From: Mark Harmstone <hellas@burntcomma.com>
Subject: [PATCH 4/5] mmdevapi: add property for device path
Message-Id: <545CDE0E.4000709@burntcomma.com>
Date: Fri, 07 Nov 2014 14:58:22 +0000

---
 dlls/mmdevapi/devenum.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/dlls/mmdevapi/devenum.c b/dlls/mmdevapi/devenum.c
index 4d77ec9..2a64edf 100644
--- a/dlls/mmdevapi/devenum.c
+++ b/dlls/mmdevapi/devenum.c
@@ -264,6 +264,42 @@ static HRESULT MMDevice_SetPropValue(const GUID *devguid, DWORD flow, REFPROPERT
     return hr;
 }
 
+static WCHAR* format_device_path(DeviceProps *props, GUID *id)
+{
+    WCHAR* s;
+
+    if (props->connection_type == AudioDeviceConnectionType_USB || props->connection_type == AudioDeviceConnectionType_PCI) {
+        static const WCHAR usbformatW[] = { '{','1','}','.','U','S','B','\\','V','I','D','_',
+            '%','0','4','X','&','P','I','D','_','%','0','4','X','\\',
+            '1','&','%','0','8','X',0 }; // "{1}.USB\VID_%04X&PID_%04X\1&%08X"
+        static const WCHAR pciformatW[] = { '{','1','}','.','H','D','A','U','D','I','O','\\','F','U','N','C','_','0','1','&',
+            'V','E','N','_','%','0','4','X','&','D','E','V','_',
+            '%','0','4','X','\\','1','&','%','0','8','X',0 }; // "{1}.HDAUDIO\FUNC_01&VEN_%04X&DEV_%04X\1&%08X"
+        UINT serial_number;
+
+        /* As hardly any audio devices have serial numbers, Windows instead
+        appears to use a persistent random number. We emulate this here
+        by instead using the last 8 hex digits of the GUID. */
+        serial_number = (id->Data4[4] << 24) | (id->Data4[5] << 16) | (id->Data4[6] << 8) | id->Data4[7];
+
+        if (props->connection_type == AudioDeviceConnectionType_USB) {
+            s = HeapAlloc(GetProcessHeap(), 0, sizeof(WCHAR) * 37);
+
+            wsprintfW( s, usbformatW, props->vendor_id, props->product_id, serial_number);
+        } else if (props->connection_type == AudioDeviceConnectionType_PCI) {
+            s = HeapAlloc(GetProcessHeap(), 0, sizeof(WCHAR) * 49);
+
+            wsprintfW( s, pciformatW, props->vendor_id, props->product_id, serial_number);
+        } else {
+            return NULL;
+        }
+
+        return s;
+    } else {
+        return NULL;
+    }
+}
+
 /* Creates or updates the state of a device
  * If GUID is null, a random guid will be assigned
  * and the device will be created
@@ -279,6 +315,10 @@ static MMDevice *MMDevice_Create(DeviceProps *props, GUID *id, EDataFlow flow, D
         {0x233164c8, 0x1b2c, 0x4c7d, {0xbc, 0x68, 0xb6, 0x71, 0x68, 0x7a, 0x25, 0x67}}, 1
     };
 
+    static const PROPERTYKEY devicepath_key = { // undocumented? - {b3f8fa53-0004-438e-9003-51a46e139bfc},2
+        {0xb3f8fa53, 0x0004, 0x438e, {0x90, 0x03, 0x51, 0xa4, 0x6e, 0x13, 0x9b, 0xfc}}, 2
+    };
+
     for (i = 0; i < MMDevice_count; ++i)
     {
         MMDevice *device = MMDevice_head[i];
@@ -329,6 +369,7 @@ static MMDevice *MMDevice_Create(DeviceProps *props, GUID *id, EDataFlow flow, D
         if (!RegCreateKeyExW(key, reg_properties, 0, NULL, 0, KEY_WRITE|KEY_READ, NULL, &keyprop, NULL))
         {
             PROPVARIANT pv;
+            WCHAR* devpath;
 
             pv.vt = VT_LPWSTR;
             pv.u.pwszVal = props->id;
@@ -342,6 +383,19 @@ static MMDevice *MMDevice_Create(DeviceProps *props, GUID *id, EDataFlow flow, D
             pv.u.ulVal = props->form_factor;
             MMDevice_SetPropValue(id, flow, &PKEY_AudioEndpoint_FormFactor, &pv);
 
+            // only create registry entry if none exists already, to allow manual override
+            if (FAILED(MMDevice_GetPropValue(id, flow, &devicepath_key, &pv)) || pv.vt != VT_LPWSTR)
+            {
+                devpath = format_device_path(props, id);
+                if (devpath) {
+                    pv.vt = VT_LPWSTR;
+                    pv.u.pwszVal = devpath;
+                    MMDevice_SetPropValue(id, flow, &devicepath_key, &pv);
+
+                    HeapFree(GetProcessHeap(), 0, devpath);
+                }
+            }
+
             RegCloseKey(keyprop);
         }
         RegCloseKey(key);