util-linux/mdev.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * mdev - Mini udev for busybox
   4  *
   5  * Copyright 2005 Rob Landley <rob@landley.net>
   6  * Copyright 2005 Frank Sorenson <frank@tuxrocks.com>
   7  *
   8  * Licensed under GPLv2, see file LICENSE in this source tree.
   9  */
  10
  11 //usage:#define mdev_trivial_usage
  12 //usage:       "[-s]"
  13 //usage:#define mdev_full_usage "\n\n"
  14 //usage:       "        -s      Scan /sys and populate /dev during system boot\n"
  15 //usage:       "\n"
  16 //usage:       "It can be run by kernel as a hotplug helper. To activate it:\n"
  17 //usage:       " echo /sbin/mdev > /proc/sys/kernel/hotplug\n"
  18 //usage:        IF_FEATURE_MDEV_CONF(
  19 //usage:       "It uses /etc/mdev.conf with lines\n"
  20 //usage:       "[-]DEVNAME UID:GID PERM"
  21 //usage:                        IF_FEATURE_MDEV_RENAME(" [>|=PATH]")
  22 //usage:                        IF_FEATURE_MDEV_EXEC(" [@|$|*PROG]")
  23 //usage:        )
  24 //usage:
  25 //usage:#define mdev_notes_usage ""
  26 //usage:        IF_FEATURE_MDEV_CONFIG(
  27 //usage:       "The mdev config file contains lines that look like:\n"
  28 //usage:       "  hd[a-z][0-9]* 0:3 660\n\n"
  29 //usage:       "That's device name (with regex match), uid:gid, and permissions.\n\n"
  30 //usage:        IF_FEATURE_MDEV_EXEC(
  31 //usage:       "Optionally, that can be followed (on the same line) by a special character\n"
  32 //usage:       "and a command line to run after creating/before deleting the corresponding\n"
  33 //usage:       "device(s). The environment variable $MDEV indicates the active device node\n"
  34 //usage:       "(which is useful if it's a regex match). For example:\n\n"
  35 //usage:       "  hdc root:cdrom 660  *ln -s $MDEV cdrom\n\n"
  36 //usage:       "The special characters are @ (run after creating), $ (run before deleting),\n"
  37 //usage:       "and * (run both after creating and before deleting). The commands run in\n"
  38 //usage:       "the /dev directory, and use system() which calls /bin/sh.\n\n"
  39 //usage:        )
  40 //usage:       "Config file parsing stops on the first matching line. If no config\n"
  41 //usage:       "entry is matched, devices are created with default 0:0 660. (Make\n"
  42 //usage:       "the last line match .* to override this.)\n\n"
  43 //usage:        )
  44
  45 #include "libbb.h"
  46 #include "xregex.h"
  47
  48 /* "mdev -s" scans /sys/class/xxx, looking for directories which have dev
  49  * file (it is of the form "M:m\n"). Example: /sys/class/tty/tty0/dev
  50  * contains "4:0\n". Directory name is taken as device name, path component
  51  * directly after /sys/class/ as subsystem. In this example, "tty0" and "tty".
  52  * Then mdev creates the /dev/device_name node.
  53  * If /sys/class/.../dev file does not exist, mdev still may act
  54  * on this device: see "@|$|*command args..." parameter in config file.
  55  *
  56  * mdev w/o parameters is called as hotplug helper. It takes device
  57  * and subsystem names from $DEVPATH and $SUBSYSTEM, extracts
  58  * maj,min from "/sys/$DEVPATH/dev" and also examines
  59  * $ACTION ("add"/"delete") and $FIRMWARE.
  60  *
  61  * If action is "add", mdev creates /dev/device_name similarly to mdev -s.
  62  * (todo: explain "delete" and $FIRMWARE)
  63  *
  64  * If /etc/mdev.conf exists, it may modify /dev/device_name's properties.
  65  * /etc/mdev.conf file format:
  66  *
  67  * [-][subsystem/]device  user:grp  mode  [>|=path] [@|$|*command args...]
  68  * [-]@maj,min[-min2]     user:grp  mode  [>|=path] [@|$|*command args...]
