Changes for kernel and Busybox

[tomato.git] / release / src / router / busybox / util-linux / mdev.c

/* vi: set sw=4 ts=4: */
/*
 * mdev - Mini udev for busybox
 *
 * Copyright 2005 Rob Landley <rob@landley.net>
 * Copyright 2005 Frank Sorenson <frank@tuxrocks.com>
 *
 * Licensed under GPLv2, see file LICENSE in this source tree.
 */

//config:config MDEV
//config:       bool "mdev"
//config:       default y
//config:       select PLATFORM_LINUX
//config:       help
//config:         mdev is a mini-udev implementation for dynamically creating device
//config:         nodes in the /dev directory.
//config:
//config:         For more information, please see docs/mdev.txt
//config:
//config:config FEATURE_MDEV_CONF
//config:       bool "Support /etc/mdev.conf"
//config:       default y
//config:       depends on MDEV
//config:       help
//config:         Add support for the mdev config file to control ownership and
//config:         permissions of the device nodes.
//config:
//config:         For more information, please see docs/mdev.txt
//config:
//config:config FEATURE_MDEV_RENAME
//config:       bool "Support subdirs/symlinks"
//config:       default y
//config:       depends on FEATURE_MDEV_CONF
//config:       help
//config:         Add support for renaming devices and creating symlinks.
//config:
//config:         For more information, please see docs/mdev.txt
//config:
//config:config FEATURE_MDEV_RENAME_REGEXP
//config:       bool "Support regular expressions substitutions when renaming device"
//config:       default y
//config:       depends on FEATURE_MDEV_RENAME
//config:       help
//config:         Add support for regular expressions substitutions when renaming
//config:         device.
//config:
//config:config FEATURE_MDEV_EXEC
//config:       bool "Support command execution at device addition/removal"
//config:       default y
//config:       depends on FEATURE_MDEV_CONF
//config:       help
//config:         This adds support for an optional field to /etc/mdev.conf for
//config:         executing commands when devices are created/removed.
//config:
//config:         For more information, please see docs/mdev.txt
//config:
//config:config FEATURE_MDEV_LOAD_FIRMWARE
//config:       bool "Support loading of firmwares"
//config:       default y
//config:       depends on MDEV
//config:       help
//config:         Some devices need to load firmware before they can be usable.
//config:
//config:         These devices will request userspace look up the files in
//config:         /lib/firmware/ and if it exists, send it to the kernel for
//config:         loading into the hardware.

//applet:IF_MDEV(APPLET(mdev, BB_DIR_SBIN, BB_SUID_DROP))

//kbuild:lib-$(CONFIG_MDEV) += mdev.o

//usage:#define mdev_trivial_usage
//usage:       "[-s]"
//usage:#define mdev_full_usage "\n\n"
//usage:       "mdev -s is to be run during boot to scan /sys and populate /dev.\n"
//usage:       "\n"
//usage:       "Bare mdev is a kernel hotplug helper. To activate it:\n"
//usage:       "        echo /sbin/mdev >/proc/sys/kernel/hotplug\n"
//usage:        IF_FEATURE_MDEV_CONF(
//usage:       "\n"
//usage:       "It uses /etc/mdev.conf with lines\n"
//usage:       "        [-]DEVNAME UID:GID PERM"
//usage:                        IF_FEATURE_MDEV_RENAME(" [>|=PATH]|[!]")
//usage:                        IF_FEATURE_MDEV_EXEC(" [@|$|*PROG]")
//usage:       "\n"
//usage:       "where DEVNAME is device name regex, @major,minor[-minor2], or\n"
//usage:       "environment variable regex. A common use of the latter is\n"
//usage:       "to load modules for hotplugged devices:\n"
//usage:       "        $MODALIAS=.* 0:0 660 @modprobe \"$MODALIAS\"\n"
//usage:        )
//usage:       "\n"
//usage:       "If /dev/mdev.seq file exists, mdev will wait for its value\n"
//usage:       "to match $SEQNUM variable. This prevents plug/unplug races.\n"
//usage:       "To activate this feature, create empty /dev/mdev.seq at boot."

