fix dependencies of FEATURE_GETOPT_LONG
[oweals/busybox.git] / util-linux / mdev.c
index b7b311aaaa5d4dfc6ad8ba44bb31aa45939a122e..2ac15e762f23282b4e26aa483f38aff97a450611 100644 (file)
@@ -1,6 +1,5 @@
 /* vi: set sw=4 ts=4: */
 /*
- *
  * mdev - Mini udev for busybox
  *
  * Copyright 2005 Rob Landley <rob@landley.net>
@@ -8,16 +7,68 @@
  *
  * Licensed under GPL version 2, see file LICENSE in this tarball for details.
  */
-
 #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.
+ * 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 $SUBSYSTEM, extracts
+ * maj,min from "/sys/$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] [@|$|*command args...]
+ * [-]$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.
+ *
+ * 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...').
+ * @:execute on creation, $:on deletion, *:on both.
+ * This happens regardless of /sys/class/.../dev existence.
+ */
+
 struct globals {
        int root_major, root_minor;
+       char *subsystem;
 };
 #define G (*(struct globals*)&bb_common_bufsiz1)
 #define root_major (G.root_major)
 #define root_minor (G.root_minor)
+#define subsystem  (G.subsystem )
 
 /* Prevent infinite loops in /sys symlinks */
 #define MAX_SYSFS_DEPTH 3
@@ -25,9 +76,9 @@ struct globals {
 /* We use additional 64+ bytes in make_device() */
 #define SCRATCH_SIZE 80
 
-#if ENABLE_FEATURE_MDEV_RENAME
 /* Builds an alias path.
  * This function potentionally reallocates the alias parameter.
+ * Only used for ENABLE_FEATURE_MDEV_RENAME
  */
 static char *build_alias(char *alias, const char *device_name)
 {
@@ -49,31 +100,19 @@ static char *build_alias(char *alias, const char *device_name)
 
        return alias;
 }
-#endif
 
-/* mknod in /dev based on a path like "/sys/block/hda/hda1" */
-/* NB: "mdev -s" may call us many times, do not leak memory/fds! */
+/* mknod in /dev based on a path like "/sys/block/hda/hda1"
+ * NB1: path parameter needs to have SCRATCH_SIZE scratch bytes
+ * after NUL, but we promise to not mangle (IOW: to restore if needed)
+ * path string.
+ * NB2: "mdev -s" may call us many times, do not leak memory/fds!
+ */
 static void make_device(char *path, int delete)
 {
-       const char *device_name;
+       char *device_name;
        int major, minor, type, len;
-       int mode = 0660;
-#if ENABLE_FEATURE_MDEV_CONF
-       struct bb_uidgid_t ugid = { 0, 0 };
+       int mode;
        parser_t *parser;
-       char *tokens[5];
-#endif
-#if ENABLE_FEATURE_MDEV_EXEC
-       char *command = NULL;
-#endif
-#if ENABLE_FEATURE_MDEV_RENAME
-       char *alias = NULL;
-       char aliaslink = aliaslink; /* for compiler */
-#endif
-       char *dev_maj_min = path + strlen(path);
-
-       /* Force the configuration file settings exactly. */
-       umask(0);
 
        /* Try to read major/minor string.  Note that the kernel puts \n after
         * the data, so we don't need to worry about null terminating the string
@@ -82,219 +121,265 @@ static void make_device(char *path, int delete)
         */
        major = -1;
        if (!delete) {
+               char *dev_maj_min = path + strlen(path);
+
                strcpy(dev_maj_min, "/dev");
                len = open_read_close(path, dev_maj_min + 1, 64);
-               *dev_maj_min++ = '\0';
+               *dev_maj_min = '\0';
                if (len < 1) {
                        if (!ENABLE_FEATURE_MDEV_EXEC)
                                return;
-                       /* no "dev" file, so just try to run script */
-                       *dev_maj_min = '\0';
-               } else if (sscanf(dev_maj_min, "%u:%u", &major, &minor) != 2) {
+                       /* no "dev" file, but we can still run scripts
+                        * based on device name */
+               } else if (sscanf(++dev_maj_min, "%u:%u", &major, &minor) != 2) {
                        major = -1;
                }
        }
 
