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 #include <linux/kernel.h> 32 #include <linux/module.h> 33 #include <linux/slab.h> 34 #include <linux/bitrev.h> 35 #include <linux/input.h> 36 #include <linux/serio.h> 37 38 #define DRIVER_DESC "RC transmitter with 5-byte Zhen Hua protocol joystick driver" 39 40 MODULE_DESCRIPTION(DRIVER_DESC); 41 MODULE_LICENSE("GPL"); 42 43 /* 44 * Constants. 45 */ 46 47 #define ZHENHUA_MAX_LENGTH 5 48 49 /* 50 * Zhen Hua data. 51 */ 52 53 struct zhenhua { 54 struct input_dev *dev; 55 int idx; 56 unsigned char data[ZHENHUA_MAX_LENGTH]; 57 char phys[32]; 58 }; 59 60 /* 61 * zhenhua_process_packet() decodes packets the driver receives from the 62 * RC transmitter. It updates the data accordingly. 63 */ 64 65 static void zhenhua_process_packet(struct zhenhua *zhenhua) 66 { 67 struct input_dev *dev = zhenhua->dev; 68 unsigned char *data = zhenhua->data; 69 70 input_report_abs(dev, ABS_Y, data[1]); 71 input_report_abs(dev, ABS_X, data[2]); 72 input_report_abs(dev, ABS_RZ, data[3]); 73 input_report_abs(dev, ABS_Z, data[4]); 74 75 input_sync(dev); 76 } 77 78 /* 79 * zhenhua_interrupt() is called by the low level driver when characters 80 * are ready for us. We then buffer them for further processing, or call the 81 * packet processing routine. 82 */ 83 84 static irqreturn_t zhenhua_interrupt(struct serio *serio, unsigned char data, unsigned int flags) 85 { 86 struct zhenhua *zhenhua = serio_get_drvdata(serio); 87 88 /* All Zhen Hua packets are 5 bytes. The fact that the first byte 89 * is allways 0xf7 and all others are in range 0x32 - 0xc8 (50-200) 90 * can be used to check and regain sync. */ 91 92 if (data == 0xef) 93 zhenhua->idx = 0; /* this byte starts a new packet */ 94 else if (zhenhua->idx == 0) 95 return IRQ_HANDLED; /* wrong MSB -- ignore this byte */ 96 97 if (zhenhua->idx < ZHENHUA_MAX_LENGTH) 98 zhenhua->data[zhenhua->idx++] = bitrev8(data); 99 100 if (zhenhua->idx == ZHENHUA_MAX_LENGTH) { 101 zhenhua_process_packet(zhenhua); 102 zhenhua->idx = 0; 103 } 104 105 return IRQ_HANDLED; 106 } 107 108 /* 109 * zhenhua_disconnect() is the opposite of zhenhua_connect() 110 */ 111 112 static void zhenhua_disconnect(struct serio *serio) 113 { 114 struct zhenhua *zhenhua = serio_get_drvdata(serio); 115 116 serio_close(serio); 117 serio_set_drvdata(serio, NULL); 118 input_unregister_device(zhenhua->dev); 119 kfree(zhenhua); 120 } 121 122 /* 123 * zhenhua_connect() is the routine that is called when someone adds a 124 * new serio device. It looks for the Twiddler, and if found, registers 125 * it as an input device. 126 */ 127 128 static int zhenhua_connect(struct serio *serio, struct serio_driver *drv) 129 { 130 struct zhenhua *zhenhua; 131 struct input_dev *input_dev; 132 int err = -ENOMEM; 133 134 zhenhua = kzalloc(sizeof(struct zhenhua), GFP_KERNEL); 135 input_dev = input_allocate_device(); 136 if (!zhenhua || !input_dev) 137 goto fail1; 138 139 zhenhua->dev = input_dev; 140 snprintf(zhenhua->phys, sizeof(zhenhua->phys), "%s/input0", serio->phys); 141 142 input_dev->name = "Zhen Hua 5-byte device"; 143 input_dev->phys = zhenhua->phys; 144 input_dev->id.bustype = BUS_RS232; 145 input_dev->id.vendor = SERIO_ZHENHUA; 146 input_dev->id.product = 0x0001; 147 input_dev->id.version = 0x0100; 148 input_dev->dev.parent = &serio->dev; 149 150 input_dev->evbit[0] = BIT(EV_ABS); 151 input_set_abs_params(input_dev, ABS_X, 50, 200, 0, 0); 152 input_set_abs_params(input_dev, ABS_Y, 50, 200, 0, 0); 153 input_set_abs_params(input_dev, ABS_Z, 50, 200, 0, 0); 154 input_set_abs_params(input_dev, ABS_RZ, 50, 200, 0, 0); 155 156 serio_set_drvdata(serio, zhenhua); 157 158 err = serio_open(serio, drv); 159 if (err) 160 goto fail2; 161 162 err = input_register_device(zhenhua->dev); 163 if (err) 164 goto fail3; 165 166 return 0; 167 168 fail3: serio_close(serio); 169 fail2: serio_set_drvdata(serio, NULL); 170 fail1: input_free_device(input_dev); 171 kfree(zhenhua); 172 return err; 173 } 174 175 /* 176 * The serio driver structure. 177 */ 178 179 static const struct serio_device_id zhenhua_serio_ids[] = { 180 { 181 .type = SERIO_RS232, 182 .proto = SERIO_ZHENHUA, 183 .id = SERIO_ANY, 184 .extra = SERIO_ANY, 185 }, 186 { 0 } 187 }; 188 189 MODULE_DEVICE_TABLE(serio, zhenhua_serio_ids); 190 191 static struct serio_driver zhenhua_drv = { 192 .driver = { 193 .name = "zhenhua", 194 }, 195 .description = DRIVER_DESC, 196 .id_table = zhenhua_serio_ids, 197 .interrupt = zhenhua_interrupt, 198 .connect = zhenhua_connect, 199 .disconnect = zhenhua_disconnect, 200 }; 201 202 module_serio_driver(zhenhua_drv); 203