Message-ID: <6950dd49-7436-ebef-eb88-940597472ce1@tavla.de>
Date:   Wed, 1 Feb 2023 22:07:30 +0100
MIME-Version: 1.0
To:     linux-bluetooth@vger.kernel.org
Content-Language: en-GB
From:   Martin Petzold <martin.petzold@tavla.de>
Subject: How to Automatically Re-Connect Bluetooth HID over GATT (HOG) Device
 when BlueZ Plugin "hog" is Disabled
Organization: TAVLA Technology GmbH
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Hi,

Linux 5.10, BlueZ 5.55

I have a remote control which implements Bluetooth LE. If I use the 
default Bluetooth daemon, I am able to pair and trust using 
bluetoothctl. If the connection is lost after a while (or days) and a 
button on the remote control is pressed, the daemon re-connects 
automatically (because the device is paired). This is basically what I need.

But, I would also like to manually set notifying for characteristics 
(Report) on the HID service within my application (Java via d-bus). This 
is not possible anymore (also not via bluetoothctl) because the "hog" 
(or "input") plugin manages the input device and the related HID 
services are now hidden.

I then added "--noplugin=input,hog" to my Bluetooth daemon. Which is 
okay, because I don't need this support for Kernel HID. Great, now the 
HID services are available (also using bluetoothctl), but the peripheral 
does not re-connect automatically any more. I always have to connect 
manually first. I also have no signal on the d-bus when I press the 
button of the remote control, when it is disconnected.

How can I enable automatic re-connect for devices, when these plugins 
are disabled?

The only other way I was thinking of is to leave the "hog" plugin 
enabled and use the operating system HID interface. However, my 
application runs as non-root which makes it complicated and also I would 
like to have direct connection and control to my device.

Thanks,

Martin