/*
 * Apple USB Touchpad (for post-February 2005 PowerBooks and MacBooks) driver
 *
 * Copyright (C) 2001-2004 Greg Kroah-Hartman (greg@kroah.com)
 * Copyright (C) 2005-2008 Johannes Berg (johannes@sipsolutions.net)
 * Copyright (C) 2005-2008 Stelian Pop (stelian@popies.net)
 * Copyright (C) 2005      Frank Arnold (frank@scirocco-5v-turbo.de)
 * Copyright (C) 2005      Peter Osterlund (petero2@telia.com)
 * Copyright (C) 2005      Michael Hanselmann (linux-kernel@hansmi.ch)
 * Copyright (C) 2006      Nicolas Boichat (nicolas@boichat.ch)
 * Copyright (C) 2007-2008 Sven Anders (anders@anduras.de)
 *
 * Thanks to Alex Harper <basilisk@foobox.net> for his inputs.
 *
 * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 */

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/usb/input.h>

/*
 * Note: We try to keep the touchpad aspect ratio while still doing only
 * simple arithmetics:
 *      0 <= x <= (xsensors - 1) * xfact
 *      0 <= y <= (ysensors - 1) * yfact
 */
struct atp_info {
        int xsensors;                           /* number of X sensors */
        int xsensors_17;                        /* 17" models have more sensors */
        int ysensors;                           /* number of Y sensors */
        int xfact;                              /* X multiplication factor */
        int yfact;                              /* Y multiplication factor */
        int datalen;                            /* size of USB transfers */
        void (*callback)(struct urb *);         /* callback function */
        int fuzz;                               /* fuzz touchpad generates */
};

static void atp_complete_geyser_1_2(struct urb *urb);
static void atp_complete_geyser_3_4(struct urb *urb);

static const struct atp_info fountain_info = {
        .xsensors       = 16,
        .xsensors_17    = 26,
        .ysensors       = 16,
        .xfact          = 64,
        .yfact          = 43,
        .datalen        = 81,
        .callback       = atp_complete_geyser_1_2,
        .fuzz           = 16,
};

static const struct atp_info geyser1_info = {
        .xsensors       = 16,
        .xsensors_17    = 26,
        .ysensors       = 16,
        .xfact          = 64,
        .yfact          = 43,
        .datalen        = 81,
        .callback       = atp_complete_geyser_1_2,
        .fuzz           = 16,
};

static const struct atp_info geyser2_info = {
        .xsensors       = 15,
        .xsensors_17    = 20,
        .ysensors       = 9,
        .xfact          = 64,
        .yfact          = 43,
        .datalen        = 64,
        .callback       = atp_complete_geyser_1_2,
        .fuzz           = 0,
};

static const struct atp_info geyser3_info = {
        .xsensors       = 20,
        .ysensors       = 10,
        .xfact          = 64,
        .yfact          = 64,
        .datalen        = 64,
        .callback       = atp_complete_geyser_3_4,
        .fuzz           = 0,
};

static const struct atp_info geyser4_info = {
        .xsensors       = 20,
        .ysensors       = 10,
        .xfact          = 64,
        .yfact          = 64,
        .datalen        = 64,
        .callback       = atp_complete_geyser_3_4,
        .fuzz           = 0,
};

#define ATP_DEVICE(prod, info)                                  \
{                                                               \
        .match_flags = USB_DEVICE_ID_MATCH_DEVICE |             \
                       USB_DEVICE_ID_MATCH_INT_CLASS |          \
                       USB_DEVICE_ID_MATCH_INT_PROTOCOL,        \
        .idVendor = 0x05ac, /* Apple */                         \
        .idProduct = (prod),                                    \
        .bInterfaceClass = 0x03,                                \
        .bInterfaceProtocol = 0x02,                             \
        .driver_info = (unsigned long) &info,                   \
}

/*
 * Table of devices (Product IDs) that work with this driver.
 * (The names come from Info.plist in AppleUSBTrackpad.kext,
 *  According to Info.plist Geyser IV is the same as Geyser III.)
 */

static const struct usb_device_id atp_table[] = {
        /* PowerBooks Feb 2005, iBooks G4 */
        ATP_DEVICE(0x020e, fountain_info),      /* FOUNTAIN ANSI */
        ATP_DEVICE(0x020f, fountain_info),      /* FOUNTAIN ISO */
        ATP_DEVICE(0x030a, fountain_info),      /* FOUNTAIN TP ONLY */
        ATP_DEVICE(0x030b, geyser1_info),       /* GEYSER 1 TP ONLY */

