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
40MODULE_DESCRIPTION(DRIVER_DESC);
41MODULE_LICENSE("GPL");
42
43/*
44 * Constants.
45 */
46
47#define ZHENHUA_MAX_LENGTH 5
48
49/*
50 * Zhen Hua data.
51 */
52
53struct 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
65static 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
84static 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
112static 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
128static 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
179static 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
189MODULE_DEVICE_TABLE(serio, zhenhua_serio_ids);
190
191static 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
202module_serio_driver(zhenhua_drv);
203