/*
 *  Driver for the Gravis Grip Multiport, a gamepad "hub" that
 *  connects up to four 9-pin digital gamepads/joysticks.
 *  Driver tested on SMP and UP kernel versions 2.4.18-4 and 2.4.18-5.
 *
 *  Thanks to Chris Gassib for helpful advice.
 *
 *  Copyright (c)      2002 Brian Bonnlander, Bill Soudan
 *  Copyright (c) 1998-2000 Vojtech Pavlik
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/gameport.h>
#include <linux/input.h>
#include <linux/delay.h>
#include <linux/proc_fs.h>
#include <linux/jiffies.h>

#define DRIVER_DESC     "Gravis Grip Multiport driver"

MODULE_AUTHOR("Brian Bonnlander");
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");

#ifdef GRIP_DEBUG
#define dbg(format, arg...) printk(KERN_ERR __FILE__ ": " format "\n" , ## arg)
#else
#define dbg(format, arg...) do {} while (0)
#endif

#define GRIP_MAX_PORTS  4
/*
 * Grip multiport state
 */

struct grip_port {
        struct input_dev *dev;
        int mode;
        int registered;

        /* individual gamepad states */
        int buttons;
        int xaxes;
        int yaxes;
        int dirty;     /* has the state been updated? */
};

struct grip_mp {
        struct gameport *gameport;
        struct grip_port *port[GRIP_MAX_PORTS];
        int reads;
        int bads;
};

/*
 * Multiport packet interpretation
 */

#define PACKET_FULL          0x80000000       /* packet is full                        */
#define PACKET_IO_FAST       0x40000000       /* 3 bits per gameport read              */
#define PACKET_IO_SLOW       0x20000000       /* 1 bit per gameport read               */
#define PACKET_MP_MORE       0x04000000       /* multiport wants to send more          */
#define PACKET_MP_DONE       0x02000000       /* multiport done sending                */

/*
 * Packet status code interpretation
 */

#define IO_GOT_PACKET        0x0100           /* Got a packet                           */
#define IO_MODE_FAST         0x0200           /* Used 3 data bits per gameport read     */
#define IO_SLOT_CHANGE       0x0800           /* Multiport physical slot status changed */
#define IO_DONE              0x1000           /* Multiport is done sending packets      */
#define IO_RETRY             0x4000           /* Try again later to get packet          */
#define IO_RESET             0x8000           /* Force multiport to resend all packets  */

/*
 * Gamepad configuration data.  Other 9-pin digital joystick devices
 * may work with the multiport, so this may not be an exhaustive list!
 * Commodore 64 joystick remains untested.
 */

#define GRIP_INIT_DELAY         2000          /*  2 ms */

#define GRIP_MODE_NONE          0
#define GRIP_MODE_RESET         1
#define GRIP_MODE_GP            2
#define GRIP_MODE_C64           3

static const int grip_btn_gp[]  = { BTN_TR, BTN_TL, BTN_A, BTN_B, BTN_C, BTN_X, BTN_Y, BTN_Z, -1 };
static const int grip_btn_c64[] = { BTN_JOYSTICK, -1 };

static const int grip_abs_gp[]  = { ABS_X, ABS_Y, -1 };
static const int grip_abs_c64[] = { ABS_X, ABS_Y, -1 };

static const int *grip_abs[] = { NULL, NULL, grip_abs_gp, grip_abs_c64 };
static const int *grip_btn[] = { NULL, NULL, grip_btn_gp, grip_btn_c64 };

static const char *grip_name[] = { NULL, NULL, "Gravis Grip Pad", "Commodore 64 Joystick" };

static const int init_seq[] = {
        1, 0, 1, 1, 0, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1,
        1, 0, 1, 0, 1, 0, 1, 1, 1, 1, 0, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1,
        1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 0, 1, 0, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1,
        0, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1 };

/* Maps multiport directional values to X,Y axis values (each axis encoded in 3 bits) */

static const int axis_map[] = { 5, 9, 1, 5, 6, 10, 2, 6, 4, 8, 0, 4, 5, 9, 1, 5 };

static int register_slot(int i, struct grip_mp *grip);

