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 RC5X_SPACE              SPACE(4)
  29 #define RC5_UNIT                888888 /* ns */
  30
  31 /* Used to register rc5_decoder clients */
  32 static LIST_HEAD(decoder_list);
  33 static DEFINE_SPINLOCK(decoder_lock);
  34
  35 enum rc5_state {
  36         STATE_INACTIVE,
  37         STATE_BIT_START,
  38         STATE_BIT_END,
  39         STATE_CHECK_RC5X,
  40         STATE_FINISHED,
  41 };
  42
  43 struct decoder_data {
  44         struct list_head        list;
  45         struct ir_input_dev     *ir_dev;
  46         int                     enabled:1;
  47
  48         /* State machine control */
  49         enum rc5_state          state;
  50         u32                     rc5_bits;
  51         int                     last_unit;
  52         unsigned                count;
  53         unsigned                wanted_bits;
  54 };
  55
  56
  57 /**
  58  * get_decoder_data()   - gets decoder data
  59  * @input_dev:  input device
  60  *
  61  * Returns the struct decoder_data that corresponds to a device
  62  */
  63
  64 static struct decoder_data *get_decoder_data(struct  ir_input_dev *ir_dev)
  65 {
  66         struct decoder_data *data = NULL;
  67
  68         spin_lock(&decoder_lock);
  69         list_for_each_entry(data, &decoder_list, list) {
  70                 if (data->ir_dev == ir_dev)
  71                         break;
  72         }
  73         spin_unlock(&decoder_lock);
  74         return data;
  75 }
  76
  77 static ssize_t store_enabled(struct device *d,
  78                              struct device_attribute *mattr,
  79                              const char *buf,
  80                              size_t len)
  81 {
  82         unsigned long value;
  83         struct ir_input_dev *ir_dev = dev_get_drvdata(d);
  84         struct decoder_data *data = get_decoder_data(ir_dev);
  85
  86         if (!data)
  87                 return -EINVAL;
  88
  89         if (strict_strtoul(buf, 10, &value) || value > 1)
  90                 return -EINVAL;
  91
  92         data->enabled = value;
  93
  94         return len;
  95 }
  96
  97 static ssize_t show_enabled(struct device *d,
  98                              struct device_attribute *mattr, char *buf)
  99 {
 100         struct ir_input_dev *ir_dev = dev_get_drvdata(d);
 101         struct decoder_data *data = get_decoder_data(ir_dev);
 102
 103         if (!data)
 104                 return -EINVAL;
 105
 106         if (data->enabled)
 107                 return sprintf(buf, "1\n");
 108         else
 109         return sprintf(buf, "0\n");
 110 }
 111
 112 static DEVICE_ATTR(enabled, S_IRUGO | S_IWUSR, show_enabled, store_enabled);
 113
 114 static struct attribute *decoder_attributes[] = {
 115         &dev_attr_enabled.attr,
 116         NULL
 117 };
 118
 119 static struct attribute_group decoder_attribute_group = {
 120         .name   = "rc5_decoder",
 121         .attrs  = decoder_attributes,
 122 };
 123
 124 /**
 125  * ir_rc5_decode() - Decode one RC-5 pulse or space
 126  * @input_dev:  the struct input_dev descriptor of the device
 127  * @duration:   duration of pulse/space in ns
 128  *
 129  * This function returns -EINVAL if the pulse violates the state machine
 130  */
 131 static int ir_rc5_decode(struct input_dev *input_dev, s64 duration)
 132 {
 133         struct decoder_data *data;
 134         struct ir_input_dev *ir_dev = input_get_drvdata(input_dev);
 135         u8 toggle;
 136         u32 scancode;
 137         int u;
 138
 139         data = get_decoder_data(ir_dev);
 140         if (!data)
 141                 return -EINVAL;
 142
 143         if (!data->enabled)
 144                 return 0;
 145
 146         if (IS_RESET(duration)) {
 147                 data->state = STATE_INACTIVE;
 148                 return 0;
 149         }
 150
 151         u = TO_UNITS(duration, RC5_UNIT);
 152         if (DURATION(u) == 0)
 153                 goto out;
 154
 155 again:
 156         IR_dprintk(2, "RC5(x) decode started at state %i (%i units, %ius)\n",
 157                    data->state, u, TO_US(duration));
 158
 159         if (DURATION(u) == 0 && data->state != STATE_FINISHED)
 160                 return 0;
 161
 162         switch (data->state) {
 163
 164         case STATE_INACTIVE:
 165                 if (IS_PULSE(u)) {
 166                         data->state = STATE_BIT_START;
 167                         data->count = 1;
 168                         /* We just need enough bits to get to STATE_CHECK_RC5X */
 169                         data->wanted_bits = RC5X_NBITS;
 170                         DECREASE_DURATION(u, 1);
 171                         goto again;
 172                 }
 173                 break;
 174
 175         case STATE_BIT_START:
 176                 if (DURATION(u) == 1) {
 177                         data->rc5_bits <<= 1;
 178                         if (IS_SPACE(u))
 179                                 data->rc5_bits |= 1;
 180                         data->count++;
 181                         data->last_unit = u;
 182
 183                         /*
 184                          * If the last bit is zero, a space will merge
 185                          * with the silence after the command.