#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.
 *
 * Leading minus in 1st field means "don't stop on this line", otherwise
 * search is stopped after the matching line is encountered.
 *
 * $envvar=regex 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 rule {
        bool keep_matching;
        bool regex_compiled;
        bool regex_has_slash;
        mode_t mode;
        int maj, min0, min1;
        struct bb_uidgid_t ugid;
        char *envvar;
        char *ren_mov;
        IF_FEATURE_MDEV_EXEC(char *r_cmd;)
        regex_t match;
};

struct globals {
        int root_major, root_minor;
        char *subsystem;
#if ENABLE_FEATURE_MDEV_CONF
        const char *filename;
        parser_t *parser;
        struct rule **rule_vec;
        unsigned rule_idx;
#endif
        struct rule cur_rule;
} FIX_ALIASING;
#define G (*(struct globals*)&bb_common_bufsiz1)
#define INIT_G() do { \
        IF_NOT_FEATURE_MDEV_CONF(G.cur_rule.maj = -1;) \
        IF_NOT_FEATURE_MDEV_CONF(G.cur_rule.mode = 0660;) \
} while (0)


/* Prevent infinite loops in /sys symlinks */
#define MAX_SYSFS_DEPTH 3

/* We use additional 64+ bytes in make_device() */
#define SCRATCH_SIZE 80

#if 0
# define dbg(...) bb_error_msg(__VA_ARGS__)
#else
# define dbg(...) ((void)0)
#endif


#if ENABLE_FEATURE_MDEV_CONF

static void make_default_cur_rule(void)
{
        memset(&G.cur_rule, 0, sizeof(G.cur_rule));
        G.cur_rule.maj = -1; /* "not a @major,minor rule" */
        G.cur_rule.mode = 0660;
}

static void clean_up_cur_rule(void)
{
        free(G.cur_rule.envvar);
        if (G.cur_rule.regex_compiled)
                regfree(&G.cur_rule.match);
        free(G.cur_rule.ren_mov);
        IF_FEATURE_MDEV_EXEC(free(G.cur_rule.r_cmd);)
        make_default_cur_rule();
}

static void parse_next_rule(void)
{
        /* Note: on entry, G.cur_rule is set to default */
        while (1) {
                char *tokens[4];
                char *val;

                /* No PARSE_EOL_COMMENTS, because command may contain '#' chars */
                if (!config_read(G.parser, tokens, 4, 3, "# \t", PARSE_NORMAL & ~PARSE_EOL_COMMENTS))
                        break;

                /* Fields: [-]regex uid:gid mode [alias] [cmd] */
                dbg("token1:'%s'", tokens[1]);

                /* 1st field */
                val = tokens[0];
                G.cur_rule.keep_matching = ('-' == val[0]);
                val += G.cur_rule.keep_matching; /* swallow leading dash */
                if (val[0] == '@') {
                        /* @major,minor[-minor2] */
                        /* (useful when name is ambiguous:
                         * "/sys/class/usb/lp0" and
                         * "/sys/class/printer/lp0")
                         */
                        int sc = sscanf(val, "@%u,%u-%u", &G.cur_rule.maj, &G.cur_rule.min0, &G.cur_rule.min1);
                        if (sc < 2 || G.cur_rule.maj < 0) {
                                bb_error_msg("bad @maj,min on line %d", G.parser->lineno);
                                goto next_rule;
                        }
                        if (sc == 2)
                                G.cur_rule.min1 = G.cur_rule.min0;
                } else {
                        if (val[0] == '$') {
                                char *eq = strchr(++val, '=');
                                if (!eq) {
                                        bb_error_msg("bad $envvar=regex on line %d", G.parser->lineno);
                                        goto next_rule;
                                }
                                G.cur_rule.envvar = xstrndup(val, eq - val);
                                val = eq + 1;
                        }
                        xregcomp(&G.cur_rule.match, val, REG_EXTENDED);
                        G.cur_rule.regex_compiled = 1;
                        G.cur_rule.regex_has_slash = (strchr(val, '/') != NULL);
                }

                /* 2nd field: uid:gid - device ownership */
                if (get_uidgid(&G.cur_rule.ugid, tokens[1], /*allow_numeric:*/ 1) == 0) {
                        bb_error_msg("unknown user/group '%s' on line %d", tokens[1], G.parser->lineno);
                        goto next_rule;
                }

                /* 3rd field: mode - device permissions */
                bb_parse_mode(tokens[2], &G.cur_rule.mode);

