drivers/media/cec-edid.c

   1 /*
   2  * cec-edid - HDMI Consumer Electronics Control EDID & CEC helper functions
   3  *
   4  * Copyright 2016 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
   5  *
   6  * This program is free software; you may redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; version 2 of the License.
   9  *
  10  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  11  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  12  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  13  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  14  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  15  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  16  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  17  * SOFTWARE.
  18  */
  19
  20 #include <linux/module.h>
  21 #include <linux/kernel.h>
  22 #include <linux/types.h>
  23 #include <media/cec-edid.h>
  24
  25 /*
  26  * This EDID is expected to be a CEA-861 compliant, which means that there are
  27  * at least two blocks and one or more of the extensions blocks are CEA-861
  28  * blocks.
  29  *
  30  * The returned location is guaranteed to be < size - 1.
  31  */
  32 static unsigned int cec_get_edid_spa_location(const u8 *edid, unsigned int size)
  33 {
  34         unsigned int blocks = size / 128;
  35         unsigned int block;
  36         u8 d;
  37
  38         /* Sanity check: at least 2 blocks and a multiple of the block size */
  39         if (blocks < 2 || size % 128)
  40                 return 0;
  41
  42         /*
  43          * If there are fewer extension blocks than the size, then update
  44          * 'blocks'. It is allowed to have more extension blocks than the size,
  45          * since some hardware can only read e.g. 256 bytes of the EDID, even
  46          * though more blocks are present. The first CEA-861 extension block
  47          * should normally be in block 1 anyway.
  48          */
  49         if (edid[0x7e] + 1 < blocks)
  50                 blocks = edid[0x7e] + 1;
  51
  52         for (block = 1; block < blocks; block++) {
  53                 unsigned int offset = block * 128;
  54
  55                 /* Skip any non-CEA-861 extension blocks */
  56                 if (edid[offset] != 0x02 || edid[offset + 1] != 0x03)
  57                         continue;
  58
  59                 /* search Vendor Specific Data Block (tag 3) */
  60                 d = edid[offset + 2] & 0x7f;
  61                 /* Check if there are Data Blocks */
  62                 if (d <= 4)
  63                         continue;
  64                 if (d > 4) {
  65                         unsigned int i = offset + 4;
  66                         unsigned int end = offset + d;
  67
  68                         /* Note: 'end' is always < 'size' */
  69                         do {
  70                                 u8 tag = edid[i] >> 5;
  71                                 u8 len = edid[i] & 0x1f;
  72
  73                                 if (tag == 3 && len >= 5 && i + len <= end)
  74                                         return i + 4;
  75                                 i += len + 1;
  76                         } while (i < end);
  77                 }
  78         }
  79         return 0;
  80 }
  81
  82 u16 cec_get_edid_phys_addr(const u8 *edid, unsigned int size,
  83                            unsigned int *offset)
  84 {
  85         unsigned int loc = cec_get_edid_spa_location(edid, size);
  86
  87         if (offset)
  88                 *offset = loc;
  89         if (loc == 0)
  90                 return CEC_PHYS_ADDR_INVALID;
  91         return (edid[loc] << 8) | edid[loc + 1];
  92 }
  93 EXPORT_SYMBOL_GPL(cec_get_edid_phys_addr);
  94
  95 void cec_set_edid_phys_addr(u8 *edid, unsigned int size, u16 phys_addr)
  96 {
  97         unsigned int loc = cec_get_edid_spa_location(edid, size);
  98         u8 sum = 0;
  99         unsigned int i;
 100
 101         if (loc == 0)
 102                 return;
 103         edid[loc] = phys_addr >> 8;
 104         edid[loc + 1] = phys_addr & 0xff;
 105         loc &= ~0x7f;
 106
 107         /* update the checksum */
 108         for (i = loc; i < loc + 127; i++)
 109                 sum += edid[i];
 110         edid[i] = 256 - sum;
 111 }
 112 EXPORT_SYMBOL_GPL(cec_set_edid_phys_addr);
 113
 114 u16 cec_phys_addr_for_input(u16 phys_addr, u8 input)
 115 {
 116         /* Check if input is sane */
 117         if (WARN_ON(input == 0 || input > 0xf))
 118                 return CEC_PHYS_ADDR_INVALID;
 119
 120         if (phys_addr == 0)
 121                 return input << 12;
 122
 123         if ((phys_addr & 0x0fff) == 0)
 124                 return phys_addr | (input << 8);
 125
 126         if ((phys_addr & 0x00ff) == 0)
 127                 return phys_addr | (input << 4);
 128
 129         if ((phys_addr & 0x000f) == 0)
 130                 return phys_addr | input;
 131
 132         /*
 133          * All nibbles are used so no valid physical addresses can be assigned
 134          * to the input.
 135          */
 136         return CEC_PHYS_ADDR_INVALID;
 137 }
 138 EXPORT_SYMBOL_GPL(cec_phys_addr_for_input);
 139
 140 int cec_phys_addr_validate(u16 phys_addr, u16 *parent, u16 *port)
 141 {
 142         int i;
 143
 144         if (parent)
 145                 *parent = phys_addr;
 146         if (port)
 147                 *port = 0;
 148         if (phys_addr == CEC_PHYS_ADDR_INVALID)
 149                 return 0;
 150         for (i = 0; i < 16; i += 4)
 151                 if (phys_addr & (0xf << i))
 152                         break;
 153         if (i == 16)
 154                 return 0;
 155         if (parent)
 156                 *parent = phys_addr & (0xfff0 << i);
 157         if (port)
 158                 *port = (phys_addr >> i) & 0xf;
 159         for (i += 4; i < 16; i += 4)
 160                 if ((phys_addr & (0xf << i)) == 0)
 161                         return -EINVAL;
 162         return 0;
 163 }
 164 EXPORT_SYMBOL_GPL(cec_phys_addr_validate);
 165
 166 MODULE_AUTHOR("Hans Verkuil <hans.verkuil@cisco.com>");
 167 MODULE_DESCRIPTION("CEC EDID helper functions");
 168 MODULE_LICENSE("GPL");