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From:   Kenny Bian <kennybian@gmail.com>
Date:   Sun, 24 Jan 2021 22:41:48 -0800
Message-ID: <CAC9s0NYvmRHQ1qrbpQtKrACi2Mp7YCTPA4oYF-TwgpnCN-vhPg@mail.gmail.com>
Subject: Re: How to add "Service Changed Indication"
To:     Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc:     "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>
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Hi Luiz,

Thank you so much for your reply. I appreciate it.

By "registering the services", do you mean "RegisterApplication()" in
https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/test/example-gatt-server#n656?
If that is the case, I believe I already registered the services.
I checked the files in /var/lib/bluetooth. According to
https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/doc/settings-storage.txt#n321,
there should be a "[ServiceChanged]" section in the "info" file. But I
don't see it in the "info" file. Is there a way to tell the "Service
Changed Indication" is actually working?
Let's suppose the "Service Changed Indication" is already enabled, is
there a way for the mobile app to check on their side to tell which
service(s) got changed?

Thanks again for your help.

On Sun, Jan 24, 2021 at 7:35 PM Luiz Augusto von Dentz
<luiz.dentz@gmail.com> wrote:
>
> Hi Kenny,
>
> On Sun, Jan 24, 2021 at 12:45 AM Kenny Bian <kennybian@gmail.com> wrote:
> >
> > Hello,
> >
> > We implemented a GATT server on Linux in Python. The code is based on
> > the code sample(https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/test/example-gatt-server).
> > The BlueZ version is 5.48. But we found a problem. The cached data in
> > /var/lib/bluetooth caused the mobile app to crash if some
> > characteristics are changed. After some research, we found "Under BLE
> > standard 'Generic Attribute'(0x1801), there is a Characteristic
> > 'Service Changed' (0x2A05) with 'indicate' property", see
> > https://github.com/espressif/esp-idf/issues/1777.
> >
> > The questions we have:
> > How to enable the "Service Changed Indication"(0x2A05) in the
> > bluetooth? Is there any code example in Python?
>
> If you are registering the services with Bluetoothd then it should
> generate the service change automatically:
>
> https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/src/gatt-database.c#n1185
>
> When a new service is registered it is indicated here:
>
> https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/src/gatt-database.c#n1452
>
>
> --
> Luiz Augusto von Dentz