Use libkmod only when requested

We support module loading through modprobe when libkmod is neither
available nor wanted.

Signed-off-by: Richard Yao <ryao@gentoo.org>

configure.ac

@@ -39,7 +39,6 @@ if test -z "$GPERF" ; then
         AC_MSG_ERROR([*** gperf not found])
 fi
 
-PKG_CHECK_MODULES(KMOD, [libkmod >= 5])
 PKG_CHECK_MODULES(BLKID,[blkid >= 2.20])
 
 # Checks for header files.
@@ -278,6 +277,34 @@ AC_SUBST([udevlibexecdir], [${with_rootlibdir}/udev])
 
 # ------------------------------------------------------------------------------
 
+AC_ARG_ENABLE([libkmod], [AS_HELP_STRING([--enable-libkmod], [Enable module loading through kmod @<:@default=disabled@:>@])], [], [with_libkmod=no])
+
+LIBKMOD=
+AS_IF([test "x$with_libkmod" != xno],
+  [AC_CHECK_LIB([kmod], [main],
+    [PKG_CHECK_MODULES(KMOD, [libkmod >= 5])
+     AC_SUBST([LIBKMOD], ["-lkmod"])
+     AC_DEFINE([HAVE_LIBKMOD], [1],
+               [Define if you have libkmod])
+    ],
+    [AC_MSG_FAILURE(
+       [--with-libkmod was given, but test for kmod failed])],
+    [-lkmod])])
+
+AM_CONDITIONAL([HAVE_LIBKMOD], [test "$with_kmod" = "yes"])
+
+# ------------------------------------------------------------------------------
+
+AC_ARG_WITH([modprobe],
+            [AS_HELP_STRING([--with-modprobe=modprobe],
+              [specify location of modprobe when -- @<:@default=$sbindir/modprobe@:>@])],
+            [],
+            [with_modprobe="${sbindir}/modprobe"])
+
+AC_SUBST([MODPROBE], ["${with_modprobe}"])
+
+# ------------------------------------------------------------------------------
+
 AC_CONFIG_FILES([Makefile
                  docs/Makefile
                  docs/gudev/Makefile

src/test/Makefile.am

@@ -28,9 +28,12 @@ test_udev_LDADD = \
 	$(top_builddir)/src/libudev/libudev-private.la \
 	$(top_builddir)/src/udev/libudev-core.la \
 	$(BLKID_LIBS) \
-	$(KMOD_LIBS) \
 	$(SELINUX_LIBS)
 
+if HAVE_LIBKMOD
+test_udev_LDADD += $(KMOD_LIBS)
+endif
+
 test_udev_CPPFLAGS = \
 	-I $(top_srcdir)/src/udev \
 	$(AM_CPPFLAGS)

src/udev/Makefile.am

@@ -6,6 +6,7 @@ udevhomedir = $(udevlibexecdir)
 
 AM_CPPFLAGS = \
 	-include $(top_builddir)/config.h \
+	-DMODPROBE=\"$(MODPROBE)\" \
 	-DROOTPREFIX=\"$(rootprefix)\" \
 	-DUDEVLIBEXECDIR=\"$(udevlibexecdir)\" \
 	-I $(top_srcdir)/src/libudev
@@ -101,13 +102,19 @@ include_HEADERS = \
 
 libudev_core_la_CFLAGS = \
 	$(AM_CFLAGS) \
-	$(BLKID_CFLAGS) \
-	$(KMOD_CFLAGS)
+	$(BLKID_CFLAGS)
+
+if HAVE_LIBKMOD
+libudev_core_la_CFLAGS += $(KMOD_CFLAGS)
+endif
 
 libudev_core_la_LIBADD = \
 	$(top_builddir)/src/libudev/libudev-private.la \
-	$(BLKID_LIBS) \
-	$(KMOD_LIBS)
+	$(BLKID_LIBS)
+
+if HAVE_LIBKMOD
+libudev_core_la_LIBADD += $(KMOD_LIBS)
+endif
 
 if HAVE_ACL
 libudev_core_la_SOURCES += \

src/udev/udev-builtin-kmod.c

@@ -27,14 +27,19 @@
 #include <fcntl.h>
 #include <sys/stat.h>
 #include <sys/wait.h>
+
+#ifdef HAVE_LIBKMOD
 #include <libkmod.h>
+#endif
 
 #include "udev.h"
+#include "util.h"
 
 static struct kmod_ctx *ctx;
 
-static int load_module(struct udev *udev, const char *alias)
+static int load_module(struct udev *udev, char *const alias)
 {
+#ifdef HAVE_LIBKMOD
         struct kmod_list *list = NULL;
         struct kmod_list *l;
         int err;
@@ -62,6 +67,10 @@ static int load_module(struct udev *udev, const char *alias)
 
         kmod_module_unref_list(list);
         return err;
+#else
+	char * const argv[] = { "-bq", alias, 0 };
+	return execute_command(MODPROBE, argv);
+#endif
 }
 
 static void udev_kmod_log(void *data, int priority, const char *file, int line,
@@ -75,8 +84,10 @@ static int builtin_kmod(struct udev_device *dev, int argc, char *argv[], bool te
         struct udev *udev = udev_device_get_udev(dev);
         int i;
 
+#ifdef HAVE_LIBKMOD
         if (!ctx)
                 return 0;
+#endif
 
         if (argc < 3 || strcmp(argv[1], "load")) {
                 log_error("expect: %s load <module>\n", argv[0]);
@@ -94,6 +105,7 @@ static int builtin_kmod(struct udev_device *dev, int argc, char *argv[], bool te
 /* called at udev startup and reload */
 static int builtin_kmod_init(struct udev *udev)
 {
+#ifdef HAVE_LIBKMOD
         if (ctx)
                 return 0;
 
@@ -104,16 +116,20 @@ static int builtin_kmod_init(struct udev *udev)
         log_debug("load module index\n");
         kmod_set_log_fn(ctx, udev_kmod_log, udev);
         kmod_load_resources(ctx);
+#endif
         return 0;
 }
 
 /* called on udev shutdown and reload request */
 static void builtin_kmod_exit(struct udev *udev)
 {
+#ifdef HAVE_LIBKMOD
         log_debug("unload module index\n");
         ctx = kmod_unref(ctx);
+#endif
 }
 
+#ifdef HAVE_LIBKMOD
 /* called every couple of seconds during event activity; 'true' if config has changed */
 static bool builtin_kmod_validate(struct udev *udev)
 {
@@ -122,13 +138,16 @@ static bool builtin_kmod_validate(struct udev *udev)
                 return false;
         return (kmod_validate_resources(ctx) != KMOD_RESOURCES_OK);
 }
+#endif
 
 const struct udev_builtin udev_builtin_kmod = {
         .name = "kmod",
         .cmd = builtin_kmod,
         .init = builtin_kmod_init,
         .exit = builtin_kmod_exit,
+#ifdef HAVE_LIBKMOD
         .validate = builtin_kmod_validate,
+#endif
         .help = "kernel module loader",
         .run_once = false,
 };