base/x11/edid_parser_x11.cc

   1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "base/x11/edid_parser_x11.h"
   6
   7 #include <X11/extensions/Xrandr.h>
   8 #include <X11/Xatom.h>
   9 #include <X11/Xlib.h>
  10
  11 #include "base/hash.h"
  12 #include "base/message_loop/message_loop.h"
  13 #include "base/strings/string_util.h"
  14 #include "base/sys_byteorder.h"
  15
  16 namespace {
  17
  18 // Returns 64-bit persistent ID for the specified manufacturer's ID and
  19 // product_code_hash, and the index of the output it is connected to.
  20 // |output_index| is used to distinguish the displays of the same type. For
  21 // example, swapping two identical display between two outputs will not be
  22 // treated as swap. The 'serial number' field in EDID isn't used here because
  23 // it is not guaranteed to have unique number and it may have the same fixed
  24 // value (like 0).
  25 int64 GetID(uint16 manufacturer_id,
  26             uint32 product_code_hash,
  27             uint8 output_index) {
  28   return ((static_cast<int64>(manufacturer_id) << 40) |
  29           (static_cast<int64>(product_code_hash) << 8) | output_index);
  30 }
  31
  32 bool IsRandRAvailable() {
  33   int randr_version_major = 0;
  34   int randr_version_minor = 0;
  35   static bool is_randr_available = XRRQueryVersion(
  36       base::MessagePumpX11::GetDefaultXDisplay(),
  37       &randr_version_major, &randr_version_minor);
  38   return is_randr_available;
  39 }
  40
  41 }  // namespace
  42
  43 namespace base {
  44
  45 bool GetEDIDProperty(XID output, unsigned long* nitems, unsigned char** prop) {
  46   if (!IsRandRAvailable())
  47     return false;
  48
  49   Display* display = base::MessagePumpX11::GetDefaultXDisplay();
  50
  51   static Atom edid_property = XInternAtom(
  52       base::MessagePumpX11::GetDefaultXDisplay(),
  53       RR_PROPERTY_RANDR_EDID, false);
  54
  55   bool has_edid_property = false;
  56   int num_properties = 0;
  57   Atom* properties = XRRListOutputProperties(display, output, &num_properties);
  58   for (int i = 0; i < num_properties; ++i) {
  59     if (properties[i] == edid_property) {
  60       has_edid_property = true;
  61       break;
  62     }
  63   }
  64   XFree(properties);
  65   if (!has_edid_property)
  66     return false;
  67
  68   Atom actual_type;
  69   int actual_format;
  70   unsigned long bytes_after;
  71   XRRGetOutputProperty(display,
  72                        output,
  73                        edid_property,
  74                        0,                // offset
  75                        128,              // length
  76                        false,            // _delete
  77                        false,            // pending
  78                        AnyPropertyType,  // req_type
  79                        &actual_type,
  80                        &actual_format,
  81                        nitems,
  82                        &bytes_after,
  83                        prop);
  84   DCHECK_EQ(XA_INTEGER, actual_type);
  85   DCHECK_EQ(8, actual_format);
  86   return true;
  87 }
  88
  89 bool GetDisplayId(XID output_id, size_t output_index, int64* display_id_out) {
  90   unsigned long nitems = 0;
  91   unsigned char* prop = NULL;
  92   if (!GetEDIDProperty(output_id, &nitems, &prop))
  93     return false;
  94
  95   bool result =
  96       GetDisplayIdFromEDID(prop, nitems, output_index, display_id_out);
  97   XFree(prop);
  98   return result;
  99 }
 100
 101 bool GetDisplayIdFromEDID(const unsigned char* prop,
 102                           unsigned long nitems,
 103                           size_t output_index,
 104                           int64* display_id_out) {
 105   uint16 manufacturer_id = 0;
 106   std::string product_name;
 107
 108   // ParseOutputDeviceData fails if it doesn't have product_name.
 109   ParseOutputDeviceData(prop, nitems, &manufacturer_id, &product_name);
 110
 111   // Generates product specific value from product_name instead of product code.
 112   // See crbug.com/240341
 113   uint32 product_code_hash = product_name.empty() ?
 114       0 : base::Hash(product_name);
 115   if (manufacturer_id != 0) {
 116     // An ID based on display's index will be assigned later if this call
 117     // fails.
 118     *display_id_out = GetID(
 119         manufacturer_id, product_code_hash, output_index);
 120     return true;
 121   }
 122   return false;
 123 }
 124
 125 bool ParseOutputDeviceData(const unsigned char* prop,
 126                            unsigned long nitems,
 127                            uint16* manufacturer_id,
 128                            std::string* human_readable_name) {
 129   // See http://en.wikipedia.org/wiki/Extended_display_identification_data
 130   // for the details of EDID data format.  We use the following data:
 131   //   bytes 8-9: manufacturer EISA ID, in big-endian
 132   //   bytes 54-125: four descriptors (18-bytes each) which may contain
 133   //     the display name.
 134   const unsigned int kManufacturerOffset = 8;
 135   const unsigned int kManufacturerLength = 2;
 136   const unsigned int kDescriptorOffset = 54;
 137   const unsigned int kNumDescriptors = 4;
 138   const unsigned int kDescriptorLength = 18;
 139   // The specifier types.
 140   const unsigned char kMonitorNameDescriptor = 0xfc;
 141
 142   if (manufacturer_id) {
 143     if (nitems < kManufacturerOffset + kManufacturerLength) {
 144       LOG(ERROR) << "too short EDID data: manifacturer id";
 145       return false;
 146     }
 147
 148     *manufacturer_id =
 149         *reinterpret_cast<const uint16*>(prop + kManufacturerOffset);
 150 #if defined(ARCH_CPU_LITTLE_ENDIAN)
 151     *manufacturer_id = base::ByteSwap(*manufacturer_id);
 152 #endif
 153   }
 154
 155   if (!human_readable_name)
 156     return true;
 157
 158   human_readable_name->clear();
 159   for (unsigned int i = 0; i < kNumDescriptors; ++i) {
 160     if (nitems < kDescriptorOffset + (i + 1) * kDescriptorLength)
 161       break;
 162
 163     const unsigned char* desc_buf =
 164         prop + kDescriptorOffset + i * kDescriptorLength;
 165     // If the descriptor contains the display name, it has the following
 166     // structure:
 167     //   bytes 0-2, 4: \0
 168     //   byte 3: descriptor type, defined above.
 169     //   bytes 5-17: text data, ending with \r, padding with spaces
 170     // we should check bytes 0-2 and 4, since it may have other values in
 171     // case that the descriptor contains other type of data.
 172     if (desc_buf[0] == 0 && desc_buf[1] == 0 && desc_buf[2] == 0 &&
 173         desc_buf[4] == 0) {
 174       if (desc_buf[3] == kMonitorNameDescriptor) {
 175         std::string found_name(
 176             reinterpret_cast<const char*>(desc_buf + 5), kDescriptorLength - 5);
 177         TrimWhitespaceASCII(found_name, TRIM_TRAILING, human_readable_name);
 178         break;
 179       }
 180     }
 181   }
 182
 183   // Verify if the |human_readable_name| consists of printable characters only.
 184   for (size_t i = 0; i < human_readable_name->size(); ++i) {
 185     char c = (*human_readable_name)[i];
 186     if (!isascii(c) || !isprint(c)) {
 187       human_readable_name->clear();
 188       LOG(ERROR) << "invalid EDID: human unreadable char in name";
 189       return false;
 190     }
 191   }
 192
 193   return true;
 194 }
 195
 196 }  // namespace base