        /* PowerBooks Oct 2005 */
        ATP_DEVICE(0x0214, geyser2_info),       /* GEYSER 2 ANSI */
        ATP_DEVICE(0x0215, geyser2_info),       /* GEYSER 2 ISO */
        ATP_DEVICE(0x0216, geyser2_info),       /* GEYSER 2 JIS */

        /* Core Duo MacBook & MacBook Pro */
        ATP_DEVICE(0x0217, geyser3_info),       /* GEYSER 3 ANSI */
        ATP_DEVICE(0x0218, geyser3_info),       /* GEYSER 3 ISO */
        ATP_DEVICE(0x0219, geyser3_info),       /* GEYSER 3 JIS */

        /* Core2 Duo MacBook & MacBook Pro */
        ATP_DEVICE(0x021a, geyser4_info),       /* GEYSER 4 ANSI */
        ATP_DEVICE(0x021b, geyser4_info),       /* GEYSER 4 ISO */
        ATP_DEVICE(0x021c, geyser4_info),       /* GEYSER 4 JIS */

        /* Core2 Duo MacBook3,1 */
        ATP_DEVICE(0x0229, geyser4_info),       /* GEYSER 4 HF ANSI */
        ATP_DEVICE(0x022a, geyser4_info),       /* GEYSER 4 HF ISO */
        ATP_DEVICE(0x022b, geyser4_info),       /* GEYSER 4 HF JIS */

        /* Terminating entry */
        { }
};
MODULE_DEVICE_TABLE(usb, atp_table);

/* maximum number of sensors */
#define ATP_XSENSORS    26
#define ATP_YSENSORS    16

/*
 * The largest possible bank of sensors with additional buffer of 4 extra values
 * on either side, for an array of smoothed sensor values.
 */
#define ATP_SMOOTHSIZE  34

/* maximum pressure this driver will report */
#define ATP_PRESSURE    300

/*
 * Threshold for the touchpad sensors. Any change less than ATP_THRESHOLD is
 * ignored.
 */
#define ATP_THRESHOLD   5

/*
 * How far we'll bitshift our sensor values before averaging them. Mitigates
 * rounding errors.
 */
#define ATP_SCALE       12

/* Geyser initialization constants */
#define ATP_GEYSER_MODE_READ_REQUEST_ID         1
#define ATP_GEYSER_MODE_WRITE_REQUEST_ID        9
#define ATP_GEYSER_MODE_REQUEST_VALUE           0x300
#define ATP_GEYSER_MODE_REQUEST_INDEX           0
#define ATP_GEYSER_MODE_VENDOR_VALUE            0x04

/**
 * enum atp_status_bits - status bit meanings
 *
 * These constants represent the meaning of the status bits.
 * (only Geyser 3/4)
 *
 * @ATP_STATUS_BUTTON: The button was pressed
 * @ATP_STATUS_BASE_UPDATE: Update of the base values (untouched pad)
 * @ATP_STATUS_FROM_RESET: Reset previously performed
 */
enum atp_status_bits {
        ATP_STATUS_BUTTON       = BIT(0),
        ATP_STATUS_BASE_UPDATE  = BIT(2),
        ATP_STATUS_FROM_RESET   = BIT(4),
};

/* Structure to hold all of our device specific stuff */
struct atp {
        char                    phys[64];
        struct usb_device       *udev;          /* usb device */
        struct usb_interface    *intf;          /* usb interface */
        struct urb              *urb;           /* usb request block */
        u8                      *data;          /* transferred data */
        struct input_dev        *input;         /* input dev */
        const struct atp_info   *info;          /* touchpad model */
        bool                    open;
        bool                    valid;          /* are the samples valid? */
        bool                    size_detect_done;
        bool                    overflow_warned;
        int                     fingers_old;    /* last reported finger count */
        int                     x_old;          /* last reported x/y, */
        int                     y_old;          /* used for smoothing */
        signed char             xy_cur[ATP_XSENSORS + ATP_YSENSORS];
        signed char             xy_old[ATP_XSENSORS + ATP_YSENSORS];
        int                     xy_acc[ATP_XSENSORS + ATP_YSENSORS];
        int                     smooth[ATP_SMOOTHSIZE];
        int                     smooth_tmp[ATP_SMOOTHSIZE];
        int                     idlecount;      /* number of empty packets */
        struct work_struct      work;
};

