The problem of scanning using USB multi-function printers in Linux (success at last)

After my investigations described in a couple of earlier posts ([1], [2]), I finally got Gentoo Linux to scan reliably via the USB connection to my Canon MP560 MFP (multi-function peripheral), a single USB device with three interfaces: scanner (Interface 0); printer (Interface 1); mass storage (Interface 2). Well, ninety-nine per cent reliably, if that isn’t a contradiction in terms. The formula for success? I had to do all the following:

  1. Stop the kernel from binding the usb-storage driver to the device.

  2. Create a UDEV rule to modify the ACL (access control list) of the device to give both the ‘lp‘ and ‘scanner‘ groups Read-Write access to the device.

  3. Create a UDEV rule to: a) change the owner of the device from ‘root‘ to my user account (fitzcarraldo); b) change the device’s group to ‘scanner‘ instead of ‘lp‘; c) give all users Read-Write access to the device (see my note about this at the end of this post).

  4. Disable the SANE backend from accessing the MP560 via the network.

Let’s look in more detail at each of these …

Stop the kernel from binding the usb-storage driver to the device

Originally I had built the usb-storage driver into the kernel (CONFIG_USB_STORAGE=y). During the course of my investigations into this problem I rebuilt the kernel with CONFIG_USB_STORAGE=m, i.e. I rebuilt the driver as an external module, although it should not matter either way.

The vendor ID (04a9) and product ID (173e) of the MP560 can be found using the lsusb command:

# lsusb | grep -i canon
Bus 001 Device 007: ID 04a9:173e Canon, Inc. MP560

If the usb-storage driver is built as an external module, the kernel configuration file will include the following:

# grep CONFIG_USB_STORAGE= /usr/src/linux/.config
CONFIG_USB_STORAGE=m

In this case, it is possible to stop the driver binding to the USB storage interface in the MP560 by creating a ‘quirk’ in the file /etc/modprobe.d/usb-storage.conf as shown below:

# cat /etc/modprobe.d/usb-storage.conf
options usb-storage quirks=04a9:173e:i

If the usb-storage driver is built into the kernel, the kernel configuration file will include the following:

# grep CONFIG_USB_STORAGE= /usr/src/linux/.config
CONFIG_USB_STORAGE=y

In this case, it is possible to stop the driver binding to the USB storage interface in the MP560 by adding a ‘quirk’ (usb-storage.quirks=<idVendor>:<idProduct>:i) to the kernel boot line as shown below (ignore the rest of the parameters shown below, as yours are likely to be different):

# grep usb-storage /boot/grub/grub.cfg
linux /vmlinuz-3.18.11-gentoo root=/dev/sda5 ro drm_kms_helper.edid_firmware=edid/1920x1080_Clevo_W230SS.bin i915.modeset=1 rcutree.rcu_idle_gp_delay=1 usb-storage.quirks=04a9:173e:i

If you edit the file /boot/grub/grub.cfg directly, the change will be lost if you rebuild or upgrade in future. The ‘proper’ way to add the quirk would be to add it to the list of kernel boot parameters in GRUB_CMDLINE_LINUX_DEFAULT in the file /etc/default/grub and regenerate grub.cfg using the command ‘grub2-mkconfig -o /boot/grub/grub.cfg‘.

Create a UDEV rules file to modify the device’s ACL

I created a UDEV rules file /etc/udev/rules.d/99-canon-mp560.rules containing the following:

# ACL settings for Canon PIXMA MP560 printer MFP
ATTR{idVendor}=="04a9", ATTR{idProduct}=="173e", GOTO="canon"
GOTO="canon_end"
 
LABEL="canon"
RUN+="/bin/setfacl -m g:scanner:rw -m g:lp:rw $env{DEVNAME}"
TEST=="/var/run/ConsoleKit/database", \
        RUN+="udev-acl --action=$env{ACTION} --device=$env{DEVNAME}"
 
LABEL="canon_end"

Create a UDEV rules file to change the owner, group and permissions of the device

The file 41-libsane.rules in my installation is the only UDEV rules file in the directory /lib/udev/rules.d/ that explicitly mentions the MP560:

# grep 173e /lib/udev/rules.d/*
/lib/udev/rules.d/41-libsane.rules:ATTRS{idVendor}=="04a9", ATTRS{idProduct}=="173e", MODE="0664", GROUP="scanner", ENV{libsane_matched}="yes"

As the USB device was always in the ‘lp‘ group (see the output of the ‘ls -la‘ command [1]), the above UDEV rule was clearly being overridden by another rule, but which one in the long list of rules files created automatically when I installed the OS and various packages (see below)?