                /* 4th field (opt): ">|=alias" or "!" to not create the node */
                val = tokens[3];
                if (ENABLE_FEATURE_MDEV_RENAME && val && strchr(">=!", val[0])) {
                        char *s = skip_non_whitespace(val);
                        G.cur_rule.ren_mov = xstrndup(val, s - val);
                        val = skip_whitespace(s);
                }

                if (ENABLE_FEATURE_MDEV_EXEC && val && val[0]) {
                        const char *s = "$@*";
                        const char *s2 = strchr(s, val[0]);
                        if (!s2) {
                                bb_error_msg("bad line %u", G.parser->lineno);
                                goto next_rule;
                        }
                        IF_FEATURE_MDEV_EXEC(G.cur_rule.r_cmd = xstrdup(val);)
                }

                return;
 next_rule:
                clean_up_cur_rule();
        } /* while (config_read) */

        dbg("config_close(G.parser)");
        config_close(G.parser);
        G.parser = NULL;

        return;
}

/* If mdev -s, we remember rules in G.rule_vec[].
 * Otherwise, there is no point in doing it, and we just
 * save only one parsed rule in G.cur_rule.
 */
static const struct rule *next_rule(void)
{
        struct rule *rule;

        /* Open conf file if we didn't do it yet */
        if (!G.parser && G.filename) {
                dbg("config_open('%s')", G.filename);
                G.parser = config_open2(G.filename, fopen_for_read);
                G.filename = NULL;
        }

        if (G.rule_vec) {
                /* mdev -s */
                /* Do we have rule parsed already? */
                if (G.rule_vec[G.rule_idx]) {
                        dbg("< G.rule_vec[G.rule_idx:%d]=%p", G.rule_idx, G.rule_vec[G.rule_idx]);
                        return G.rule_vec[G.rule_idx++];
                }
                make_default_cur_rule();
        } else {
                /* not mdev -s */
                clean_up_cur_rule();
        }

        /* Parse one more rule if file isn't fully read */
        rule = &G.cur_rule;
        if (G.parser) {
                parse_next_rule();
                if (G.rule_vec) { /* mdev -s */
                        rule = memcpy(xmalloc(sizeof(G.cur_rule)), &G.cur_rule, sizeof(G.cur_rule));
                        G.rule_vec = xrealloc_vector(G.rule_vec, 4, G.rule_idx);
                        G.rule_vec[G.rule_idx++] = rule;
                        dbg("> G.rule_vec[G.rule_idx:%d]=%p", G.rule_idx, G.rule_vec[G.rule_idx]);
                }
        }

        return rule;
}

#else

# define next_rule() (&G.cur_rule)

#endif

/* 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)
{
        char *dest;

        /* ">bar/": rename to bar/device_name */
        /* ">bar[/]baz": rename to bar[/]baz */
        dest = strrchr(alias, '/');
        if (dest) { /* ">bar/[baz]" ? */
                *dest = '\0'; /* mkdir bar */
                bb_make_directory(alias, 0755, FILEUTILS_RECUR);
                *dest = '/';
                if (dest[1] == '\0') { /* ">bar/" => ">bar/device_name" */
                        dest = alias;
                        alias = concat_path_file(alias, device_name);
                        free(dest);
                }
        }

        return alias;
}

/* 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)
{
        char *device_name, *subsystem_slash_devname;
        int major, minor, type, len;

        dbg("%s('%s', delete:%d)", __func__, path, delete);

        /* 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
         * because sscanf() will stop at the first nondigit, which \n is.
         * We also depend on path having writeable space after it.
         */
        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';
                if (len < 1) {
                        if (!ENABLE_FEATURE_MDEV_EXEC)
                                return;
                        /* 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;
                }
        }
        /* else: for delete, -1 still deletes the node, but < -1 suppresses that */

        /* Determine device name, type, major and minor */
        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. */
        type = S_IFCHR;
        if (strstr(path, "/block/") || (G.subsystem && strncmp(G.subsystem, "block", 5) == 0))
                type = S_IFBLK;

        /* Make path point to "subsystem/device_name" */
        subsystem_slash_devname = NULL;
        /* Check for coldplug invocations first */
        if (strncmp(path, "/sys/block/", 11) == 0) /* legacy case */
                path += sizeof("/sys/") - 1;
        else if (strncmp(path, "/sys/class/", 11) == 0)
                path += sizeof("/sys/class/") - 1;
        else {
                /* Example of a hotplug invocation:
                 * SUBSYSTEM="block"
                 * DEVPATH="/sys" + "/devices/virtual/mtd/mtd3/mtdblock3"
                 * ("/sys" is added by mdev_main)
                 * - path does not contain subsystem
                 */
                subsystem_slash_devname = concat_path_file(G.subsystem, device_name);
                path = subsystem_slash_devname;
        }

