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

[Mike Looijmans]

On 05-03-18 09:22, Quentin Schulz wrote:
> 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.

I'd rather have this in a seperate bootscript, like this (which performs the 
same but applies a filter):
https://github.com/topic-embedded-products/meta-topic/tree/master/recipes-core/module-init-tools

This gives users a choice as to whether or not they want this to happen.

Another note: Since this runs at each and every boot, it'd be wise to optimize 
this for performance. That "sort -u" might be bad for performance, and 
modprobe doesn't mind if modules were already probed.



> 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 at 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.
> 



Kind regards,

Mike Looijmans
System Expert

TOPIC Products
Materiaalweg 4, NL-5681 RJ Best
Postbus 440, NL-5680 AK Best
Telefoon: +31 (0) 499 33 69 79
E-mail: mike.looijmans at topicproducts.com
Website: www.topicproducts.com

Please consider the environment before printing this e-mail