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Diffstat (limited to 'chromium/ui/display/util/edid_parser.cc')
| -rw-r--r-- | chromium/ui/display/util/edid_parser.cc | 197 |
1 files changed, 197 insertions, 0 deletions
diff --git a/chromium/ui/display/util/edid_parser.cc b/chromium/ui/display/util/edid_parser.cc new file mode 100644 index 00000000000..b95eef4c626 --- /dev/null +++ b/chromium/ui/display/util/edid_parser.cc @@ -0,0 +1,197 @@ +// Copyright 2014 The Chromium Authors. All rights reserved. +// Use of this source code is governed by a BSD-style license that can be +// found in the LICENSE file. + +#include "ui/display/util/edid_parser.h" + +#include <algorithm> + +#include "base/hash.h" +#include "base/strings/string_util.h" +#include "base/sys_byteorder.h" + +namespace ui { + +namespace { + +// Returns 64-bit persistent ID for the specified manufacturer's ID and +// product_code_hash, and the index of the output it is connected to. +// |output_index| is used to distinguish the displays of the same type. For +// example, swapping two identical display between two outputs will not be +// treated as swap. The 'serial number' field in EDID isn't used here because +// it is not guaranteed to have unique number and it may have the same fixed +// value (like 0). +int64_t GetID(uint16_t manufacturer_id, + uint32_t product_code_hash, + uint8_t output_index) { + return ((static_cast<int64_t>(manufacturer_id) << 40) | + (static_cast<int64_t>(product_code_hash) << 8) | output_index); +} + +} // namespace + +bool GetDisplayIdFromEDID(const std::vector<uint8_t>& edid, + uint8_t output_index, + int64_t* display_id_out) { + uint16_t manufacturer_id = 0; + std::string product_name; + + // ParseOutputDeviceData fails if it doesn't have product_name. + ParseOutputDeviceData(edid, &manufacturer_id, &product_name); + + // Generates product specific value from product_name instead of product code. + // See crbug.com/240341 + uint32_t product_code_hash = product_name.empty() ? + 0 : base::Hash(product_name); + if (manufacturer_id != 0) { + // An ID based on display's index will be assigned later if this call + // fails. + *display_id_out = GetID( + manufacturer_id, product_code_hash, output_index); + return true; + } + return false; +} + +bool ParseOutputDeviceData(const std::vector<uint8_t>& edid, + uint16_t* manufacturer_id, + std::string* human_readable_name) { + // See http://en.wikipedia.org/wiki/Extended_display_identification_data + // for the details of EDID data format. We use the following data: + // bytes 8-9: manufacturer EISA ID, in big-endian + // bytes 54-125: four descriptors (18-bytes each) which may contain + // the display name. + const unsigned int kManufacturerOffset = 8; + const unsigned int kManufacturerLength = 2; + const unsigned int kDescriptorOffset = 54; + const unsigned int kNumDescriptors = 4; + const unsigned int kDescriptorLength = 18; + // The specifier types. + const unsigned char kMonitorNameDescriptor = 0xfc; + + if (manufacturer_id) { + if (edid.size() < kManufacturerOffset + kManufacturerLength) { + LOG(ERROR) << "too short EDID data: manifacturer id"; + return false; + } + + *manufacturer_id = + *reinterpret_cast<const uint16_t*>(&edid[kManufacturerOffset]); +#if defined(ARCH_CPU_LITTLE_ENDIAN) + *manufacturer_id = base::ByteSwap(*manufacturer_id); +#endif + } + + if (!human_readable_name) + return true; + + human_readable_name->clear(); + for (unsigned int i = 0; i < kNumDescriptors; ++i) { + if (edid.size() < kDescriptorOffset + (i + 1) * kDescriptorLength) + break; + + size_t offset = kDescriptorOffset + i * kDescriptorLength; + // If the descriptor contains the display name, it has the