 186                          */
 187                         if (IS_PULSE(u) && data->count == data->wanted_bits) {
 188                                 data->state = STATE_FINISHED;
 189                                 goto again;
 190                         }
 191
 192                         data->state = STATE_BIT_END;
 193                         return 0;
 194                 }
 195                 break;
 196
 197         case STATE_BIT_END:
 198                 if (IS_TRANSITION(u, data->last_unit)) {
 199                         if (data->count == data->wanted_bits)
 200                                 data->state = STATE_FINISHED;
 201                         else if (data->count == CHECK_RC5X_NBITS)
 202                                 data->state = STATE_CHECK_RC5X;
 203                         else
 204                                 data->state = STATE_BIT_START;
 205
 206                         DECREASE_DURATION(u, 1);
 207                         goto again;
 208                 }
 209                 break;
 210
 211         case STATE_CHECK_RC5X:
 212                 if (IS_SPACE(u) && DURATION(u) >= DURATION(RC5X_SPACE)) {
 213                         /* RC5X */
 214                         data->wanted_bits = RC5X_NBITS;
 215                         DECREASE_DURATION(u, DURATION(RC5X_SPACE));
 216                 } else {
 217                         /* RC5 */
 218                         data->wanted_bits = RC5_NBITS;
 219                 }
 220                 data->state = STATE_BIT_START;
 221                 goto again;
 222
 223         case STATE_FINISHED:
 224                 if (data->wanted_bits == RC5X_NBITS) {
 225                         /* RC5X */
 226                         u8 xdata, command, system;
 227                         xdata    = (data->rc5_bits & 0x0003F) >> 0;
 228                         command  = (data->rc5_bits & 0x00FC0) >> 6;
 229                         system   = (data->rc5_bits & 0x1F000) >> 12;
 230                         toggle   = (data->rc5_bits & 0x20000) ? 1 : 0;
 231                         command += (data->rc5_bits & 0x01000) ? 0 : 0x40;
 232                         scancode = system << 16 | command << 8 | xdata;
 233
 234                         IR_dprintk(1, "RC5X scancode 0x%06x (toggle: %u)\n",
 235                                    scancode, toggle);
 236
 237                 } else {
 238                         /* RC5 */
 239                         u8 command, system;
 240                         command  = (data->rc5_bits & 0x0003F) >> 0;
 241                         system   = (data->rc5_bits & 0x007C0) >> 6;
 242                         toggle   = (data->rc5_bits & 0x00800) ? 1 : 0;
 243                         command += (data->rc5_bits & 0x01000) ? 0 : 0x40;
 244                         scancode = system << 8 | command;
 245
 246                         IR_dprintk(1, "RC5 scancode 0x%04x (toggle: %u)\n",
 247                                    scancode, toggle);
 248                 }
 249
 250                 ir_keydown(input_dev, scancode, toggle);
 251                 data->state = STATE_INACTIVE;
 252                 return 0;
 253         }
 254
 255 out:
 256         IR_dprintk(1, "RC5(x) decode failed at state %i (%i units, %ius)\n",
 257                    data->state, u, TO_US(duration));
 258         data->state = STATE_INACTIVE;
 259         return -EINVAL;
 260 }
 261
 262 static int ir_rc5_register(struct input_dev *input_dev)
 263 {
 264         struct ir_input_dev *ir_dev = input_get_drvdata(input_dev);
 265         struct decoder_data *data;
 266         int rc;
 267
 268         rc = sysfs_create_group(&ir_dev->dev.kobj, &decoder_attribute_group);
 269         if (rc < 0)
 270                 return rc;
 271
 272         data = kzalloc(sizeof(*data), GFP_KERNEL);
 273         if (!data) {
 274                 sysfs_remove_group(&ir_dev->dev.kobj, &decoder_attribute_group);
 275                 return -ENOMEM;
 276         }
 277
 278         data->ir_dev = ir_dev;
 279         data->enabled = 1;
 280
 281         spin_lock(&decoder_lock);
 282         list_add_tail(&data->list, &decoder_list);
 283         spin_unlock(&decoder_lock);
 284
 285         return 0;
 286 }
 287
 288 static int ir_rc5_unregister(struct input_dev *input_dev)
 289 {
 290         struct ir_input_dev *ir_dev = input_get_drvdata(input_dev);
 291         static struct decoder_data *data;
 292
 293         data = get_decoder_data(ir_dev);
 294         if (!data)
 295                 return 0;
 296
 297         sysfs_remove_group(&ir_dev->dev.kobj, &decoder_attribute_group);
 298
 299         spin_lock(&decoder_lock);
 300         list_del(&data->list);
 301         spin_unlock(&decoder_lock);
 302
 303         return 0;
 304 }
 305
 306 static struct ir_raw_handler rc5_handler = {
 307         .decode         = ir_rc5_decode,
 308         .raw_register   = ir_rc5_register,
 309         .raw_unregister = ir_rc5_unregister,
 310 };
 311
 312 static int __init ir_rc5_decode_init(void)
 313 {
 314         ir_raw_handler_register(&rc5_handler);
 315
 316         printk(KERN_INFO "IR RC5(x) protocol handler initialized\n");
 317         return 0;
 318 }
 319
 320 static void __exit ir_rc5_decode_exit(void)
 321 {
 322         ir_raw_handler_unregister(&rc5_handler);
 323 }
 324
 325 module_init(ir_rc5_decode_init);
 326 module_exit(ir_rc5_decode_exit);
 327
 328 MODULE_LICENSE("GPL");
 329 MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@redhat.com>");
 330 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
 331 MODULE_DESCRIPTION("RC5(x) IR protocol decoder");