drivers/media/rc/ir-nec-decoder.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 // ir-nec-decoder.c - handle NEC IR Pulse/Space protocol
   3 //
   4 // Copyright (C) 2010 by Mauro Carvalho Chehab
   5
   6 #include <linux/bitrev.h>
   7 #include <linux/module.h>
   8 #include "rc-core-priv.h"
   9
  10 #define NEC_NBITS               32
  11 #define NEC_UNIT                562500  /* ns */
  12 #define NEC_HEADER_PULSE        (16 * NEC_UNIT)
  13 #define NECX_HEADER_PULSE       (8  * NEC_UNIT) /* Less common NEC variant */
  14 #define NEC_HEADER_SPACE        (8  * NEC_UNIT)
  15 #define NEC_REPEAT_SPACE        (4  * NEC_UNIT)
  16 #define NEC_BIT_PULSE           (1  * NEC_UNIT)
  17 #define NEC_BIT_0_SPACE         (1  * NEC_UNIT)
  18 #define NEC_BIT_1_SPACE         (3  * NEC_UNIT)
  19 #define NEC_TRAILER_PULSE       (1  * NEC_UNIT)
  20 #define NEC_TRAILER_SPACE       (10 * NEC_UNIT) /* even longer in reality */
  21 #define NECX_REPEAT_BITS        1
  22
  23 enum nec_state {
  24         STATE_INACTIVE,
  25         STATE_HEADER_SPACE,
  26         STATE_BIT_PULSE,
  27         STATE_BIT_SPACE,
  28         STATE_TRAILER_PULSE,
  29         STATE_TRAILER_SPACE,
  30 };
  31
  32 /**
  33  * ir_nec_decode() - Decode one NEC pulse or space
  34  * @dev:        the struct rc_dev descriptor of the device
  35  * @ev:         the struct ir_raw_event descriptor of the pulse/space
  36  *
  37  * This function returns -EINVAL if the pulse violates the state machine
  38  */
  39 static int ir_nec_decode(struct rc_dev *dev, struct ir_raw_event ev)
  40 {
  41         struct nec_dec *data = &dev->raw->nec;
  42         u32 scancode;
  43         enum rc_proto rc_proto;
  44         u8 address, not_address, command, not_command;
  45
  46         if (!is_timing_event(ev)) {
  47                 if (ev.reset)
  48                         data->state = STATE_INACTIVE;
  49                 return 0;
  50         }
  51
  52         dev_dbg(&dev->dev, "NEC decode started at state %d (%uus %s)\n",
  53                 data->state, TO_US(ev.duration), TO_STR(ev.pulse));
  54
  55         switch (data->state) {
  56
  57         case STATE_INACTIVE:
  58                 if (!ev.pulse)
  59                         break;
  60
  61                 if (eq_margin(ev.duration, NEC_HEADER_PULSE, NEC_UNIT * 2)) {
  62                         data->is_nec_x = false;
  63                         data->necx_repeat = false;
  64                 } else if (eq_margin(ev.duration, NECX_HEADER_PULSE, NEC_UNIT / 2))
  65                         data->is_nec_x = true;
  66                 else
  67                         break;
  68
  69                 data->count = 0;
  70                 data->state = STATE_HEADER_SPACE;
  71                 return 0;
  72
  73         case STATE_HEADER_SPACE:
  74                 if (ev.pulse)
  75                         break;
  76
  77                 if (eq_margin(ev.duration, NEC_HEADER_SPACE, NEC_UNIT)) {
  78                         data->state = STATE_BIT_PULSE;
  79                         return 0;
  80                 } else if (eq_margin(ev.duration, NEC_REPEAT_SPACE, NEC_UNIT / 2)) {
  81                         data->state = STATE_TRAILER_PULSE;
  82                         return 0;
  83                 }
  84
  85                 break;
  86
  87         case STATE_BIT_PULSE:
  88                 if (!ev.pulse)
  89                         break;
  90
  91                 if (!eq_margin(ev.duration, NEC_BIT_PULSE, NEC_UNIT / 2))
  92                         break;
  93
  94                 data->state = STATE_BIT_SPACE;
  95                 return 0;
  96
  97         case STATE_BIT_SPACE:
  98                 if (ev.pulse)
  99                         break;
 100
 101                 if (data->necx_repeat && data->count == NECX_REPEAT_BITS &&
 102                     geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2)) {
 103                         dev_dbg(&dev->dev, "Repeat last key\n");
 104                         rc_repeat(dev);
 105                         data->state = STATE_INACTIVE;
 106                         return 0;
 107                 } else if (data->count > NECX_REPEAT_BITS)
 108                         data->necx_repeat = false;
 109
 110                 data->bits <<= 1;
 111                 if (eq_margin(ev.duration, NEC_BIT_1_SPACE, NEC_UNIT / 2))
 112                         data->bits |= 1;
 113                 else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2))
 114                         break;
 115                 data->count++;
 116
 117                 if (data->count == NEC_NBITS)
 118                         data->state = STATE_TRAILER_PULSE;
 119                 else
 120                         data->state = STATE_BIT_PULSE;
 121
 122                 return 0;
 123
 124         case STATE_TRAILER_PULSE:
 125                 if (!ev.pulse)
 126                         break;
 127
 128                 if (!eq_margin(ev.duration, NEC_TRAILER_PULSE, NEC_UNIT / 2))
 129                         break;
 130
 131                 data->state = STATE_TRAILER_SPACE;
 132                 return 0;
 133
 134         case STATE_TRAILER_SPACE:
 135                 if (ev.pulse)
 136                         break;
 137
 138                 if (!geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2))
 139                         break;
 140
 141                 if (data->count == NEC_NBITS) {
 142                         address     = bitrev8((data->bits >> 24) & 0xff);
 143                         not_address = bitrev8((data->bits >> 16) & 0xff);
 144                         command     = bitrev8((data->bits >>  8) & 0xff);
 145                         not_command = bitrev8((data->bits >>  0) & 0xff);
 146
 147                         scancode = ir_nec_bytes_to_scancode(address,
 148                                                             not_address,
 149                                                             command,
 150                                                             not_command,
 151                                                             &rc_proto);
 152
 153                         if (data->is_nec_x)
 154                                 data->necx_repeat = true;
 155
 156                         rc_keydown(dev, rc_proto, scancode, 0);
 157                 } else {
 158                         rc_repeat(dev);
 159                 }
 160
 161                 data->state = STATE_INACTIVE;
 162                 return 0;
 163         }
 164
 165         dev_dbg(&dev->dev, "NEC decode failed at count %d state %d (%uus %s)\n",
 166                 data->count, data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 167         data->state = STATE_INACTIVE;
 168         return -EINVAL;
 169 }
 170
 171 /**
 172  * ir_nec_scancode_to_raw() - encode an NEC scancode ready for modulation.
