When going to Windows' "Device manager" and clicking on (almost) any device in the list one piece of information in the "General" tab is called "Location". That is a string that is either:
That info is available through Windows' Unified device property model APIs.
What I'm looking for is to get that information from a given IMFActivate object.
Is there a way to do so? I can't find how to get "device" info from that activation object. The only piece of data I have is it's "symbolic link" (in my case, this string: \\?\usb#vid_04b4&pid_8888&mi_00#9&4fe28be&0&0000#{e5323777-f976-4f5b-9b55-b94699c46e44}\global) but that link's format is nothing like the string I see in "Location".
Thus my question: how to get device's "Location" string, given its IMFActivate object?
UPDATE
Here's the code I'm using to "convert" the symbolic link, provided by IMFActivate to a device id string, recognizable by setup-api functions and then extracting the "location string":
CString symLink2Location(const CString & _symLink)
{
DEVINST di;
CString devId = _symLink;
devId = devId.Left( devId.Find(L"#{") );
devId.Replace(L"\\\\?\\", L"");
devId.Replace(L"#", L"\\");
const auto rc = CM_Locate_DevNodeW(&di, devId.GetBuffer(), CM_LOCATE_DEVNODE_NORMAL);
if(rc == CR_SUCCESS){
DEVPROPTYPE dpt;
ULONG sz = MAX_PATH;
WCHAR prop[MAX_PATH];
if(CM_Get_DevNode_PropertyW(di, &DEVPKEY_Device_LocationInfo, &dpt, (PBYTE)&prop, &sz, 0) == CR_SUCCESS){
if(dpt == DEVPROP_TYPE_STRING){
return prop;
}
}
}
return L"";
}
UPDATE 2
Here are the 3 audio input devices as seen in devmgmt.msc under "Sound, video and game controllers":
\\?\SWD#MMDEVAPI#{0.0.1.00000000}.{751fe058-cef2-4d28-bbeb-e438981938d7}#{2eef81be-33fa-4800-9670-1cd474972c3f})\\?\SWD#MMDEVAPI#{0.0.1.00000000}.{59267d2e-940b-45f5-8655-45372787bd85}#{2eef81be-33fa-4800-9670-1cd474972c3f})\\?\SWD#MMDEVAPI#{0.0.1.00000000}.{26a4f608-cbd8-4206-b958-d57ee6847153}#{2eef81be-33fa-4800-9670-1cd474972c3f})All 3 are USB devices, all 3 are listed when calling MFEnumDeviceSources but their "symbolic link" doesn't resolve into a hardware device.
the string returned from IMFAttributes::Get[Allocated]String with MF_DEVSOURCE_ATTRIBUTE_SOURCE_TYPE_VIDCAP_SYMBOLIC_LINK or MF_DEVSOURCE_ATTRIBUTE_SOURCE_TYPE_AUDCAP_SYMBOLIC_LINK this is device interface string which we can use as input to CM_Get_Device_Interface_PropertyW. for get location information (if it present) need do 3 steps:
CM_Get_Device_Interface_PropertyW with
DEVPKEY_Device_InstanceId - as result we got device instance
identifier of a deviceCM_Locate_DevNodeWCM_Get_DevNode_PropertyW with
DEVPKEY_Device_LocationInfocode example:
CONFIGRET PrintLocation(PCWSTR pszDeviceInterface)
{
ULONG cb = 0, rcb = 64;
static volatile UCHAR guz;
PVOID stack = alloca(guz);
DEVPROPTYPE PropertyType;
CONFIGRET err;
union {
PVOID pv;
PWSTR sz;
PBYTE pb;
};
do
{
if (cb < rcb)
{
rcb = cb = RtlPointerToOffset(pv = alloca(rcb - cb), stack);
}
if (!(err = CM_Get_Device_Interface_PropertyW(pszDeviceInterface, &DEVPKEY_Device_InstanceId, &PropertyType, pb, &rcb, 0)))
{
if (PropertyType == DEVPROP_TYPE_STRING)
{
DbgPrint("InstanceId=%S\n", sz);
DEVINST dnDevInst;
if (!(err = CM_Locate_DevNodeW(&dnDevInst, sz, CM_LOCATE_DEVNODE_NORMAL)))
{
do
{
if (cb < rcb)
{
rcb = cb = RtlPointerToOffset(pv = alloca(rcb - cb), stack);
}
if (!(err = CM_Get_DevNode_PropertyW(dnDevInst, &DEVPKEY_Device_LocationInfo, &PropertyType, pb, &rcb, 0)))
{
if (PropertyType == DEVPROP_TYPE_STRING)
{
DbgPrint("Location=%S\n", sz);
}
else
{
err = CR_WRONG_TYPE;
}
}
} while (err == CR_BUFFER_SMALL);
}
}
else
{
err = CR_WRONG_TYPE;
}
break;
}
} while (err == CR_BUFFER_SMALL);
return err;
}
of course if hardcode buffer size, function can make more simply
CONFIGRET PrintLocationSimp(PCWSTR pszDeviceInterface)
{
WCHAR buf[1024];
DEVPROPTYPE PropertyType;
ULONG BufferSize = sizeof(buf);
CONFIGRET err;
if (!(err = CM_Get_Device_Interface_PropertyW(pszDeviceInterface, &DEVPKEY_Device_InstanceId, &PropertyType, (PBYTE)buf, &BufferSize, 0)))
{
if (PropertyType == DEVPROP_TYPE_STRING)
{
DbgPrint("InstanceId=%S\n", buf);
DEVINST dnDevInst;
if (!(err = CM_Locate_DevNodeW(&dnDevInst, buf, CM_LOCATE_DEVNODE_NORMAL)))
{
BufferSize = sizeof(buf);
if (!(err = CM_Get_DevNode_PropertyW(dnDevInst, &DEVPKEY_Device_LocationInfo, &PropertyType, (PBYTE)buf, &BufferSize, 0)))
{
if (PropertyType == DEVPROP_TYPE_STRING)
{
DbgPrint("Location=%S\n", buf);
}
else
{
err = CR_WRONG_TYPE;
}
}
}
}
else
{
err = CR_WRONG_TYPE;
}
}
return err;
}
and for IMFActivate we can use next code:
void mftest()
{
IMFAttributes *pAttributes;
if (SUCCEEDED(MFCreateAttributes(&pAttributes, 1)))
{
UINT32 count, cchLength;
IMFActivate **ppDevices, *pDevice;
if (SUCCEEDED(pAttributes->SetGUID(
MF_DEVSOURCE_ATTRIBUTE_SOURCE_TYPE, MF_DEVSOURCE_ATTRIBUTE_SOURCE_TYPE_VIDCAP_GUID)) &&
SUCCEEDED(MFEnumDeviceSources(pAttributes, &ppDevices, &count)) &&
count)
{
PVOID pv = ppDevices;
do
{
pDevice = *ppDevices++;
PWSTR pszDeviceInterface;
if (SUCCEEDED(pDevice->GetAllocatedString(
MF_DEVSOURCE_ATTRIBUTE_SOURCE_TYPE_VIDCAP_SYMBOLIC_LINK, &pszDeviceInterface, &cchLength)))
{
DbgPrint("%S\n", pszDeviceInterface);
PrintLocation(pszDeviceInterface);
CoTaskMemFree(pszDeviceInterface);
}
} while (--count);
CoTaskMemFree(pv);
}
pAttributes->Release();
}
}