On 17/07/2020 12:54, Brian Potkin wrote:> I am very much attracted by
the idea of a USB connected printer becoming
immediately available when it is plugged in, so a Recommends: ipp-usb
would be ok with me.
Yes, I would very much like this, too, for Ubuntu into which both CUPS
and ipp-usb get synced.
However, it is as well to be aware that there is a
difference in user experience compared to the situation when driverless
printing was fully introduced on buster.
In the later case, a user who pressed on with the installation of vendor
drivers was generally successful in getting to use them with a wireless
or ethernet connection. With ipp-usb, on the other hand, printing and
scanning can only take place through IPP-over-USB (AFAIK). Users who
expect their previous setup methods to work will probably be due a
disappointment.
We must make users aware of the changes:
Most modern printers do not need any more printer drivers specific to
manufacturer and model of the printer. They use standard protocols for
both printing and scanning, we have here the so-called driverless IPP
Printing/Scanning. If it is told that a printer supports
AirPrint/AirScan, Mopria, Wi-Fi Direct Print, or IPP Everywhere it is
such a printer and if it has a scanner built in, the scanner is also
covered and does not need a specific driver. Even fax sending is
supported via command line, but the desktop applications do not support
this yet.
This works both via network connection and via USB. In case of USB a
netwwork printer gets emulated on the local machine, on port 60000 (and
following ports if more than one device is connected).
- An existing print queue for a USB printer can cease to work. Such a
queue should get removed.
- Most probably another queue got already created automatically. This
queue should work.
- If no queue gets generated, even not after re-plugging the printer, to
create a print queue check for detected/discovered printers in the web
interface of CUPS or in system-config-printers, always under network
printers, even if your device is on USB. Under the model/driver entries
look for entries containing "driverless" or "IPP Everywhere".
- One can easily rename print queues with system-config-printer, should
one want to continue with the old queue's name.
- For scanning, select in your scan software an entry which contains
"eSCL" or "AirScan". If your device is on USB, the entry which you used
previously will not work any more (and perhaps not even appear). If you
do not get asked for which scanner to select and the software simply
does not work, look for a function to change your scanner in the menus.
I believe scanning to be possible only with sane-escl and sane-airscan.
sane-escl is not yet in unstable to test.
sane-escl is built-in in the sane-backends package from version 1.0.29
on, so it is most probably available. But it is highly recommended to
use sane-airscan instead, as the former does not support the ADF on the
scanners and does not support WSD, only eSCL. Also all further
development is concentrated on sane-airscan now. sane-airscan supports
the eSCL and WSD protocols and will soon get IPP Scan added.
sane-airscan got already packaged for Debian, it is currently in the NEW
queue.
Recommends: ipp-usb | ippusbxd is an option that does not seem to benefit
a Debian user. ippusbxd is supported upstream but there may be plans for
its future we are unaware of. I'm a little unsure about its removal from
unstable, but, overall, there does not appear to a glaring downside to it.
It would simplify the rewriting of the relevant sections of the wiki if
only one daemon was available. :)
ippusbxd is still supported upstream on OpenPrinting, but due to the
fact that ipp-usb works much better, I highly recommend that
- CUPS gets "Recommends: ipp-usb"
- ipp-usb and ippusbxd get a mechanism that only one gets installed at a
time and the "Recommends: ipp-usb" in CUPS triggers a switch-over to
ipp-usb.
- Leave ippusbxd in the distro, for experimental, IoT, ... purposes.
There are contributors who are working on improving it. I do not
actively working on it by myself. Most probably it will get made working
well some day because of Chrome OS.
Till