/*
 * Returns whether an odd or even number of bits are on in pkt.
 */

static int bit_parity(u32 pkt)
{
        int x = pkt ^ (pkt >> 16);
        x ^= x >> 8;
        x ^= x >> 4;
        x ^= x >> 2;
        x ^= x >> 1;
        return x & 1;
}

/*
 * Poll gameport; return true if all bits set in 'onbits' are on and
 * all bits set in 'offbits' are off.
 */

static inline int poll_until(u8 onbits, u8 offbits, int u_sec, struct gameport* gp, u8 *data)
{
        int i, nloops;

        nloops = gameport_time(gp, u_sec);
        for (i = 0; i < nloops; i++) {
                *data = gameport_read(gp);
                if ((*data & onbits) == onbits &&
                    (~(*data) & offbits) == offbits)
                        return 1;
        }
        dbg("gameport timed out after %d microseconds.\n", u_sec);
        return 0;
}

/*
 * Gets a 28-bit packet from the multiport.
 *
 * After getting a packet successfully, commands encoded by sendcode may
 * be sent to the multiport.
 *
 * The multiport clock value is reflected in gameport bit B4.
 *
 * Returns a packet status code indicating whether packet is valid, the transfer
 * mode, and any error conditions.
 *
 * sendflags:      current I/O status
 * sendcode:   data to send to the multiport if sendflags is nonzero
 */

static int mp_io(struct gameport* gameport, int sendflags, int sendcode, u32 *packet)
{
        u8  raw_data;            /* raw data from gameport */
        u8  data_mask;           /* packet data bits from raw_data */
        u32 pkt;                 /* packet temporary storage */
        int bits_per_read;       /* num packet bits per gameport read */
        int portvals = 0;        /* used for port value sanity check */
        int i;

        /* Gameport bits B0, B4, B5 should first be off, then B4 should come on. */

        *packet = 0;
        raw_data = gameport_read(gameport);
        if (raw_data & 1)
                return IO_RETRY;

        for (i = 0; i < 64; i++) {
                raw_data = gameport_read(gameport);
                portvals |= 1 << ((raw_data >> 4) & 3); /* Demux B4, B5 */
        }

        if (portvals == 1) {                            /* B4, B5 off */
                raw_data = gameport_read(gameport);
                portvals = raw_data & 0xf0;

                if (raw_data & 0x31)
                        return IO_RESET;
                gameport_trigger(gameport);

                if (!poll_until(0x10, 0, 308, gameport, &raw_data))
                        return IO_RESET;
        } else
                return IO_RETRY;

        /* Determine packet transfer mode and prepare for packet construction. */

        if (raw_data & 0x20) {                 /* 3 data bits/read */
                portvals |= raw_data >> 4;     /* Compare B4-B7 before & after trigger */

                if (portvals != 0xb)
                        return 0;
                data_mask = 7;
                bits_per_read = 3;
                pkt = (PACKET_FULL | PACKET_IO_FAST) >> 28;
        } else {                                 /* 1 data bit/read */
                data_mask = 1;
                bits_per_read = 1;
                pkt = (PACKET_FULL | PACKET_IO_SLOW) >> 28;
        }

        /* Construct a packet.  Final data bits must be zero. */

        while (1) {
                if (!poll_until(0, 0x10, 77, gameport, &raw_data))
                        return IO_RESET;
                raw_data = (raw_data >> 5) & data_mask;

                if (pkt & PACKET_FULL)
                        break;
                pkt = (pkt << bits_per_read) | raw_data;

                if (!poll_until(0x10, 0, 77, gameport, &raw_data))
                        return IO_RESET;
        }

        if (raw_data)
                return IO_RESET;

        /* If 3 bits/read used, drop from 30 bits to 28. */

        if (bits_per_read == 3) {
                pkt = (pkt & 0xffff0000) | ((pkt << 1) & 0xffff);
                pkt = (pkt >> 2) | 0xf0000000;
        }

        if (bit_parity(pkt) == 1)
                return IO_RESET;

        /* Acknowledge packet receipt */

        if (!poll_until(0x30, 0, 77, gameport, &raw_data))
                return IO_RESET;

        raw_data = gameport_read(gameport);

        if (raw_data & 1)
                return IO_RESET;

        gameport_trigger(gameport);

        if (!poll_until(0, 0x20, 77, gameport, &raw_data))
                return IO_RESET;

