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 563 /* us */ 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.overflow) 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, 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, 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"); 279