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mdev: enlarge inline documentation

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This commit is contained in:
Denis Vlasenko 2009-04-19 23:38:08 +00:00
parent dcd78c4d0f
commit 11c17f75a7
1 changed files with 22 additions and 6 deletions
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28
util-linux/mdev.c
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@ -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 {