#define dbg_dump(msg, tab) \
        if (debug > 1) {                                                \
                int __i;                                                \
                printk(KERN_DEBUG "appletouch: %s", msg);               \
                for (__i = 0; __i < ATP_XSENSORS + ATP_YSENSORS; __i++) \
                        printk(" %02x", tab[__i]);                      \
                printk("\n");                                           \
        }

#define dprintk(format, a...)                                           \
        do {                                                            \
                if (debug)                                              \
                        printk(KERN_DEBUG format, ##a);                 \
        } while (0)

MODULE_AUTHOR("Johannes Berg");
MODULE_AUTHOR("Stelian Pop");
MODULE_AUTHOR("Frank Arnold");
MODULE_AUTHOR("Michael Hanselmann");
MODULE_AUTHOR("Sven Anders");
MODULE_DESCRIPTION("Apple PowerBook and MacBook USB touchpad driver");
MODULE_LICENSE("GPL");

/*
 * Make the threshold a module parameter
 */
static int threshold = ATP_THRESHOLD;
module_param(threshold, int, 0644);
MODULE_PARM_DESC(threshold, "Discard any change in data from a sensor"
                            " (the trackpad has many of these sensors)"
                            " less than this value.");

static int debug;
module_param(debug, int, 0644);
MODULE_PARM_DESC(debug, "Activate debugging output");

/*
 * By default newer Geyser devices send standard USB HID mouse
 * packets (Report ID 2). This code changes device mode, so it
 * sends raw sensor reports (Report ID 5).
 */
static int atp_geyser_init(struct atp *dev)
{
        struct usb_device *udev = dev->udev;
        char *data;
        int size;
        int i;
        int ret;

        data = kmalloc(8, GFP_KERNEL);
        if (!data) {
                dev_err(&dev->intf->dev, "Out of memory\n");
                return -ENOMEM;
        }

        size = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
                        ATP_GEYSER_MODE_READ_REQUEST_ID,
                        USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
                        ATP_GEYSER_MODE_REQUEST_VALUE,
                        ATP_GEYSER_MODE_REQUEST_INDEX, data, 8, 5000);

        if (size != 8) {
                dprintk("atp_geyser_init: read error\n");
                for (i = 0; i < 8; i++)
                        dprintk("appletouch[%d]: %d\n", i, data[i]);

                dev_err(&dev->intf->dev, "Failed to read mode from device.\n");
                ret = -EIO;
                goto out_free;
        }

        /* Apply the mode switch */
        data[0] = ATP_GEYSER_MODE_VENDOR_VALUE;

        size = usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
                        ATP_GEYSER_MODE_WRITE_REQUEST_ID,
                        USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
                        ATP_GEYSER_MODE_REQUEST_VALUE,
                        ATP_GEYSER_MODE_REQUEST_INDEX, data, 8, 5000);

        if (size != 8) {
                dprintk("atp_geyser_init: write error\n");
                for (i = 0; i < 8; i++)
                        dprintk("appletouch[%d]: %d\n", i, data[i]);

                dev_err(&dev->intf->dev, "Failed to request geyser raw mode\n");
                ret = -EIO;
                goto out_free;
        }
        ret = 0;
out_free:
        kfree(data);
        return ret;
}

/*
 * Reinitialise the device. This usually stops stream of empty packets
 * coming from it.
 */
static void atp_reinit(struct work_struct *work)
{
        struct atp *dev = container_of(work, struct atp, work);
        int retval;

        dprintk("appletouch: putting appletouch to sleep (reinit)\n");
        atp_geyser_init(dev);

        retval = usb_submit_urb(dev->urb, GFP_ATOMIC);
        if (retval)
                dev_err(&dev->intf->dev,
                        "atp_reinit: usb_submit_urb failed with error %d\n",
                        retval);
}

static int atp_calculate_abs(struct atp *dev, int offset, int nb_sensors,
                             int fact, int *z, int *fingers)
{
        int i, pass;

        /*
         * Use offset to point xy_sensors at the first value in dev->xy_acc
         * for whichever dimension we're looking at this particular go-round.
         */
        int *xy_sensors = dev->xy_acc + offset;

        /* values to calculate mean */
        int pcum = 0, psum = 0;
        int is_increasing = 0;

        *fingers = 0;

        for (i = 0; i < nb_sensors; i++) {
                if (xy_sensors[i] < threshold) {
                        if (is_increasing)
                                is_increasing = 0;

