Bluetooth HFP DDI IOCTLs

Article
03/06/2023

Windows 8 introduces a set of I/O control codes (IOCTLs) as part of a DDI that allows the audio driver to work with the Hands-free profile (HFP) class driver, to operate a Bluetooth audio bypass connection.

Unless otherwise stated, the following is true for all the IOCTLs in this section:

If the request is successful, the Information member of the STATUS_BLOCK structure is set to the size, in bytes, of the output buffer. Otherwise, the Information member is set to zero. The Status member is set to an NTSTATUS value.
All IOCTLS require IRQL <= PASSIVE_LEVEL.
The audio driver should use the IOCTLs with the IRP_MJ_DEVICE_CONTROL request.

For most of the IOCTL function codes, the audio driver must initialize the FileObject pointer in the IO_STACK_LOCATION for the HFP driver when the audio driver initializes a device control IRP to send to the HFP driver. The audio driver typically retrieves the file object pointer by calling IoGetDeviceObjectPointer.

The audio driver will likely send many of these requests on an arbitrary thread (in other words, an “asynchronous” request). In these cases the audio driver will need to build the IRP itself using the IoAllocateIrp method, and set fields in the IRP directly rather than calling IoBuildDeviceIoControlRequest.

The following topics provide more details about these Windows 8 IOCTLs:

IOCTL_BTHHFP_DEVICE_GET_DESCRIPTOR

IOCTL_BTHHFP_DEVICE_GET_VOLUMEPROPERTYVALUES

IOCTL_BTHHFP_DEVICE_GET_KSNODETYPES

IOCTL_BTHHFP_DEVICE_GET_CONTAINERID

IOCTL_BTHHFP_DEVICE_REQUEST_CONNECT

IOCTL_BTHHFP_DEVICE_REQUEST_DISCONNECT

IOCTL_BTHHFP_DEVICE_GET_CONNECTION_STATUS_UPDATE

IOCTL_BTHHFP_SPEAKER_SET_VOLUME

IOCTL_BTHHFP_SPEAKER_GET_VOLUME_STATUS_UPDATE

IOCTL_BTHHFP_MIC_SET_VOLUME

IOCTL_BTHHFP_MIC_GET_VOLUME_STATUS_UPDATE