--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toys/pending/mdev.c	Sat Mar 16 10:54:38 2013 -0500
@@ -0,0 +1,209 @@
+/* mdev.c - Populate /dev directory and handle hotplug events
+ *
+ * Copyright 2005, 2008 Rob Landley <rob@landley.net>
+ * Copyright 2005 Frank Sorenson <frank@tuxrocks.com>
+
+USE_MDEV(NEWTOY(mdev, "s", TOYFLAG_USR|TOYFLAG_BIN|TOYFLAG_UMASK))
+
+config MDEV
+  bool "mdev"
+  default n
+  help
+    usage: mdev [-s]
+
+    Create devices in /dev using information from /sys.
+
+    -s	Scan all entries in /sys to populate /dev.
+
+config MDEV_CONF
+  bool "Configuration file for mdev"
+  default y
+  depends on MDEV
+  help
+    The mdev config file (/etc/mdev.conf) contains lines that look like:
+    hd[a-z][0-9]* 0:3 660
+
+    Each line must contain three whitespace separated fields. The first
+    field is a regular expression matching one or more device names, and
+    the second and third fields are uid:gid and file permissions for
+    matching devies.
+*/
+
+#include "toys.h"
+#include "lib/xregcomp.h"
+
+// todo, open() block devices to trigger partition scanning.
+
+// mknod in /dev based on a path like "/sys/block/hda/hda1"
+static void make_device(char *path)
+{
+  char *device_name, *s, *temp;
+  int major, minor, type, len, fd;
+  int mode = 0660;
+  uid_t uid = 0;
+  gid_t gid = 0;
+
+  // Try to read major/minor string
+
+  temp = strrchr(path, '/');
+  fd = open(path, O_RDONLY);
+  *temp=0;
+  temp = toybuf;
+  len = read(fd, temp, 64);
+  close(fd);
+  if (len<1) return;
+  temp[len] = 0;
+
+  // Determine device name, type, major and minor
+
+  device_name = strrchr(path, '/') + 1;
+  type = path[5]=='c' ? S_IFCHR : S_IFBLK;
+  major = minor = 0;
+  sscanf(temp, "%u:%u", &major, &minor);
+
+  // If we have a config file, look up permissions for this device
+
+  if (CFG_MDEV_CONF) {
+    char *conf, *pos, *end;
+
+    // mmap the config file
+    if (-1!=(fd = open("/etc/mdev.conf", O_RDONLY))) {
+      len = fdlength(fd);
+      conf = mmap(NULL, len, PROT_READ, MAP_PRIVATE, fd, 0);
+      if (conf) {
+        int line = 0;
+
+        // Loop through lines in mmaped file
+        for (pos = conf; pos-conf<len;) {
+          int field;
+          char *end2;
+
+          line++;
+          // find end of this line
+          for(end = pos; end-conf<len && *end!='\n'; end++);
+
+          // Three fields: regex, uid:gid, mode
+          for (field = 3; field; field--) {
+            // Skip whitespace
+            while (pos<end && isspace(*pos)) pos++;
+            if (pos==end || *pos=='#') break;
+            for (end2 = pos;
+              end2<end && !isspace(*end2) && *end2!='#'; end2++);
+            switch(field) {
+              // Regex to match this device
+              case 3:
+              {
+                char *regex = strndup(pos, end2-pos);
+                regex_t match;
+                regmatch_t off;
+                int result;
+
+                // Is this it?
+                xregcomp(&match, regex, REG_EXTENDED);
+                result=regexec(&match, device_name, 1, &off, 0);
+                regfree(&match);
+                free(regex);
+
+                // If not this device, skip rest of line
+                if (result || off.rm_so
+                  || off.rm_eo!=strlen(device_name))
+                    goto end_line;
+
+                break;
+              }
+              // uid:gid
+              case 2:
+              {
+                char *s2;
+
+                // Find :
+                for(s = pos; s<end2 && *s!=':'; s++);
+                if (s==end2) goto end_line;
+
+                // Parse UID
+                uid = strtoul(pos,&s2,10);
+                if (s!=s2) {
+                  struct passwd *pass;
+                  char *str = strndup(pos, s-pos);
+                  pass = getpwnam(str);
+                  free(str);
+                  if (!pass) goto end_line;
+                  uid = pass->pw_uid;
+                }
+                s++;
+                // parse GID
+                gid = strtoul(s,&s2,10);
+                if (end2!=s2) {
+                  struct group *grp;
+                  char *str = strndup(s, end2-s);
+                  grp = getgrnam(str);
+                  free(str);
+                  if (!grp) goto end_line;
+                  gid = grp->gr_gid;
+                }
+                break;
+              }
+              // mode
+              case 1:
+              {
+                mode = strtoul(pos, &pos, 8);
+                if (pos!=end2) goto end_line;
+                goto found_device;
+              }
+            }
+            pos=end2;
+          }
+end_line:
+          // Did everything parse happily?
+          if (field && field!=3) error_exit("Bad line %d", line);
+
+          // Next line
+          pos = ++end;
+        }
+found_device:
+        munmap(conf, len);
+      }
+      close(fd);
+    }
+  }
+
+  sprintf(temp, "/dev/%s", device_name);
+  if (mknod(temp, mode | type, makedev(major, minor)) && errno != EEXIST)
+    perror_exit("mknod %s failed", temp);
+
+  if (CFG_MDEV_CONF) mode=chown(temp, uid, gid);
+}
+
+static int callback(struct dirtree *node)
+{
+  // Entries in /sys/class/block aren't char devices, so skip 'em.  (We'll
+  // get block devices out of /sys/block.)
+  if(!strcmp(node->name, "block")) return 0;
+
+  // Does this directory have a "dev" entry in it?
+  // This is path based because the hotplug callbacks are
+  if (S_ISDIR(node->st.st_mode) || S_ISLNK(node->st.st_mode)) {
+    int len=4;
+    char *dev = dirtree_path(node, &len);
+    strcpy(dev+len, "/dev");
+    if (!access(dev, R_OK)) make_device(dev);
+    free(dev);
+  }
+
+  // Circa 2.6.25 the entries more than 2 deep are all either redundant
+  // (mouse#, event#) or unnamed (every usb_* entry is called "device").
+
+  return (node->parent && node->parent->parent) ? 0 : DIRTREE_RECURSE;
+}
+
+void mdev_main(void)
+{
+  // Handle -s
+
+  if (toys.optflags) {
+    dirtree_read("/sys/class", callback);
+    dirtree_read("/sys/block", callback);
+  }
+
+  // hotplug support goes here
+}