  69  * [-]$envvar=val         user:grp  mode  [>|=path] [@|$|*command args...]
  70  *
  71  * Leading minus in 1st field means "don't stop on this line", otherwise
  72  * search is stopped after the matching line is encountered.
  73  *
  74  * The device name or "subsystem/device" combo is matched against 1st field
  75  * (which is a regex), or maj,min is matched against 1st field,
  76  * or specified environment variable (as regex) is matched against 1st field.
  77  *
  78  * $envvar=val format is useful for loading modules for hot-plugged devices
  79  * which do not have driver loaded yet. In this case /sys/class/.../dev
  80  * does not exist, but $MODALIAS is set to needed module's name
  81  * (actually, an alias to it) by kernel. This rule instructs mdev
  82  * to load the module and exit:
  83  *    $MODALIAS=.* 0:0 660 @modprobe "$MODALIAS"
  84  * The kernel will generate another hotplug event when /sys/class/.../dev
  85  * file appears.
  86  *
  87  * When line matches, the device node is created, chmod'ed and chown'ed,
  88  * moved to path, and if >path, a symlink to moved node is created,
  89  * all this if /sys/class/.../dev exists.
  90  *    Examples:
  91  *    =loop/      - moves to /dev/loop
  92  *    >disk/sda%1 - moves to /dev/disk/sdaN, makes /dev/sdaN a symlink
  93  *
  94  * Then "command args..." is executed (via sh -c 'command args...').
  95  * @:execute on creation, $:on deletion, *:on both.
  96  * This happens regardless of /sys/class/.../dev existence.
  97  */
  98
  99 struct globals {
 100         int root_major, root_minor;
 101         char *subsystem;
 102 } FIX_ALIASING;
 103 #define G (*(struct globals*)&bb_common_bufsiz1)
 104
 105 /* Prevent infinite loops in /sys symlinks */
 106 #define MAX_SYSFS_DEPTH 3
 107
 108 /* We use additional 64+ bytes in make_device() */
 109 #define SCRATCH_SIZE 80
 110
 111 /* Builds an alias path.
 112  * This function potentionally reallocates the alias parameter.
 113  * Only used for ENABLE_FEATURE_MDEV_RENAME
 114  */
 115 static char *build_alias(char *alias, const char *device_name)
 116 {
 117         char *dest;
 118
 119         /* ">bar/": rename to bar/device_name */
 120         /* ">bar[/]baz": rename to bar[/]baz */
 121         dest = strrchr(alias, '/');
 122         if (dest) { /* ">bar/[baz]" ? */
 123                 *dest = '\0'; /* mkdir bar */
 124                 bb_make_directory(alias, 0755, FILEUTILS_RECUR);
 125                 *dest = '/';
 126                 if (dest[1] == '\0') { /* ">bar/" => ">bar/device_name" */
 127                         dest = alias;
 128                         alias = concat_path_file(alias, device_name);
 129                         free(dest);
 130                 }
 131         }
 132
 133         return alias;
 134 }
 135
 136 /* mknod in /dev based on a path like "/sys/block/hda/hda1"
 137  * NB1: path parameter needs to have SCRATCH_SIZE scratch bytes
 138  * after NUL, but we promise to not mangle (IOW: to restore if needed)
 139  * path string.
 140  * NB2: "mdev -s" may call us many times, do not leak memory/fds!
 141  */
 142 static void make_device(char *path, int delete)
 143 {
 144         char *device_name, *subsystem_slash_devname;
 145         int major, minor, type, len;
 146         mode_t mode;
 147         parser_t *parser;
 148
 149         /* Try to read major/minor string.  Note that the kernel puts \n after
 150          * the data, so we don't need to worry about null terminating the string
 151          * because sscanf() will stop at the first nondigit, which \n is.
 152          * We also depend on path having writeable space after it.
