diff options
| -rw-r--r-- | util-linux/mdev.c | 28 |
1 files changed, 22 insertions, 6 deletions
diff --git a/util-linux/mdev.c b/util-linux/mdev.c index ea1edcc40..8fc8a3df4 100644 --- a/util-linux/mdev.c +++ b/util-linux/mdev.c @@ -15,6 +15,8 @@ * contains "4:0\n". Directory name is taken as device name, path component * directly after /sys/class/ as subsystem. In this example, "tty0" and "tty". * Then mdev creates the /dev/device_name node. + * If /sys/class/.../dev file does not exist, mdev still may act + * on this device: see "@|$|*command args..." parameter in config file. * * mdev w/o parameters is called as hotplug helper. It takes device * and subsystem names from $DEVPATH and $SUBSYSTEM, extracts @@ -29,20 +31,34 @@ * * [-][subsystem/]device user:grp mode [>|=path] [@|$|*command args...] * [-]@maj,min[-min2] user:grp mode [>|=path] [@|$|*command args...] - * - * The device name or "subsystem/device" combo is matched against 1st field - * (which is a regex), or maj,min is matched against 1st field. + * [-]$envvar=val user:grp mode [>|=path] [@|$|*command args...] * * Leading minus in 1st field means "don't stop on this line", otherwise * search is stopped after the matching line is encountered. * - * When line matches, the device node is created, chmod'ed and chown'ed. - * Then it moved to path, and if >path, a symlink to moved node is created + * The device name or "subsystem/device" combo is matched against 1st field + * (which is a regex), or maj,min is matched against 1st field, + * or specified environment variable (as regex) is matched against 1st field. + * + * $envvar=val format is useful for loading modules for hot-plugged devices + * which do not have driver loaded yet. In this case /sys/class/.../dev + * does not exist, but $MODALIAS is set to needed module's name + * (actually, an alias to it) by kernel. This rule instructs mdev + * to load the module and exit: + * $MODALIAS=.* 0:0 660 @modprobe "$MODALIAS" + * The kernel will generate another hotplug event when /sys/class/.../dev + * file appears. + * + * When line matches, the device node is created, chmod'ed and chown'ed, + * moved to path, and if >path, a symlink to moved node is created, + * all this if /sys/class/.../dev exists. * Examples: * =loop/ - moves to /dev/loop * >disk/sda%1 - moves to /dev/disk/sdaN, makes /dev/sdaN a symlink - * Then "command args" is executed (via sh -c 'command args'). + * + * Then "command args..." is executed (via sh -c 'command args...'). * @:execute on creation, $:on deletion, *:on both. + * This happens regardless of /sys/class/.../dev existence. */ struct globals { |