        /* Determine device name, type, major and minor */
-       device_name = bb_basename(path);
+       device_name = (char*) bb_basename(path);
        /* http://kernel.org/doc/pending/hotplug.txt says that only
         * "/sys/block/..." is for block devices. "/sys/bus" etc is not.
-        * But since 2.6.25 block devices are also in /sys/class/block.
-        * We use strstr("/block/") to forestall future surprises. */
+        * But since 2.6.25 block devices are also in /sys/class/block,
+        * we use strstr("/block/") to forestall future surprises. */
        type = S_IFCHR;
        if (strstr(path, "/block/"))
                type = S_IFBLK;
 
-#if ENABLE_FEATURE_MDEV_CONF
-       parser = config_open2("/etc/mdev.conf", fopen_for_read);
+       /* 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 we have config file, look up user settings */
-       while (config_read(parser, tokens, 4, 3, "# \t", PARSE_NORMAL)) {
-               regmatch_t off[1 + 9*ENABLE_FEATURE_MDEV_RENAME_REGEXP];
-               char *val;
-
-               /* Fields: regex uid:gid mode [alias] [cmd] */
-
-               /* 1st field: @<numeric maj,min>... */
-               if (tokens[0][0] == '@') {
-                       /* @major,minor[-last] */
-                       /* (useful when name is ambiguous:
-                        * "/sys/class/usb/lp0" and
-                        * "/sys/class/printer/lp0") */
-                       int cmaj, cmin0, cmin1, sc;
-                       if (major < 0)
-                               continue; /* no dev, no match */
-                       sc = sscanf(tokens[0], "@%u,%u-%u", &cmaj, &cmin0, &cmin1);
-                       if (sc < 1 || major != cmaj
-                        || (sc == 2 && minor != cmin0)
-                        || (sc == 3 && (minor < cmin0 || minor > cmin1))
-                       ) {
-                               continue; /* no match */
+       if (ENABLE_FEATURE_MDEV_CONF)
+               parser = config_open2("/etc/mdev.conf", fopen_for_read);
+
+       do {
+               int keep_matching;
+               struct bb_uidgid_t ugid;
+               char *tokens[4];
+               char *command = NULL;
+               char *alias = NULL;
+               char aliaslink = aliaslink; /* for compiler */
+
+               /* Defaults in case we won't match any line */
+               ugid.uid = ugid.gid = 0;
+               keep_matching = 0;
+               mode = 0660;
+
+               if (ENABLE_FEATURE_MDEV_CONF
+                && config_read(parser, tokens, 4, 3, "# \t", PARSE_NORMAL)
+               ) {
+                       char *val;
+                       char *str_to_match;
+                       regmatch_t off[1 + 9 * ENABLE_FEATURE_MDEV_RENAME_REGEXP];
+
+                       val = tokens[0];
+                       keep_matching = ('-' == val[0]);
+                       val += keep_matching; /* swallow leading dash */
+
+                       /* Match against either "subsystem/device_name"
+                        * or "device_name" alone */
+                       str_to_match = strchr(val, '/') ? path : device_name;
+
+                       /* Fields: regex uid:gid mode [alias] [cmd] */
+
+                       if (val[0] == '@') {
+                               /* @major,minor[-minor2] */
+                               /* (useful when name is ambiguous:
+                                * "/sys/class/usb/lp0" and
+                                * "/sys/class/printer/lp0") */
+                               int cmaj, cmin0, cmin1, sc;
+                               if (major < 0)
+                                       continue; /* no dev, no match */
+                               sc = sscanf(val, "@%u,%u-%u", &cmaj, &cmin0, &cmin1);
+                               if (sc < 1 || major != cmaj
+                                || (sc == 2 && minor != cmin0)
+                                || (sc == 3 && (minor < cmin0 || minor > cmin1))
+                               ) {
+                                       continue; /* this line doesn't match */
+                               }
+                               goto line_matches;
                        }
-               } else { /* ... or regex to match device name */
-                       regex_t match;
-                       int result;
-
-                       /* Is this it? */
-                       xregcomp(&match, tokens[0], REG_EXTENDED);
-                       result = regexec(&match, device_name, ARRAY_SIZE(off), off, 0);
-                       regfree(&match);
-
-                       //bb_error_msg("matches:");
-                       //for (int i = 0; i < ARRAY_SIZE(off); i++) {
-                       //      if (off[i].rm_so < 0) continue;
-                       //      bb_error_msg("match %d: '%.*s'\n", i,
-                       //              (int)(off[i].rm_eo - off[i].rm_so),
-                       //              device_name + off[i].rm_so);
-                       //}
-
-                       /* If not this device, skip rest of line */
-                       /* (regexec returns whole pattern as "range" 0) */
-                       if (result || off[0].rm_so
-                        || ((int)off[0].rm_eo != (int)strlen(device_name))
-                       ) {
-                               continue;
+                       if (val[0] == '$') {
+                               /* regex to match an environment variable */
+                               char *eq = strchr(++val, '=');
+                               if (!eq)
+                                       continue;
+                               *eq = '\0';
+                               str_to_match = getenv(val);
+                               if (!str_to_match)
+                                       continue;
+                               str_to_match -= strlen(val) + 1;
+                               *eq = '=';
                        }
-               }
-
-               /* This line matches: stop parsing the file
-                * after parsing the rest of fields */
-
-               /* 2nd field: uid:gid - device ownership */
-               parse_chown_usergroup_or_die(&ugid, tokens[1]);
-
-               /* 3rd field: mode - device permissions */
-               mode = strtoul(tokens[2], NULL, 8);
-
-               val = tokens[3];