#if ENABLE_FEATURE_MDEV_CONF
        G.rule_idx = 0; /* restart from the beginning (think mdev -s) */
#endif
        for (;;) {
                const char *str_to_match;
                regmatch_t off[1 + 9 * ENABLE_FEATURE_MDEV_RENAME_REGEXP];
                char *command;
                char *alias;
                char aliaslink = aliaslink; /* for compiler */
                const char *node_name;
                const struct rule *rule;

                str_to_match = "";

                rule = next_rule();

#if ENABLE_FEATURE_MDEV_CONF
                if (rule->maj >= 0) {  /* @maj,min rule */
                        if (major != rule->maj)
                                continue;
                        if (minor < rule->min0 || minor > rule->min1)
                                continue;
                        memset(off, 0, sizeof(off));
                        goto rule_matches;
                }
                if (rule->envvar) { /* $envvar=regex rule */
                        str_to_match = getenv(rule->envvar);
                        dbg("getenv('%s'):'%s'", rule->envvar, str_to_match);
                        if (!str_to_match)
                                continue;
                } else {
                        /* regex to match [subsystem/]device_name */
                        str_to_match = (rule->regex_has_slash ? path : device_name);
                }

                if (rule->regex_compiled) {
                        int regex_match = regexec(&rule->match, str_to_match, ARRAY_SIZE(off), off, 0);
                        dbg("regex_match for '%s':%d", str_to_match, regex_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 (regex_match != 0
                        /* regexec returns whole pattern as "range" 0 */
                         || off[0].rm_so != 0
                         || (int)off[0].rm_eo != (int)strlen(str_to_match)
                        ) {
                                continue; /* this rule doesn't match */
                        }
                }
                /* else: it's final implicit "match-all" rule */
 rule_matches:
#endif
                dbg("rule matched");

                /* Build alias name */
                alias = NULL;
                if (ENABLE_FEATURE_MDEV_RENAME && rule->ren_mov) {
                        aliaslink = rule->ren_mov[0];
                        if (aliaslink == '!') {
                                /* "!": suppress node creation/deletion */
                                major = -2;
                        }
                        else if (aliaslink == '>' || aliaslink == '=') {
                                if (ENABLE_FEATURE_MDEV_RENAME_REGEXP) {
                                        char *s;
                                        char *p;
                                        unsigned n;

                                        /* substitute %1..9 with off[1..9], if any */
                                        n = 0;
                                        s = rule->ren_mov;
                                        while (*s)
                                                if (*s++ == '%')
                                                        n++;

                                        p = alias = xzalloc(strlen(rule->ren_mov) + n * strlen(str_to_match));
                                        s = rule->ren_mov + 1;
                                        while (*s) {
                                                *p = *s;
                                                if ('%' == *s) {
                                                        unsigned 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(rule->ren_mov + 1);
                                }
                        }
                }
                dbg("alias:'%s'", alias);

                command = NULL;
                IF_FEATURE_MDEV_EXEC(command = rule->r_cmd;)
                if (command) {
                        const char *s = "$@*";
                        const char *s2 = strchr(s, command[0]);

                        /* Are we running this command now?
                         * Run $cmd on delete, @cmd on create, *cmd on both
                         */
                        if (s2 - s != delete) {
                                /* We are here if: '*',
                                 * or: '@' and delete = 0,
                                 * or: '$' and delete = 1
                                 */
                                command++;
                        } else {
                                command = NULL;
                        }
                }
                dbg("command:'%s'", command);

                /* "Execute" the line we found */
                node_name = device_name;
                if (ENABLE_FEATURE_MDEV_RENAME && alias) {
                        node_name = alias = build_alias(alias, device_name);
                        dbg("alias2:'%s'", alias);
                }