 153          */
 154         major = -1;
 155         if (!delete) {
 156                 char *dev_maj_min = path + strlen(path);
 157
 158                 strcpy(dev_maj_min, "/dev");
 159                 len = open_read_close(path, dev_maj_min + 1, 64);
 160                 *dev_maj_min = '\0';
 161                 if (len < 1) {
 162                         if (!ENABLE_FEATURE_MDEV_EXEC)
 163                                 return;
 164                         /* no "dev" file, but we can still run scripts
 165                          * based on device name */
 166                 } else if (sscanf(++dev_maj_min, "%u:%u", &major, &minor) != 2) {
 167                         major = -1;
 168                 }
 169         }
 170         /* else: for delete, -1 still deletes the node, but < -1 suppresses that */
 171
 172         /* Determine device name, type, major and minor */
 173         device_name = (char*) bb_basename(path);
 174         /* http://kernel.org/doc/pending/hotplug.txt says that only
 175          * "/sys/block/..." is for block devices. "/sys/bus" etc is not.
 176          * But since 2.6.25 block devices are also in /sys/class/block.
 177          * We use strstr("/block/") to forestall future surprises. */
 178         type = S_IFCHR;
 179         if (strstr(path, "/block/") || (G.subsystem && strncmp(G.subsystem, "block", 5) == 0))
 180                 type = S_IFBLK;
 181
 182         /* Make path point to "subsystem/device_name" */
 183         subsystem_slash_devname = NULL;
 184         /* Check for coldplug invocations first */
 185         if (strncmp(path, "/sys/block/", 11) == 0) /* legacy case */
 186                 path += sizeof("/sys/") - 1;
 187         else if (strncmp(path, "/sys/class/", 11) == 0)
 188                 path += sizeof("/sys/class/") - 1;
 189         else {
 190                 /* Example of a hotplug invocation:
 191                  * SUBSYSTEM="block"
 192                  * DEVPATH="/sys" + "/devices/virtual/mtd/mtd3/mtdblock3"
 193                  * ("/sys" is added by mdev_main)
 194                  * - path does not contain subsystem
 195                  */
 196                 subsystem_slash_devname = concat_path_file(G.subsystem, device_name);
 197                 path = subsystem_slash_devname;
 198         }
 199
 200         /* If we have config file, look up user settings */
 201         if (ENABLE_FEATURE_MDEV_CONF)
 202                 parser = config_open2("/etc/mdev.conf", fopen_for_read);
 203
 204         do {
 205                 int keep_matching;
 206                 struct bb_uidgid_t ugid;
 207                 char *tokens[4];
 208                 char *command = NULL;
 209                 char *alias = NULL;
 210                 char aliaslink = aliaslink; /* for compiler */
 211
 212                 /* Defaults in case we won't match any line */
 213                 ugid.uid = ugid.gid = 0;
 214                 keep_matching = 0;
 215                 mode = 0660;
 216
 217                 if (ENABLE_FEATURE_MDEV_CONF
 218                  && config_read(parser, tokens, 4, 3, "# \t", PARSE_NORMAL)
 219                 ) {
 220                         char *val;
 221                         char *str_to_match;
 222                         regmatch_t off[1 + 9 * ENABLE_FEATURE_MDEV_RENAME_REGEXP];
 223
 224                         val = tokens[0];
 225                         keep_matching = ('-' == val[0]);
 226                         val += keep_matching; /* swallow leading dash */
 227
 228                         /* Match against either "subsystem/device_name"
 229                          * or "device_name" alone */
 230                         str_to_match = strchr(val, '/') ? path : device_name;
 231
 232                         /* Fields: regex uid:gid mode [alias] [cmd] */
 233
 234                         if (val[0] == '@') {
 235                                 /* @major,minor[-minor2] */
 236                                 /* (useful when name is ambiguous:
 237                                  * "/sys/class/usb/lp0" and
 238                                  * "/sys/class/printer/lp0") */
 239                                 int cmaj, cmin0, cmin1, sc;
 240                                 if (major < 0)
 241                                         continue; /* no dev, no match */
 242                                 sc = sscanf(val, "@%u,%u-%u", &cmaj, &cmin0, &cmin1);
 243                                 if (sc < 1
 244                                  || major != cmaj
 245                                  || (sc == 2 && minor != cmin0)
 246                                  || (sc == 3 && (minor < cmin0 || minor > cmin1))
 247                                 ) {
 248                                         continue; /* this line doesn't match */
 249                                 }
 250                                 goto line_matches;
 251                         }
 252                         if (val[0] == '$') {
 253                                 /* regex to match an environment variable */
 254                                 char *eq = strchr(++val, '=');
 255                                 if (!eq)
 256                                         continue;
 257                                 *eq = '\0';
 258                                 str_to_match = getenv(val);
 259                                 if (!str_to_match)
 260                                         continue;
 261                                 str_to_match -= strlen(val) + 1;
 262                                 *eq = '=';
 263                         }
 264                         /* else: regex to match [subsystem/]device_name */
 265
 266                         {
 267                                 regex_t match;
 268                                 int result;
 269
 270                                 xregcomp(&match, val, REG_EXTENDED);
