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Subject: Re: Bluetooth printer connection error
To:     Bastien Nocera <hadess@hadess.net>, linux-bluetooth@vger.kernel.org
References: <3a6fa942-bec5-5e5f-391d-197d1c1eafa6@vivier.eu>
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 <73236e71-781f-1dea-13d5-61fdc45d5e13@vivier.eu>
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 <ab6ae9d9-9104-5454-d93d-b734c0eb9eba@vivier.eu>
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 <8066fc64-5528-0952-e23a-49026bea39fc@vivier.eu>
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From:   Laurent Vivier <laurent@vivier.eu>
Message-ID: <44276263-6c6a-c6ea-d544-d8b161e7b6d0@vivier.eu>
Date:   Thu, 10 Dec 2020 10:41:33 +0100
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Le 10/12/2020 à 10:35, Bastien Nocera a écrit :
> On Wed, 2020-12-09 at 22:45 +0100, Laurent Vivier wrote:
>> Le 09/12/2020 à 21:27, Bastien Nocera a écrit :
>>> On Wed, 2020-12-09 at 20:04 +0100, Laurent Vivier wrote:
>>>> Le 09/12/2020 à 12:34, Bastien Nocera a écrit :
>>>>> On Wed, 2020-12-09 at 12:14 +0100, Laurent Vivier wrote:
>>>> ...
>>>>>>> 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.
>>>>>
>>>>> I don't remember how this used to work, but you'll probably
>>>>> only
>>>>> see
>>>>> something if the printer is visible.
>>>>>
>>>>> You might be able to get the printer to work by adding:
>>>>> bluetooth://DC0D309023C7
>>>>> as a printer in the printer settings of your favourite desktop
>>>>> environment, if it actually uses SPP.
>>>>>
>>>>> running the cups backend with:
>>>>> /usr/lib/cups/backend/bluetooth --get-deviceid
>>>>> bluetooth://DC0D309023C7
>>>>>
>>>>> should show you whether it can get autoconfigured for CUPS use.
>>>>>
>>>>
>>>> Thank you Bastien, it's exactly what I needed to know.
>>>>
>>>> Correct me if I'm wrong but it seems there is a bug in the
>>>> cups/bluetooth
>>>> command:
>>>
>>> Sigh. No, it's not a bug, it's just that the cups tool was never
>>> ported
>>> from the bluez 4.x to the current bluez 5.x API...
>>>
>>> Until that's ported (if ever, given the low number of Bluetooth
>>> printers around...), you could try to extract the IEEE1284 ID
>>> using:
>>> sdptool records DC:0D:30:90:23:C7
>>
>> $ sdptool records DC:0D:30:90:23:C7
>> Service Name: SPP Dev
>> Service RecHandle: 0x10001
>> Service Class ID List:
>>   "Serial Port" (0x1101)
>> Protocol Descriptor List:
>>   "L2CAP" (0x0100)
>>   "RFCOMM" (0x0003)
>>     Channel: 1
>> Language Base Attr List:
>>   code_ISO639: 0x656e
>>   encoding:    0x6a
>>   base_offset: 0x100
>>
>> It doesn't seem to provide an IEEE1284 ID.
>>
>>>
>>> But I'm not certain that this working is necessary to actually try
>>> a
>>> print. Have you tested that?
>>>
>>
>> Not sure what to do...
>>
>> If I try to add the printer using the GUI, it doesn't appear in the
>> list and I cannot add it
>> manually (Fedora 33/GNOME 3.38.2) in GUI.
>>
>> If I add it with the following command line:
>>
>>   lpadmin -p M02 -E -v bluetooth://DC0D309023C7 -P
>> /usr/share/cups/model/Phomemo/Phomemo-M02.ppd.gz
>>
>> It doesn't print anything.
>>
>> But I had some selinux related error:
>>
>> setroubleshoot[13488]: SELinux interdit à bluetooth d'utiliser
>> l'accès connect sur le
>> bluetooth_socket Inconnu.Pour des messages SELinux exhaustifs, lancez
>> sealert -l
>> 965e2270-948f-4791-93f0-3b856c162cea
>> setroubleshoot[13488]: SELinux interdit à bluetooth d'utiliser
>> l'accès connect sur le
>> bluetooth_socket Inconnu.
>> ...
>>
>> So I ran:
>>
>>   ausearch -c "bluetooth" --raw | audit2allow -M my-bluetooth
>>   semodule -X 300 -i my-bluetooth.pp
>>
>> And now what I have in the syslogs is:
>>
>> cupsd[1185]: REQUEST localhost - - "POST /printers/M02 HTTP/1.1" 200
>> 499560 Print-Job successful-ok
>> DC0D309023C7[14310]: sdp_send_req_w4_rsp: Error sending
>> data:Permission denied
> 
> Well, that's not going to work.
> 
> I'm afraid that's about as far as I can help you. Ideally, you would
> port the bluez cups code to the current 5.x API, and then add support
> for your devices, but it's likely a difficult task without access to
> non-SPP/HCRP hardware.
> 
> I'd recommend writing a new cups backend, replacing the bluetooth one
> for this case (see https://www.cups.org/doc/man-backend.html for the
> API).
> 
> Launching without a command-line argument would list the paired phomemo
> printers, and printing would search the RFCOMM channel on the remote
> device (see bluez's sdp.c in the cups backend), and connect to it to
> send the data in the format you expect (see bluez's spp.c in the cups
> backend).
> 
> There might be additional refinements I'm missing, but that should be
> able to get you started.
> 
> Good luck.
>

Thank you for your help.

I will try to do that.

Thanks,
Laurent