        /* Return if we just wanted the packet or multiport wants to send more */

        *packet = pkt;
        if ((sendflags == 0) || ((sendflags & IO_RETRY) && !(pkt & PACKET_MP_DONE)))
                return IO_GOT_PACKET;

        if (pkt & PACKET_MP_MORE)
                return IO_GOT_PACKET | IO_RETRY;

        /* Multiport is done sending packets and is ready to receive data */

        if (!poll_until(0x20, 0, 77, gameport, &raw_data))
                return IO_GOT_PACKET | IO_RESET;

        raw_data = gameport_read(gameport);
        if (raw_data & 1)
                return IO_GOT_PACKET | IO_RESET;

        /* Trigger gameport based on bits in sendcode */

        gameport_trigger(gameport);
        do {
                if (!poll_until(0x20, 0x10, 116, gameport, &raw_data))
                        return IO_GOT_PACKET | IO_RESET;

                if (!poll_until(0x30, 0, 193, gameport, &raw_data))
                        return IO_GOT_PACKET | IO_RESET;

                if (raw_data & 1)
                        return IO_GOT_PACKET | IO_RESET;

                if (sendcode & 1)
                        gameport_trigger(gameport);

                sendcode >>= 1;
        } while (sendcode);

        return IO_GOT_PACKET | IO_MODE_FAST;
}

/*
 * Disables and restores interrupts for mp_io(), which does the actual I/O.
 */

static int multiport_io(struct gameport* gameport, int sendflags, int sendcode, u32 *packet)
{
        int status;
        unsigned long flags;

        local_irq_save(flags);
        status = mp_io(gameport, sendflags, sendcode, packet);
        local_irq_restore(flags);

        return status;
}

/*
 * Puts multiport into digital mode.  Multiport LED turns green.
 *
 * Returns true if a valid digital packet was received, false otherwise.
 */

static int dig_mode_start(struct gameport *gameport, u32 *packet)
{
        int i;
        int flags, tries = 0, bads = 0;

        for (i = 0; i < ARRAY_SIZE(init_seq); i++) {     /* Send magic sequence */
                if (init_seq[i])
                        gameport_trigger(gameport);
                udelay(GRIP_INIT_DELAY);
        }

        for (i = 0; i < 16; i++)            /* Wait for multiport to settle */
                udelay(GRIP_INIT_DELAY);

        while (tries < 64 && bads < 8) {    /* Reset multiport and try getting a packet */

                flags = multiport_io(gameport, IO_RESET, 0x27, packet);

                if (flags & IO_MODE_FAST)
                        return 1;

                if (flags & IO_RETRY)
                        tries++;
                else
                        bads++;
        }
        return 0;
}

/*
 * Packet structure: B0-B15   => gamepad state
 *                   B16-B20  => gamepad device type
 *                   B21-B24  => multiport slot index (1-4)
 *
 * Known device types: 0x1f (grip pad), 0x0 (no device).  Others may exist.
 *
 * Returns the packet status.
 */

static int get_and_decode_packet(struct grip_mp *grip, int flags)
{
        struct grip_port *port;
        u32 packet;
        int joytype = 0;
        int slot;

        /* Get a packet and check for validity */

        flags &= IO_RESET | IO_RETRY;
        flags = multiport_io(grip->gameport, flags, 0, &packet);
        grip->reads++;

        if (packet & PACKET_MP_DONE)
                flags |= IO_DONE;

        if (flags && !(flags & IO_GOT_PACKET)) {
                grip->bads++;
                return flags;
        }

        /* Ignore non-gamepad packets, e.g. multiport hardware version */

        slot = ((packet >> 21) & 0xf) - 1;
        if ((slot < 0) || (slot > 3))
                return flags;

        port = grip->port[slot];

