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      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
    197