following + // structure: + // bytes 0-2, 4: \0 + // byte 3: descriptor type, defined above. + // bytes 5-17: text data, ending with \r, padding with spaces + // we should check bytes 0-2 and 4, since it may have other values in + // case that the descriptor contains other type of data. + if (edid[offset] == 0 && edid[offset + 1] == 0 && edid[offset + 2] == 0 && + edid[offset + 3] == kMonitorNameDescriptor && edid[offset + 4] == 0) { + std::string found_name(reinterpret_cast<const char*>(&edid[offset + 5]), + kDescriptorLength - 5); + base::TrimWhitespaceASCII( + found_name, base::TRIM_TRAILING, human_readable_name); + break; + } + } + + // Verify if the |human_readable_name| consists of printable characters only. + for (size_t i = 0; i < human_readable_name->size(); ++i) { + char c = (*human_readable_name)[i]; + if (!isascii(c) || !isprint(c)) { + human_readable_name->clear(); + LOG(ERROR) << "invalid EDID: human unreadable char in name"; + return false; + } + } + + return true; +} + +bool ParseOutputOverscanFlag(const std::vector<uint8_t>& edid, + bool* flag) { + // See http://en.wikipedia.org/wiki/Extended_display_identification_data + // for the extension format of EDID. Also see EIA/CEA-861 spec for + // the format of the extensions and how video capability is encoded. + // - byte 0: tag. should be 02h. + // - byte 1: revision. only cares revision 3 (03h). + // - byte 4-: data block. + const unsigned int kExtensionBase = 128; + const unsigned int kExtensionSize = 128; + const unsigned int kNumExtensionsOffset = 126; + const unsigned int kDataBlockOffset = 4; + const unsigned char kCEAExtensionTag = '\x02'; + const unsigned char kExpectedExtensionRevision = '\x03'; + const unsigned char kExtendedTag = 7; + const unsigned char kExtendedVideoCapabilityTag = 0; + const unsigned int kPTOverscan = 4; + const unsigned int kITOverscan = 2; + const unsigned int kCEOverscan = 0; + + if (edid.size() <= kNumExtensionsOffset) + return false; + + unsigned char num_extensions = edid[kNumExtensionsOffset]; + + for (size_t i = 0; i < num_extensions; ++i) { + // Skip parsing the whole extension if size is not enough. + if (edid.size() < kExtensionBase + (i + 1) * kExtensionSize) + break; + + size_t extension_offset = kExtensionBase + i * kExtensionSize; + unsigned char tag = edid[extension_offset]; + unsigned char revision = edid[extension_offset + 1]; + if (tag != kCEAExtensionTag || revision != kExpectedExtensionRevision) + continue; + + unsigned char timing_descriptors_start = std::min( + edid[extension_offset + 2], static_cast<unsigned char>(kExtensionSize)); + + for (size_t data_offset = extension_offset + kDataBlockOffset; + data_offset < extension_offset + timing_descriptors_start;) { + // A data block is encoded as: + // - byte 1 high 3 bits: tag. '07' for extended tags. + // - byte 1 remaining bits: the length of data block. + // - byte 2: the extended tag. '0' for video capability. + // - byte 3: the capability. + unsigned char tag = edid[data_offset] >> 5; + unsigned char payload_length = edid[data_offset] & 0x1f; + if (data_offset + payload_length > edid.size()) + break; + + if (tag != kExtendedTag || payload_length < 2 || + edid[data_offset + 1] != kExtendedVideoCapabilityTag) { + data_offset += payload_length + 1; + continue; + } + + // The difference between preferred, IT, and CE video formats + // doesn't matter. Sets |flag| to true if any of these flags are true. + if ((edid[data_offset + 2] & (1 << kPTOverscan)) || + (edid[data_offset + 2] & (1 << kITOverscan)) || + (edid[data_offset + 2] & (1 << kCEOverscan))) { + *flag = true; + } else { + *flag = false; + } + return true; + } + } + + return false; +} + +} // namespace ui |