        /*
         * Handle "reset" packets, which occur at startup, and when gamepads
         * are removed or plugged in.  May contain configuration of a new gamepad.
         */

        joytype = (packet >> 16) & 0x1f;
        if (!joytype) {

                if (port->registered) {
                        printk(KERN_INFO "grip_mp: removing %s, slot %d\n",
                               grip_name[port->mode], slot);
                        input_unregister_device(port->dev);
                        port->registered = 0;
                }
                dbg("Reset: grip multiport slot %d\n", slot);
                port->mode = GRIP_MODE_RESET;
                flags |= IO_SLOT_CHANGE;
                return flags;
        }

        /* Interpret a grip pad packet */

        if (joytype == 0x1f) {

                int dir = (packet >> 8) & 0xf;          /* eight way directional value */
                port->buttons = (~packet) & 0xff;
                port->yaxes = ((axis_map[dir] >> 2) & 3) - 1;
                port->xaxes = (axis_map[dir] & 3) - 1;
                port->dirty = 1;

                if (port->mode == GRIP_MODE_RESET)
                        flags |= IO_SLOT_CHANGE;

                port->mode = GRIP_MODE_GP;

                if (!port->registered) {
                        dbg("New Grip pad in multiport slot %d.\n", slot);
                        if (register_slot(slot, grip)) {
                                port->mode = GRIP_MODE_RESET;
                                port->dirty = 0;
                        }
                }
                return flags;
        }

        /* Handle non-grip device codes.  For now, just print diagnostics. */

        {
                static int strange_code = 0;
                if (strange_code != joytype) {
                        printk(KERN_INFO "Possible non-grip pad/joystick detected.\n");
                        printk(KERN_INFO "Got joy type 0x%x and packet 0x%x.\n", joytype, packet);
                        strange_code = joytype;
                }
        }
        return flags;
}

/*
 * Returns true if all multiport slot states appear valid.
 */

static int slots_valid(struct grip_mp *grip)
{
        int flags, slot, invalid = 0, active = 0;

        flags = get_and_decode_packet(grip, 0);
        if (!(flags & IO_GOT_PACKET))
                return 0;

        for (slot = 0; slot < 4; slot++) {
                if (grip->port[slot]->mode == GRIP_MODE_RESET)
                        invalid = 1;
                if (grip->port[slot]->mode != GRIP_MODE_NONE)
                        active = 1;
        }

        /* Return true if no active slot but multiport sent all its data */
        if (!active)
                return (flags & IO_DONE) ? 1 : 0;

        /* Return false if invalid device code received */
        return invalid ? 0 : 1;
}

/*
 * Returns whether the multiport was placed into digital mode and
 * able to communicate its state successfully.
 */

static int multiport_init(struct grip_mp *grip)
{
        int dig_mode, initialized = 0, tries = 0;
        u32 packet;

        dig_mode = dig_mode_start(grip->gameport, &packet);
        while (!dig_mode && tries < 4) {
                dig_mode = dig_mode_start(grip->gameport, &packet);
                tries++;
        }

        if (dig_mode)
                dbg("multiport_init(): digital mode activated.\n");
        else {
                dbg("multiport_init(): unable to activate digital mode.\n");
                return 0;
        }

        /* Get packets, store multiport state, and check state's validity */
        for (tries = 0; tries < 4096; tries++) {
                if (slots_valid(grip)) {
                        initialized = 1;
                        break;
                }
        }
        dbg("multiport_init(): initialized == %d\n", initialized);
        return initialized;
}

/*
 * Reports joystick state to the linux input layer.
 */

static void report_slot(struct grip_mp *grip, int slot)
{
        struct grip_port *port = grip->port[slot];
        int i;

        /* Store button states with linux input driver */

        for (i = 0; i < 8; i++)
                input_report_key(port->dev, grip_btn_gp[i], (port->buttons >> i) & 1);

        /* Store axis states with linux driver */

        input_report_abs(port->dev, ABS_X, port->xaxes);
        input_report_abs(port->dev, ABS_Y, port->yaxes);

