macos - 在 OSX 上查找与 CoreAudio 设备关联的 USB VID/PID

Question

我需要确定任意 CoreAduio AudioDevice 与哪个物理 USB 设备相关(通过 VID/PID/SerialNumber)。 CoreAudio 允许查询各种设备属性，例如传输类型(在我的例子中是 USB)、UID(跨 session 和机器唯一)和一些配置字符串。

IOKit 和 CoreAudio 的音频部分都有音频设备的表示，但我不清楚如何弥合两者之间的差距。 (好像我应该能够查询 AudioDevice 的 IOAudioDevice...)

Answer 1

我找到了以下 post from an Apple CoreAudio engineer描述如何从 AudioDeviceID 获取 IOUSBDeviceInterface:

There is no direct mapping between the two. But the best way to do it would be:

1. get the UID string for the device from the HAL
2. Make a matching dictionary that searches for IOAudioEngine objects
3. Iterate through the matching services until you find the one with the UID property that matches what you got from the HAL
4. Walk the IORegistry from here to find the USB object you are looking for

这就是代码的样子:

#include <IOKit/IOKitLib.h>
#include <IOKit/audio/IOAudioDefines.h>
#include <IOKit/usb/USB.h>

AudioDeviceID deviceID = ...

// get device UID for AudioDevice ID
AudioObjectPropertyAddress address = {kAudioDevicePropertyDeviceUID, kAudioObjectPropertyScopeOutput, 0};
UInt32 size = sizeof(CFStringRef);
CFStringRef uid = NULL;
OSStatus err = AudioObjectGetPropertyData(deviceID, &address, 0, NULL, &size, &uid);

NSNumber *vid, *pid;

// find matching IOAudioEngine object
io_iterator_t it;
if (IOServiceGetMatchingServices(kIOMasterPortDefault, IOServiceMatching(kIOAudioEngineClassName), &it) == KERN_SUCCESS) {
    io_service_t service;
    while ((service = IOIteratorNext(it)) != 0) {
        CFStringRef uniqueID = IORegistryEntryCreateCFProperty(service, CFSTR(kIOAudioEngineGlobalUniqueIDKey), kCFAllocatorDefault, 0);
        if (uniqueID && CFEqual(uniqueID, uid)) {
            vid = CFBridgingRelease(IORegistryEntryCreateCFProperty(service, CFSTR(kUSBVendorID), kCFAllocatorDefault, 0));
            pid = CFBridgingRelease(IORegistryEntryCreateCFProperty(service, CFSTR(kUSBProductID), kCFAllocatorDefault, 0));
        }
        CFRelease(uniqueID);
        if (vid || pid) break;
    }
    IOObjectRelease(it);
}