 271                                 result = regexec(&match, str_to_match, ARRAY_SIZE(off), off, 0);
 272                                 regfree(&match);
 273                                 //bb_error_msg("matches:");
 274                                 //for (int i = 0; i < ARRAY_SIZE(off); i++) {
 275                                 //      if (off[i].rm_so < 0) continue;
 276                                 //      bb_error_msg("match %d: '%.*s'\n", i,
 277                                 //              (int)(off[i].rm_eo - off[i].rm_so),
 278                                 //              device_name + off[i].rm_so);
 279                                 //}
 280
 281                                 /* If no match, skip rest of line */
 282                                 /* (regexec returns whole pattern as "range" 0) */
 283                                 if (result
 284                                  || off[0].rm_so
 285                                  || ((int)off[0].rm_eo != (int)strlen(str_to_match))
 286                                 ) {
 287                                         continue; /* this line doesn't match */
 288                                 }
 289                         }
 290  line_matches:
 291                         /* This line matches. Stop parsing after parsing
 292                          * the rest the line unless keep_matching == 1 */
 293
 294                         /* 2nd field: uid:gid - device ownership */
 295                         if (get_uidgid(&ugid, tokens[1], /*allow_numeric:*/ 1) == 0)
 296                                 bb_error_msg("unknown user/group %s on line %d", tokens[1], parser->lineno);
 297
 298                         /* 3rd field: mode - device permissions */
 299                         bb_parse_mode(tokens[2], &mode);
 300
 301                         val = tokens[3];
 302                         /* 4th field (opt): ">|=alias" or "!" to not create the node */
 303
 304                         if (ENABLE_FEATURE_MDEV_RENAME && val) {
 305                                 char *a, *s, *st;
 306
 307                                 a = val;
 308                                 s = strchrnul(val, ' ');
 309                                 st = strchrnul(val, '\t');
 310                                 if (st < s)
 311                                         s = st;
 312                                 st = (s[0] && s[1]) ? s+1 : NULL;
 313
 314                                 aliaslink = a[0];
 315                                 if (aliaslink == '!' && s == a+1) {
 316                                         val = st;
 317                                         /* "!": suppress node creation/deletion */
 318                                         major = -2;
 319                                 }
 320                                 else if (aliaslink == '>' || aliaslink == '=') {
 321                                         val = st;
 322                                         s[0] = '\0';
 323                                         if (ENABLE_FEATURE_MDEV_RENAME_REGEXP) {
 324                                                 char *p;
 325                                                 unsigned i, n;
 326
 327                                                 /* substitute %1..9 with off[1..9], if any */
 328                                                 n = 0;
 329                                                 s = a;
 330                                                 while (*s)
 331                                                         if (*s++ == '%')
 332                                                                 n++;
 333
 334                                                 p = alias = xzalloc(strlen(a) + n * strlen(str_to_match));
 335                                                 s = a + 1;
 336                                                 while (*s) {
 337                                                         *p = *s;
 338                                                         if ('%' == *s) {
 339                                                                 i = (s[1] - '0');
 340                                                                 if (i <= 9 && off[i].rm_so >= 0) {
 341                                                                         n = off[i].rm_eo - off[i].rm_so;
 342                                                                         strncpy(p, str_to_match + off[i].rm_so, n);
 343                                                                         p += n - 1;
 344                                                                         s++;
 345                                                                 }
 346                                                         }
 347                                                         p++;
 348                                                         s++;
 349                                                 }
 350                                         } else {
 351                                                 alias = xstrdup(a + 1);
 352                                         }
 353                                 }
 354                         }
 355
 356                         if (ENABLE_FEATURE_MDEV_EXEC && val) {
 357                                 const char *s = "$@*";
 358                                 const char *s2 = strchr(s, val[0]);
 359
 360                                 if (!s2) {
 361                                         bb_error_msg("bad line %u", parser->lineno);
 362                                         if (ENABLE_FEATURE_MDEV_RENAME)
 363                                                 free(alias);
 364                                         continue;
 365                                 }
 366
 367                                 /* Are we running this command now?
