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"); 280