Re: [BlueZ PATCH v2] doc: Add Advertisement Monitoring API

[Szymon Janc <szymon.janc@codecoup.pl>]

Hi,

On Thursday, 16 April 2020 05:09:03 CEST Miao-chen Chou wrote:
> This patch proposes an Advertisement Monitoring API for an application to
> register a job of monitoring ADV reports with content filter and RSSI
> thresholds.
> 
> Signed-off-by: Miao-chen Chou <mcchou@chromium.org>
> ---
> 
> Changes in v2:
> - Rename the interfaces and functions.
> - Adopt the object manager mechanism so that a client can expose
> multiple monitor objects and expect to get notified on whether the
> monitor has been activated or not.
> - Change the contract of DeviceFound so that it is called to indicate
> the starting point of monitoring on a device instead of reporting every
> ADV. In other words, the client is expected to monitor corresponding
> device events.
> 
>  doc/advertisement-monitor-api.txt | 127 ++++++++++++++++++++++++++++++
>  1 file changed, 127 insertions(+)
>  create mode 100644 doc/advertisement-monitor-api.txt
> 
> diff --git a/doc/advertisement-monitor-api.txt
> b/doc/advertisement-monitor-api.txt new file mode 100644
> index 000000000..6491dab29
> --- /dev/null
> +++ b/doc/advertisement-monitor-api.txt
> @@ -0,0 +1,127 @@
> +BlueZ D-Bus Advertisement Monitor API Description
> +*************************************************
> +
> +This API allows an client to specify a job of monitoring advertisements by
> +registering the root of hierarchy and then exposing advertisement monitors
> +under the root with filtering conditions, thresholds of RSSI and timers
> +of RSSI thresholds.
> +
> +Once a monitoring job is activated by BlueZ, the client can expect to get
> +notified on the targeted advertisements no matter if there is an ongoing
> +discovery session (a discovery session is started/stopped with methods in
> +org.bluez.Adapter1 interface).
> +
> +Advertisement Monitor hierarchy
> +===============================
> +Service		org.bluez
> +Interface	org.bluez.AdvertisementMonitor1
> +Object path	freely definable
> +
> +Methods		void Release() [noreply]
> +
> +			This gets called as a signal for a client to 
perform
> +			clean-up when (1)a monitor cannot be activated 
after it
> +			was exposed or (2)a monitor has been 
deactivated.
> +
> +		void Activate() [noreply]

Isn't is enough for RegisterApplication to return to ack this?

> +
> +			After a monitor was exposed, this gets called as 
a
> +			signal for client to get acknowledged when a 
monitor
> +			has been activated, so the client can expect to 
receive
> +			calls on DeviceFound() or DeviceLost().
> +
> +		void DeviceFound(object device) [noreply]
> +
> +			This gets called to notify the client of finding 
the
> +			targeted device. Once receiving the call, the 
client
> +			should start to monitor the corresponding device 
to
> +			retrieve the changes on RSSI and advertisement 
content.
> +
> +		void DeviceLost(object device) [noreply]
> +
> +			This gets called to notify the client of losing 
the
> +			targeted device. Once receiving this call, the 
client
> +			should stop monitoring the corresponding device.
> +
> +Properties	uint8 Type [read-only]
> +
> +			The type of a monitor can be the following 
values. More
> +			will be added.
> +			0x01 - Patterns with logic OR applied
> +				Supported only if "patterns-with-
logic-or-
> +				applied" is supported.
> +
> +		(Int16, Uint16, Int16, Uint16) RSSIThreshholdsAndTimers 
[read-only,
> optional] +
> +			This contains HighRSSIThreshold, 
HighRSSIThresholdTimer,
> +			LowRSSIThreshold, LowRSSIThresholdTimer in 
order. The
> +			unit of HighRSSIThreshold and LowRSSIThreshold 
is dBm.
> +			The unit of HighRSSIThresholdTimer and
> +			LowRSSIThresholdTimer is second.
> +
> +			If these are provided, RSSI would be used as a 
factor to
> +			notify the client of whether a device stays in 
range or
> +			move out of range. A device is considered in-
range when
> +			the RSSIs of the received advertisement(s) 
during
> +			HighRSSIThresholdTimer seconds exceed 
HighRSSIThreshold.
> +			Likewise, a device is considered out-of-range 
when the
> +			RSSIs of the received advertisement(s) during
> +			LowRSSIThresholdTimer do not reach 
LowRSSIThreshold.
> +
> +		array{(uint8, uint8, string)} Patterns [read-only, 
optional]
> +
> +			If Type is set to 0x01, this must exist and has 
at least
> +			one entry in the array.
> +
> +			The structure of a pattern contains the 
following.
> +			uint8 start_position
> +				The index in an AD data field where 
the search
> +				should start. The beginning of an AD 
data field
> +				is index 0.
> +			uint8 AD_data_type
> +				See https://www.bluetooth.com/
specifications/
> +				assigned-numbers/generic-access-
profile/ for
> +				the possible allowed value.
> +			string content_of_pattern
> +				This is the value of the pattern.
> +
> +=======================================
> +Service		org.bluez
> +Interface	org.bluez.AdvertisementMonitorManager1
> +Object path	/org/bluez/{hci0,hci1,...}
> +Methods		void RegisterApplication(object application)
> +
> +			This registers a hierarchy of advertisement 
monitors.
> +			The application object path together with the D-
Bus
> +			system bus connection ID define the 
identification of
> +			the application registering advertisement 
monitors.
> +
> +			Possible errors: 
org.bluez.Error.InvalidArguments
> +					 
org.bluez.Error.AlreadyExists
> +
> +		void UnregisterApplication(object application)
> +
> +			This unregisters advertisement monitors that 
have been
> +			previously registered. The object path parameter 
must
> +			match the same value that has been used on
> +			registration.
> +
> +			Possible errors: 
org.bluez.Error.InvalidArguments
> +					 
org.bluez.Error.DoesNotExist
> +
> +Properties	array{string} SupportedFeatures [read-only]
> +
> +			This reflects the supported features of 
advertisement
> +			monitoring. An application should check this 
before
> +			instantiate and expose an object of
> +			org.bluez.AdvertisementMonitor1.
> +
> +			Here are the potential features. More will be 
added.
> +			software-based-filtering
> +				The filtering process is mainly done 
in BlueZ.
> +			patterns-with-logic-or-applied
> +				Logic OR would be applied among the 
patterns
> +				provided by a monitor object.
> +			rssi-monitoring
> +				Values of RSSIThreshholdsAndTimers 
would be
> +				applied during the filtering process.


I'm bit confused about this API. Why can't this be achieved with (possible 
extended)  SetDiscoveryFilter? We could just add extra prop to Device1 to 
indicate that device is "present".


-- 
pozdrawiam
Szymon Janc