HPLIP should "avoid_reset_quirk" for mass-storage for Linux Kernel >= 3.1

[Johannes Meixner]

At least for some HP all-in-one USB devices
with a mass-storage interface any print job
(and perhaps any scan) that lasts longer
than 30 seconds gets aborted since
Linux kernel >= 3.1.

See
https://bugzilla.novell.com/show_bug.cgi?id=751712
and for a summary see in particular
https://bugzilla.novell.com/show_bug.cgi?id=751712#c10

The issue was already reported but misunderstood
by the HPLIP team
https://answers.launchpad.net/hplip/+question/191200

Summary of the issue:

When a HP all-in-one USB device has a mass-storage interface
starting in 3.1 the kernel continually polls this mass-storage
interface.

At least for some HP all-in-one USB devices the mass-storage
interface becomes unaccessible or non-responsive
while a print job is printing out (perhaps also while
scanning happens).

When the mass-storage interface becomes unaccessible
or non-responsive the kernel will after 30 seconds
by default reset the whole HP all-in-one USB device
which means that the currently printing job (or perhaps
also a currently ongoing scan) gets aborted.

In the end this means that any print job (and perhaps any scan)
that lasts longer than 30 seconds gets aborted.

Proposal for a solution:

The basic idea is to tell the kernel not do do its
default USB device reset when the mass-storage interface
becomes unaccessible or non-responsive.

This can be done via the special file
/sys/bus/usb/devices/<something>/avoid_reset_quirk

For example on an openSUSE 12.2 system I have:
--------------------------------------------------------------
# lsusb
Bus 001 Device 002: ID 03f0:2b17 Hewlett-Packard LaserJet 1020

# cat /sys/bus/usb/devices/1-1/idVendor
03f0

# cat /sys/bus/usb/devices/1-1/idProduct
2b17

# ls -l /sys/bus/usb/devices/1-1/avoid_reset_quirk
-rw-r--r-- 1 root root ... /sys/bus/usb/devices/1-1/avoid_reset_quirk
--------------------------------------------------------------

I.e. the "<something>" does not match "Bus 001 Device 002"
but via the idVendor and idProduct files it is possible
to find the right
/sys/bus/usb/devices/<something>/avoid_reset_quirk
that actually matches the HP device.

By default only root has permissions to use
/sys/bus/usb/devices/<something>/avoid_reset_quirk
but the CUPS backend "hp" runs as user lp group lp
so that

-rw-rw-r-- root lp ... /sys/bus/usb/devices/1-1/avoid_reset_quirk

is needed.

The group lp and the group read/write permissions
could be set via appropriate udev rules.

In the end while a print job is submitted, the CUPS backend "hp"
should enable the "avoid_reset_quirk" and after the print job
had finished the CUPS backend "hp" may re-enable the kernel's
default USB device reset.