                /*
                 * Makes the finger detection more versatile.  For example,
                 * two fingers with no gap will be detected.  Also, my
                 * tests show it less likely to have intermittent loss
                 * of multiple finger readings while moving around (scrolling).
                 *
                 * Changes the multiple finger detection to counting humps on
                 * sensors (transitions from nonincreasing to increasing)
                 * instead of counting transitions from low sensors (no
                 * finger reading) to high sensors (finger above
                 * sensor)
                 *
                 * - Jason Parekh <jasonparekh@gmail.com>
                 */

                } else if (i < 1 ||
                    (!is_increasing && xy_sensors[i - 1] < xy_sensors[i])) {
                        (*fingers)++;
                        is_increasing = 1;
                } else if (i > 0 && (xy_sensors[i - 1] - xy_sensors[i] > threshold)) {
                        is_increasing = 0;
                }
        }

        if (*fingers < 1)     /* No need to continue if no fingers are found. */
                return 0;

        /*
         * Use a smoothed version of sensor data for movement calculations, to
         * combat noise without needing to rely so heavily on a threshold.
         * This improves tracking.
         *
         * The smoothed array is bigger than the original so that the smoothing
         * doesn't result in edge values being truncated.
         */

        memset(dev->smooth, 0, 4 * sizeof(dev->smooth[0]));
        /* Pull base values, scaled up to help avoid truncation errors. */
        for (i = 0; i < nb_sensors; i++)
                dev->smooth[i + 4] = xy_sensors[i] << ATP_SCALE;
        memset(&dev->smooth[nb_sensors + 4], 0, 4 * sizeof(dev->smooth[0]));

        for (pass = 0; pass < 4; pass++) {
                /* Handle edge. */
                dev->smooth_tmp[0] = (dev->smooth[0] + dev->smooth[1]) / 2;

                /* Average values with neighbors. */
                for (i = 1; i < nb_sensors + 7; i++)
                        dev->smooth_tmp[i] = (dev->smooth[i - 1] +
                                              dev->smooth[i] * 2 +
                                              dev->smooth[i + 1]) / 4;

                /* Handle other edge. */
                dev->smooth_tmp[i] = (dev->smooth[i - 1] + dev->smooth[i]) / 2;

                memcpy(dev->smooth, dev->smooth_tmp, sizeof(dev->smooth));
        }

        for (i = 0; i < nb_sensors + 8; i++) {
                /*
                 * Skip values if they're small enough to be truncated to 0
                 * by scale. Mostly noise.
                 */
                if ((dev->smooth[i] >> ATP_SCALE) > 0) {
                        pcum += dev->smooth[i] * i;
                        psum += dev->smooth[i];
                }
        }

        if (psum > 0) {
                *z = psum >> ATP_SCALE;        /* Scale down pressure output. */
                return pcum * fact / psum;
        }

        return 0;
}

static inline void atp_report_fingers(struct input_dev *input, int fingers)
{
        input_report_key(input, BTN_TOOL_FINGER, fingers == 1);
        input_report_key(input, BTN_TOOL_DOUBLETAP, fingers == 2);
        input_report_key(input, BTN_TOOL_TRIPLETAP, fingers > 2);
}

/* Check URB status and for correct length of data package */

#define ATP_URB_STATUS_SUCCESS          0
#define ATP_URB_STATUS_ERROR            1
#define ATP_URB_STATUS_ERROR_FATAL      2

static int atp_status_check(struct urb *urb)
{
        struct atp *dev = urb->context;
        struct usb_interface *intf = dev->intf;

        switch (urb->status) {
        case 0:
                /* success */
                break;
        case -EOVERFLOW:
                if (!dev->overflow_warned) {
                        dev_warn(&intf->dev,
                                "appletouch: OVERFLOW with data length %d, actual length is %d\n",
                                dev->info->datalen, dev->urb->actual_length);
                        dev->overflow_warned = true;
                }
                /* fall through */
        case -ECONNRESET:
        case -ENOENT:
        case -ESHUTDOWN:
                /* This urb is terminated, clean up */
                dev_dbg(&intf->dev,
                        "atp_complete: urb shutting down with status: %d\n",
                        urb->status);
                return ATP_URB_STATUS_ERROR_FATAL;

        default:
                dev_dbg(&intf->dev,
                        "atp_complete: nonzero urb status received: %d\n",
                        urb->status);
                return ATP_URB_STATUS_ERROR;
        }

