DRIVER_NAME
                           ": buffer_count is out of range (must be >= 2)");
                return -EINVAL;
        }

        printk(KERN_INFO DRIVER_NAME ": loaded\n");

        b3dfg_class = class_create(THIS_MODULE, DRIVER_NAME);
        if (IS_ERR(b3dfg_class))
                return PTR_ERR(b3dfg_class);

        r = alloc_chrdev_region(&b3dfg_devt, 0, B3DFG_MAX_DEVS, DRIVER_NAME);
        if (r)
                goto err1;

        r = pci_register_driver(&b3dfg_driver);
        if (r)
                goto err2;

        return r;

err2:
        unregister_chrdev_region(b3dfg_devt, B3DFG_MAX_DEVS);
err1:
        class_destroy(b3dfg_class);
        return r;
}

static void __exit b3dfg_module_exit(void)
{
        printk(KERN_INFO DRIVER_NAME ": unloaded\n");
        pci_unregister_driver(&b3dfg_driver);
        unregister_chrdev_region(b3dfg_devt, B3DFG_MAX_DEVS);
        class_destroy(b3dfg_class);
}

module_init(b3dfg_module_init);
module_exit(b3dfg_module_exit);