root/drivers/input/joystick/zhenhua.c

DEFINITIONS

1. zhenhua_process_packet
2. zhenhua_interrupt
3. zhenhua_disconnect
4. zhenhua_connect

   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 
  43 MODULE_DESCRIPTION(DRIVER_DESC);
  44 MODULE_LICENSE("GPL");
  45 
  46 /*
  47  * Constants.
  48  */
  49 
  50 #define ZHENHUA_MAX_LENGTH 5
  51 
  52 /*
  53  * Zhen Hua data.
  54  */
  55 
  56 struct 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 
  68 static 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 
  87 static 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 
 115 static 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 
 131 static 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 
 182 static 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 
 192 MODULE_DEVICE_TABLE(serio, zhenhua_serio_ids);
 193 
 194 static 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 
 205 module_serio_driver(zhenhua_drv);