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zhenhua.c
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1 /*
2  * derived from "twidjoy.c"
3  *
4  * Copyright (c) 2008 Martin Kebert
5  * Copyright (c) 2001 Arndt Schoenewald
6  * Copyright (c) 2000-2001 Vojtech Pavlik
7  * Copyright (c) 2000 Mark Fletcher
8  *
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 <[email protected]> - but I am not a C-programmer nor kernel
28  * coder :-(
29  */
30 
31 /*
32  * This program is free software; you can redistribute it and/or modify
33  * it under the terms of the GNU General Public License as published by
34  * the Free Software Foundation; either version 2 of the License, or
35  * (at your option) any later version.
36  *
37  * This program is distributed in the hope that it will be useful,
38  * but WITHOUT ANY WARRANTY; without even the implied warranty of
39  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
40  * GNU General Public License for more details.
41  *
42  * You should have received a copy of the GNU General Public License
43  * along with this program; if not, write to the Free Software
44  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
45  */
46 
47 #include <linux/kernel.h>
48 #include <linux/module.h>
49 #include <linux/slab.h>
50 #include <linux/input.h>
51 #include <linux/serio.h>
52 #include <linux/init.h>
53 
54 #define DRIVER_DESC "RC transmitter with 5-byte Zhen Hua protocol joystick driver"
55 
57 MODULE_LICENSE("GPL");
58 
59 /*
60  * Constants.
61  */
62 
63 #define ZHENHUA_MAX_LENGTH 5
64 
65 /*
66  * Zhen Hua data.
67  */
68 
69 struct zhenhua {
70  struct input_dev *dev;
71  int idx;
72  unsigned char data[ZHENHUA_MAX_LENGTH];
73  char phys[32];
74 };
75 
76 
77 /* bits in all incoming bytes needs to be "reversed" */
78 static int zhenhua_bitreverse(int x)
79 {
80  x = ((x & 0xaa) >> 1) | ((x & 0x55) << 1);
81  x = ((x & 0xcc) >> 2) | ((x & 0x33) << 2);
82  x = ((x & 0xf0) >> 4) | ((x & 0x0f) << 4);
83  return x;
84 }
85 
86 /*
87  * zhenhua_process_packet() decodes packets the driver receives from the
88  * RC transmitter. It updates the data accordingly.
89  */
90 
91 static void zhenhua_process_packet(struct zhenhua *zhenhua)
92 {
93  struct input_dev *dev = zhenhua->dev;
94  unsigned char *data = zhenhua->data;
95 
96  input_report_abs(dev, ABS_Y, data[1]);
97  input_report_abs(dev, ABS_X, data[2]);
98  input_report_abs(dev, ABS_RZ, data[3]);
99  input_report_abs(dev, ABS_Z, data[4]);
100 
101  input_sync(dev);
102 }
103 
104 /*
105  * zhenhua_interrupt() is called by the low level driver when characters
106  * are ready for us. We then buffer them for further processing, or call the
107  * packet processing routine.
108  */
109 
110 static irqreturn_t zhenhua_interrupt(struct serio *serio, unsigned char data, unsigned int flags)
111 {
112  struct zhenhua *zhenhua = serio_get_drvdata(serio);
113 
114  /* All Zhen Hua packets are 5 bytes. The fact that the first byte
115  * is allways 0xf7 and all others are in range 0x32 - 0xc8 (50-200)
116  * can be used to check and regain sync. */
117 
118  if (data == 0xef)
119  zhenhua->idx = 0; /* this byte starts a new packet */
120  else if (zhenhua->idx == 0)
121  return IRQ_HANDLED; /* wrong MSB -- ignore this byte */
122 
123  if (zhenhua->idx < ZHENHUA_MAX_LENGTH)
124  zhenhua->data[zhenhua->idx++] = zhenhua_bitreverse(data);
125 
126  if (zhenhua->idx == ZHENHUA_MAX_LENGTH) {
127  zhenhua_process_packet(zhenhua);
128  zhenhua->idx = 0;
129  }
130 
131  return IRQ_HANDLED;
132 }
133 
134 /*
135  * zhenhua_disconnect() is the opposite of zhenhua_connect()
136  */
137 
138 static void zhenhua_disconnect(struct serio *serio)
139 {
140  struct zhenhua *zhenhua = serio_get_drvdata(serio);
141 
142  serio_close(serio);
143  serio_set_drvdata(serio, NULL);
144  input_unregister_device(zhenhua->dev);
145  kfree(zhenhua);
146 }
147 
148 /*
149  * zhenhua_connect() is the routine that is called when someone adds a
150  * new serio device. It looks for the Twiddler, and if found, registers
151  * it as an input device.
152  */
153 
154 static int zhenhua_connect(struct serio *serio, struct serio_driver *drv)
155 {
156  struct zhenhua *zhenhua;
157  struct input_dev *input_dev;
158  int err = -ENOMEM;
159 
160  zhenhua = kzalloc(sizeof(struct zhenhua), GFP_KERNEL);
161  input_dev = input_allocate_device();
162  if (!zhenhua || !input_dev)
163  goto fail1;
164 
165  zhenhua->dev = input_dev;
166  snprintf(zhenhua->phys, sizeof(zhenhua->phys), "%s/input0", serio->phys);
167 
168  input_dev->name = "Zhen Hua 5-byte device";
169  input_dev->phys = zhenhua->phys;
170  input_dev->id.bustype = BUS_RS232;
171  input_dev->id.vendor = SERIO_ZHENHUA;
172  input_dev->id.product = 0x0001;
173  input_dev->id.version = 0x0100;
174  input_dev->dev.parent = &serio->dev;
175 
176  input_dev->evbit[0] = BIT(EV_ABS);
177  input_set_abs_params(input_dev, ABS_X, 50, 200, 0, 0);
178  input_set_abs_params(input_dev, ABS_Y, 50, 200, 0, 0);
179  input_set_abs_params(input_dev, ABS_Z, 50, 200, 0, 0);
180  input_set_abs_params(input_dev, ABS_RZ, 50, 200, 0, 0);
181 
182  serio_set_drvdata(serio, zhenhua);
183 
184  err = serio_open(serio, drv);
185  if (err)
186  goto fail2;
187 
188  err = input_register_device(zhenhua->dev);
189  if (err)
190  goto fail3;
191 
192  return 0;
193 
194  fail3: serio_close(serio);
195  fail2: serio_set_drvdata(serio, NULL);
196  fail1: input_free_device(input_dev);
197  kfree(zhenhua);
198  return err;
199 }
200 
201 /*
202  * The serio driver structure.
203  */
204 
205 static struct serio_device_id zhenhua_serio_ids[] = {
206  {
207  .type = SERIO_RS232,
208  .proto = SERIO_ZHENHUA,
209  .id = SERIO_ANY,
210  .extra = SERIO_ANY,
211  },
212  { 0 }
213 };
214 
215 MODULE_DEVICE_TABLE(serio, zhenhua_serio_ids);
216 
217 static struct serio_driver zhenhua_drv = {
218  .driver = {
219  .name = "zhenhua",
220  },
221  .description = DRIVER_DESC,
222  .id_table = zhenhua_serio_ids,
223  .interrupt = zhenhua_interrupt,
224  .connect = zhenhua_connect,
225  .disconnect = zhenhua_disconnect,
226 };
227 
228 module_serio_driver(zhenhua_drv);