I'm not using the printer part of the DX4400 but I know that works ok having tested it previously.
Scanner is detected with "sane-find-scanner":
found USB scanner (vendor=0x04b8 [Language Error], product=0x083f [Language Error]) at libusb:002:013
And "scanimage -L" gives the following output:
device `snapscan:libusb:002:013' is a Acer Color MFP01 flatbed scanner
xsane allows me to preview and scan, but the output is pretty much inverted, save that although the background is black, foreground objects are all the same shade of green.
I'm assuming at this stage it's a driver issue given the "Acer" model detected above.
I've tried installing the iscan-proprietary-drivers and iscan-firmware SlackBuilds for 14.1, and editing "/etc/sane.d/dll.conf", commenting out "epson, epson2" and inserting "epkowa". But it doesn't appear to load the other drivers.
At one point I did get "invalid argument" when trying to use the epkowa backend.
I'm just wondering whether using a older version of Slackware might work (12.2 for example)?
There are numerous examples online of people using this MFP - it's listed as supported and I've made various adjustments suggested online via other forums (which, to be fair, were usually other distros such as Ubuntu or Arch).
Anyone had success using the DX4400 on up-to-date Slack?