        /* Tell the receiver of the events to process them */

        input_sync(port->dev);

        port->dirty = 0;
}

/*
 * Get the multiport state.
 */

static void grip_poll(struct gameport *gameport)
{
        struct grip_mp *grip = gameport_get_drvdata(gameport);
        int i, npkts, flags;

        for (npkts = 0; npkts < 4; npkts++) {
                flags = IO_RETRY;
                for (i = 0; i < 32; i++) {
                        flags = get_and_decode_packet(grip, flags);
                        if ((flags & IO_GOT_PACKET) || !(flags & IO_RETRY))
                                break;
                }
                if (flags & IO_DONE)
                        break;
        }

        for (i = 0; i < 4; i++)
                if (grip->port[i]->dirty)
                        report_slot(grip, i);
}

/*
 * Called when a joystick device file is opened
 */

static int grip_open(struct input_dev *dev)
{
        struct grip_mp *grip = input_get_drvdata(dev);

        gameport_start_polling(grip->gameport);
        return 0;
}

/*
 * Called when a joystick device file is closed
 */

static void grip_close(struct input_dev *dev)
{
        struct grip_mp *grip = input_get_drvdata(dev);

        gameport_stop_polling(grip->gameport);
}

/*
 * Tell the linux input layer about a newly plugged-in gamepad.
 */

static int register_slot(int slot, struct grip_mp *grip)
{
        struct grip_port *port = grip->port[slot];
        struct input_dev *input_dev;
        int j, t;
        int err;

        port->dev = input_dev = input_allocate_device();
        if (!input_dev)
                return -ENOMEM;

        input_dev->name = grip_name[port->mode];
        input_dev->id.bustype = BUS_GAMEPORT;
        input_dev->id.vendor = GAMEPORT_ID_VENDOR_GRAVIS;
        input_dev->id.product = 0x0100 + port->mode;
        input_dev->id.version = 0x0100;
        input_dev->dev.parent = &grip->gameport->dev;

        input_set_drvdata(input_dev, grip);

        input_dev->open = grip_open;
        input_dev->close = grip_close;

        input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);

        for (j = 0; (t = grip_abs[port->mode][j]) >= 0; j++)
                input_set_abs_params(input_dev, t, -1, 1, 0, 0);

        for (j = 0; (t = grip_btn[port->mode][j]) >= 0; j++)
                if (t > 0)
                        set_bit(t, input_dev->keybit);

        err = input_register_device(port->dev);
        if (err) {
                input_free_device(port->dev);
                return err;
        }

        port->registered = 1;

        if (port->dirty)                    /* report initial state, if any */
                report_slot(grip, slot);

        return 0;
}

static int grip_connect(struct gameport *gameport, struct gameport_driver *drv)
{
        struct grip_mp *grip;
        int err;

        if (!(grip = kzalloc(sizeof(struct grip_mp), GFP_KERNEL)))
                return -ENOMEM;

        grip->gameport = gameport;

        gameport_set_drvdata(gameport, grip);

        err = gameport_open(gameport, drv, GAMEPORT_MODE_RAW);
        if (err)
                goto fail1;

        gameport_set_poll_handler(gameport, grip_poll);
        gameport_set_poll_interval(gameport, 20);

        if (!multiport_init(grip)) {
                err = -ENODEV;
                goto fail2;
        }

        if (!grip->port[0]->mode && !grip->port[1]->mode && !grip->port[2]->mode && !grip->port[3]->mode) {
                /* nothing plugged in */
                err = -ENODEV;
                goto fail2;
        }

        return 0;

fail2:  gameport_close(gameport);
fail1:  gameport_set_drvdata(gameport, NULL);
        kfree(grip);
        return err;
}

static void grip_disconnect(struct gameport *gameport)
{
        struct grip_mp *grip = gameport_get_drvdata(gameport);
        int i;

        for (i = 0; i < 4; i++)
                if (grip->port[i]->registered)
                        input_unregister_device(grip->port[i]->dev);
        gameport_close(gameport);
        gameport_set_drvdata(gameport, NULL);
        kfree(grip);
}

static struct gameport_driver grip_drv = {
        .driver         = {
                .name   = "grip_mp",
        },
        .description    = DRIVER_DESC,
        .connect        = grip_connect,
        .disconnect     = grip_disconnect,
};

static int __init grip_init(void)
{
        return gameport_register_driver(&grip_drv);
}

static void __exit grip_exit(void)
{
        gameport_unregister_driver(&grip_drv);
}

module_init(grip_init);
module_exit(grip_exit);