drivers/media/rc/img-ir/img-ir-rc6.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * ImgTec IR Decoder setup for Philips RC-6 protocol.
   4  *
   5  * Copyright 2012-2014 Imagination Technologies Ltd.
   6  */
   7
   8 #include "img-ir-hw.h"
   9
  10 /* Convert RC6 data to a scancode */
  11 static int img_ir_rc6_scancode(int len, u64 raw, u64 enabled_protocols,
  12                                 struct img_ir_scancode_req *request)
  13 {
  14         unsigned int addr, cmd, mode, trl1, trl2;
  15
  16         /*
  17          * Due to a side effect of the decoder handling the double length
  18          * Trailer bit, the header information is a bit scrambled, and the
  19          * raw data is shifted incorrectly.
  20          * This workaround effectively recovers the header bits.
  21          *
  22          * The Header field should look like this:
  23          *
  24          * StartBit ModeBit2 ModeBit1 ModeBit0 TrailerBit
  25          *
  26          * But what we get is:
  27          *
  28          * ModeBit2 ModeBit1 ModeBit0 TrailerBit1 TrailerBit2
  29          *
  30          * The start bit is not important to recover the scancode.
  31          */
  32
  33         raw     >>= 27;
  34
  35         trl1    = (raw >>  17)  & 0x01;
  36         trl2    = (raw >>  16)  & 0x01;
  37
  38         mode    = (raw >>  18)  & 0x07;
  39         addr    = (raw >>   8)  & 0xff;
  40         cmd     =  raw          & 0xff;
  41
  42         /*
  43          * Due to the above explained irregularity the trailer bits cannot
  44          * have the same value.
  45          */
  46         if (trl1 == trl2)
  47                 return -EINVAL;
  48
  49         /* Only mode 0 supported for now */
  50         if (mode)
  51                 return -EINVAL;
  52
  53         request->protocol = RC_PROTO_RC6_0;
  54         request->scancode = addr << 8 | cmd;
  55         request->toggle   = trl2;
  56         return IMG_IR_SCANCODE;
  57 }
  58
  59 /* Convert RC6 scancode to RC6 data filter */
  60 static int img_ir_rc6_filter(const struct rc_scancode_filter *in,
  61                                  struct img_ir_filter *out, u64 protocols)
  62 {
  63         /* Not supported by the hw. */
  64         return -EINVAL;
  65 }
  66
  67 /*
  68  * RC-6 decoder
  69  * see http://www.sbprojects.com/knowledge/ir/rc6.php
  70  */
  71 struct img_ir_decoder img_ir_rc6 = {
  72         .type           = RC_PROTO_BIT_RC6_0,
  73         .control        = {
  74                 .bitorien       = 1,
  75                 .code_type      = IMG_IR_CODETYPE_BIPHASE,
  76                 .decoden        = 1,
  77                 .decodinpol     = 1,
  78         },
  79         /* main timings */
  80         .tolerance      = 20,
  81         /*
  82          * Due to a quirk in the img-ir decoder, default header values do
  83          * not work, the values described below were extracted from
  84          * successful RTL test cases.
  85          */
  86         .timings        = {
  87                 /* leader symbol */
  88                 .ldr = {
  89                         .pulse  = { 650 },
  90                         .space  = { 660 },
  91                 },
  92                 /* 0 symbol */
  93                 .s00 = {
  94                         .pulse  = { 370 },
  95                         .space  = { 370 },
  96                 },
  97                 /* 01 symbol */
  98                 .s01 = {
  99                         .pulse  = { 370 },
 100                         .space  = { 370 },
 101                 },
 102                 /* free time */
 103                 .ft  = {
 104                         .minlen = 21,
 105                         .maxlen = 21,
 106                         .ft_min = 2666, /* 2.666 ms */
 107                 },
 108         },
 109
 110         /* scancode logic */
 111         .scancode       = img_ir_rc6_scancode,
 112         .filter         = img_ir_rc6_filter,
 113 };