[sane-devel] escl backend and ippusbxd

[Till Kamppeter]

Rolf, please do not add a break dependency against ippusbxd. It is most 
probably only some models which cause problems.

If you want to use eSCL via the network it does not matter whether 
ippusbxd is running or not. You only need to make sure to select the 
correct scanner entry in the client software.

The selected entry should nowhere contain "USB".

Principally eSCL scanning works also via IPP-over-USB, with the device 
connected via USB and either ippusbxd or ipp-usb running. ipp-usb is the 
more reliable of the two but it is rather new and does not have the wide 
penetration in Linux distributions therefore. It is also written in Go 
and some OS vendors (like Google with Chrome OS) refuse Go applications 
because of there larger memory footprint.

To select scanning through this connection use entries with "USB" in 
your scanning client software.

I am able to both print and scan via network and USB and with one of 
ippusbxd or ipp-usb permanently running, with both the "escl" and 
"airscan" backends. This I have tested on two HP devices, the HP DeskJet 
2540 and the HP OfficeJet Pro 8730.

To reach this state I have done a lot of debugging with the authors of 
the two SANE backends, Thierry and Alexander. I appreciate their great 
collaboration a lot and they will most probably help you, too, if your 
device does not work, independent whether you want to use it via network 
or USB. Please speak up on the list here or post an issue at the 
appropriate backend or IPP-over-USB daemon upstream.

Naturally it can happen that things do not work for one or another 
hardware model, it already happens with the two eSCL/AirScan backends 
alone. So please report if you have a problem.

    Till


On 20/03/2020 12:04, Rolf Bensch wrote:
> Hello,
> 
> I've seen that some people need to purge |ippusbxd| before they can use 
> their scanner with escl backend (e.g. 
> https://gitlab.com/sane-project/backends/-/issues/256#note_307051019).
> 
> Is this a fix rule? Then I'd like to add a break dependency to 
> |ippusbxd| in my Ubuntu ppa.
> 
> Cheers,
> Rolf
>