                if (!delete && major >= 0) {
                        dbg("mknod('%s',%o,(%d,%d))", node_name, rule->mode | type, major, minor);
                        if (mknod(node_name, rule->mode | type, makedev(major, minor)) && errno != EEXIST)
                                bb_perror_msg("can't create '%s'", node_name);
                        if (major == G.root_major && minor == G.root_minor)
                                symlink(node_name, "root");
                        if (ENABLE_FEATURE_MDEV_CONF) {
                                chmod(node_name, rule->mode);
                                chown(node_name, rule->ugid.uid, rule->ugid.gid);
                        }
                        if (ENABLE_FEATURE_MDEV_RENAME && alias) {
                                if (aliaslink == '>') {
//TODO: on devtmpfs, device_name already exists and symlink() fails.
//End result is that instead of symlink, we have two nodes.
//What should be done?
                                        symlink(node_name, 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", G.subsystem);
                        putenv(s);
                        putenv(s1);
                        if (system(command) == -1)
                                bb_perror_msg("can't run '%s'", command);
                        bb_unsetenv_and_free(s1);
                        bb_unsetenv_and_free(s);
                }

                if (delete && major >= -1) {
                        if (ENABLE_FEATURE_MDEV_RENAME && alias) {
                                if (aliaslink == '>')
                                        unlink(device_name);
                        }
                        unlink(node_name);
                }

                if (ENABLE_FEATURE_MDEV_RENAME)
                        free(alias);

                /* We found matching line.
                 * Stop unless it was prefixed with '-'
                 */
                if (!ENABLE_FEATURE_MDEV_CONF || !rule->keep_matching)
                        break;
        } /* for (;;) */

        free(subsystem_slash_devname);
}

/* File callback for /sys/ traversal */
static int FAST_FUNC fileAction(const char *fileName,
                struct stat *statbuf UNUSED_PARAM,
                void *userData,
                int depth UNUSED_PARAM)
{
        size_t len = strlen(fileName) - 4; /* can't underflow */
        char *scratch = userData;

        /* len check is for paranoid reasons */
        if (strcmp(fileName + len, "/dev") != 0 || len >= PATH_MAX)
                return FALSE;

        strcpy(scratch, fileName);
        scratch[len] = '\0';
        make_device(scratch, /*delete:*/ 0);

        return TRUE;
}

/* Directory callback for /sys/ traversal */
static int FAST_FUNC dirAction(const char *fileName UNUSED_PARAM,
                struct stat *statbuf UNUSED_PARAM,
                void *userData UNUSED_PARAM,
                int depth)
{
        /* Extract device subsystem -- the name of the directory
         * under /sys/class/ */
        if (1 == depth) {
                free(G.subsystem);
                G.subsystem = strrchr(fileName, '/');
                if (G.subsystem)
                        G.subsystem = xstrdup(G.subsystem + 1);
        }

        return (depth >= MAX_SYSFS_DEPTH ? SKIP : TRUE);
}

/* For the full gory details, see linux/Documentation/firmware_class/README
 *
 * Firmware loading works like this:
 * - kernel sets FIRMWARE env var
 * - userspace checks /lib/firmware/$FIRMWARE
 * - userspace waits for /sys/$DEVPATH/loading to appear
 * - userspace writes "1" to /sys/$DEVPATH/loading
 * - userspace copies /lib/firmware/$FIRMWARE into /sys/$DEVPATH/data
 * - userspace writes "0" (worked) or "-1" (failed) to /sys/$DEVPATH/loading
 * - kernel loads firmware into device
 */
static void load_firmware(const char *firmware, const char *sysfs_path)
{
        int cnt;
        int firmware_fd, loading_fd;

        /* check for /lib/firmware/$FIRMWARE */
        xchdir("/lib/firmware");
        firmware_fd = open(firmware, O_RDONLY); /* can fail */

        /* check for /sys/$DEVPATH/loading ... give 30 seconds to appear */
        xchdir(sysfs_path);
        for (cnt = 0; cnt < 30; ++cnt) {
                loading_fd = open("loading", O_WRONLY);
                if (loading_fd >= 0)
                        goto loading;
                sleep(1);
        }
        goto out;

 loading:
        cnt = 0;
        if (firmware_fd >= 0) {
                int data_fd;

                /* tell kernel we're loading by "echo 1 > /sys/$DEVPATH/loading" */
                if (full_write(loading_fd, "1", 1) != 1)
                        goto out;

                /* load firmware into /sys/$DEVPATH/data */
                data_fd = open("data", O_WRONLY);
                if (data_fd < 0)
                        goto out;
                cnt = bb_copyfd_eof(firmware_fd, data_fd);
                if (ENABLE_FEATURE_CLEAN_UP)
                        close(data_fd);
        }

