Busybox modprobe has a couple of irritating quirks:

 - attempting to modprobe a module that is already loaded yields "Failed
to load module", whereas modutils quietly ignores such a request.

 - if a module genuinely can't be loaded due to missing symbols or
similar problems, modprobe doesn't produce any useful diagnostics
because the output from insmod has been redirected to /dev/null.

Here's a patch to address these issue

Patch by Philip Blundell

1 files changed, 33 insertions, 4 deletions

diff --git a/modutils/modprobe.c b/modutils/modprobe.c
index b4bff5100..07cbb6fc7 100644
--- a/modutils/modprobe.c
+++ b/modutils/modprobe.c
@@ -319,6 +319,32 @@ static struct dep_t *build_dep ( void )
         return first;
 }
 
+/* return 1 = loaded, 0 = not loaded, -1 = can't tell */
+static int already_loaded (const char *name)
+{
+        int fd;
+        char buffer[256];
+
+        fd = open ("/proc/modules", O_RDONLY);
+        if (fd < 0)
+                return -1;
+
+        while ( reads ( fd, buffer, sizeof( buffer ))) {
+                char *p;
+
+                p = strchr (buffer, ' ');
+                if (p) {
+                        *p = 0;
+                        if (strcmp (name, buffer) == 0) {
+                                close (fd);
+                                return 1;
+                        }
+                }
+        }
+
+        close (fd);
+        return 0;
+}
 
 static int mod_process ( struct mod_list_t *list, int do_insert )
 {
@@ -326,10 +352,13 @@ static int mod_process ( struct mod_list_t *list, int do_insert )
         int rc = 1;
 
         while ( list ) {
-                if ( do_insert )
-                        snprintf ( lcmd, sizeof( lcmd ) - 1, "insmod %s %s %s %s %s 2>/dev/null", do_syslog ? "-s" : "", autoclean ? "-k" : "", quiet ? "-q" : "", list-> m_module, list-> m_options ? list-> m_options : "" );
-                else
-                        snprintf ( lcmd, sizeof( lcmd ) - 1, "rmmod %s %s 2>/dev/null", do_syslog ? "-s" : "", list-> m_module );
+                if ( do_insert ) {
+                        if (already_loaded (list->m_module) != 1)
+                                snprintf ( lcmd, sizeof( lcmd ) - 1, "insmod %s %s %s %s %s", do_syslog ? "-s" : "", autoclean ? "-k" : "", quiet ? "-q" : "", list-> m_module, list-> m_options ? list-> m_options : "" );
+                } else {
+                        if (already_loaded (list->m_module) != 0)
+                                snprintf ( lcmd, sizeof( lcmd ) - 1, "rmmod %s %s", do_syslog ? "-s" : "", list-> m_module );
+                }
                 
                 if ( verbose )
                         printf ( "%s\n", lcmd );