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); 206