AllocateGPADL
status_t status = AllocateGPADL(fRingBufferLength, &fRingBuffer, &fRingGPADL);
return device->AllocateGPADL(length, _buffer, _gpadl);
status_t AllocateGPADL(uint32 length, void** _buffer, uint32* _gpadl);
return vmbus->AllocateGPADL(channel, length, _buffer, _gpadl);
status_t AllocateGPADL(uint32 channelID, uint32 length, void** _buffer,