diff options
Diffstat (limited to 'util-linux/mdev.c')
| -rw-r--r-- | util-linux/mdev.c | 46 |
1 files changed, 42 insertions, 4 deletions
diff --git a/util-linux/mdev.c b/util-linux/mdev.c index 43527f6..003a27b 100644 --- a/util-linux/mdev.c +++ b/util-linux/mdev.c @@ -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] */ |