Received-SPF: pass (google.com: domain of linux-bluetooth-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <CAC9s0NazfjTcapy52XSdJSKSmoAQmBom_JTfgROKRkVmAbaMDg@mail.gmail.com>
In-Reply-To: <CAC9s0NazfjTcapy52XSdJSKSmoAQmBom_JTfgROKRkVmAbaMDg@mail.gmail.com>
From:   Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date:   Sun, 24 Jan 2021 19:35:23 -0800
Message-ID: <CABBYNZJrb=jpuaUAC9DxRSnRrReZRQgPTKwgqQYBN-3KWoUxQA@mail.gmail.com>
Subject: Re: How to add "Service Changed Indication"
To:     Kenny Bian <kennybian@gmail.com>
Cc:     "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

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