 368                                  * Run $cmd on delete, @cmd on create, *cmd on both
 369                                  */
 370                                 if (s2 - s != delete) {
 371                                         /* We are here if: '*',
 372                                          * or: '@' and delete = 0,
 373                                          * or: '$' and delete = 1
 374                                          */
 375                                         command = xstrdup(val + 1);
 376                                 }
 377                         }
 378                 }
 379
 380                 /* End of field parsing */
 381
 382                 /* "Execute" the line we found */
 383                 {
 384                         const char *node_name;
 385
 386                         node_name = device_name;
 387                         if (ENABLE_FEATURE_MDEV_RENAME && alias)
 388                                 node_name = alias = build_alias(alias, device_name);
 389
 390                         if (!delete && major >= 0) {
 391                                 if (mknod(node_name, mode | type, makedev(major, minor)) && errno != EEXIST)
 392                                         bb_perror_msg("can't create '%s'", node_name);
 393                                 if (major == G.root_major && minor == G.root_minor)
 394                                         symlink(node_name, "root");
 395                                 if (ENABLE_FEATURE_MDEV_CONF) {
 396                                         chmod(node_name, mode);
 397                                         chown(node_name, ugid.uid, ugid.gid);
 398                                 }
 399                                 if (ENABLE_FEATURE_MDEV_RENAME && alias) {
 400                                         if (aliaslink == '>')
 401                                                 symlink(node_name, device_name);
 402                                 }
 403                         }
 404
 405                         if (ENABLE_FEATURE_MDEV_EXEC && command) {
 406                                 /* setenv will leak memory, use putenv/unsetenv/free */
 407                                 char *s = xasprintf("%s=%s", "MDEV", node_name);
 408                                 char *s1 = xasprintf("%s=%s", "SUBSYSTEM", G.subsystem);
 409                                 putenv(s);
 410                                 putenv(s1);
 411                                 if (system(command) == -1)
 412                                         bb_perror_msg("can't run '%s'", command);
 413                                 bb_unsetenv_and_free(s1);
 414                                 bb_unsetenv_and_free(s);
 415                                 free(command);
 416                         }
 417
 418                         if (delete && major >= -1) {
 419                                 if (ENABLE_FEATURE_MDEV_RENAME && alias) {
 420                                         if (aliaslink == '>')
 421                                                 unlink(device_name);
 422                                 }
 423                                 unlink(node_name);
 424                         }
 425
 426                         if (ENABLE_FEATURE_MDEV_RENAME)
 427                                 free(alias);
 428                 }
 429
 430                 /* We found matching line.
