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// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "media/midi/usb_midi_descriptor_parser.h"
#include "base/logging.h"
#include "base/ranges/algorithm.h"
#include "base/strings/stringprintf.h"
namespace midi {
namespace {
// The constants below are specified in USB spec, USB audio spec
// and USB midi spec.
enum DescriptorType {
TYPE_DEVICE = 1,
TYPE_CONFIGURATION = 2,
TYPE_STRING = 3,
TYPE_INTERFACE = 4,
TYPE_ENDPOINT = 5,
TYPE_DEVICE_QUALIFIER = 6,
TYPE_OTHER_SPEED_CONFIGURATION = 7,
TYPE_INTERFACE_POWER = 8,
TYPE_CS_INTERFACE = 36,
TYPE_CS_ENDPOINT = 37,
};
enum DescriptorSubType {
SUBTYPE_MS_DESCRIPTOR_UNDEFINED = 0,
SUBTYPE_MS_HEADER = 1,
SUBTYPE_MIDI_IN_JACK = 2,
SUBTYPE_MIDI_OUT_JACK = 3,
SUBTYPE_ELEMENT = 4,
};
enum JackType {
JACK_TYPE_UNDEFINED = 0,
JACK_TYPE_EMBEDDED = 1,
JACK_TYPE_EXTERNAL = 2,
};
const uint8_t kAudioInterfaceClass = 1;
const uint8_t kAudioMidiInterfaceSubclass = 3;
bool DecodeBcd(uint8_t byte, int* decoded) {
// Write decoded decimal value from |byte| into |decoded|. If either nibble in
// |byte| exceeds decimal 10, returns false.
const uint8_t k_nibble_ten = 0xa;
const uint8_t nibble_major = (byte & 0xf0) >> 4;
const uint8_t nibble_minor = byte & 0x0f;
if (nibble_major >= k_nibble_ten || nibble_minor >= k_nibble_ten) {
return false;
}
*decoded = nibble_major * 10 + nibble_minor;
return true;
}
} // namespace
std::string UsbMidiDescriptorParser::DeviceInfo::BcdVersionToString(
uint16_t version) {
const int byte_1 = version >> 8;
const int byte_2 = version & 0xff;
int version_major, version_minor;
if (!DecodeBcd(byte_1, &version_major) ||
!DecodeBcd(byte_2, &version_minor)) {
return base::StringPrintf("Invalid BCD $%02x.%02x", byte_1, byte_2);
}
return base::StringPrintf("%d.%02d", version_major, version_minor);
}
UsbMidiDescriptorParser::UsbMidiDescriptorParser()
: is_parsing_usb_midi_interface_(false),
current_endpoint_address_(0),
current_cable_number_(0) {}
UsbMidiDescriptorParser::~UsbMidiDescriptorParser() = default;
bool UsbMidiDescriptorParser::Parse(UsbMidiDevice* device,
const uint8_t* data,
size_t size,
std::vector<UsbMidiJack>* jacks) {
jacks->clear();
bool result = ParseInternal(device, data, size, jacks);
if (!result)
jacks->clear();
Clear();
return result;
}
bool UsbMidiDescriptorParser::ParseDeviceInfo(const uint8_t* data,
size_t size,
DeviceInfo* info) {
*info = DeviceInfo();
for (const uint8_t* current = data; current < data + size;
current += current[0]) {
uint8_t length = current[0];
if (length < 2) {
DVLOG(1) << "Descriptor Type is not accessible.";
return false;
}
if (current + length > data + size) {
DVLOG(1) << "The header size is incorrect.";
return false;
}
DescriptorType descriptor_type = static_cast<DescriptorType>(current[1]);
if (descriptor_type != TYPE_DEVICE)
continue;
// We assume that ParseDevice doesn't modify |*info| if it returns false.
return ParseDevice(current, length, info);
}
// No DEVICE descriptor is found.
return false;
}
bool UsbMidiDescriptorParser::ParseInternal(UsbMidiDevice* device,
const uint8_t* data,
size_t size,
std::vector<UsbMidiJack>* jacks) {
for (const uint8_t* current = data; current < data + size;
current += current[0]) {
uint8_t length = current[0];
if (length < 2) {
DVLOG(1) << "Descriptor Type is not accessible.";
return false;
}
if (current + length > data + size) {
DVLOG(1) << "The header size is incorrect.";
return false;
}
DescriptorType descriptor_type = static_cast<DescriptorType>(current[1]);
if (descriptor_type != TYPE_INTERFACE && !is_parsing_usb_midi_interface_)
continue;
switch (descriptor_type) {
case TYPE_INTERFACE:
if (!ParseInterface(current, length))
return false;
break;
case TYPE_CS_INTERFACE:
// We are assuming that the corresponding INTERFACE precedes
// the CS_INTERFACE descriptor, as specified.
