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         IR_dprintk(2, "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,
 103                         NEC_TRAILER_SPACE, NEC_UNIT / 2)) {
 104                                 IR_dprintk(1, "Repeat last key\n");
 105                                 rc_repeat(dev);
 106                                 data->state = STATE_INACTIVE;
 107                                 return 0;
 108
 109                 } else if (data->count > NECX_REPEAT_BITS)
 110                         data->necx_repeat = false;
 111
 112                 data->bits <<= 1;
 113                 if (eq_margin(ev.duration, NEC_BIT_1_SPACE, NEC_UNIT / 2))
 114                         data->bits |= 1;
 115                 else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2))
 116                         break;
 117                 data->count++;
 118
 119                 if (data->count == NEC_NBITS)
 120                         data->state = STATE_TRAILER_PULSE;
 121                 else
 122                         data->state = STATE_BIT_PULSE;
 123
 124                 return 0;
 125
 126         case STATE_TRAILER_PULSE:
 127                 if (!ev.pulse)
 128                         break;
 129
 130                 if (!eq_margin(ev.duration, NEC_TRAILER_PULSE, NEC_UNIT / 2))
 131                         break;
 132
 133                 data->state = STATE_TRAILER_SPACE;
 134                 return 0;
 135
 136         case STATE_TRAILER_SPACE:
 137                 if (ev.pulse)
 138                         break;
 139
 140                 if (!geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2))
 141                         break;
 142
 143                 if (data->count == NEC_NBITS) {
 144                         address     = bitrev8((data->bits >> 24) & 0xff);
 145                         not_address = bitrev8((data->bits >> 16) & 0xff);
 146                         command     = bitrev8((data->bits >>  8) & 0xff);
 147                         not_command = bitrev8((data->bits >>  0) & 0xff);
 148
 149                         scancode = ir_nec_bytes_to_scancode(address,
 150                                                             not_address,
 151                                                             command,
 152                                                             not_command,
 153                                                             &rc_proto);
 154
 155                         if (data->is_nec_x)
 156                                 data->necx_repeat = true;
 157
 158                         rc_keydown(dev, rc_proto, scancode, 0);
 159                 } else {
 160                         rc_repeat(dev);
 161                 }
 162
 163                 data->state = STATE_INACTIVE;
 164                 return 0;
 165         }
 166
 167         IR_dprintk(1, "NEC decode failed at count %d state %d (%uus %s)\n",
 168                    data->count, data->state, TO_US(ev.duration), TO_STR(ev.pulse));
 169         data->state = STATE_INACTIVE;
 170         return -EINVAL;
 171 }
 172
 173 /**
 174  * ir_nec_scancode_to_raw() - encode an NEC scancode ready for modulation.
 175  * @protocol:   specific protocol to use
 176  * @scancode:   a single NEC scancode.
 177  */
 178 static u32 ir_nec_scancode_to_raw(enum rc_proto protocol, u32 scancode)
 179 {
 180         unsigned int addr, addr_inv, data, data_inv;
 181
 182         data = scancode & 0xff;
 183
 184         if (protocol == RC_PROTO_NEC32) {
 185                 /* 32-bit NEC (used by Apple and TiVo remotes) */
 186                 /* scan encoding: aaAAddDD */
 187                 addr_inv   = (scancode >> 24) & 0xff;
 188                 addr       = (scancode >> 16) & 0xff;
 189                 data_inv   = (scancode >>  8) & 0xff;
 190         } else if (protocol == RC_PROTO_NECX) {
 191                 /* Extended NEC */
 192                 /* scan encoding AAaaDD */
 193                 addr       = (scancode >> 16) & 0xff;
 194                 addr_inv   = (scancode >>  8) & 0xff;
 195                 data_inv   = data ^ 0xff;
 196         } else {
 197                 /* Normal NEC */
 198                 /* scan encoding: AADD */
 199                 addr       = (scancode >>  8) & 0xff;
 200                 addr_inv   = addr ^ 0xff;
 201                 data_inv   = data ^ 0xff;
 202         }
 203
 204         /* raw encoding: ddDDaaAA */
 205         return data_inv << 24 |
 206                data     << 16 |
 207                addr_inv <<  8 |
 208                addr;
 209 }
 210
 211 static const struct ir_raw_timings_pd ir_nec_timings = {
 212         .header_pulse   = NEC_HEADER_PULSE,
 213         .header_space   = NEC_HEADER_SPACE,
 214         .bit_pulse      = NEC_BIT_PULSE,
 215         .bit_space[0]   = NEC_BIT_0_SPACE,
 216         .bit_space[1]   = NEC_BIT_1_SPACE,
 217         .trailer_pulse  = NEC_TRAILER_PULSE,
 218         .trailer_space  = NEC_TRAILER_SPACE,
 219         .msb_first      = 0,
 220 };
 221
 222 /**
 223  * ir_nec_encode() - Encode a scancode as a stream of raw events
 224  *
 225  * @protocol:   protocol to encode
 226  * @scancode:   scancode to encode
 227  * @events:     array of raw ir events to write into
 228  * @max:        maximum size of @events
 229  *
 230  * Returns:     The number of events written.
 231  *              -ENOBUFS if there isn't enough space in the array to fit the
 232  *              encoding. In this case all @max events will have been written.
 233  */
 234 static int ir_nec_encode(enum rc_proto protocol, u32 scancode,
 235                          struct ir_raw_event *events, unsigned int max)
 236 {
 237         struct ir_raw_event *e = events;
 238         int ret;
 239         u32 raw;
 240
 241         /* Convert a NEC scancode to raw NEC data */
 242         raw = ir_nec_scancode_to_raw(protocol, scancode);
 243
 244         /* Modulate the raw data using a pulse distance modulation */
 245         ret = ir_raw_gen_pd(&e, max, &ir_nec_timings, NEC_NBITS, raw);
 246         if (ret < 0)
 247                 return ret;
 248
 249         return e - events;
 250 }
 251
 252 static struct ir_raw_handler nec_handler = {
 253         .protocols      = RC_PROTO_BIT_NEC | RC_PROTO_BIT_NECX |
 254                                                         RC_PROTO_BIT_NEC32,
 255         .decode         = ir_nec_decode,
 256         .encode         = ir_nec_encode,
 257         .carrier        = 38000,
 258 };
 259
 260 static int __init ir_nec_decode_init(void)
 261 {
 262         ir_raw_handler_register(&nec_handler);
 263
 264         printk(KERN_INFO "IR NEC protocol handler initialized\n");
 265         return 0;
 266 }
 267
 268 static void __exit ir_nec_decode_exit(void)
 269 {
 270         ir_raw_handler_unregister(&nec_handler);
 271 }
 272
 273 module_init(ir_nec_decode_init);
 274 module_exit(ir_nec_decode_exit);
 275
 276 MODULE_LICENSE("GPL v2");
 277 MODULE_AUTHOR("Mauro Carvalho Chehab");
 278 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
 279 MODULE_DESCRIPTION("NEC IR protocol decoder");