        /* drop incomplete datasets */
        if (dev->urb->actual_length != dev->info->datalen) {
                dprintk("appletouch: incomplete data package"
                        " (first byte: %d, length: %d).\n",
                        dev->data[0], dev->urb->actual_length);
                return ATP_URB_STATUS_ERROR;
        }

        return ATP_URB_STATUS_SUCCESS;
}

static void atp_detect_size(struct atp *dev)
{
        int i;

        /* 17" Powerbooks have extra X sensors */
        for (i = dev->info->xsensors; i < ATP_XSENSORS; i++) {
                if (dev->xy_cur[i]) {

                        dev_info(&dev->intf->dev,
                                "appletouch: 17\" model detected.\n");

                        input_set_abs_params(dev->input, ABS_X, 0,
                                             (dev->info->xsensors_17 - 1) *
                                                        dev->info->xfact - 1,
                                             dev->info->fuzz, 0);
                        break;
                }
        }
}

/*
 * USB interrupt callback functions
 */

/* Interrupt function for older touchpads: FOUNTAIN/GEYSER1/GEYSER2 */

static void atp_complete_geyser_1_2(struct urb *urb)
{
        int x, y, x_z, y_z, x_f, y_f;
        int retval, i, j;
        int key, fingers;
        struct atp *dev = urb->context;
        int status = atp_status_check(urb);

        if (status == ATP_URB_STATUS_ERROR_FATAL)
                return;
        else if (status == ATP_URB_STATUS_ERROR)
                goto exit;

        /* reorder the sensors values */
        if (dev->info == &geyser2_info) {
                memset(dev->xy_cur, 0, sizeof(dev->xy_cur));

                /*
                 * The values are laid out like this:
                 * Y1, Y2, -, Y3, Y4, -, ..., X1, X2, -, X3, X4, -, ...
                 * '-' is an unused value.
                 */

                /* read X values */
                for (i = 0, j = 19; i < 20; i += 2, j += 3) {
                        dev->xy_cur[i] = dev->data[j];
                        dev->xy_cur[i + 1] = dev->data[j + 1];
                }

                /* read Y values */
                for (i = 0, j = 1; i < 9; i += 2, j += 3) {
                        dev->xy_cur[ATP_XSENSORS + i] = dev->data[j];
                        dev->xy_cur[ATP_XSENSORS + i + 1] = dev->data[j + 1];
                }
        } else {
                for (i = 0; i < 8; i++) {
                        /* X values */
                        dev->xy_cur[i +  0] = dev->data[5 * i +  2];
                        dev->xy_cur[i +  8] = dev->data[5 * i +  4];
                        dev->xy_cur[i + 16] = dev->data[5 * i + 42];
                        if (i < 2)
                                dev->xy_cur[i + 24] = dev->data[5 * i + 44];

                        /* Y values */
                        dev->xy_cur[ATP_XSENSORS + i] = dev->data[5 * i +  1];
                        dev->xy_cur[ATP_XSENSORS + i + 8] = dev->data[5 * i + 3];
                }
        }

        dbg_dump("sample", dev->xy_cur);

        if (!dev->valid) {
                /* first sample */
                dev->valid = true;
                dev->x_old = dev->y_old = -1;

                /* Store first sample */
                memcpy(dev->xy_old, dev->xy_cur, sizeof(dev->xy_old));

                /* Perform size detection, if not done already */
                if (unlikely(!dev->size_detect_done)) {
                        atp_detect_size(dev);
                        dev->size_detect_done = true;
                        goto exit;
                }
        }

        for (i = 0; i < ATP_XSENSORS + ATP_YSENSORS; i++) {
                /* accumulate the change */
                signed char change = dev->xy_old[i] - dev->xy_cur[i];
                dev->xy_acc[i] -= change;

                /* prevent down drifting */
                if (dev->xy_acc[i] < 0)
                        dev->xy_acc[i] = 0;
        }

        memcpy(dev->xy_old, dev->xy_cur, sizeof(dev->xy_old));

        dbg_dump("accumulator", dev->xy_acc);

        x = atp_calculate_abs(dev, 0, ATP_XSENSORS,
                              dev->info->xfact, &x_z, &x_f);
        y = atp_calculate_abs(dev, ATP_XSENSORS, ATP_YSENSORS,
                              dev->info->yfact, &y_z, &y_f);
        key = dev->data[dev->info->datalen - 1] & ATP_STATUS_BUTTON;

        fingers = max(x_f, y_f);

        if (x && y && fingers == dev->fingers_old) {
                if (dev->x_old != -1) {
                        x = (dev->x_old * 7 + x) >> 3;
                        y = (dev->y_old * 7 + y) >> 3;
                        dev->x_old = x;
                        dev->y_old = y;

