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Reply-To: yunhanw@nestlabs.com
From:   Yunhan Wang <yunhanw@nestlabs.com>
Date:   Thu, 13 Dec 2018 15:10:25 -0800
Message-ID: <CALvjcs8wE7ntp6F23ALKU_3=CziqHgQ1OGgqdqO299sMoeKamQ@mail.gmail.com>
Subject: Re: BLE advertisement re-enabling after ble connection goes away
To:     Martin Turon <mturon@google.com>,
        Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
        Marcel Holtmann <marcel@holtmann.org>
Cc:     linux-bluetooth@vger.kernel.org
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Sender: linux-bluetooth-owner@vger.kernel.org
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Hi, Luiz

From what you describes, it seems Bluez is taking the responsibility
to reenable the advertisement after the previous ble connection goes
away.

When I did local test, the ble peripheral is using bluez, I create
gatt server and ble advertisment using Bluez DBus API,  when remote
connection in central disconnects, I see kernel in Bluez do receive
HCI_EV_DISCONN_COMPLETE event, and trigger
hci_req_reenable_advertising.

Maybe you can share the code location where Bluez is reenabling the
advertisement after ble connection goes away?

Thanks
Best wishes
Yunhan

On Thu, Dec 13, 2018 at 2:30 PM Martin Turon <mturon@google.com> wrote:
>
> Hi Luiz,
>
> Is this behavior also expected on raw hci sockets?  Because my observatio=
n is that when working with raw hci over such sockets, auto-reenable does n=
ot occur.
>
>     #define BTPROTO_HCI                 1
>     #define HCI_CHANNEL_USER         1
>
>     struct sockaddr_hci shci;
>     shci.hci_family =3D AF_BLUETOOTH;
>     shci.hci_dev =3D s_ble_hci_device;
>     shci.hci_channel =3D HCI_CHANNEL_USER;
>
>     s =3D socket(PF_BLUETOOTH, SOCK_RAW, BTPROTO_HCI);
>     rc =3D bind(s, (struct sockaddr *)&shci, sizeof(shci));
>
> Also, which API allows the user to control the advertising instances you =
describe?  Are they automatically created by the kernel when HCI is sent to=
 a raw socket to enable advertising?
>
> Thanks,
> Martin
>
> _____________________________
> Martin Turon  |  Google
>
>
>
> On Thu, Dec 13, 2018 at 1:49 PM Luiz Augusto von Dentz <luiz.dentz@gmail.=
com> wrote:
>>
>> Hi Yunhan,
>>
>> The BlueZ API operates a bit different than HCI, it keeps re-enabling th=
e advertisement if there is any instance active, but the user can stop this=
 by removing its instance once a connection is made, this is considered mor=
e convenient than having the user to reprogram the advertisement on every d=
isconnection.
>>
>> On Thu, 13 Dec 2018, 18:38 Yunhan Wang <yunhanw@nestlabs.com wrote:
>>>
>>> +Martin
>>>
>>> Hi, Luiz and Marcel
>>>
>>> When I take a look at the bluetooth code, it seems it is re-enabling
>>> ble advertisement after ble connection goes away. Any idea?
>>>
>>> https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth.git=
/tree/net/bluetooth/hci_event.c#n2634
>>> https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth.git=
/tree/net/bluetooth/hci_event.c#n2712
>>> https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth.git=
/tree/net/bluetooth/hci_request.c#n1386
>>> https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth.git=
/tree/net/bluetooth/hci_request.c#n1734
>>>
>>> Thanks
>>> Best wishes
>>> Yunhan
>>> On Wed, Dec 5, 2018 at 6:54 PM Yunhan Wang <yunhanw@nestlabs.com> wrote=
:
>>> >
>>> > Hi, Luiz and Marcel
>>> >
>>> > May I have a question on ble behavior on BLE re-advertisement?
>>> >
>>> > According to Bluetooth spec Vol. 3 (the host volume), 9.2.4.2, "The
>>> > device shall remain in general discoverable mode until a connection i=
s
>>> > established or the Host terminates the mode."
>>> >
>>> > There is no description on re-enabling the advertising "after"
>>> > disconnection, so the responsibility for re-enabling the advertising
>>> > is bluez or kernel or application code? In other words, does kernel o=
r
>>> > bluez or application would re-enable the ble advertisement after ble
>>> > disconnection happens?
>>> >
>>> > Thanks
>>> > Best wishes
>>> > Yunhan.