# ls -F1 /lib/udev/rules.d/
10-ft-rockey.rules
10-virtualbox.rules
40-gentoo.rules
40-usb-media-players.rules
41-libsane.rules
42-usb-hid-pm.rules
50-udev-default.rules
56-hpmud.rules
60-block.rules
60-cdrom_id.rules
60-drm.rules
60-evdev.rules
60-persistent-alsa.rules
60-persistent-input.rules
60-persistent-storage-tape.rules
60-persistent-storage.rules
60-persistent-v4l.rules
60-serial.rules
61-accelerometer.rules
64-btrfs.rules
69-cd-sensors.rules
70-libgphoto2.rules
70-mouse.rules
70-printers.rules
70-touchpad.rules
70-udev-acl.rules
75-net-description.rules
75-probe_mtd.rules
77-mm-cinterion-port-types.rules
77-mm-ericsson-mbm.rules
77-mm-huawei-net-port-types.rules
77-mm-longcheer-port-types.rules
77-mm-mtk-port-types.rules
77-mm-nokia-port-types.rules
77-mm-pcmcia-device-blacklist.rules
77-mm-platform-serial-whitelist.rules
77-mm-simtech-port-types.rules
77-mm-telit-port-types.rules
77-mm-usb-device-blacklist.rules
77-mm-usb-serial-adapters-greylist.rules
77-mm-x22x-port-types.rules
77-mm-zte-port-types.rules
77-nm-olpc-mesh.rules
78-sound-card.rules
80-drivers.rules
80-mm-candidate.rules
80-net-name-slot.rules
80-udisks2.rules
85-regulatory.rules
90-alsa-restore.rules
90-libgpod.rules
90-network.rules
90-pulseaudio.rules
95-cd-devices.rules
95-upower-battery-recall-dell.rules
95-upower-battery-recall-fujitsu.rules
95-upower-battery-recall-gateway.rules
95-upower-battery-recall-ibm.rules
95-upower-battery-recall-lenovo.rules
95-upower-battery-recall-toshiba.rules
95-upower-csr.rules
95-upower-hid.rules
95-upower-wup.rules
97-hid2hci.rules
99-fuse.rules
99-ntfs3g.rules
99-nvidia.rules

Anyway, I created a UDEV rules file /etc/udev/rules.d/95-libsane.rules to change the owner of the MP560 USB device from ‘root‘ to me (i.e. user name ‘fitzcarraldo‘), to put the device in the ‘scanner‘ group instead of the ‘lp‘ group, and to give all users Read-Write permission for the device:

ATTRS{idVendor}=="04a9", ATTRS{idProduct}=="173e", MODE="0666", OWNER="fitzcarraldo", GROUP="scanner", ENV{libsane_matched}="yes"

So I now have two user-created UDEV rules files:

# ls /etc/udev/rules.d/
95-libsane.rules 99-canon-mp560.rules

Note that user-created UDEV rules files should be put in the directory /etc/udev/rules.d/, not the directory /lib/udev/rules.d/ which is reserved for UDEV rules installed when you install the OS and by packages you install later. Unfortunately, there is no consistency in UDEV rules file names and their contents between Linux distributions, which makes debugging UDEV rules even more difficult. Higher numbered rules files override lower-numbered rules files.

I then switched off the MP560 and switched it on again. The two UDEV rules files I created had worked as intended. The ownership and group of the device had changed, and so had the permissions and ACL:

# ls -la /dev/bus/usb/001
total 0
drwxr-xr-x  2 root         root       200 Jul 29 10:10 .
drwxr-xr-x  4 root         root        80 Jul 29 09:56 ..
crw-rw-r--  1 root         usb     189, 0 Jul 29 11:25 001
crw-rw-r--  1 root         usb     189, 1 Jul 29 09:56 002
crw-rw-r--  1 root         usb     189, 2 Jul 29 11:25 003
crw-rw-r--  1 root         usb     189, 3 Jul 29 09:56 004
crw-rw-r--  1 root         usb     189, 4 Jul 29 11:25 005
crw-rw-r--  1 root         usb     189, 5 Jul 29 11:25 006
crw-rw-r--  1 root         usb     189, 7 Jul 29 11:25 008
crw-rw-rw-+ 1 fitzcarraldo scanner 189, 8 Jul 29 11:27 009

# getfacl /dev/bus/usb/001/009
getfacl: Removing leading '/' from absolute path names
# file: dev/bus/usb/001/009
# owner: fitzcarraldo
# group: scanner
user::rw-
user:fitzcarraldo:rw-
group::rw-
group:lp:rw-
group:scanner:rw-
mask::rw-
other::rw-

Disable the SANE backend from accessing the MP560 via the network

Although scanning via the USB connection sometimes still works if I have also specified a network connection in the file /etc/sane.d/pixma.conf, apparently the two interfaces should not normally be enabled simultaneously. See the post [sane-devel] Pixma 530 series – tested and not working by SANE developer Rolf Bensch:

Please disconnect the scanner from network and try again. The backend
has problems if both network and USB are connected at once.

