drivers/media/IR/ir-rc5-decoder.c

   1 /* ir-rc5-decoder.c - handle RC5(x) IR Pulse/Space protocol
   2  *
   3  * Copyright (C) 2010 by Mauro Carvalho Chehab <mchehab@redhat.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  *  it under the terms of the GNU General Public License as published by
   7  *  the Free Software Foundation version 2 of the License.
   8  *
   9  *  This program is distributed in the hope that it will be useful,
  10  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  *  GNU General Public License for more details.
  13  */
  14
  15 /*
  16  * This code handles 14 bits RC5 protocols and 20 bits RC5x protocols.
  17  * There are other variants that use a different number of bits.
  18  * This is currently unsupported.
  19  * It considers a carrier of 36 kHz, with a total of 14/20 bits, where
  20  * the first two bits are start bits, and a third one is a filing bit
  21  */
  22
  23 #include "ir-core-priv.h"
  24
  25 #define RC5_NBITS               14
  26 #define RC5X_NBITS              20
  27 #define CHECK_RC5X_NBITS        8
  28 #define RC5_UNIT                888888 /* ns */
  29 #define RC5_BIT_START           (1 * RC5_UNIT)
  30 #define RC5_BIT_END             (1 * RC5_UNIT)
  31 #define RC5X_SPACE              (4 * RC5_UNIT)
  32
  33 /* Used to register rc5_decoder clients */
  34 static LIST_HEAD(decoder_list);
  35 static DEFINE_SPINLOCK(decoder_lock);
  36
  37 enum rc5_state {
  38         STATE_INACTIVE,
  39         STATE_BIT_START,
  40         STATE_BIT_END,
  41         STATE_CHECK_RC5X,
  42         STATE_FINISHED,
  43 };
  44
  45 struct decoder_data {
  46         struct list_head        list;
  47         struct ir_input_dev     *ir_dev;
  48         int                     enabled:1;
  49
  50         /* State machine control */
  51         enum rc5_state          state;
  52         u32                     rc5_bits;
  53         struct ir_raw_event     prev_ev;
  54         unsigned                count;
  55         unsigned                wanted_bits;
  56 };
  57
  58
  59 /**
  60  * get_decoder_data()   - gets decoder data
  61  * @input_dev:  input device
  62  *
  63  * Returns the struct decoder_data that corresponds to a device
  64  */
  65
  66 static struct decoder_data *get_decoder_data(struct  ir_input_dev *ir_dev)
  67 {
  68         struct decoder_data *data = NULL;
  69
  70         spin_lock(&decoder_lock);
  71         list_for_each_entry(data, &decoder_list, list) {
  72                 if (data->ir_dev == ir_dev)
  73                         break;
  74         }
  75         spin_unlock(&decoder_lock);
  76         return data;
  77 }
  78
  79 static ssize_t store_enabled(struct device *d,
  80                              struct device_attribute *mattr,
  81                              const char *buf,
  82                              size_t len)
  83 {
  84         unsigned long value;
  85         struct ir_input_dev *ir_dev = dev_get_drvdata(d);
  86         struct decoder_data *data = get_decoder_data(ir_dev);
  87
  88         if (!data)
  89                 return -EINVAL;
  90
  91         if (strict_strtoul(buf, 10, &value) || value > 1)
  92                 return -EINVAL;
  93
  94         data->enabled = value;
  95
  96         return len;
  97 }
  98
  99 static ssize_t show_enabled(struct device *d,
 100                              struct device_attribute *mattr, char *buf)
 101 {
 102         struct ir_input_dev *ir_dev = dev_get_drvdata(d);
 103         struct decoder_data *data = get_decoder_data(ir_dev);
 104
 105         if (!data)
 106                 return -EINVAL;
 107
 108         if (data->enabled)
 109                 return sprintf(buf, "1\n");
 110         else
 111         return sprintf(buf, "0\n");
 112 }
 113
 114 static DEVICE_ATTR(enabled, S_IRUGO | S_IWUSR, show_enabled, store_enabled);