        /* Tell kernel result by "echo [0|-1] > /sys/$DEVPATH/loading"
         * Note: we emit -1 if firmware file wasn't found.
         * There are cases when otherwise kernel would wait for minutes
         * before timing out.
         */
        if (cnt > 0)
                full_write(loading_fd, "0", 1);
        else
                full_write(loading_fd, "-1", 2);

 out:
        if (ENABLE_FEATURE_CLEAN_UP) {
                close(firmware_fd);
                close(loading_fd);
        }
}

int mdev_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int mdev_main(int argc UNUSED_PARAM, char **argv)
{
        RESERVE_CONFIG_BUFFER(temp, PATH_MAX + SCRATCH_SIZE);

        INIT_G();

#if ENABLE_FEATURE_MDEV_CONF
        G.filename = "/etc/mdev.conf";
#endif

        /* We can be called as hotplug helper */
        /* Kernel cannot provide suitable stdio fds for us, do it ourself */
        bb_sanitize_stdio();

        /* Force the configuration file settings exactly */
        umask(0);

        xchdir("/dev");

        if (argv[1] && strcmp(argv[1], "-s") == 0) {
                /* Scan:
                 * mdev -s
                 */
                struct stat st;

#if ENABLE_FEATURE_MDEV_CONF
                /* Same as xrealloc_vector(NULL, 4, 0): */
                G.rule_vec = xzalloc((1 << 4) * sizeof(*G.rule_vec));
#endif
                xstat("/", &st);
                G.root_major = major(st.st_dev);
                G.root_minor = minor(st.st_dev);

                /* ACTION_FOLLOWLINKS is needed since in newer kernels
                 * /sys/block/loop* (for example) are symlinks to dirs,
                 * not real directories.
                 * (kernel's CONFIG_SYSFS_DEPRECATED makes them real dirs,
                 * but we can't enforce that on users)
                 */
                if (access("/sys/class/block", F_OK) != 0) {
                        /* Scan obsolete /sys/block only if /sys/class/block
                         * doesn't exist. Otherwise we'll have dupes.
                         * Also, do not complain if it doesn't exist.
                         * Some people configure kernel to have no blockdevs.
                         */
                        recursive_action("/sys/block",
                                ACTION_RECURSE | ACTION_FOLLOWLINKS | ACTION_QUIET,
                                fileAction, dirAction, temp, 0);
                }
                recursive_action("/sys/class",
                        ACTION_RECURSE | ACTION_FOLLOWLINKS,
                        fileAction, dirAction, temp, 0);
        } else {
                char *fw;
                char *seq;
                char *action;
                char *env_path;
                static const char keywords[] ALIGN1 = "remove\0add\0";
                enum { OP_remove = 0, OP_add };
                smalluint op;

                /* Hotplug:
                 * 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");
                G.subsystem = getenv("SUBSYSTEM");
                if (!action || !env_path /*|| !G.subsystem*/)
                        bb_show_usage();
                fw = getenv("FIRMWARE");
                op = index_in_strings(keywords, action);
                /* 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; /* 2000 msec */
                        do {
                                int seqlen;
                                char seqbuf[sizeof(int)*3 + 2];

                                seqlen = open_read_close("mdev.seq", seqbuf, sizeof(seqbuf) - 1);
                                if (seqlen < 0) {
                                        seq = NULL;
                                        break;
                                }
                                seqbuf[seqlen] = '\0';
                                if (seqbuf[0] == '\n' /* seed file? */
                                 || strcmp(seq, seqbuf) == 0 /* correct idx? */
                                ) {
                                        break;
                                }
                                usleep(32*1000);
                        } while (--timeout);
                }

                snprintf(temp, PATH_MAX, "/sys%s", env_path);
                if (op == OP_remove) {
                        /* Ignoring "remove firmware". It was reported
                         * to happen and to cause erroneous deletion
                         * of device nodes. */
                        if (!fw)
                                make_device(temp, /*delete:*/ 1);
                }
                else if (op == OP_add) {
                        make_device(temp, /*delete:*/ 0);
                        if (ENABLE_FEATURE_MDEV_LOAD_FIRMWARE) {
                                if (fw)
                                        load_firmware(fw, temp);
                        }
                }

                if (seq) {
                        xopen_xwrite_close("mdev.seq", utoa(xatou(seq) + 1));
                }
        }

        if (ENABLE_FEATURE_CLEAN_UP)
                RELEASE_CONFIG_BUFFER(temp);

        return EXIT_SUCCESS;
}