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From:   Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date:   Fri, 14 Dec 2018 03:21:24 +0200
Message-ID: <CABBYNZ+-jWMU4-AKt-90WMtzMs0sasefrZnf2ZZ1Ev7vTjbb8Q@mail.gmail.com>
Subject: Re: BLE advertisement re-enabling after ble connection goes away
To:     Yunhan Wang <yunhanw@nestlabs.com>
Cc:     mturon@google.com, Marcel Holtmann <marcel@holtmann.org>,
        "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>
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Hi Yunhan,

You already answered your question, it is reenabled by
hci_req_reenable_advertising


On Fri, Dec 14, 2018 at 1:13 AM Yunhan Wang <yunhanw@nestlabs.com> wrote:
>
> Hi, Luiz
>
> Rephrasing a little bit..
>
> From what you describes, it seems Bluez is taking the responsibility
> to reenable the advertisement in peripheral side 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 in peripheral
> side 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
> On Thu, Dec 13, 2018 at 3:10 PM Yunhan Wang <yunhanw@nestlabs.com> wrote:
> >
> > 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 observ=
ation is that when working with raw hci over such sockets, auto-reenable do=
es not 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));

Raw socket commands might actually work but here you are using it with
a user channel which afaik disables the stack processing.

> > > Also, which API allows the user to control the advertising instances =
you describe?  Are they automatically created by the kernel when HCI is sen=
t to a raw socket to enable advertising?

Nope you need to use the management interface to use the advertising
instances, or better yet use the D-Bus API:

https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/doc/advertising-api=
.txt

> > > Thanks,
> > > Martin
> > >
> > > _____________________________
> > > Martin Turon  |  Google
> > >
> > >
> > >
> > > On Thu, Dec 13, 2018 at 1:49 PM Luiz Augusto von Dentz <luiz.dentz@gm=
ail.com> wrote:
> > >>
> > >> Hi Yunhan,
> > >>
> > >> The BlueZ API operates a bit different than HCI, it keeps re-enablin=
g the 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=
 more convenient than having the user to reprogram the advertisement on eve=
ry disconnection.
> > >>
> > >> 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-enablin=
g
> > >>> 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> w=
rote:
> > >>> >
> > >>> > 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, "T=
he
> > >>> > device shall remain in general discoverable mode until a connecti=
on is
> > >>> > 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 advertis=
ing
> > >>> > is bluez or kernel or application code? In other words, does kern=
el or
> > >>> > bluez or application would re-enable the ble advertisement after =
ble
> > >>> > disconnection happens?
> > >>> >
> > >>> > Thanks
> > >>> > Best wishes
> > >>> > Yunhan.


--=20
Luiz Augusto von Dentz