 115
 116 static struct attribute *decoder_attributes[] = {
 117         &dev_attr_enabled.attr,
 118         NULL
 119 };
 120
 121 static struct attribute_group decoder_attribute_group = {
 122         .name   = "rc5_decoder",
 123         .attrs  = decoder_attributes,
 124 };
 125
 126 /**
 127  * ir_rc5_decode() - Decode one RC-5 pulse or space
 128  * @input_dev:  the struct input_dev descriptor of the device
 129  * @ev:         the struct ir_raw_event descriptor of the pulse/space
 130  *
 131  * This function returns -EINVAL if the pulse violates the state machine
 132  */
 133 static int ir_rc5_decode(struct input_dev *input_dev, struct ir_raw_event ev)
 134 {
 135         struct decoder_data *data;
 136         struct ir_input_dev *ir_dev = input_get_drvdata(input_dev);
 137         u8 toggle;
 138         u32 scancode;
 139
 140         data = get_decoder_data(ir_dev);
 141         if (!data)
 142                 return -EINVAL;
 143
 144         if (!data->enabled)
 145                 return 0;
 146
 147         if (IS_RESET(ev)) {
 148                 data->state = STATE_INACTIVE;
 149                 return 0;
 150         }
 151
 152         if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
 153                 goto out;
 154
 155 again:
 156         IR_dprintk(2, "RC5(x) decode started at state %i (%uus %s)\n",
 157                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 158
 159         if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
 160                 return 0;
 161
 162         switch (data->state) {
 163
 164         case STATE_INACTIVE:
 165                 if (!ev.pulse)
 166                         break;
 167
 168                 data->state = STATE_BIT_START;
 169                 data->count = 1;
 170                 /* We just need enough bits to get to STATE_CHECK_RC5X */
 171                 data->wanted_bits = RC5X_NBITS;
 172                 decrease_duration(&ev, RC5_BIT_START);
 173                 goto again;
 174
 175         case STATE_BIT_START:
 176                 if (!eq_margin(ev.duration, RC5_BIT_START, RC5_UNIT / 2))
 177                         break;
 178
 179                 data->rc5_bits <<= 1;
 180                 if (!ev.pulse)
 181                         data->rc5_bits |= 1;
 182                 data->count++;
 183                 data->prev_ev = ev;
 184                 data->state = STATE_BIT_END;
 185                 return 0;
 186
 187         case STATE_BIT_END:
 188                 if (!is_transition(&ev, &data->prev_ev))
 189                         break;
 190
 191                 if (data->count == data->wanted_bits)
 192                         data->state = STATE_FINISHED;
 193                 else if (data->count == CHECK_RC5X_NBITS)
 194                         data->state = STATE_CHECK_RC5X;
 195                 else
 196                         data->state = STATE_BIT_START;
 197
 198                 decrease_duration(&ev, RC5_BIT_END);
 199                 goto again;
 200
 201         case STATE_CHECK_RC5X:
 202                 if (!ev.pulse && geq_margin(ev.duration, RC5X_SPACE, RC5_UNIT / 2)) {
 203                         /* RC5X */
 204                         data->wanted_bits = RC5X_NBITS;
 205                         decrease_duration(&ev, RC5X_SPACE);
 206                 } else {
 207                         /* RC5 */
 208                         data->wanted_bits = RC5_NBITS;
 209                 }
 210                 data->state = STATE_BIT_START;
 211                 goto again;
 212
 213         case STATE_FINISHED:
 214                 if (ev.pulse)
 215                         break;
 216
 217                 if (data->wanted_bits == RC5X_NBITS) {
 218                         /* RC5X */
 219                         u8 xdata, command, system;