Therefore, to try using SANE to access the MP560 via USB, I disabled network access to the MP560 by commenting out the URI in the relevant SANE backend configuration file, which in the case of the MP560 is the file /etc/sane.d/pixma.conf. I commented out the line ‘bjnp://192.168.1.78‘ which I had previously inserted to enable me to scan via my home network because the USB connection was unreliable.

Trying to scan

I then checked if the USB-connected scanner is detected by SANE when running as root user and when running under my user account:

# scanimage -L
device `pixma:04A9173E_1653C4' is a CANON Canon PIXMA MP560 multi-function peripheral
# sane-find-scanner -q
found USB scanner (vendor=0x04a9 [Canon], product=0x173e [MP560 series]) at libusb:001:010
# exit
exit
$ scanimage -L
device `pixma:04A9173E_1653C4' is a CANON Canon PIXMA MP560 multi-function peripheral
$ sane-find-scanner -q
found USB scanner (vendor=0x04a9 [Canon], product=0x173e [MP560 series]) at libusb:001:010

The test using the scanimage command worked:

$ scanimage -d pixma:04A9173E_1653C4 -T
scanimage: scanning image of size 638x877 pixels at 24 bits/pixel
scanimage: acquiring RGB frame, 8 bits/sample
scanimage: reading one scanline, 1914 bytes...  PASS
scanimage: reading one byte...          PASS
scanimage: stepped read, 2 bytes...     PASS
scanimage: stepped read, 4 bytes...     PASS
scanimage: stepped read, 8 bytes...     PASS
scanimage: stepped read, 16 bytes...    PASS
scanimage: stepped read, 32 bytes...    PASS
scanimage: stepped read, 64 bytes...    PASS
scanimage: stepped read, 128 bytes...   PASS
scanimage: stepped read, 256 bytes...   PASS
scanimage: stepped read, 512 bytes...   PASS
scanimage: stepped read, 1024 bytes...  PASS
scanimage: stepped read, 2048 bytes...  PASS
scanimage: stepped read, 2047 bytes...  PASS
scanimage: stepped read, 1023 bytes...  PASS
scanimage: stepped read, 511 bytes...   PASS
scanimage: stepped read, 255 bytes...   PASS
scanimage: stepped read, 127 bytes...   PASS
scanimage: stepped read, 63 bytes...    PASS
scanimage: stepped read, 31 bytes...    PASS
scanimage: stepped read, 15 bytes...    PASS
scanimage: stepped read, 7 bytes...     PASS
scanimage: stepped read, 3 bytes...     PASS

So I tried to scan an A4 page from the command line:

$ scanimage -d pixma:04A9173E_1653C4 -l 0 -t 0 -x 215 -y 297 --resolution 150 --mode Color | convert - scanned-page.png

That worked, so I launched XSane, one of the GUI scanner applications:

$ xsane

That also worked.

Sometimes either scanimage or a GUI scanner application (XSane, gscan2pdf, Simple Scan or whatever) hangs, but, more often than not, scanning now works via the USB connection. However, if either scanimage or a GUI scanner application hangs, I kill them, run them again and then they usually work.

Importantly, printing still works, even though I have changed the USB device group from ‘lp‘ to ‘scanner‘.

So I have satisfied my curiosity and managed to get the MP560 to scan when connected to my laptop via USB, even though it already worked fine when using a network connection instead.