 173  * @protocol:   specific protocol to use
 174  * @scancode:   a single NEC scancode.
 175  */
 176 static u32 ir_nec_scancode_to_raw(enum rc_proto protocol, u32 scancode)
 177 {
 178         unsigned int addr, addr_inv, data, data_inv;
 179
 180         data = scancode & 0xff;
 181
 182         if (protocol == RC_PROTO_NEC32) {
 183                 /* 32-bit NEC (used by Apple and TiVo remotes) */
 184                 /* scan encoding: aaAAddDD */
 185                 addr_inv   = (scancode >> 24) & 0xff;
 186                 addr       = (scancode >> 16) & 0xff;
 187                 data_inv   = (scancode >>  8) & 0xff;
 188         } else if (protocol == RC_PROTO_NECX) {
 189                 /* Extended NEC */
 190                 /* scan encoding AAaaDD */
 191                 addr       = (scancode >> 16) & 0xff;
 192                 addr_inv   = (scancode >>  8) & 0xff;
 193                 data_inv   = data ^ 0xff;
 194         } else {
 195                 /* Normal NEC */
 196                 /* scan encoding: AADD */
 197                 addr       = (scancode >>  8) & 0xff;
 198                 addr_inv   = addr ^ 0xff;
 199                 data_inv   = data ^ 0xff;
 200         }
 201
 202         /* raw encoding: ddDDaaAA */
 203         return data_inv << 24 |
 204                data     << 16 |
 205                addr_inv <<  8 |
 206                addr;
 207 }
 208
 209 static const struct ir_raw_timings_pd ir_nec_timings = {
 210         .header_pulse   = NEC_HEADER_PULSE,
 211         .header_space   = NEC_HEADER_SPACE,
 212         .bit_pulse      = NEC_BIT_PULSE,
 213         .bit_space[0]   = NEC_BIT_0_SPACE,
 214         .bit_space[1]   = NEC_BIT_1_SPACE,
 215         .trailer_pulse  = NEC_TRAILER_PULSE,
 216         .trailer_space  = NEC_TRAILER_SPACE,
 217         .msb_first      = 0,
 218 };
 219
 220 /**
 221  * ir_nec_encode() - Encode a scancode as a stream of raw events
 222  *
 223  * @protocol:   protocol to encode
 224  * @scancode:   scancode to encode
 225  * @events:     array of raw ir events to write into
 226  * @max:        maximum size of @events
 227  *
 228  * Returns:     The number of events written.
 229  *              -ENOBUFS if there isn't enough space in the array to fit the
 230  *              encoding. In this case all @max events will have been written.
 231  */
 232 static int ir_nec_encode(enum rc_proto protocol, u32 scancode,
 233                          struct ir_raw_event *events, unsigned int max)
 234 {
 235         struct ir_raw_event *e = events;
 236         int ret;
 237         u32 raw;
 238
 239         /* Convert a NEC scancode to raw NEC data */
 240         raw = ir_nec_scancode_to_raw(protocol, scancode);
 241
 242         /* Modulate the raw data using a pulse distance modulation */
 243         ret = ir_raw_gen_pd(&e, max, &ir_nec_timings, NEC_NBITS, raw);
 244         if (ret < 0)
 245                 return ret;
 246
 247         return e - events;
 248 }
 249
 250 static struct ir_raw_handler nec_handler = {
 251         .protocols      = RC_PROTO_BIT_NEC | RC_PROTO_BIT_NECX |
 252                                                         RC_PROTO_BIT_NEC32,
 253         .decode         = ir_nec_decode,
 254         .encode         = ir_nec_encode,
 255         .carrier        = 38000,
 256         .min_timeout    = NEC_TRAILER_SPACE,
 257 };
 258
 259 static int __init ir_nec_decode_init(void)
 260 {
 261         ir_raw_handler_register(&nec_handler);
 262
 263         printk(KERN_INFO "IR NEC protocol handler initialized\n");
 264         return 0;
 265 }
 266
 267 static void __exit ir_nec_decode_exit(void)
 268 {
 269         ir_raw_handler_unregister(&nec_handler);
 270 }
 271
 272 module_init(ir_nec_decode_init);
 273 module_exit(ir_nec_decode_exit);
 274
 275 MODULE_LICENSE("GPL v2");
 276 MODULE_AUTHOR("Mauro Carvalho Chehab");
 277 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
 278 MODULE_DESCRIPTION("NEC IR protocol decoder");