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Subject: Re: [BlueZ PATCH v1 1/3] doc: Add Advertisement Monitor Device
 Tracking event
From:   Marcel Holtmann <marcel@holtmann.org>
In-Reply-To: <CAGPPCLB9j4Bgb=rraxdOBK+iACVO7+jJAHsPRn7B4JpTr3v-cQ@mail.gmail.com>
Date:   Wed, 29 Sep 2021 15:26:32 +0200
Cc:     Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
        linux-bluetooth <linux-bluetooth@vger.kernel.org>,
        CrosBT Upstreaming <chromeos-bluetooth-upstreaming@chromium.org>,
        Miao-chen Chou <mcchou@google.com>,
        Yun-Hao Chung <howardchung@google.com>,
        Alain Michaud <alainmichaud@google.com>
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References: <20210927201657.593569-1-mmandlik@google.com>
 <20210927131456.BlueZ.v1.1.I7f6bdb9282c1e12ffc6c662674678f2b1cb69182@changeid>
 <AB183B14-B822-4A1D-BC13-B997C0A2F7F5@holtmann.org>
 <CAGPPCLB9j4Bgb=rraxdOBK+iACVO7+jJAHsPRn7B4JpTr3v-cQ@mail.gmail.com>
To:     Manish Mandlik <mmandlik@google.com>
Precedence: bulk

Hi Manish,

can we please stop top-posting and follow the general rules of this mailing list.

> The controller sends advertising reports in addition to this event. This event is reported only when there are active and matched advertisement monitors. 
> 
> Whenever an advertisement matches a Monitor, the controller sends this event with Monitor_state set to 1, indicating that it has started monitoring that particular device. After that it may send one or more advertising reports based on the configured Sampling_period for that Monitor. Once the controller stops monitoring that device, it sends the same event again with Monitor_state set to 0 to notify the host that it has stopped monitoring that particular device.
> 
> Since this event is sent only twice (at start and end of monitoring) per monitoring period [1], combining this with the Sampling_period - 0xFF (send only one advertisement report per monitoring period) [2], we can drastically reduce the number of events generated by the controller during background scanning but still have the DeviceFound/DeviceLost functionality in bluetoothd.
> 
> So, it will be better to keep this event separate than the Device Found event as it is triggered only during monitoring. Please let me know what you think about this.
> [1]: https://docs.microsoft.com/en-us/windows-hardware/drivers/bluetooth/microsoft-defined-bluetooth-hci-commands-and-events#hci_vs_msft_le_monitor_device_event
> [2]: https://docs.microsoft.com/en-us/windows-hardware/drivers/bluetooth/microsoft-defined-bluetooth-hci-commands-and-events#hci_vs_msft_le_monitor_advertisement

This is what I was thinking:

diff --git a/doc/mgmt-api.txt b/doc/mgmt-api.txt
index 97d33e30a15d..fa9121c3bc87 100644
--- a/doc/mgmt-api.txt
+++ b/doc/mgmt-api.txt
@@ -4263,6 +4263,7 @@ Device Found Event
                1       Legacy Pairing
                2       Not Connectable
                3       Reserved (not in use)
+               4       Device Tracked
 
        For the RSSI field a value of 127 indicates that the RSSI is
        not available. That can happen with Bluetooth 1.1 and earlier
@@ -4910,3 +4911,19 @@ Controller Resume Event
        Address_Type. Otherwise, Address and Address_Type will both be zero.
 
        This event will be sent to all management sockets.
+
+Device Lost Event
+=================
+
+       Event Code:             0x002f
+       Controller Index:       <controller id>
+       Event Parameters:       Address (6 Octets)
+                               Address_Type (1 Octet)
+
+       This event indicates that a tracked device was no longer found
+       during monitoring.
+
+       Possible values for the Address_Type parameter:
+               0       BR/EDR
+               1       LE Public
+               2       LE Random

I really don’t get why we would make it more complicated for mgmt-api and thus bluetoothd.

Regards

Marcel