5ff9629b8
Denis Vlasenko
2009-04-17
Subject
mdev: add large comment, fix a buglet with subsystem and /sys/block
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util-linux/mdev.c+42 -4
| @@ -10,6 +10,41 @@ | |
| #include "libbb.h" | |
| #include "xregex.h" | |
| + | /* "mdev -s" scans /sys/class/xxx, looking for directories which have dev |
| + | * file (it is of the form "M:m\n"). Example: /sys/class/tty/tty0/dev |
| + | * 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. |
| + | * |
| + | * mdev w/o parameters is called as hotplug helper. It takes device |
| + | * and subsystem names from $DEVPATH and $SUBSYSTEM, extracts |
| + | * maj,min from "/sys/$DEVPATH/dev" and also examines |
| + | * $ACTION ("add"/"delete") and $FIRMWARE. |
| + | * |
| + | * If action is "add", mdev creates /dev/device_name similarly to mdev -s. |
| + | * (todo: explain "delete" and $FIRMWARE) |
| + | * |
| + | * If /etc/mdev.conf exists, it may modify /dev/device_name's properties. |
| + | * /etc/mdev.conf file format: |
| + | * |
| + | * [-][subsystem/]device user:grp mode [>|=path] [@|$|*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. |
| + | * |
| + | * 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 |
| + | * 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'). |
| + | * @:execute on creation, $:on deletion, *:on both. |
| + | */ |
| + | |
| struct globals { | |
| int root_major, root_minor; | |
| char *subsystem; | |
| @@ -96,8 +131,11 @@ static void make_device(char *path, int delete) | |
| if (strstr(path, "/block/")) | |
| type = S_IFBLK; | |
| - | /* Make path point to subsystem/device_name */ |
| - | path += sizeof("/sys/class/") - 1; |
| + | /* Make path point to "subsystem/device_name" */ |
| + | if (path[5] == 'b') /* legacy /sys/block? */ |
| + | path += sizeof("/sys/") - 1; |
| + | else |
| + | path += sizeof("/sys/class/") - 1; |
| #if !ENABLE_FEATURE_MDEV_CONF | |
| mode = 0660; | |
| @@ -131,8 +169,8 @@ static void make_device(char *path, int delete) | |
| keep_matching = ('-' == val[0]); | |
| val += keep_matching; /* swallow leading dash */ | |
| - | /* Match against either subsystem/device_name |
| - | * or device_name alone */ |
| + | /* Match against either "subsystem/device_name" |
| + | * or "device_name" alone */ |
| name = strchr(val, '/') ? path : (char *) device_name; | |
| /* Fields: regex uid:gid mode [alias] [cmd] */ | |