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Date: Fri, 26 Jun 2015 07:34:30 -0500
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Subject: Re: Another PropertiesChanged observation
From: Neil Martin <neil@vnp.com>
To: Jakub Pawlowski <jpawlowski@google.com>
Cc: linux-bluetooth <linux-bluetooth@vger.kernel.org>
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Hi Jakub,

Thanks for the response.  That makes sense - I'll give that a try.

I'm running this on a Raspberry Pi with a Medialink USB adapter which
(I believe) has a Broadcom chipset.

Neil

On Thu, Jun 25, 2015 at 9:30 PM, Jakub Pawlowski <jpawlowski@google.com> wrote:
> Hi Neil,
>
> On Thu, Jun 25, 2015 at 2:53 PM, Neil Martin <neil@vnp.com> wrote:
>> Hi,
>>
>> I've noticed that the bluetoothd console output shows a steady stream
>> of RSSI updates, yet only a fraction of these seem to translate into a
>> DBus PropertiesChanged signal.
>>
>> I've just seen 50 or so messages from bluetoothd of the form:
>>
>> bluetoothd[3867]: src/adapter.c:device_found_callback() hci0 addr
>> D0:4F:7E:2B:74:31, rssi -91 flags 0x0000 eir_len 15
>>
>> while only seeing a single PropertiesChanged signal from dbus-monitor
>> with an RSSI update.
>
> That's because by default there is a threshold of 8db:
>
> #define RSSI_THRESHOLD 8
>
> http://git.kernel.org/cgit/bluetooth/bluez.git/tree/src/device.c#n88
>
> So if RSSI is changed less than 8dB you don't get any updates through D-Bus.
>
> If you want to get updates through D-Bus, you should call
> SetDiscoveryFilter first, see doc:
> "If one or more discovery filters have been set, the RSSI
> delta-threshold, that is imposed by StartDiscovery by default, will
> not be applied."
> http://git.kernel.org/cgit/bluetooth/bluez.git/tree/doc/adapter-api.txt#n48
>
>
> Can I ask what kind of controller do you use ? Some just don't do
> packet deduplication during scan, and would report all  packets
> received, that would explain flow of events from kernel.
>
> Jakub
>
>>
>> Neil
>> --
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