This implementation of getconfig is written in perl. It processes rules from meta-configuration files. All meta-configuration files have a .cfg suffix.
Lines starting with a pound-sign (#) are comments, and are ignored. Blank lines that consist only of white space are also treated as comments and ignored.
The first non-comment line must be a signature string followed by the file format version number. The signature string is
"Xorg getconfig rules file. Version: "
The currently defined version is "1.0". Files that do not have the correct signature string are ignored.
The remaining non-comment lines define rules. The start of a new rule is indicated by a line with no leading white space. Subsequent lines making up a rule must be indented with white space. Logical lines within a rule may be split over multiple physical lines by using the usual continuation convention ('\' at the end of the line). The first logical line of each rule is a perl expression. It may be any valid perl expression whose evaluated (with 'eval') result may be used as the argument to a perl 'if' statement. The second logical line should be the name of the Xorg video driver to use when the rule is true, and subsequent logical lines of each rule, if present, are additional configuration output for the video device's xorg.conf Device section. The driver name and additional lines of configuration information are written to standard output when the rule is chosen as the successful rule.
Pseudo rules consisting of perl expressions may be present in the file for the purpose of defining custom perl variables or setting the weight to use for the following rules. Pseudo rules are rules that consist of a single logical line only, and the are never candidates themselves for the successful rule.
Several perl variables are pre-defined, and may be used within rules. They include:
$vendor PCI vendor ID $device PCI device ID $revision PCI revision ID $subsys PCI subsystem ID $subsysVendor PCI subsystem vendor ID $class PCI class $XorgVersion Xorg version, as a 'v' string $XorgVersionNumeric Xorg numeric version $XorgVersionMajor Xorg major version $XorgVersionMinor Xorg minor version $XorgVersionPatch Xorg patch version $XorgVersionSnap Xorg snap version $weight current rule weight
The $weight variable deterines the weight of the rules as they are processed. The weight for subsequent rules may be set with a pseudo rule that sets or changes the value of $weight. The default weight, and the weight used for built-in rules is 500. The meta-configuration files are processed in an unpredictable order. The weighting of the rules is used to determine their relative priority
After processing all of the rules, both built-in and those read from the meta-configration files, the getconfig program chooses as the successful rule the last and highest weighted rule that evaluates to true.
/etc/X11 /tmp/Xorg-KEM/etc/X11 <modulepath> /tmp/Xorg-KEM/lib/X11/getconfig
where <modulepath> is the Xorg server's module search path.