# Architecture
Source: [https://docs.qualcomm.com/doc/80-70015-13/topic/bt_architecture_overview.html](https://docs.qualcomm.com/doc/80-70015-13/topic/bt_architecture_overview.html)
The Bluetooth software architecture consists of open-source and Qualcomm proprietary
software.
The following figure shows how the user space and kernel space components interact
through a socket interface. In the user space, the sample test applications interact
with the BlueZ Bluetooth daemon to run Bluetooth functions.
Figure : Bluetooth software architecture
The Bluetooth software architecture consists of user space, kernel space, and Bluetooth
controller.
## User space components
The user space contains the following Bluetooth applications, daemon, and interface
layers:
| Component | Description |
| --- | --- |
| Bluetooth daemon (bluetoothd) |
- A central daemon.
- Contains DBUS interfaces for the user interface and other
subsystems.
- Reduces exposure to low-level details.
- Extends with plugins.
|
| Bluetooth-tools |
- Contains Bluetooth test applications.
|
| bluetoothctl |
- A test tool to verify Bluetooth functionality.
- Provides options to verify using a command-line interface
(CLI).
|
| mpris-proxy |
- A proxy DBUS service for Media Player Remote Interfacing
Specification (MPRIS).
|
| obexctl |
- A test tool to verify OBEX functionality.
|
| OBEX daemon (obexd) |
- A daemon for the OBEX profile.
- Contains DBUS interfaces for the user interface.
|
| ofono |
- Provides a test application for HFP.
- Searches for modem and then enables HFP audio gateway
role.
|
| ofono-tests | Provides options to perform the following functions:
- Dial
- Answer
- Create multiparty
- Hold and answer
- Swap
- Release calls
|
| PulseAudio |
- A sound server for portable operating system interface
(POSIX).
- Facilitates advanced operations on sound data that passes
between the applications and hardware.
|
## Kernel space components
The kernel space contains the following core components and drivers:
| Component | Description |
| --- | --- |
| Bluetooth management (btmgmt) |
- Enables user space to control kernel operations.
- Supports GAP functionalities such as adapter settings,
device discovery, and device pairing.
|
| BlueZ Host Control Interface (HCI) core |
- Sends and receives HCI commands/events from the user
space HCI component to the Qualcomm Bluetooth driver
through the raw socket.
|
| HCI |
- A layer in the Bluetooth protocol stack.
- Defines how the host and the Bluetooth radio controller
must interact.
|
| Logical Link Control and Adaption Protocol (L2CAP) |
- Breaks large data packets into smaller frames for
transmission. The destined component re-assembles the
frames.
- Handles quality-of-service (QoS) requirements.
|
| Qualcomm Bluetooth driver |
- Handles the Bluetooth general-purpose input/output
(GPIO) configurations.
- Enables or disables the regulators to turn the chip on
or off.
- Handles the download of Bluetooth patch and nonvolatile
(NV) during the Bluetooth on sequence.
|
| Radio Frequency Communications (RFCOMM) |
- Creates reliable and stream-based channels.
- Contains 30 ports. In contrast, the Transmission Control
Protocol (TCP) has 65,535 ports.
- Each RFCOMM connection is encapsulated in a L2CAP
connection.
|
| Session
Description Protocol (SDP) |
- Provides the means for client applications to discover
the existing services provided by server
applications.
- Provides the attributes of services, which include the
type or class of service offered, and the mechanism or
protocol information required to use the service.
|
| SLIMbus Bluetooth driver |
- Configures, opens, and closes the SLIMbus ports for
Bluetooth audio use cases.
|
| Synchronous Connection Oriented (SCO) |
- A type of data link in Bluetooth.
- Provides links that are point-to-point connections
between a master device and a single slave device.
|
| Universal asynchronous receiver/transmitter (UART) serial
driver |
- A teletype (TTY) serial driver facilitates communication
with the Bluetooth controller.
|
## Bluetooth controller components
The Bluetooth controller components include the Link Manager Protocol (LMP), link
controller, and baseband and RF system of the connectivity chipset.
Last Published: Oct 14, 2024
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