 431                  * Stop unless it was prefixed with '-' */
 432                 if (ENABLE_FEATURE_MDEV_CONF && !keep_matching)
 433                         break;
 434
 435         /* end of "while line is read from /etc/mdev.conf" */
 436         } while (ENABLE_FEATURE_MDEV_CONF);
 437
 438         if (ENABLE_FEATURE_MDEV_CONF)
 439                 config_close(parser);
 440         free(subsystem_slash_devname);
 441 }
 442
 443 /* File callback for /sys/ traversal */
 444 static int FAST_FUNC fileAction(const char *fileName,
 445                 struct stat *statbuf UNUSED_PARAM,
 446                 void *userData,
 447                 int depth UNUSED_PARAM)
 448 {
 449         size_t len = strlen(fileName) - 4; /* can't underflow */
 450         char *scratch = userData;
 451
 452         /* len check is for paranoid reasons */
 453         if (strcmp(fileName + len, "/dev") != 0 || len >= PATH_MAX)
 454                 return FALSE;
 455
 456         strcpy(scratch, fileName);
 457         scratch[len] = '\0';
 458         make_device(scratch, /*delete:*/ 0);
 459
 460         return TRUE;
 461 }
 462
 463 /* Directory callback for /sys/ traversal */
 464 static int FAST_FUNC dirAction(const char *fileName UNUSED_PARAM,
 465                 struct stat *statbuf UNUSED_PARAM,
 466                 void *userData UNUSED_PARAM,
 467                 int depth)
 468 {
 469         /* Extract device subsystem -- the name of the directory
 470          * under /sys/class/ */
 471         if (1 == depth) {
 472                 free(G.subsystem);
 473                 G.subsystem = strrchr(fileName, '/');
 474                 if (G.subsystem)
 475                         G.subsystem = xstrdup(G.subsystem + 1);
 476         }
 477
 478         return (depth >= MAX_SYSFS_DEPTH ? SKIP : TRUE);
 479 }
 480
 481 /* For the full gory details, see linux/Documentation/firmware_class/README
 482  *
 483  * Firmware loading works like this:
 484  * - kernel sets FIRMWARE env var
 485  * - userspace checks /lib/firmware/$FIRMWARE
 486  * - userspace waits for /sys/$DEVPATH/loading to appear
 487  * - userspace writes "1" to /sys/$DEVPATH/loading
 488  * - userspace copies /lib/firmware/$FIRMWARE into /sys/$DEVPATH/data
 489  * - userspace writes "0" (worked) or "-1" (failed) to /sys/$DEVPATH/loading
 490  * - kernel loads firmware into device
 491  */
 492 static void load_firmware(const char *firmware, const char *sysfs_path)
 493 {
 494         int cnt;
 495         int firmware_fd, loading_fd, data_fd;
 496
 497         /* check for /lib/firmware/$FIRMWARE */
 498         xchdir("/lib/firmware");
 499         firmware_fd = xopen(firmware, O_RDONLY);
 500
 501         /* in case we goto out ... */
 502         data_fd = -1;
 503
 504         /* check for /sys/$DEVPATH/loading ... give 30 seconds to appear */
 505         xchdir(sysfs_path);
 506         for (cnt = 0; cnt < 30; ++cnt) {
 507                 loading_fd = open("loading", O_WRONLY);
 508                 if (loading_fd != -1)
 509                         goto loading;
 510                 sleep(1);
 511         }
 512         goto out;
 513
 514  loading:
 515         /* tell kernel we're loading by "echo 1 > /sys/$DEVPATH/loading" */
 516         if (full_write(loading_fd, "1", 1) != 1)
 517                 goto out;
 518
 519         /* load firmware into /sys/$DEVPATH/data */
 520         data_fd = open("data", O_WRONLY);
 521         if (data_fd == -1)
 522                 goto out;
 523         cnt = bb_copyfd_eof(firmware_fd, data_fd);
 524
 525         /* tell kernel result by "echo [0|-1] > /sys/$DEVPATH/loading" */
 526         if (cnt > 0)
 527                 full_write(loading_fd, "0", 1);
 528         else
 529                 full_write(loading_fd, "-1", 2);
 530
 531  out:
 532         if (ENABLE_FEATURE_CLEAN_UP) {
 533                 close(firmware_fd);
 534                 close(loading_fd);
 535                 close(data_fd);
 536         }
 537 }
 538
 539 int mdev_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 540 int mdev_main(int argc UNUSED_PARAM, char **argv)
 541 {
 542         RESERVE_CONFIG_BUFFER(temp, PATH_MAX + SCRATCH_SIZE);
 543
 544         /* We can be called as hotplug helper */
 545         /* Kernel cannot provide suitable stdio fds for us, do it ourself */
 546         bb_sanitize_stdio();
 547
 548         /* Force the configuration file settings exactly */
 549         umask(0);
 550
 551         xchdir("/dev");
 552
 553         if (argv[1] && strcmp(argv[1], "-s") == 0) {
 554                 /* Scan:
 555                  * mdev -s
 556                  */
 557                 struct stat st;
 558
 559                 xstat("/", &st);
 560                 G.root_major = major(st.st_dev);
 561                 G.root_minor = minor(st.st_dev);
 562
 563                 /* ACTION_FOLLOWLINKS is needed since in newer kernels
 564                  * /sys/block/loop* (for example) are symlinks to dirs,
 565                  * not real directories.
