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;
To:     Bastien Nocera <hadess@hadess.net>, linux-bluetooth@vger.kernel.org
References: <3a6fa942-bec5-5e5f-391d-197d1c1eafa6@vivier.eu>
 <e885258a0b9a3ba15640553e9f002cdfc89f4b79.camel@hadess.net>
From:   Laurent Vivier <laurent@vivier.eu>
Subject: Re: Bluetooth printer connection error
Message-ID: <73236e71-781f-1dea-13d5-61fdc45d5e13@vivier.eu>
Date:   Wed, 9 Dec 2020 12:14:33 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.5.0
MIME-Version: 1.0
In-Reply-To: <e885258a0b9a3ba15640553e9f002cdfc89f4b79.camel@hadess.net>
Content-Type: text/plain; charset=utf-8
Content-Language: fr
Content-Transfer-Encoding: 8bit
Precedence: bulk

Le 09/12/2020 à 12:00, Bastien Nocera a écrit :
> On Tue, 2020-12-08 at 22:25 +0100, Laurent Vivier wrote:
>> Hi,
>>
>> TL;DR:
>>
>> I can pair my bluetooth printer but it fails to connect:
>>
>>   $ bluetoothctl connect DC:0D:30:90:23:C7
>>
>>   Attempting to connect to DC:0D:30:90:23:C7
>>   [CHG] Device DC:0D:30:90:23:C7 Connected: yes
>>   [CHG] Device DC:0D:30:90:23:C7 ServicesResolved: yes
>>   Failed to connect: org.bluez.Error.NotAvailable
>>
>> What do I need to add to my system to have this working?
> 
> As I mentioned in the original bug:
> https://bugzilla.redhat.com/show_bug.cgi?id=1904686
> 
> I don't expect the "connect" command to do anything. There's nothing to
> "connect" to, as bluez doesn't create rfcomm device nodes automatically
> when "connecting" to devices with serial profiles (otherwise one
> couldn't connect to them with other applications without going through
> the device node...).

Yes, I didn't understand what you meant...

My question is: what piece of code I need to write or modify to have the
"connect" operation working?

> If the printer has uses the SPP or HCRP printing profiles, you should
> see it when using:
> /usr/lib/cups/backend/bluetooth
> without any arguments.

As I don't see it once it is paired, I guess it is not using one of
these profiles.

> Otherwise any apps or driver that supports the printer should be able
> to create a serial link directly to the device without creating a
> device node in /dev.
> 
> FWIW, looks like the printer uses a proprietary protocol between their
> own app and the printer, and that they don't provide Linux support.
> Short of reverse engineering that protocol, the printer is unlikely to
> work with Linux.

I've written the CUPS driver that works fine with the rfcomm device.
In fact, it's not proprietary, it's ESC/POS protocol.

https://github.com/vivier/phomemo-tools

I'm working on my code to use python-escpos rather than my hack and I'd
like to integrate smoothly the printer in the bluetooth stack.

It works also with USB, but it's a shame not to use bluetooth with a
printer that has an internal battery.


Thanks,
Laurent