linux/drivers/input/joystick/zhenhua.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 *  derived from "twidjoy.c"
   4 *
   5 *  Copyright (c) 2008 Martin Kebert
   6 *  Copyright (c) 2001 Arndt Schoenewald
   7 *  Copyright (c) 2000-2001 Vojtech Pavlik
   8 *  Copyright (c) 2000 Mark Fletcher
   9 */
  10
  11/*
  12 * Driver to use 4CH RC transmitter using Zhen Hua 5-byte protocol (Walkera Lama,
  13 * EasyCopter etc.) as a joystick under Linux.
  14 *
  15 * RC transmitters using Zhen Hua 5-byte protocol are cheap four channels
  16 * transmitters for control a RC planes or RC helicopters with possibility to
  17 * connect on a serial port.
  18 * Data coming from transmitter is in this order:
  19 * 1. byte = synchronisation byte
  20 * 2. byte = X axis
  21 * 3. byte = Y axis
  22 * 4. byte = RZ axis
  23 * 5. byte = Z axis
  24 * (and this is repeated)
  25 *
  26 * For questions or feedback regarding this driver module please contact:
  27 * Martin Kebert <gkmarty@gmail.com> - but I am not a C-programmer nor kernel
  28 * coder :-(
  29 */
  30
  31/*
  32 */
  33
  34#include <linux/kernel.h>
  35#include <linux/module.h>
  36#include <linux/slab.h>
  37#include <linux/bitrev.h>
  38#include <linux/input.h>
  39#include <linux/serio.h>
  40
  41#define DRIVER_DESC     "RC transmitter with 5-byte Zhen Hua protocol joystick driver"
  42
  43MODULE_DESCRIPTION(DRIVER_DESC);
  44MODULE_LICENSE("GPL");
  45
  46/*
  47 * Constants.
  48 */
  49
  50#define ZHENHUA_MAX_LENGTH 5
  51
  52/*
  53 * Zhen Hua data.
  54 */
  55
  56struct zhenhua {
  57        struct input_dev *dev;
  58        int idx;
  59        unsigned char data[ZHENHUA_MAX_LENGTH];
  60        char phys[32];
  61};
  62
  63/*
  64 * zhenhua_process_packet() decodes packets the driver receives from the
  65 * RC transmitter. It updates the data accordingly.
  66 */
  67
  68static void zhenhua_process_packet(struct zhenhua *zhenhua)
  69{
  70        struct input_dev *dev = zhenhua->dev;
  71        unsigned char *data = zhenhua->data;
  72
  73        input_report_abs(dev, ABS_Y, data[1]);
  74        input_report_abs(dev, ABS_X, data[2]);
  75        input_report_abs(dev, ABS_RZ, data[3]);
  76        input_report_abs(dev, ABS_Z, data[4]);
  77
  78        input_sync(dev);
  79}
  80
  81/*
  82 * zhenhua_interrupt() is called by the low level driver when characters
  83 * are ready for us. We then buffer them for further processing, or call the
  84 * packet processing routine.
  85 */
  86
  87static irqreturn_t zhenhua_interrupt(struct serio *serio, unsigned char data, unsigned int flags)
  88{
  89        struct zhenhua *zhenhua = serio_get_drvdata(serio);
  90
  91        /* All Zhen Hua packets are 5 bytes. The fact that the first byte
  92         * is allways 0xf7 and all others are in range 0x32 - 0xc8 (50-200)
  93         * can be used to check and regain sync. */
  94
  95        if (data == 0xef)
  96                zhenhua->idx = 0;       /* this byte starts a new packet */
  97        else if (zhenhua->idx == 0)
  98                return IRQ_HANDLED;     /* wrong MSB -- ignore this byte */
  99
 100        if (zhenhua->idx < ZHENHUA_MAX_LENGTH)
 101                zhenhua->data[zhenhua->idx++] = bitrev8(data);
 102
 103        if (zhenhua->idx == ZHENHUA_MAX_LENGTH) {
 104                zhenhua_process_packet(zhenhua);
 105                zhenhua->idx = 0;
 106        }
 107
 108        return IRQ_HANDLED;
 109}
 110
 111/*
 112 * zhenhua_disconnect() is the opposite of zhenhua_connect()
 113 */
 114
 115static void zhenhua_disconnect(struct serio *serio)
 116{
 117        struct zhenhua *zhenhua = serio_get_drvdata(serio);
 118
 119        serio_close(serio);
 120        serio_set_drvdata(serio, NULL);
 121        input_unregister_device(zhenhua->dev);
 122        kfree(zhenhua);
 123}
 124
 125/*
 126 * zhenhua_connect() is the routine that is called when someone adds a
 127 * new serio device. It looks for the Twiddler, and if found, registers
 128 * it as an input device.
 129 */
 130
 131static int zhenhua_connect(struct serio *serio, struct serio_driver *drv)
 132{
 133        struct zhenhua *zhenhua;
 134        struct input_dev *input_dev;
 135        int err = -ENOMEM;
 136
 137        zhenhua = kzalloc(sizeof(struct zhenhua), GFP_KERNEL);
 138        input_dev = input_allocate_device();
 139        if (!zhenhua || !input_dev)
 140                goto fail1;
 141
 142        zhenhua->dev = input_dev;
 143        snprintf(zhenhua->phys, sizeof(zhenhua->phys), "%s/input0", serio->phys);
 144
 145        input_dev->name = "Zhen Hua 5-byte device";
 146        input_dev->phys = zhenhua->phys;
 147        input_dev->id.bustype = BUS_RS232;
 148        input_dev->id.vendor = SERIO_ZHENHUA;
 149        input_dev->id.product = 0x0001;
 150        input_dev->id.version = 0x0100;
 151        input_dev->dev.parent = &serio->dev;
 152
 153        input_dev->evbit[0] = BIT(EV_ABS);
 154        input_set_abs_params(input_dev, ABS_X, 50, 200, 0, 0);
 155        input_set_abs_params(input_dev, ABS_Y, 50, 200, 0, 0);
 156        input_set_abs_params(input_dev, ABS_Z, 50, 200, 0, 0);
 157        input_set_abs_params(input_dev, ABS_RZ, 50, 200, 0, 0);
 158
 159        serio_set_drvdata(serio, zhenhua);
 160
 161        err = serio_open(serio, drv);
 162        if (err)
 163                goto fail2;
 164
 165        err = input_register_device(zhenhua->dev);
 166        if (err)
 167                goto fail3;
 168
 169        return 0;
 170
 171 fail3: serio_close(serio);
 172 fail2: serio_set_drvdata(serio, NULL);
 173 fail1: input_free_device(input_dev);
 174        kfree(zhenhua);
 175        return err;
 176}
 177
 178/*
 179 * The serio driver structure.
 180 */
 181
 182static const struct serio_device_id zhenhua_serio_ids[] = {
 183        {
 184                .type   = SERIO_RS232,
 185                .proto  = SERIO_ZHENHUA,
 186                .id     = SERIO_ANY,
 187                .extra  = SERIO_ANY,
 188        },
 189        { 0 }
 190};
 191
 192MODULE_DEVICE_TABLE(serio, zhenhua_serio_ids);
 193
 194static struct serio_driver zhenhua_drv = {
 195        .driver         = {
 196                .name   = "zhenhua",
 197        },
 198        .description    = DRIVER_DESC,
 199        .id_table       = zhenhua_serio_ids,
 200        .interrupt      = zhenhua_interrupt,
 201        .connect        = zhenhua_connect,
 202        .disconnect     = zhenhua_disconnect,
 203};
 204
 205module_serio_driver(zhenhua_drv);
 206