[PATCH] busybox: mdev: make mdev auto load modules at boot

[Quentin Schulz <quentin.schulz@bootlin.com>]

Thanks to the MODALIAS line at the beginning of mdev.conf, mdev supports
module auto probing on hotplug.

However, this does not work for cold plugged modules (i.e. modules for
devices that were probed before mdev is added as hotplug handler).
Running mdev -s to replay hotplug events does not work in that case.

Let's manually modprobe all modules in the rootfs.

Taken from:
 - https://github.com/buildroot/buildroot/commit/07f46c2b6daec44a6176039c90be67e66c4c2e42
 - https://github.com/buildroot/buildroot/commit/b4fc5a180c81689a982d5c595844331684c14f51

We need xargs to support zero termination of args so let's enable this
configuration in the fragment for mdev.

Signed-off-by: Quentin Schulz <quentin.schulz@bootlin.com>
---
 meta/recipes-core/busybox/busybox/mdev.cfg | 2 ++
 meta/recipes-core/busybox/files/mdev       | 1 +
 2 files changed, 3 insertions(+)

diff --git a/meta/recipes-core/busybox/busybox/mdev.cfg b/meta/recipes-core/busybox/busybox/mdev.cfg
index 6aefe90e43..0d60fc9560 100644
--- a/meta/recipes-core/busybox/busybox/mdev.cfg
+++ b/meta/recipes-core/busybox/busybox/mdev.cfg
@@ -9,3 +9,5 @@ CONFIG_SETSID=y
 CONFIG_CTTYHACK=y
 
 CONFIG_FEATURE_SHADOWPASSWDS=y
+
+CONFIG_FEATURE_XARGS_SUPPORT_ZERO_TERM=y
diff --git a/meta/recipes-core/busybox/files/mdev b/meta/recipes-core/busybox/files/mdev
index 8c9c06e96c..165b275256 100755
--- a/meta/recipes-core/busybox/files/mdev
+++ b/meta/recipes-core/busybox/files/mdev
@@ -9,6 +9,7 @@ touch /dev/mdev.seq
 #sysctl -w kernel.hotplug=/sbin/mdev
 echo "/sbin/mdev" > /proc/sys/kernel/hotplug
 mdev -s
+find /sys/ -name modalias -print0 | xargs -0 sort -u -z | xargs -0 modprobe -abq
 
 #
 # We might have mounted something over /dev, see if /dev/initctl is there.
-- 
2.14.1