/*
 * Surface2.0/SUR40/PixelSense input driver
 *
 * Copyright (c) 2013 by Florian 'floe' Echtler <floe@butterbrot.org>
 *
 * Derived from the USB Skeleton driver 1.1,
 * Copyright (c) 2003 Greg Kroah-Hartman (greg@kroah.com)
 *
 * and from the Apple USB BCM5974 multitouch driver,
 * Copyright (c) 2008 Henrik Rydberg (rydberg@euromail.se)
 *
 * and from the generic hid-multitouch driver,
 * Copyright (c) 2010-2012 Stephane Chatty <chatty@enac.fr>
 *
 * 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.
 */

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/completion.h>
#include <linux/uaccess.h>
#include <linux/usb.h>
#include <linux/printk.h>
#include <linux/input-polldev.h>
#include <linux/input/mt.h>
#include <linux/usb/input.h>

/* read 512 bytes from endpoint 0x86 -> get header + blobs */
struct sur40_header {

        __le16 type;       /* always 0x0001 */
        __le16 count;      /* count of blobs (if 0: continue prev. packet) */

        __le32 packet_id;  /* unique ID for all packets in one frame */

        __le32 timestamp;  /* milliseconds (inc. by 16 or 17 each frame) */
        __le32 unknown;    /* "epoch?" always 02/03 00 00 00 */

} __packed;

struct sur40_blob {

        __le16 blob_id;

        u8 action;         /* 0x02 = enter/exit, 0x03 = update (?) */
        u8 unknown;        /* always 0x01 or 0x02 (no idea what this is?) */

        __le16 bb_pos_x;   /* upper left corner of bounding box */
        __le16 bb_pos_y;

        __le16 bb_size_x;  /* size of bounding box */
        __le16 bb_size_y;

        __le16 pos_x;      /* finger tip position */
        __le16 pos_y;

        __le16 ctr_x;      /* centroid position */
        __le16 ctr_y;

        __le16 axis_x;     /* somehow related to major/minor axis, mostly: */
        __le16 axis_y;     /* axis_x == bb_size_y && axis_y == bb_size_x */

        __le32 angle;      /* orientation in radians relative to x axis -
                              actually an IEEE754 float, don't use in kernel */

        __le32 area;       /* size in pixels/pressure (?) */

        u8 padding[32];

} __packed;

/* combined header/blob data */
struct sur40_data {
        struct sur40_header header;
        struct sur40_blob   blobs[];
} __packed;


/* version information */
#define DRIVER_SHORT   "sur40"
#define DRIVER_AUTHOR  "Florian 'floe' Echtler <floe@butterbrot.org>"
#define DRIVER_DESC    "Surface2.0/SUR40/PixelSense input driver"

/* vendor and device IDs */
#define ID_MICROSOFT 0x045e
#define ID_SUR40     0x0775

/* sensor resolution */
#define SENSOR_RES_X 1920
#define SENSOR_RES_Y 1080

/* touch data endpoint */
#define TOUCH_ENDPOINT 0x86

/* polling interval (ms) */
#define POLL_INTERVAL 10

/* maximum number of contacts FIXME: this is a guess? */
#define MAX_CONTACTS 64

/* control commands */
#define SUR40_GET_VERSION 0xb0 /* 12 bytes string    */
#define SUR40_UNKNOWN1    0xb3 /*  5 bytes           */
#define SUR40_UNKNOWN2    0xc1 /* 24 bytes           */

#define SUR40_GET_STATE   0xc5 /*  4 bytes state (?) */
#define SUR40_GET_SENSORS 0xb1 /*  8 bytes sensors   */