                        if (debug > 1)
                                printk(KERN_DEBUG "appletouch: "
                                        "X: %3d Y: %3d Xz: %3d Yz: %3d\n",
                                        x, y, x_z, y_z);

                        input_report_key(dev->input, BTN_TOUCH, 1);
                        input_report_abs(dev->input, ABS_X, x);
                        input_report_abs(dev->input, ABS_Y, y);
                        input_report_abs(dev->input, ABS_PRESSURE,
                                         min(ATP_PRESSURE, x_z + y_z));
                        atp_report_fingers(dev->input, fingers);
                }
                dev->x_old = x;
                dev->y_old = y;

        } else if (!x && !y) {

                dev->x_old = dev->y_old = -1;
                dev->fingers_old = 0;
                input_report_key(dev->input, BTN_TOUCH, 0);
                input_report_abs(dev->input, ABS_PRESSURE, 0);
                atp_report_fingers(dev->input, 0);

                /* reset the accumulator on release */
                memset(dev->xy_acc, 0, sizeof(dev->xy_acc));
        }

        if (fingers != dev->fingers_old)
                dev->x_old = dev->y_old = -1;
        dev->fingers_old = fingers;

        input_report_key(dev->input, BTN_LEFT, key);
        input_sync(dev->input);

 exit:
        retval = usb_submit_urb(dev->urb, GFP_ATOMIC);
        if (retval)
                dev_err(&dev->intf->dev,
                        "atp_complete: usb_submit_urb failed with result %d\n",
                        retval);
}

/* Interrupt function for older touchpads: GEYSER3/GEYSER4 */

static void atp_complete_geyser_3_4(struct urb *urb)
{
        int x, y, x_z, y_z, x_f, y_f;
        int retval, i, j;
        int key, fingers;
        struct atp *dev = urb->context;
        int status = atp_status_check(urb);

        if (status == ATP_URB_STATUS_ERROR_FATAL)
                return;
        else if (status == ATP_URB_STATUS_ERROR)
                goto exit;

        /* Reorder the sensors values:
         *
         * The values are laid out like this:
         * -, Y1, Y2, -, Y3, Y4, -, ..., -, X1, X2, -, X3, X4, ...
         * '-' is an unused value.
         */

        /* read X values */
        for (i = 0, j = 19; i < 20; i += 2, j += 3) {
                dev->xy_cur[i] = dev->data[j + 1];
                dev->xy_cur[i + 1] = dev->data[j + 2];
        }
        /* read Y values */
        for (i = 0, j = 1; i < 9; i += 2, j += 3) {
                dev->xy_cur[ATP_XSENSORS + i] = dev->data[j + 1];
                dev->xy_cur[ATP_XSENSORS + i + 1] = dev->data[j + 2];
        }

        dbg_dump("sample", dev->xy_cur);

        /* Just update the base values (i.e. touchpad in untouched state) */
        if (dev->data[dev->info->datalen - 1] & ATP_STATUS_BASE_UPDATE) {

                dprintk("appletouch: updated base values\n");

                memcpy(dev->xy_old, dev->xy_cur, sizeof(dev->xy_old));
                goto exit;
        }

        for (i = 0; i < ATP_XSENSORS + ATP_YSENSORS; i++) {
                /* calculate the change */
                dev->xy_acc[i] = dev->xy_cur[i] - dev->xy_old[i];

                /* this is a round-robin value, so couple with that */
                if (dev->xy_acc[i] > 127)
                        dev->xy_acc[i] -= 256;

                if (dev->xy_acc[i] < -127)
                        dev->xy_acc[i] += 256;

                /* prevent down drifting */
                if (dev->xy_acc[i] < 0)
                        dev->xy_acc[i] = 0;
        }

        dbg_dump("accumulator", dev->xy_acc);

        x = atp_calculate_abs(dev, 0, ATP_XSENSORS,
                              dev->info->xfact, &x_z, &x_f);
        y = atp_calculate_abs(dev, ATP_XSENSORS, ATP_YSENSORS,
                              dev->info->yfact, &y_z, &y_f);

        key = dev->data[dev->info->datalen - 1] & ATP_STATUS_BUTTON;

        fingers = max(x_f, y_f);

        if (x && y && fingers == dev->fingers_old) {
                if (dev->x_old != -1) {
                        x = (dev->x_old * 7 + x) >> 3;
                        y = (dev->y_old * 7 + y) >> 3;
                        dev->x_old = x;
                        dev->y_old = y;

