For Minimilistic Object Oriented Kernel, Bluetooth 3.0 has been designed and integrated into it !!

1. Amritendu Mondal
Deepankar Patra
Mahesh Gupta
Re-engineering & Integrating
Bluetooth 3.0 Device Driver in MOOL

2. Linux Bluetooth Driver Architecture
10-08-20132
 Bluetooth stack is divided into two parts
 Controller Stack:
 Implemented in the silicon device containing Bluetooth radio &
a µ-processor
 Device Specific
 Host Stack:
 Implemented as a part of OS.
 BluetoothApplications interact with this

3. Controller Stack (Device Specific)
10-08-20133
 Contains following interfaces
 ACL (Asynchronous connectionless link)
 SCO (Synchronous Connection Oriented link)
 LMP (Link Management Protocol)
 HCI (Host Controller Interface)
 LELL (Low Energy Link Layer)

4. Host Stack (OS Specific)
10-08-20134
 L2CAP (Logical Link Controller andAdaptation Protocol)
 Passes packets to either HCI or on a host less system directly to
the link manager /ACL link.
 BNEP (Bluetooth Network Encapsulation Protocol)
 Bound to L2CAP
 Used for delivering network packets on top of L2CAP
 RFCOMM (Radio Frequency Communication)
 Bound to L2CAP
 Provides simple reliable data stream to users

5. Host Stack (OS Specific)
10-08-20135
 CMTP (CAPI MessageTransport Protocol)
 Used to transfer common ISDN application interface messages
 Data is transferred via L2CAP
 HIDP (Human Interface Device Profile)
 Provides support for Devices such as Keyboard, mouse etc.
 Designed to provide low latency link with low power
requirements.
 SDP (Service Discovery Protocol)
 Bound to L2CAP

6. Our Work
10-08-20136
 Re-engineering Bluetooth 3.0 device driver from C to object
oriented C++ code
 Integrating Re-engineered Bluetooth 3.0 in MOOL

7. Why Integrating Bluetooth 3.0 and
What’s new in it?
10-08-20137
 It gives 8 times more speedup than the previous version
 L2CAP is enhanced(EL2CAP), which adds an additional
ERTM(Enhanced Retransmission Mode) to the core
specification.
 A new featureAMP(Alternate Mac/Phy) is added to increase
the transmission speed
 All the stack protocols are affected due to these changes

8. Why Re-engineering?
10-08-20138
 Changes in signature of multiple functions, and in many cases
change in the implementation of the same also in Bluetooth
3.0 made it difficult to integrate it in MOOL
 Newly introduced features, likeAMP, require significant
effort to update the current code, as the code is not
modularized.

9. Why Re-engineering?
10-08-20139
 Some functions written only for the use of Bluetooth device,
can be extracted into a different class and reused in other
device drivers also(e.g. CRC extraction from packets).

10. Re-engineering Bluetooth 3.0
10-08-201310
 Controller Stack:
 Controller Stack is device specific.
 Each driver file is implemented by different vendors
independently.
 usb_driver instance is common which is initialized with function
pointers.
 Each such function pointer has specific action.
 But the implementation differs as the device does, so no
function level abstraction is possible at controller stack level

11. Re-engineering Bluetooth 3.0
10-08-201311
 Host Stack:
 This is OS specific and common for all devices
 Lots of scope was there for OO abstraction
 All the procedures related to one Protocol, kept in one file
initially, was broken up into multiple classes according their
functionalities

12. An Example of Code Modularization
10-08-201312
 Previously the entire L2CAP protocol was implemented in
two files l2cap_core.c and l2cap_sock.c.
 We divided the functions in l2cap_core.c into some classes,
which are:
 L2cap_core_channel
 L2cap_core_seq_list
 L2cap_core_sls
 L2cap_core_connection
 L2cap_core_signalling
 L2cap_core_hci

13. Code Conversion Steps
10-08-201313
 Take a specific protocol
 Extract feature wise independent functions
 Put them into unique classes
 Make static functions private, and non static ones public
 Write wrapper functions for the public methods and call the
class functions inside them
 Put all the class definitions in a .h file and their
implementations in a .cc file

14. Problems Faced
10-08-201314
 C++ keywords used as variable names in C drivers
 Structure declarations inside sizeof() is allowed in C, but not
in C++
 enum constructs were not supported and replaced with
macros
 (void *) casting needed to be casted to a specific type
 Support for some built-in C functions is not there in C++,
e.g. __builtin_choose_expr(evaluates one of two expressions
based on compile time evaluated condition)