-               /* 4th field (opt): >alias */
-#if ENABLE_FEATURE_MDEV_RENAME
-               if (!val)
-                       break;
-               aliaslink = *val;
-               if (aliaslink == '>' || aliaslink == '=') {
-                       char *s;
-#if ENABLE_FEATURE_MDEV_RENAME_REGEXP
-                       char *p;
-                       unsigned i, n;
-#endif
-                       char *a = val;
-                       s = strchrnul(val, ' ');
-                       val = (s[0] && s[1]) ? s+1 : NULL;
-                       s[0] = '\0';
-#if ENABLE_FEATURE_MDEV_RENAME_REGEXP
-                       /* substitute %1..9 with off[1..9], if any */
-                       n = 0;
-                       s = a;
-                       while (*s)
-                               if (*s++ == '%')
-                                       n++;
-
-                       p = alias = xzalloc(strlen(a) + n * strlen(device_name));
-                       s = a + 1;
-                       while (*s) {
-                               *p = *s;
-                               if ('%' == *s) {
-                                       i = (s[1] - '0');
-                                       if (i <= 9 && off[i].rm_so >= 0) {
-                                               n = off[i].rm_eo - off[i].rm_so;
-                                               strncpy(p, device_name + off[i].rm_so, n);
-                                               p += n - 1;
-                                               s++;
+                       /* else: regex to match [subsystem/]device_name */
+
+                       {
+                               regex_t match;
+                               int result;
+
+                               xregcomp(&match, val, REG_EXTENDED);
+                               result = regexec(&match, str_to_match, ARRAY_SIZE(off), off, 0);
+                               regfree(&match);
+                               //bb_error_msg("matches:");
+                               //for (int i = 0; i < ARRAY_SIZE(off); i++) {
+                               //      if (off[i].rm_so < 0) continue;
+                               //      bb_error_msg("match %d: '%.*s'\n", i,
+                               //              (int)(off[i].rm_eo - off[i].rm_so),
+                               //              device_name + off[i].rm_so);
+                               //}
+
+                               /* If no match, skip rest of line */
+                               /* (regexec returns whole pattern as "range" 0) */
+                               if (result || off[0].rm_so
+                                || ((int)off[0].rm_eo != (int)strlen(str_to_match))
+                               ) {
+                                       continue; /* this line doesn't match */
+                               }
+                       }
+ line_matches:
+                       /* This line matches. Stop parsing after parsing
+                        * the rest the line unless keep_matching == 1 */
+
+                       /* 2nd field: uid:gid - device ownership */
+                       if (get_uidgid(&ugid, tokens[1], 1) == 0)
+                               bb_error_msg("unknown user/group %s", tokens[1]);
+
+                       /* 3rd field: mode - device permissions */
+                       mode = strtoul(tokens[2], NULL, 8);
+
+                       val = tokens[3];
+                       /* 4th field (opt): >|=alias */
+
+                       if (ENABLE_FEATURE_MDEV_RENAME && val) {
+                               aliaslink = val[0];
+                               if (aliaslink == '>' || aliaslink == '=') {
+                                       char *a, *s, *st;
+                                       char *p;
+                                       unsigned i, n;
+
+                                       a = val;
+                                       s = strchrnul(val, ' ');
+                                       st = strchrnul(val, '\t');
+                                       if (st < s)
+                                               s = st;
+                                       val = (s[0] && s[1]) ? s+1 : NULL;
+                                       s[0] = '\0';
+
+                                       if (ENABLE_FEATURE_MDEV_RENAME_REGEXP) {
+                                               /* substitute %1..9 with off[1..9], if any */
+                                               n = 0;
+                                               s = a;
+                                               while (*s)
+                                                       if (*s++ == '%')
+                                                               n++;
+
+                                               p = alias = xzalloc(strlen(a) + n * strlen(str_to_match));
+                                               s = a + 1;
+                                               while (*s) {
+                                                       *p = *s;
+                                                       if ('%' == *s) {
+                                                               i = (s[1] - '0');
+                                                               if (i <= 9 && off[i].rm_so >= 0) {
+                                                                       n = off[i].rm_eo - off[i].rm_so;
+                                                                       strncpy(p, str_to_match + off[i].rm_so, n);
+                                                                       p += n - 1;
+                                                                       s++;
+                                                               }
+                                                       }
+                                                       p++;
+                                                       s++;
+                                               }
+                                       } else {
+                                               alias = xstrdup(a + 1);
                                        }
                                }
-                               p++;
-                               s++;
                        }
-#else
-                       alias = xstrdup(a + 1);
-#endif
-               }
-#endif /* ENABLE_FEATURE_MDEV_RENAME */
 