                        if (debug > 1)
                                printk(KERN_DEBUG "appletouch: X: %3d Y: %3d "
                                       "Xz: %3d Yz: %3d\n",
                                       x, y, x_z, y_z);

                        input_report_key(dev->input, BTN_TOUCH, 1);
                        input_report_abs(dev->input, ABS_X, x);
                        input_report_abs(dev->input, ABS_Y, y);
                        input_report_abs(dev->input, ABS_PRESSURE,
                                         min(ATP_PRESSURE, x_z + y_z));
                        atp_report_fingers(dev->input, fingers);
                }
                dev->x_old = x;
                dev->y_old = y;

        } else if (!x && !y) {

                dev->x_old = dev->y_old = -1;
                dev->fingers_old = 0;
                input_report_key(dev->input, BTN_TOUCH, 0);
                input_report_abs(dev->input, ABS_PRESSURE, 0);
                atp_report_fingers(dev->input, 0);

                /* reset the accumulator on release */
                memset(dev->xy_acc, 0, sizeof(dev->xy_acc));
        }

        if (fingers != dev->fingers_old)
                dev->x_old = dev->y_old = -1;
        dev->fingers_old = fingers;

        input_report_key(dev->input, BTN_LEFT, key);
        input_sync(dev->input);

        /*
         * Geysers 3/4 will continue to send packets continually after
         * the first touch unless reinitialised. Do so if it's been
         * idle for a while in order to avoid waking the kernel up
         * several hundred times a second.
         */

        /*
         * Button must not be pressed when entering suspend,
         * otherwise we will never release the button.
         */
        if (!x && !y && !key) {
                dev->idlecount++;
                if (dev->idlecount == 10) {
                        dev->x_old = dev->y_old = -1;
                        dev->idlecount = 0;
                        schedule_work(&dev->work);
                        /* Don't resubmit urb here, wait for reinit */
                        return;
                }
        } else
                dev->idlecount = 0;

 exit:
        retval = usb_submit_urb(dev->urb, GFP_ATOMIC);
        if (retval)
                dev_err(&dev->intf->dev,
                        "atp_complete: usb_submit_urb failed with result %d\n",
                        retval);
}

static int atp_open(struct input_dev *input)
{
        struct atp *dev = input_get_drvdata(input);

        if (usb_submit_urb(dev->urb, GFP_KERNEL))
                return -EIO;

        dev->open = true;
        return 0;
}

static void atp_close(struct input_dev *input)
{
        struct atp *dev = input_get_drvdata(input);

        usb_kill_urb(dev->urb);
        cancel_work_sync(&dev->work);
        dev->open = false;
}

static int atp_handle_geyser(struct atp *dev)
{
        if (dev->info != &fountain_info) {
                /* switch to raw sensor mode */
                if (atp_geyser_init(dev))
                        return -EIO;

                dev_info(&dev->intf->dev, "Geyser mode initialized.\n");
        }

        return 0;
}

static int atp_probe(struct usb_interface *iface,
                     const struct usb_device_id *id)
{
        struct atp *dev;
        struct input_dev *input_dev;
        struct usb_device *udev = interface_to_usbdev(iface);
        struct usb_host_interface *iface_desc;
        struct usb_endpoint_descriptor *endpoint;
        int int_in_endpointAddr = 0;
        int i, error = -ENOMEM;
        const struct atp_info *info = (const struct atp_info *)id->driver_info;

        /* set up the endpoint information */
        /* use only the first interrupt-in endpoint */
        iface_desc = iface->cur_altsetting;
        for (i = 0; i < iface_desc->desc.bNumEndpoints; i++) {
                endpoint = &iface_desc->endpoint[i].desc;
                if (!int_in_endpointAddr && usb_endpoint_is_int_in(endpoint)) {
                        /* we found an interrupt in endpoint */
                        int_in_endpointAddr = endpoint->bEndpointAddress;
                        break;
                }
        }
        if (!int_in_endpointAddr) {
                dev_err(&iface->dev, "Could not find int-in endpoint\n");
                return -EIO;
        }