A note on the version of SANE

For information, I currently have Version 1.0.25_pre20150725 (daily snapshot from 25 July 2015) of the package sane-backends installed:

$ eix -I sane-backends
[I] media-gfx/sane-backends
     Available versions:  1.0.24-r5 (~)1.0.25_pre20150628 (~)1.0.25_pre20150725[1] {avahi doc gphoto2 ipv6 snmp systemd threads usb v4l xinetd ABI_MIPS="n32 n64 o32" ABI_PPC="32 64" ABI_S390="32 64" ABI_X86="32 64 x32" SANE_BACKENDS="+abaton +agfafocus +apple +artec +artec_eplus48u +as6e +avision +bh +canon +canon630u +canon_dr -canon_pp +cardscan +coolscan +coolscan2 +coolscan3 +dc210 +dc240 +dc25 +dell1600n_net +dmc +epjitsu +epson +epson2 +fujitsu +genesys +gt68xx +hp +hp3500 +hp3900 +hp4200 +hp5400 +hp5590 +hpljm1005 -hpsj5s +hs2p +ibm +kodak +kodakaio +kvs1025 +kvs20xx kvs40xx +leo +lexmark +ma1509 +magicolor +matsushita +microtek +microtek2 +mustek -mustek_pp +mustek_usb mustek_usb2 +nec +net +niash +p5 +pie +pixma +plustek +plustek_pp -pnm +qcam +ricoh +rts8891 +s9036 +sceptre +sharp +sm3600 +sm3840 +snapscan +sp15c +st400 +stv680 +tamarack +teco1 +teco2 +teco3 +test +u12 +umax +umax1220u +umax_pp +xerox_mfp"}
     Installed versions:  1.0.25_pre20150725[1](01:39:24 25/07/15)(avahi gphoto2 ipv6 usb v4l -doc -snmp -systemd -threads -xinetd ABI_MIPS="-n32 -n64 -o32" ABI_PPC="-32 -64" ABI_S390="-32 -64" ABI_X86="32 64 -x32" SANE_BACKENDS="abaton agfafocus apple artec artec_eplus48u as6e avision bh canon canon630u canon_dr cardscan coolscan coolscan2 coolscan3 dc210 dc240 dc25 dell1600n_net dmc epjitsu epson epson2 fujitsu genesys gt68xx hp hp3500 hp3900 hp4200 hp5400 hp5590 hpljm1005 hs2p ibm kodak kodakaio kvs1025 kvs20xx leo lexmark ma1509 magicolor matsushita microtek microtek2 mustek mustek_usb nec net niash p5 pie pixma plustek plustek_pp qcam ricoh rts8891 s9036 sceptre sharp sm3600 sm3840 snapscan sp15c st400 stv680 tamarack teco1 teco2 teco3 test u12 umax umax1220u umax_pp xerox_mfp -canon_pp -hpsj5s -kvs40xx -mustek_pp -mustek_usb2 -pnm")
     Homepage:            http://www.sane-project.org/
     Description:         Scanner Access Now Easy - Backends

[1] "local_overlay" /usr/local/portage

However, the same symptoms occurred with versions 1.0.24-r5, 1.0.25_pre20150628 and 1.0.25_pre20150725 of the sane-backends package, so I believe the problem was not version-specific.

A note about scanning in Linux
An early developer’s Web site for the SANE pixma backend has the following warning:

If you grant a group a full permission to access the scanner (by using udev, hotplug, resmgr etc.), every members in the group will have full access rights not only for the scanner part but also for the other parts of the device i.e. printer, memory-card reader and fax. These users can bypass your system’s security policy and do everything with the device intentionally and unintentionally.

It is all very well to say that, but it is the only way I could get the backend to work reliably (almost). And, judging by the number of people who posted on the Web that they had to do the same with other Linux distributions, other manufacturers and models of MFPs, this is a common requirement in order to get Linux to work with MFP scanners. It’s not impressive when people have to resort to this to get something to work.

Note that the success of the approach described in this post is dependent on the contents and order of all the UDEV rules files. Just because the rules files I have posted above work in my case does not guarantee they will work in your case too. It depends what rules files your installation already has, what are their precise contents and in what order they are. In my opinion this is not a good concept.

I stand by my comments in the Conclusion of my first post regarding this problem. To have to jump through so many hoops to be able to scan using Linux on a computer connected to a MFP via USB is ridiculous in my opinion. The fact that it works reliably via a network connection does not alter that. I have been ‘scratching an itch’ as I enjoy tinkering, but I feel sorry for users who just need something that works without having to mess around for hours or days.

Background

  1. The problem of scanning using USB multi-function printers in Linux
  2. The problem of scanning using USB multi-function printers in Linux (continued)

About Fitzcarraldo
A Linux user with an interest in all things technical.

One Response to The problem of scanning using USB multi-function printers in Linux (success at last)

  1. Pingback: The problem of scanning using USB multi-function printers in Linux (continued) | Fitzcarraldo's Blog

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: