Novell LINUX ENTERPRISE SERVER 11 - ADMINISTRATION Administration Manual page 150

The serial devices rule is not available in 50-udev-default.rules any-
more, but it is still worth considering. It consists of two match keys (KERNEL and
ATTRS) and one assign key (SYMLINK). The KERNEL key searches for all devices of
the ttyUSB type. Using the * wild card, this key matches several of these devices.
The second match key, ATTRS, checks whether the product attribute file in sysfs
for any ttyUSB device contains a certain string. The assign key (SYMLINK) triggers
the addition of a symbolic link to this device under /dev/pilot. The operator used
in this key (+=) tells udev to additionally perform this action, even if previous or later
rules add other symbolic links. As this rule contains two match keys, it is only applied
if both conditions are met.
The printer rule deals with USB printers and contains two match keys which must
both apply to get the entire rule applied (SUBSYSTEM and KERNEL). Three assign
keys deal with the naming for this device type (NAME), the creation of symbolic device
links (SYMLINK) and the group membership for this device type (GROUP). Using the
* wild card in the KERNEL key makes it match several lp printer devices. Substitutions
are used in both, the NAME and the SYMLINK keys to extend these strings by the internal
device name. For example, the symlink to the first lp USB printer would read /dev/
usblp0.
The kernel firmware loader rule makes udev load additional firmware by an
external helper script during runtime. The SUBSYSTEM match key searches for the
firmware subsystem. The ACTION key checks whether any device belonging to the
firmware subsystem has been added. The RUN+= key triggers the execution of the
firmware.sh script to locate the firmware that is to be loaded.
Some general characteristics are common to all rules:
• Each rule consists of one or more key value pairs separated by a comma.
• A key's operation is determined by the operator. udev rules support several different
operators.
• Each given value must be enclosed by quotation marks.
• Each line of the rules file represents one rule. If a rule is longer than just one line,
use \ to join the different lines just as you would do in shell syntax.
• udev rules support a shell-style pattern that matches the *, ?, and [] patterns.
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