Comment 13 for bug 1890464

$ getfacl /dev/bus/usb/001/004
getfacl: Removing leading '/' from absolute path names
# file: dev/bus/usb/001/004
# owner: root
# group: lp
user::rw-
group::rw-
other::r--

That reminds me of an alternative way:

sudo chmod o+w /dev/bus/usb/001/004

The problem with that (if I remember correctly) is that the position of the scanner may change if other USB devices are added or removed. And it's still not working out of the box.

I don't seem able to scan using scanimage, whether I'm in the lp group or not or irrespective of file permissions. (Not sure about the proper syntax, though.)

$ scanimage -d brother2:bus4 --format=png --verbose >testimage.png
scanimage: open of device brother2:bus4 failed: Invalid argument
$ scanimage -d 'brother2:bus4;dev3' --format=png --verbose >testimage.png
scanimage: open of device brother2:bus4;dev3 failed: Invalid argument
$ scanimage -d brother2:/dev/bus/usb/001/004 --format=png --verbose >testimage.png
scanimage: open of device brother2:/dev/bus/usb/001/004 failed: Invalid argument