 566                  * (kernel's CONFIG_SYSFS_DEPRECATED makes them real dirs,
 567                  * but we can't enforce that on users)
 568                  */
 569                 if (access("/sys/class/block", F_OK) != 0) {
 570                         /* Scan obsolete /sys/block only if /sys/class/block
 571                          * doesn't exist. Otherwise we'll have dupes.
 572                          * Also, do not complain if it doesn't exist.
 573                          * Some people configure kernel to have no blockdevs.
 574                          */
 575                         recursive_action("/sys/block",
 576                                 ACTION_RECURSE | ACTION_FOLLOWLINKS | ACTION_QUIET,
 577                                 fileAction, dirAction, temp, 0);
 578                 }
 579                 recursive_action("/sys/class",
 580                         ACTION_RECURSE | ACTION_FOLLOWLINKS,
 581                         fileAction, dirAction, temp, 0);
 582         } else {
 583                 char *fw;
 584                 char *seq;
 585                 char *action;
 586                 char *env_path;
 587                 static const char keywords[] ALIGN1 = "remove\0add\0";
 588                 enum { OP_remove = 0, OP_add };
 589                 smalluint op;
 590
 591                 /* Hotplug:
 592                  * env ACTION=... DEVPATH=... SUBSYSTEM=... [SEQNUM=...] mdev
 593                  * ACTION can be "add" or "remove"
 594                  * DEVPATH is like "/block/sda" or "/class/input/mice"
 595                  */
 596                 action = getenv("ACTION");
 597                 env_path = getenv("DEVPATH");
 598                 G.subsystem = getenv("SUBSYSTEM");
 599                 if (!action || !env_path /*|| !G.subsystem*/)
 600                         bb_show_usage();
 601                 fw = getenv("FIRMWARE");
 602                 op = index_in_strings(keywords, action);
 603                 /* If it exists, does /dev/mdev.seq match $SEQNUM?
 604                  * If it does not match, earlier mdev is running
 605                  * in parallel, and we need to wait */
 606                 seq = getenv("SEQNUM");
 607                 if (seq) {
 608                         int timeout = 2000 / 32; /* 2000 msec */
 609                         do {
 610                                 int seqlen;
 611                                 char seqbuf[sizeof(int)*3 + 2];
 612
 613                                 seqlen = open_read_close("mdev.seq", seqbuf, sizeof(seqbuf-1));
 614                                 if (seqlen < 0) {
 615                                         seq = NULL;
 616                                         break;
 617                                 }
 618                                 seqbuf[seqlen] = '\0';
 619                                 if (seqbuf[0] == '\n' /* seed file? */
 620                                  || strcmp(seq, seqbuf) == 0 /* correct idx? */
 621                                 ) {
 622                                         break;
 623                                 }
 624                                 usleep(32*1000);
 625                         } while (--timeout);
 626                 }
 627
 628                 snprintf(temp, PATH_MAX, "/sys%s", env_path);
 629                 if (op == OP_remove) {
 630                         /* Ignoring "remove firmware". It was reported
 631                          * to happen and to cause erroneous deletion
 632                          * of device nodes. */
 633                         if (!fw)
 634                                 make_device(temp, /*delete:*/ 1);
 635                 }
 636                 else if (op == OP_add) {
 637                         make_device(temp, /*delete:*/ 0);
 638                         if (ENABLE_FEATURE_MDEV_LOAD_FIRMWARE) {
 639                                 if (fw)
 640                                         load_firmware(fw, temp);
 641                         }
 642                 }
 643
 644                 if (seq) {
 645                         xopen_xwrite_close("mdev.seq", utoa(xatou(seq) + 1));
 646                 }
 647         }
 648
 649         if (ENABLE_FEATURE_CLEAN_UP)
 650                 RELEASE_CONFIG_BUFFER(temp);
 651
 652         return EXIT_SUCCESS;
 653 }