mdev: provide $SUBSYSTEM (by Vladimir)

function                                             old     new   delta
make_device                                         1265    1340     +75
dirAction                                             14      60     +46
mdev_main                                            676     695     +19
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/0 up/down: 140/0)             Total: 140 bytes

1 files changed, 26 insertions, 7 deletions

diff --git a/util-linux/mdev.c b/util-linux/mdev.c
index ca5eaca48..3b0ef351e 100644
--- a/util-linux/mdev.c
+++ b/util-linux/mdev.c
@@ -14,10 +14,12 @@
 
 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
@@ -111,7 +113,7 @@ static void make_device(char *path, int delete)
         /* 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;
+                char *val = tokens[0];
 
                 /* Fields: regex uid:gid mode [alias] [cmd] */
 
@@ -134,10 +136,15 @@ static void make_device(char *path, int delete)
                 } else { /* ... or regex to match device name */
                         regex_t match;
                         int result;
+                        const char *dev_name_or_subsystem = device_name;
+                        if ('/' == val[0] && subsystem) {
+                                dev_name_or_subsystem = subsystem;
+                                val++;
+                        }
 
                         /* Is this it? */
-                        xregcomp(&match, tokens[0], REG_EXTENDED);
-                        result = regexec(&match, device_name, ARRAY_SIZE(off), off, 0);
+                        xregcomp(&match, val, REG_EXTENDED);
+                        result = regexec(&match, dev_name_or_subsystem, ARRAY_SIZE(off), off, 0);
                         regfree(&match);
 
                         //bb_error_msg("matches:");
@@ -151,7 +158,7 @@ static void make_device(char *path, int delete)
                         /* 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))
+                         || ((int)off[0].rm_eo != (int)strlen(dev_name_or_subsystem))
                         ) {
                                 continue;
                         }
@@ -276,10 +283,14 @@ static void make_device(char *path, int delete)
 #if ENABLE_FEATURE_MDEV_EXEC
         if (command) {
                 /* setenv will leak memory, use putenv/unsetenv/free */
-                char *s = xasprintf("MDEV=%s", device_name);
+                char *s = xasprintf("%s=%s", "MDEV", device_name);
+                char *s1 = xasprintf("%s=%s", "SUBSYSTEM", subsystem);
                 putenv(s);
+                putenv(s1);
                 if (system(command) == -1)
                         bb_perror_msg_and_die("can't run '%s'", command);
+                unsetenv("SUBSYSTEM");
+                free(s1);
                 unsetenv("MDEV");
                 free(s);
                 free(command);
@@ -326,6 +337,13 @@ 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) {
+                subsystem = strrchr(fileName, '/');
+                if (subsystem)
+                        subsystem++;
+        }
+
         return (depth >= MAX_SYSFS_DEPTH ? SKIP : TRUE);
 }
 
@@ -445,13 +463,14 @@ int mdev_main(int argc UNUSED_PARAM, char **argv)
                 char *env_path;
 
                 /* 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");