Regression: epson scanner unusable with stretch version of debs from sane-backends

[D J Gardner]

I expect this is related: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=890922

I have an Epson L210 printer/scanner. It requires the epkowa driver from Epson. Under Raspbian Jessie it works without issue, on upgrading to Raspbian Stretch, the scanner fails to respond do scan requests, giving various errors, and is not recognised correctly.

I rebuilt the Jessie source package (sane-backends_1.0.24-8+deb8u2) on Stretch, installed the .debs and rebooted, the scanner became functional once more.
For confirmation, I rebuilt the Stretch package (sane-backends_1.0.25-4.1), and the problems returned.
I also built the latest -experimental version from http://ftp.debian.org/debian/pool/main/s/sane-backends/ There are packaging conflicts with this version, with the libsane package renamed to libsane1. Installing with --auto-deconfigure results in a working scanner and an unhappy package system. (it wants to uninstall various broken packages)

NB. Earlier in the process of trying to get sane working, I manually made symlinks between /usr/lib/sane (where the Epson package installs libsane-epkowa) and /usr/lib/arm-linux-gnueabihf/sane where other drivers now live. I don't know if this is a necessary step.

With sane-backends_1.0.24-8+deb8u2:
===================================
$ sane-find-scanner
[deleted]
found USB scanner (vendor=0x04b8 [EPSON], product=0x08a1 [EPSON L210 Series]) at libusb:001:010
[deleted]
$ scanimage -L
device `epkowa:usb:001:010' is a Epson L210/L350/L351 Series flatbed scanner
$ scanimage > /tmp/foo

With sane-backends_1.0.25-4.1:
==============================
$sane-find-scanner
found USB scanner (vendor=0x04b8 [EPSON], product=0x08a1 [EPSON L210 Series]) at libusb:001:010

$ scanimage -L
device `epson2:libusb:001:010' is a Epson PID 08A1 flatbed scanner
device `epkowa:usb:001:010' is a Epson (unknown model) flatbed scanner

$ scanimage > /tmp/scan4 (after reboot, hence different device numbers)
[very long wait]
scanimage: open of device epson2:libusb:001:007 failed: Error during device I/O

$ scanimage -d 'epkowa:usb:001:010' > /tmp/scan5 (after restarting printer, hence different device
numbers)
[multi-minute wait]
scanimage: open of device epkowa:usb:001:010 failed: Invalid argument

[ The same errors were given from xsane, depending on which printer was selected.
 Other values of -d tried: 'epkowa' 'epkowa:/dev/usb/001/010' with identical results.]

with sane-backends_1.0.27-1~experimental3
=========================================
$ scanimage -L
device `epson2:libusb:001:011' is a Epson PID 08A1 flatbed scanner
device `epkowa:usb:001:011' is a Epson L210/L350/L351 Series flatbed scanner

scanimage > /tmp/scan7
[success!]

Damaged package system with -experimental
=========================================
$ dpkg -l '*sane*'
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-===============-============-============-===================================
iF libsane:armhf 1.0.25-4.1 armhf API library for scanners
ii libsane-common 1.0.27-1~exp all API library for scanners -- documen
ii libsane-extras: 1.0.22.4 armhf API library for scanners -- extra b
ii libsane-extras- 1.0.22.4 armhf API library for scanners -- documen
ii libsane-extras- 1.0.22.4 armhf API development library for scanner
ii libsane1:armhf 1.0.27-1~exp armhf API library for scanners
ii sane 1.0.14-12 armhf scanner graphical frontends
ii sane-utils 1.0.27-1~exp armhf API library for scanners -- utiliti
ii xsane 0.999-5 armhf featureful graphical frontend for S
ii xsane-common 0.999-5 all xsane architecture independent file

$ sudo apt-get install -f
Reading package lists... Done
Building dependency tree
Reading state information... Done
Correcting dependencies... Done
The following packages will be REMOVED:
  colord iscan libsane sane xsane
0 upgraded, 0 newly installed, 5 to remove and 75 not upgraded.
1 not fully installed or removed.
After this operation, 11.6 MB disk space will be freed.
Do you want to continue? [Y/n] n
Abort.

2 suggested fixes:
1) Make reverting to 1.0.24 easy for people as a known bug.
2) Upgrade to 1.0.27, which fixes the regression.
a) Either Raspbian or debian packager reverts the libsane->libsane1 breaking change or provides a
matching libsane_1.0.27 transitional package that will not trigger the removal of all
packages that depend on libsane
b) Raspbian then make libsane_1.0.27 available for stretch.