-#if ENABLE_FEATURE_MDEV_EXEC
-               /* The rest (opt): command to run */
-               if (!val)
-                       break;
-               {
-                       const char *s = "@$*";
-                       const char *s2 = strchr(s, *val);
+                       if (ENABLE_FEATURE_MDEV_EXEC && val) {
+                               const char *s = "$@*";
+                               const char *s2 = strchr(s, val[0]);
 
-                       if (!s2)
-                               bb_error_msg_and_die("bad line %u", parser->lineno);
+                               if (!s2) {
+                                       bb_error_msg("bad line %u", parser->lineno);
+                                       if (ENABLE_FEATURE_MDEV_RENAME)
+                                               free(alias);
+                                       continue;
+                               }
 
-                       /* Correlate the position in the "@$*" with the delete
-                        * step so that we get the proper behavior:
-                        * @cmd: run on create
-                        * $cmd: run on delete
-                        * *cmd: run on both
-                        */
-                       if ((s2 - s + 1) /*1/2/3*/ & /*1/2*/ (1 + delete)) {
-                               command = xstrdup(val + 1);
+                               /* Are we running this command now?
+                                * Run $cmd on delete, @cmd on create, *cmd on both
+                                */
+                               if (s2-s != delete)
+                                       command = xstrdup(val + 1);
                        }
                }
-#endif
-               /* end of field parsing */
-               break; /* we found matching line, stop */
-       } /* end of "while line is read from /etc/mdev.conf" */
 
-       config_close(parser);
-#endif /* ENABLE_FEATURE_MDEV_CONF */
+               /* End of field parsing */
 
-       if (!delete && major >= 0) {
-
-               if (ENABLE_FEATURE_MDEV_RENAME)
-                       unlink(device_name);
+               /* "Execute" the line we found */
+               {
+                       const char *node_name;
+
+                       node_name = device_name;
+                       if (ENABLE_FEATURE_MDEV_RENAME && alias)
+                               node_name = alias = build_alias(alias, device_name);
+
+                       if (!delete && major >= 0) {
+                               if (mknod(node_name, mode | type, makedev(major, minor)) && errno != EEXIST)
+                                       bb_perror_msg_and_die("mknod %s", node_name);
+                               if (major == root_major && minor == root_minor)
+                                       symlink(node_name, "root");
+                               if (ENABLE_FEATURE_MDEV_CONF) {
+                                       chmod(node_name, mode);
+                                       chown(node_name, ugid.uid, ugid.gid);
+                               }
+                               if (ENABLE_FEATURE_MDEV_RENAME && alias) {
+                                       if (aliaslink == '>')
+                                               symlink(node_name, device_name);
+                               }
+                       }
 
-               if (mknod(device_name, mode | type, makedev(major, minor)) && errno != EEXIST)
-                       bb_perror_msg_and_die("mknod %s", device_name);
+                       if (ENABLE_FEATURE_MDEV_EXEC && command) {
+                               /* setenv will leak memory, use putenv/unsetenv/free */
+                               char *s = xasprintf("%s=%s", "MDEV", node_name);
+                               char *s1 = xasprintf("%s=%s", "SUBSYSTEM", subsystem);
+                               putenv(s);
+                               putenv(s1);
+                               if (system(command) == -1)
+                                       bb_perror_msg("can't run '%s'", command);
+                               unsetenv("SUBSYSTEM");
+                               free(s1);
+                               unsetenv("MDEV");
+                               free(s);
+                               free(command);
+                       }
 