/*
 * Note: an earlier, non-public version of this driver used USB_RECIP_ENDPOINT
 * here by mistake which is very likely to have corrupted the firmware EEPROM
 * on two separate SUR40 devices. Thanks to Alan Stern who spotted this bug.
 * Should you ever run into a similar problem, the background story to this
 * incident and instructions on how to fix the corrupted EEPROM are available
 * at https://floe.butterbrot.org/matrix/hacking/surface/brick.html
*/

struct sur40_state {

        struct usb_device *usbdev;
        struct device *dev;
        struct input_polled_dev *input;

        struct sur40_data *bulk_in_buffer;
        size_t bulk_in_size;
        u8 bulk_in_epaddr;

        char phys[64];
};

static int sur40_command(struct sur40_state *dev,
                         u8 command, u16 index, void *buffer, u16 size)
{
        return usb_control_msg(dev->usbdev, usb_rcvctrlpipe(dev->usbdev, 0),
                               command,
                               USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
                               0x00, index, buffer, size, 1000);
}

/* Initialization routine, called from sur40_open */
static int sur40_init(struct sur40_state *dev)
{
        int result;
        u8 buffer[24];

        /* stupidly replay the original MS driver init sequence */
        result = sur40_command(dev, SUR40_GET_VERSION, 0x00, buffer, 12);
        if (result < 0)
                return result;

        result = sur40_command(dev, SUR40_GET_VERSION, 0x01, buffer, 12);
        if (result < 0)
                return result;

        result = sur40_command(dev, SUR40_GET_VERSION, 0x02, buffer, 12);
        if (result < 0)
                return result;

        result = sur40_command(dev, SUR40_UNKNOWN2,    0x00, buffer, 24);
        if (result < 0)
                return result;

        result = sur40_command(dev, SUR40_UNKNOWN1,    0x00, buffer,  5);
        if (result < 0)
                return result;

        result = sur40_command(dev, SUR40_GET_VERSION, 0x03, buffer, 12);

        /*
         * Discard the result buffer - no known data inside except
         * some version strings, maybe extract these sometime...
         */

        return result;
}

/*
 * Callback routines from input_polled_dev
 */

/* Enable the device, polling will now start. */
static void sur40_open(struct input_polled_dev *polldev)
{
        struct sur40_state *sur40 = polldev->private;

        dev_dbg(sur40->dev, "open\n");
        sur40_init(sur40);
}

/* Disable device, polling has stopped. */
static void sur40_close(struct input_polled_dev *polldev)
{
        struct sur40_state *sur40 = polldev->private;

        dev_dbg(sur40->dev, "close\n");
        /*
         * There is no known way to stop the device, so we simply
         * stop polling.
         */
}

/*
 * This function is called when a whole contact has been processed,
 * so that it can assign it to a slot and store the data there.
 */
static void sur40_report_blob(struct sur40_blob *blob, struct input_dev *input)
{
        int wide, major, minor;

        int bb_size_x = le16_to_cpu(blob->bb_size_x);
        int bb_size_y = le16_to_cpu(blob->bb_size_y);

        int pos_x = le16_to_cpu(blob->pos_x);
        int pos_y = le16_to_cpu(blob->pos_y);

        int ctr_x = le16_to_cpu(blob->ctr_x);
        int ctr_y = le16_to_cpu(blob->ctr_y);

        int slotnum = input_mt_get_slot_by_key(input, blob->blob_id);
        if (slotnum < 0 || slotnum >= MAX_CONTACTS)
                return;

        input_mt_slot(input, slotnum);
        input_mt_report_slot_state(input, MT_TOOL_FINGER, 1);
        wide = (bb_size_x > bb_size_y);
        major = max(bb_size_x, bb_size_y);
        minor = min(bb_size_x, bb_size_y);

        input_report_abs(input, ABS_MT_POSITION_X, pos_x);
        input_report_abs(input, ABS_MT_POSITION_Y, pos_y);
        input_report_abs(input, ABS_MT_TOOL_X, ctr_x);
        input_report_abs(input, ABS_MT_TOOL_Y, ctr_y);

        /* TODO: use a better orientation measure */
        input_report_abs(input, ABS_MT_ORIENTATION, wide);
        input_report_abs(input, ABS_MT_TOUCH_MAJOR, major);
        input_report_abs(input, ABS_MT_TOUCH_MINOR, minor);
}