if (!ParseCSInterface(device, current, length))
return false;
break;
case TYPE_ENDPOINT:
// We are assuming that endpoints are contained in an interface.
if (!ParseEndpoint(current, length))
return false;
break;
case TYPE_CS_ENDPOINT:
// We are assuming that the corresponding ENDPOINT precedes
// the CS_ENDPOINT descriptor, as specified.
if (!ParseCSEndpoint(current, length, jacks))
return false;
break;
default:
// Ignore uninteresting types.
break;
}
}
return true;
}
bool UsbMidiDescriptorParser::ParseDevice(const uint8_t* data,
size_t size,
DeviceInfo* info) {
if (size < 0x12) {
DVLOG(1) << "DEVICE header size is incorrect.";
return false;
}
info->vendor_id = data[8] | (data[9] << 8);
info->product_id = data[0xa] | (data[0xb] << 8);
info->bcd_device_version = data[0xc] | (data[0xd] << 8);
info->manufacturer_index = data[0xe];
info->product_index = data[0xf];
return true;
}
bool UsbMidiDescriptorParser::ParseInterface(const uint8_t* data, size_t size) {
if (size != 9) {
DVLOG(1) << "INTERFACE header size is incorrect.";
return false;
}
incomplete_jacks_.clear();
uint8_t interface_class = data[5];
uint8_t interface_subclass = data[6];
// All descriptors of endpoints contained in this interface
// precede the next INTERFACE descriptor.
is_parsing_usb_midi_interface_ =
interface_class == kAudioInterfaceClass &&
interface_subclass == kAudioMidiInterfaceSubclass;
return true;
}
bool UsbMidiDescriptorParser::ParseCSInterface(UsbMidiDevice* device,
const uint8_t* data,
size_t size) {
// Descriptor Type and Descriptor Subtype should be accessible.
if (size < 3) {
DVLOG(1) << "CS_INTERFACE header size is incorrect.";
return false;
}
DescriptorSubType subtype = static_cast<DescriptorSubType>(data[2]);
if (subtype != SUBTYPE_MIDI_OUT_JACK &&
subtype != SUBTYPE_MIDI_IN_JACK)
return true;
if (size < 6) {
DVLOG(1) << "CS_INTERFACE (MIDI JACK) header size is incorrect.";
return false;
}
uint8_t jack_type = data[3];
uint8_t id = data[4];
if (jack_type == JACK_TYPE_EMBEDDED) {
// We can't determine the associated endpoint now.
incomplete_jacks_.push_back(UsbMidiJack(device, id, 0, 0));
}
return true;
}
bool UsbMidiDescriptorParser::ParseEndpoint(const uint8_t* data, size_t size) {
if (size < 4) {
DVLOG(1) << "ENDPOINT header size is incorrect.";
return false;
}
current_endpoint_address_ = data[2];
current_cable_number_ = 0;
return true;
}
bool UsbMidiDescriptorParser::ParseCSEndpoint(const uint8_t* data,
size_t size,
std::vector<UsbMidiJack>* jacks) {
const size_t kSizeForEmptyJacks = 4;
// CS_ENDPOINT must be of size 4 + n where n is the number of associated
// jacks.
if (size < kSizeForEmptyJacks) {
DVLOG(1) << "CS_ENDPOINT header size is incorrect.";
return false;
}
uint8_t num_jacks = data[3];
if (size != kSizeForEmptyJacks + num_jacks) {
DVLOG(1) << "CS_ENDPOINT header size is incorrect.";
return false;
}
for (size_t i = 0; i < num_jacks; ++i) {
uint8_t jack = data[kSizeForEmptyJacks + i];
auto it =
base::ranges::find(incomplete_jacks_, jack, &UsbMidiJack::jack_id);
if (it == incomplete_jacks_.end()) {
DVLOG(1) << "A non-existing MIDI jack is associated.";
return false;
}
if (current_cable_number_ > 0xf) {
DVLOG(1) << "Cable number should range from 0x0 to 0xf.";
return false;
}
// CS_ENDPOINT follows ENDPOINT and hence we can use the following
// member variables.
it->cable_number = current_cable_number_++;
it->endpoint_address = current_endpoint_address_;
jacks->push_back(*it);
incomplete_jacks_.erase(it);
}
return true;
}
void UsbMidiDescriptorParser::Clear() {
is_parsing_usb_midi_interface_ = false;
current_endpoint_address_ = 0;
current_cable_number_ = 0;
incomplete_jacks_.clear();
}
} // namespace midi