-               if (major == root_major && minor == root_minor)
-                       symlink(device_name, "root");
+                       if (delete) {
+                               if (ENABLE_FEATURE_MDEV_RENAME && alias) {
+                                       if (aliaslink == '>')
+                                               unlink(device_name);
+                               }
+                               unlink(node_name);
+                       }
 
-#if ENABLE_FEATURE_MDEV_CONF
-               chown(device_name, ugid.uid, ugid.gid);
+                       if (ENABLE_FEATURE_MDEV_RENAME)
+                               free(alias);
+               }
 
-#if ENABLE_FEATURE_MDEV_RENAME
-               if (alias) {
-                       alias = build_alias(alias, device_name);
+               /* We found matching line.
+                * Stop unless it was prefixed with '-' */
+               if (ENABLE_FEATURE_MDEV_CONF && !keep_matching)
+                       break;
 
-                       /* move the device, and optionally
-                        * make a symlink to moved device node */
-                       if (rename(device_name, alias) == 0 && aliaslink == '>')
-                               symlink(alias, device_name);
+       /* end of "while line is read from /etc/mdev.conf" */
+       } while (ENABLE_FEATURE_MDEV_CONF);
 
-                       free(alias);
-               }
-#endif
-#endif
-       }
-
-#if ENABLE_FEATURE_MDEV_EXEC
-       if (command) {
-               /* setenv will leak memory, use putenv/unsetenv/free */
-               char *s = xasprintf("MDEV=%s", device_name);
-               putenv(s);
-               if (system(command) == -1)
-                       bb_perror_msg_and_die("can't run '%s'", command);
-               unsetenv("MDEV");
-               free(s);
-               free(command);
-       }
-#endif
-
-       if (delete) {
-               unlink(device_name);
-               /* At creation time, device might have been moved
-                * and a symlink might have been created. Undo that. */
-#if ENABLE_FEATURE_MDEV_RENAME
-               if (alias) {
-                       alias = build_alias(alias, device_name);
-                       unlink(alias);
-                       free(alias);
-               }
-#endif
-       }
+       if (ENABLE_FEATURE_MDEV_CONF)
+               config_close(parser);
 }
 
 /* File callback for /sys/ traversal */
@@ -323,6 +408,15 @@ static int FAST_FUNC dirAction(const char *fileName UNUSED_PARAM,
                void *userData UNUSED_PARAM,
                int depth)
 {
+       /* Extract device subsystem -- the name of the directory
+        * under /sys/class/ */
+       if (1 == depth) {
+               free(subsystem);
+               subsystem = strrchr(fileName, '/');
+               if (subsystem)
+                       subsystem = xstrdup(subsystem + 1);
+       }
+
        return (depth >= MAX_SYSFS_DEPTH ? SKIP : TRUE);
 }
 
@@ -337,7 +431,7 @@ static int FAST_FUNC dirAction(const char *fileName UNUSED_PARAM,
  * - userspace writes "0" (worked) or "-1" (failed) to /sys/$DEVPATH/loading
  * - kernel loads firmware into device
  */
-static void load_firmware(const char *const firmware, const char *const sysfs_path)
+static void load_firmware(const char *firmware, const char *sysfs_path)
 {
        int cnt;
        int firmware_fd, loading_fd, data_fd;
@@ -360,17 +454,17 @@ static void load_firmware(const char *const firmware, const char *const sysfs_pa
        goto out;
 
  loading:
-       /* tell kernel we're loading by `echo 1 > /sys/$DEVPATH/loading` */
+       /* tell kernel we're loading by "echo 1 > /sys/$DEVPATH/loading" */
        if (full_write(loading_fd, "1", 1) != 1)
                goto out;
 
-       /* load firmware by `cat /lib/firmware/$FIRMWARE > /sys/$DEVPATH/data */
+       /* load firmware into /sys/$DEVPATH/data */
        data_fd = open("data", O_WRONLY);
        if (data_fd == -1)
                goto out;
        cnt = bb_copyfd_eof(firmware_fd, data_fd);
 
-       /* tell kernel result by `echo [0|-1] > /sys/$DEVPATH/loading` */
+       /* tell kernel result by "echo [0|-1] > /sys/$DEVPATH/loading" */
        if (cnt > 0)
                full_write(loading_fd, "0", 1);
        else
@@ -391,22 +485,14 @@ int mdev_main(int argc UNUSED_PARAM, char **argv)
 