/* core function: poll for new input data */
static void sur40_poll(struct input_polled_dev *polldev)
{

        struct sur40_state *sur40 = polldev->private;
        struct input_dev *input = polldev->input;
        int result, bulk_read, need_blobs, packet_blobs, i;
        u32 uninitialized_var(packet_id);

        struct sur40_header *header = &sur40->bulk_in_buffer->header;
        struct sur40_blob *inblob = &sur40->bulk_in_buffer->blobs[0];

        dev_dbg(sur40->dev, "poll\n");

        need_blobs = -1;

        do {

                /* perform a blocking bulk read to get data from the device */
                result = usb_bulk_msg(sur40->usbdev,
                        usb_rcvbulkpipe(sur40->usbdev, sur40->bulk_in_epaddr),
                        sur40->bulk_in_buffer, sur40->bulk_in_size,
                        &bulk_read, 1000);

                dev_dbg(sur40->dev, "received %d bytes\n", bulk_read);

                if (result < 0) {
                        dev_err(sur40->dev, "error in usb_bulk_read\n");
                        return;
                }

                result = bulk_read - sizeof(struct sur40_header);

                if (result % sizeof(struct sur40_blob) != 0) {
                        dev_err(sur40->dev, "transfer size mismatch\n");
                        return;
                }

                /* first packet? */
                if (need_blobs == -1) {
                        need_blobs = le16_to_cpu(header->count);
                        dev_dbg(sur40->dev, "need %d blobs\n", need_blobs);
                        packet_id = le32_to_cpu(header->packet_id);
                }

                /*
                 * Sanity check. when video data is also being retrieved, the
                 * packet ID will usually increase in the middle of a series
                 * instead of at the end.
                 */
                if (packet_id != header->packet_id)
                        dev_warn(sur40->dev, "packet ID mismatch\n");

                packet_blobs = result / sizeof(struct sur40_blob);
                dev_dbg(sur40->dev, "received %d blobs\n", packet_blobs);

                /* packets always contain at least 4 blobs, even if empty */
                if (packet_blobs > need_blobs)
                        packet_blobs = need_blobs;

                for (i = 0; i < packet_blobs; i++) {
                        need_blobs--;
                        dev_dbg(sur40->dev, "processing blob\n");
                        sur40_report_blob(&(inblob[i]), input);
                }

        } while (need_blobs > 0);

        input_mt_sync_frame(input);
        input_sync(input);
}

/* Initialize input device parameters. */
static void sur40_input_setup(struct input_dev *input_dev)
{
        __set_bit(EV_KEY, input_dev->evbit);
        __set_bit(EV_ABS, input_dev->evbit);

        input_set_abs_params(input_dev, ABS_MT_POSITION_X,
                             0, SENSOR_RES_X, 0, 0);
        input_set_abs_params(input_dev, ABS_MT_POSITION_Y,
                             0, SENSOR_RES_Y, 0, 0);

        input_set_abs_params(input_dev, ABS_MT_TOOL_X,
                             0, SENSOR_RES_X, 0, 0);
        input_set_abs_params(input_dev, ABS_MT_TOOL_Y,
                             0, SENSOR_RES_Y, 0, 0);

        /* max value unknown, but major/minor axis
         * can never be larger than screen */
        input_set_abs_params(input_dev, ABS_MT_TOUCH_MAJOR,
                             0, SENSOR_RES_X, 0, 0);
        input_set_abs_params(input_dev, ABS_MT_TOUCH_MINOR,
                             0, SENSOR_RES_Y, 0, 0);

        input_set_abs_params(input_dev, ABS_MT_ORIENTATION, 0, 1, 0, 0);

        input_mt_init_slots(input_dev, MAX_CONTACTS,
                            INPUT_MT_DIRECT | INPUT_MT_DROP_UNUSED);
}

