[sane-devel] Passing all scanner usage through local saned

[Till Kamppeter]

On 11/05/2024 11:40, thierryh at vivaldi.net wrote:
> 
> As far as the eSCL protocol is concerned (as I've already pointed out), the 
> capacities on display are lesser.
> Admittedly, this will suit most users, but that won't always be the case, as of 
> late: https://gitlab.com/sane-project/backends/-/issues/747
> 

Good to know that. Another reason to add/switch to IPP Scan on the long run.

In the beginning I wanted to use IPP Scan, as we use already IPP for printing. 
Then Michael Sweet told me that available hardware is not using IPP Scan but 
only eSCL or WSD and so it would be better to do the Scanner Applications with 
eSCL and therefore I started wit eSCL, not looking for somebody adding IPP Scan 
support to sane-airscan and letting Akarshan do the Scanner Application support 
eSCL-based.

Later on I came already to thoughts that sooner or late we will have to use IPP 
Scan, even if there is no hardware device using it. IPP Scan is much more 
powerful and versatile for enterprise network scanning, as for each device, 
independent whether printer, scanner, or multi-function device, one has common 
things like IPP System Service. Also IPP has encryption (IPPS) and OAuth2 
authentication. This would also cover the problem

-----
- all users can use the scanners instead of just users in the lp or
scanner group previously. I suppose this can be solved with a firewall
(firewalls can filter the uid of local sockets).
-----

mentioned in the end of the initial  mail of this thread.

Now you are telling that eSCL supports less functionality than SANE's own 
network protocol does, I assume that IPP Scan, which is thoroughly designed by 
the Printer Working Group (PWG, www.pwg.org) as part of the whole IPP, is most 
probably at least superior compared to eSCL perhaps even to SANE's protocol.

So then we should proceed as follows:

- Akarshan completes the eSCL-based Scanner Application support, so that we have 
Scanner Applications at least.

- Somebody starts an IPPScan (as a client) backend ort adds IPP Scan support to 
the sane-airscan backend.

- Somebody adds IPP Scan (as a server) to PAPPL.

This way we get a more future-proof and versatile network scanning protocol for 
everyone which also integrates well for printing.

    Till