        /* We can be called as hotplug helper */
        /* Kernel cannot provide suitable stdio fds for us, do it ourself */
-#if 1
        bb_sanitize_stdio();
-#else
-       /* Debug code */
-       /* Replace LOGFILE by other file or device name if you need */
-#define LOGFILE "/dev/console"
-       /* Just making sure fd 0 is not closed,
-        * we don't really intend to read from it */
-       xmove_fd(xopen("/", O_RDONLY), STDIN_FILENO);
-       xmove_fd(xopen(LOGFILE, O_WRONLY|O_APPEND), STDOUT_FILENO);
-       xmove_fd(xopen(LOGFILE, O_WRONLY|O_APPEND), STDERR_FILENO);
-#endif
+
+       /* Force the configuration file settings exactly */
+       umask(0);
 
        xchdir("/dev");
 
-       if (argv[1] && !strcmp(argv[1], "-s")) {
+       if (argv[1] && strcmp(argv[1], "-s") == 0) {
                /* Scan:
                 * mdev -s
                 */
@@ -436,29 +522,38 @@ int mdev_main(int argc UNUSED_PARAM, char **argv)
                        ACTION_RECURSE | ACTION_FOLLOWLINKS,
                        fileAction, dirAction, temp, 0);
        } else {
+               char *fw;
                char *seq;
                char *action;
                char *env_path;
-               char seqbuf[sizeof(int)*3 + 2];
-               int seqlen = seqlen; /* for compiler */
 
                /* Hotplug:
-                * env ACTION=... DEVPATH=... [SEQNUM=...] mdev
+                * env ACTION=... DEVPATH=... SUBSYSTEM=... [SEQNUM=...] mdev
                 * ACTION can be "add" or "remove"
                 * DEVPATH is like "/block/sda" or "/class/input/mice"
                 */
                action = getenv("ACTION");
                env_path = getenv("DEVPATH");
-               if (!action || !env_path)
+               subsystem = getenv("SUBSYSTEM");
+               if (!action || !env_path /*|| !subsystem*/)
                        bb_show_usage();
+               fw = getenv("FIRMWARE");
 
+               /* If it exists, does /dev/mdev.seq match $SEQNUM?
+                * If it does not match, earlier mdev is running
+                * in parallel, and we need to wait */
                seq = getenv("SEQNUM");
                if (seq) {
-                       int timeout = 2000 / 32;
+                       int timeout = 2000 / 32; /* 2000 msec */
                        do {
+                               int seqlen;
+                               char seqbuf[sizeof(int)*3 + 2];
+
                                seqlen = open_read_close("mdev.seq", seqbuf, sizeof(seqbuf-1));
-                               if (seqlen < 0)
+                               if (seqlen < 0) {
+                                       seq = NULL;
                                        break;
+                               }
                                seqbuf[seqlen] = '\0';
                                if (seqbuf[0] == '\n' /* seed file? */
                                 || strcmp(seq, seqbuf) == 0 /* correct idx? */
@@ -470,19 +565,22 @@ int mdev_main(int argc UNUSED_PARAM, char **argv)
                }
 
                snprintf(temp, PATH_MAX, "/sys%s", env_path);
-               if (!strcmp(action, "remove"))
-                       make_device(temp, 1);
-               else if (!strcmp(action, "add")) {
+               if (strcmp(action, "remove") == 0) {
+                       /* Ignoring "remove firmware". It was reported
+                        * to happen and to cause erroneous deletion
+                        * of device nodes. */
+                       if (!fw)
+                               make_device(temp, 1);
+               }
+               else if (strcmp(action, "add") == 0) {
                        make_device(temp, 0);
-
                        if (ENABLE_FEATURE_MDEV_LOAD_FIRMWARE) {
-                               char *fw = getenv("FIRMWARE");
                                if (fw)
                                        load_firmware(fw, temp);
                        }
                }
 
-               if (seq && seqlen >= 0) {
+               if (seq) {
                        xopen_xwrite_close("mdev.seq", utoa(xatou(seq) + 1));
                }
        }
@@ -490,5 +588,5 @@ int mdev_main(int argc UNUSED_PARAM, char **argv)
        if (ENABLE_FEATURE_CLEAN_UP)
                RELEASE_CONFIG_BUFFER(temp);
 
-       return 0;
+       return EXIT_SUCCESS;
 }