/* Check candidate USB interface. */
static int sur40_probe(struct usb_interface *interface,
                       const struct usb_device_id *id)
{
        struct usb_device *usbdev = interface_to_usbdev(interface);
        struct sur40_state *sur40;
        struct usb_host_interface *iface_desc;
        struct usb_endpoint_descriptor *endpoint;
        struct input_polled_dev *poll_dev;
        int error;

        /* Check if we really have the right interface. */
        iface_desc = &interface->altsetting[0];
        if (iface_desc->desc.bInterfaceClass != 0xFF)
                return -ENODEV;

        /* Use endpoint #4 (0x86). */
        endpoint = &iface_desc->endpoint[4].desc;
        if (endpoint->bEndpointAddress != TOUCH_ENDPOINT)
                return -ENODEV;

        /* Allocate memory for our device state and initialize it. */
        sur40 = kzalloc(sizeof(struct sur40_state), GFP_KERNEL);
        if (!sur40)
                return -ENOMEM;

        poll_dev = input_allocate_polled_device();
        if (!poll_dev) {
                error = -ENOMEM;
                goto err_free_dev;
        }

        /* Set up polled input device control structure */
        poll_dev->private = sur40;
        poll_dev->poll_interval = POLL_INTERVAL;
        poll_dev->open = sur40_open;
        poll_dev->poll = sur40_poll;
        poll_dev->close = sur40_close;

        /* Set up regular input device structure */
        sur40_input_setup(poll_dev->input);

        poll_dev->input->name = "Samsung SUR40";
        usb_to_input_id(usbdev, &poll_dev->input->id);
        usb_make_path(usbdev, sur40->phys, sizeof(sur40->phys));
        strlcat(sur40->phys, "/input0", sizeof(sur40->phys));
        poll_dev->input->phys = sur40->phys;
        poll_dev->input->dev.parent = &interface->dev;

        sur40->usbdev = usbdev;
        sur40->dev = &interface->dev;
        sur40->input = poll_dev;

        /* use the bulk-in endpoint tested above */
        sur40->bulk_in_size = usb_endpoint_maxp(endpoint);
        sur40->bulk_in_epaddr = endpoint->bEndpointAddress;
        sur40->bulk_in_buffer = kmalloc(sur40->bulk_in_size, GFP_KERNEL);
        if (!sur40->bulk_in_buffer) {
                dev_err(&interface->dev, "Unable to allocate input buffer.");
                error = -ENOMEM;
                goto err_free_polldev;
        }

        error = input_register_polled_device(poll_dev);
        if (error) {
                dev_err(&interface->dev,
                        "Unable to register polled input device.");
                goto err_free_buffer;
        }

        /* we can register the device now, as it is ready */
        usb_set_intfdata(interface, sur40);
        dev_dbg(&interface->dev, "%s is now attached\n", DRIVER_DESC);

        return 0;

err_free_buffer:
        kfree(sur40->bulk_in_buffer);
err_free_polldev:
        input_free_polled_device(sur40->input);
err_free_dev:
        kfree(sur40);

        return error;
}

/* Unregister device & clean up. */
static void sur40_disconnect(struct usb_interface *interface)
{
        struct sur40_state *sur40 = usb_get_intfdata(interface);

        input_unregister_polled_device(sur40->input);
        input_free_polled_device(sur40->input);
        kfree(sur40->bulk_in_buffer);
        kfree(sur40);

        usb_set_intfdata(interface, NULL);
        dev_dbg(&interface->dev, "%s is now disconnected\n", DRIVER_DESC);
}

static const struct usb_device_id sur40_table[] = {
        { USB_DEVICE(ID_MICROSOFT, ID_SUR40) },  /* Samsung SUR40 */
        { }                                      /* terminating null entry */
};
MODULE_DEVICE_TABLE(usb, sur40_table);

/* USB-specific object needed to register this driver with the USB subsystem. */
static struct usb_driver sur40_driver = {
        .name = DRIVER_SHORT,
        .probe = sur40_probe,
        .disconnect = sur40_disconnect,
        .id_table = sur40_table,
};

module_usb_driver(sur40_driver);

MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");