 220                         xdata    = (data->rc5_bits & 0x0003F) >> 0;
 221                         command  = (data->rc5_bits & 0x00FC0) >> 6;
 222                         system   = (data->rc5_bits & 0x1F000) >> 12;
 223                         toggle   = (data->rc5_bits & 0x20000) ? 1 : 0;
 224                         command += (data->rc5_bits & 0x01000) ? 0 : 0x40;
 225                         scancode = system << 16 | command << 8 | xdata;
 226
 227                         IR_dprintk(1, "RC5X scancode 0x%06x (toggle: %u)\n",
 228                                    scancode, toggle);
 229
 230                 } else {
 231                         /* RC5 */
 232                         u8 command, system;
 233                         command  = (data->rc5_bits & 0x0003F) >> 0;
 234                         system   = (data->rc5_bits & 0x007C0) >> 6;
 235                         toggle   = (data->rc5_bits & 0x00800) ? 1 : 0;
 236                         command += (data->rc5_bits & 0x01000) ? 0 : 0x40;
 237                         scancode = system << 8 | command;
 238
 239                         IR_dprintk(1, "RC5 scancode 0x%04x (toggle: %u)\n",
 240                                    scancode, toggle);
 241                 }
 242
 243                 ir_keydown(input_dev, scancode, toggle);
 244                 data->state = STATE_INACTIVE;
 245                 return 0;
 246         }
 247
 248 out:
 249         IR_dprintk(1, "RC5(x) decode failed at state %i (%uus %s)\n",
 250                    data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 251         data->state = STATE_INACTIVE;
 252         return -EINVAL;
 253 }
 254
 255 static int ir_rc5_register(struct input_dev *input_dev)
 256 {
 257         struct ir_input_dev *ir_dev = input_get_drvdata(input_dev);
 258         struct decoder_data *data;
 259         int rc;
 260
 261         rc = sysfs_create_group(&ir_dev->dev.kobj, &decoder_attribute_group);
 262         if (rc < 0)
 263                 return rc;
 264
 265         data = kzalloc(sizeof(*data), GFP_KERNEL);
 266         if (!data) {
 267                 sysfs_remove_group(&ir_dev->dev.kobj, &decoder_attribute_group);
 268                 return -ENOMEM;
 269         }
 270
 271         data->ir_dev = ir_dev;
 272         data->enabled = 1;
 273
 274         spin_lock(&decoder_lock);
 275         list_add_tail(&data->list, &decoder_list);
 276         spin_unlock(&decoder_lock);
 277
 278         return 0;
 279 }
 280
 281 static int ir_rc5_unregister(struct input_dev *input_dev)
 282 {
 283         struct ir_input_dev *ir_dev = input_get_drvdata(input_dev);
 284         static struct decoder_data *data;
 285
 286         data = get_decoder_data(ir_dev);
 287         if (!data)
 288                 return 0;
 289
 290         sysfs_remove_group(&ir_dev->dev.kobj, &decoder_attribute_group);
 291
 292         spin_lock(&decoder_lock);
 293         list_del(&data->list);
 294         spin_unlock(&decoder_lock);
 295
 296         return 0;
 297 }
 298
 299 static struct ir_raw_handler rc5_handler = {
 300         .decode         = ir_rc5_decode,
 301         .raw_register   = ir_rc5_register,
 302         .raw_unregister = ir_rc5_unregister,
 303 };
 304
 305 static int __init ir_rc5_decode_init(void)
 306 {
 307         ir_raw_handler_register(&rc5_handler);
 308
 309         printk(KERN_INFO "IR RC5(x) protocol handler initialized\n");
 310         return 0;
 311 }
 312
 313 static void __exit ir_rc5_decode_exit(void)
 314 {
 315         ir_raw_handler_unregister(&rc5_handler);
 316 }
 317
 318 module_init(ir_rc5_decode_init);
 319 module_exit(ir_rc5_decode_exit);
 320
 321 MODULE_LICENSE("GPL");
 322 MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@redhat.com>");
 323 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
 324 MODULE_DESCRIPTION("RC5(x) IR protocol decoder");