Proximity (Link Loss) and Find Me

by: INdT/OpenBossa BlueZ team

Proximity (PXP) and Find Me (FMP) profiles are publicly available since second half of June. BlueZ does not officially support LE GATT profiles yet. There are pending kernel patches related to interleaved BR/LE discovery, security manager and passive scanning that require more feedback from the community and review. This process takes time, in the meanwhile we would like to share the status and reference to the source code.

First of all, it needs to be clear that Proximity and Find Me are distinct profiles located under the same proximity/ sub-directory, only because they share a common GATT service: Immediate Alert Service.

Proximity’s Link Loss is functional, Path Loss requires tuning and real hardware to test against it, and thus is disabled by default in the configuration file (proximity.conf). After creating a device D-Bus object which supports Link Loss (i.e. a LE device on the Proximity Reporter role), the “high” alert level is automatically written on the remote device, meaning that UI is not necessary to enable alert level (unless you want change it to “mild” or “none”). The “test-proximity” script (under the test/ sub-directory) can be used to change alert levels and also test Find Me (which basically consists of writing some alert level to a characteristic of the Immediate Alert Service).

For LE profiles, the new Bluetooth Management kernel interface (mgmt) is required, mainly due to Security Manager requirements. Even though device discovery works on both interfaces (HCI and Management), only mgmt can be used for current LE GATT profiles, because they require at least security mode 1 level 2.

For re-connections, it is planned to trigger automatic connections based on user (or platform specific) events. For instance, automatic connections would be enabled during a configurable time when the user unlocks the screen (Desktop, phone, tablet, …). The idea is to control connections based on profile requirements and user input. Power saving mode (when scanning) is not being addressed since automatic connection has a small active period.

Much of the code is still under development. While it is not upstream, it can be found in the repositories below.

userspace: git:// proximity-devel
kernel: git:// proximity-devel