        /* allocate memory for our device state and initialize it */
        dev = kzalloc(sizeof(struct atp), GFP_KERNEL);
        input_dev = input_allocate_device();
        if (!dev || !input_dev) {
                dev_err(&iface->dev, "Out of memory\n");
                goto err_free_devs;
        }

        dev->udev = udev;
        dev->intf = iface;
        dev->input = input_dev;
        dev->info = info;
        dev->overflow_warned = false;

        dev->urb = usb_alloc_urb(0, GFP_KERNEL);
        if (!dev->urb)
                goto err_free_devs;

        dev->data = usb_alloc_coherent(dev->udev, dev->info->datalen, GFP_KERNEL,
                                       &dev->urb->transfer_dma);
        if (!dev->data)
                goto err_free_urb;

        usb_fill_int_urb(dev->urb, udev,
                         usb_rcvintpipe(udev, int_in_endpointAddr),
                         dev->data, dev->info->datalen,
                         dev->info->callback, dev, 1);

        error = atp_handle_geyser(dev);
        if (error)
                goto err_free_buffer;

        usb_make_path(udev, dev->phys, sizeof(dev->phys));
        strlcat(dev->phys, "/input0", sizeof(dev->phys));

        input_dev->name = "appletouch";
        input_dev->phys = dev->phys;
        usb_to_input_id(dev->udev, &input_dev->id);
        input_dev->dev.parent = &iface->dev;

        input_set_drvdata(input_dev, dev);

        input_dev->open = atp_open;
        input_dev->close = atp_close;

        set_bit(EV_ABS, input_dev->evbit);

        input_set_abs_params(input_dev, ABS_X, 0,
                             (dev->info->xsensors - 1) * dev->info->xfact - 1,
                             dev->info->fuzz, 0);
        input_set_abs_params(input_dev, ABS_Y, 0,
                             (dev->info->ysensors - 1) * dev->info->yfact - 1,
                             dev->info->fuzz, 0);
        input_set_abs_params(input_dev, ABS_PRESSURE, 0, ATP_PRESSURE, 0, 0);

        set_bit(EV_KEY, input_dev->evbit);
        set_bit(BTN_TOUCH, input_dev->keybit);
        set_bit(BTN_TOOL_FINGER, input_dev->keybit);
        set_bit(BTN_TOOL_DOUBLETAP, input_dev->keybit);
        set_bit(BTN_TOOL_TRIPLETAP, input_dev->keybit);
        set_bit(BTN_LEFT, input_dev->keybit);

        error = input_register_device(dev->input);
        if (error)
                goto err_free_buffer;

        /* save our data pointer in this interface device */
        usb_set_intfdata(iface, dev);

        INIT_WORK(&dev->work, atp_reinit);

        return 0;

 err_free_buffer:
        usb_free_coherent(dev->udev, dev->info->datalen,
                          dev->data, dev->urb->transfer_dma);
 err_free_urb:
        usb_free_urb(dev->urb);
 err_free_devs:
        usb_set_intfdata(iface, NULL);
        kfree(dev);
        input_free_device(input_dev);
        return error;
}

static void atp_disconnect(struct usb_interface *iface)
{
        struct atp *dev = usb_get_intfdata(iface);

        usb_set_intfdata(iface, NULL);
        if (dev) {
                usb_kill_urb(dev->urb);
                input_unregister_device(dev->input);
                usb_free_coherent(dev->udev, dev->info->datalen,
                                  dev->data, dev->urb->transfer_dma);
                usb_free_urb(dev->urb);
                kfree(dev);
        }
        dev_info(&iface->dev, "input: appletouch disconnected\n");
}

static int atp_recover(struct atp *dev)
{
        int error;

        error = atp_handle_geyser(dev);
        if (error)
                return error;

        if (dev->open && usb_submit_urb(dev->urb, GFP_KERNEL))
                return -EIO;

        return 0;
}

static int atp_suspend(struct usb_interface *iface, pm_message_t message)
{
        struct atp *dev = usb_get_intfdata(iface);

        usb_kill_urb(dev->urb);
        return 0;
}

static int atp_resume(struct usb_interface *iface)
{
        struct atp *dev = usb_get_intfdata(iface);

        if (dev->open && usb_submit_urb(dev->urb, GFP_KERNEL))
                return -EIO;

        return 0;
}

static int atp_reset_resume(struct usb_interface *iface)
{
        struct atp *dev = usb_get_intfdata(iface);

        return atp_recover(dev);
}

static struct usb_driver atp_driver = {
        .name           = "appletouch",
        .probe          = atp_probe,
        .disconnect     = atp_disconnect,
        .suspend        = atp_suspend,
        .resume         = atp_resume,
        .reset_resume   = atp_reset_resume,
        .id_table       = atp_table,
};

module_usb_driver(atp_driver);