[Buildroot] [PATCH 4/4] package/busybox: add service to load kernel modules at boot
Angelo Compagnucci
angelo at amarulasolutions.com
Tue Jun 28 09:11:30 UTC 2022
On Tue, Jun 28, 2022 at 11:03 AM Andreas Ziegler <br015 at umbiko.net> wrote:
> Hi Angelo,
>
> On 2022-06-28 07:56, Angelo Compagnucci wrote:
> > On Sat, Jun 25, 2022 at 7:02 AM Andreas Ziegler <br015 at umbiko.net>
> > wrote:
> >
> >> Hi Angelo,
> >>
> >> On 2022-06-21 13:31, Angelo Compagnucci
> >> <angelo at amarulasolutions.com>
> >> wrote:
> >>
> >>>>
> >>>>
> >>>> On 20/06/2022 23:40, Angelo Compagnucci wrote:
> >>>>> In cases where no hotplug is available (by choice or by the
> >> lack of a
> >>>>> proper hotplug method for a device), this service can be used
> >> to load
> >>>>> kernel module drivers by reading the /etc/modules file.
> >>>>
> >>>> Do you have a concrete example of something that needs this?
> >> It's
> >>>> kind
> >>>> of a
> >>>> hack for e.g. a device connected to a serial port that isn't
> >> described
> >>>> in
> >>>> DT
> >>>> (e.g. on an x86 platform), right?
> >>>>
> >>>
> >>> Wifi card connected on SDIO with an out of tree kernel module.
> >>>
> >>>
> >>>> I'm not altogether sure if it is worth making an init script
> >> for
> >>>> that.
> >>>>
> >>>
> >>> Most distros out there have the /etc/modules loaded at boot time.
> >>>
> >>>
> >>>> Also, this would belong to the initscripts package because it
> >> would
> >>>> also
> >>>> be
> >>>> needed if busybox isn't used at all (it would of course require
> >> kmod).
> >>>>
> >>>
> >>> Right, I'll fix it
> >>>
> >>>
> >>>>
> >>>>
> >>>>>
> >>>>> Signed-off-by: Angelo Compagnucci <angelo at amarulasolutions.com>
> >>>>> ---
> >>>>> package/busybox/S02modules | 56
> >> ++++++++++++++++++++++++++++++++++++++
> >>>>> package/busybox/busybox.mk [1] | 2 ++
> >>>>> 2 files changed, 58 insertions(+)
> >>>>> create mode 100644 package/busybox/S02modules
> >>>>>
> >>>>> diff --git a/package/busybox/S02modules
> >> b/package/busybox/S02modules
> >>
> >> S02 is a bit early, [mu]dev use S10.
> >
> > Can you point me to these [mu]dev scripts?
> >
> >>>>> new file mode 100644
> >>>>> index 0000000000..f25712e1ca
> >>>>> --- /dev/null
> >>>>> +++ b/package/busybox/S02modules
> >>>>> @@ -0,0 +1,56 @@
> >>>>> +#!/bin/sh
> >>>>> +
> >>>>> +MODULES="modules"
> >>>>> +
> >>>>> +load_unload() {
> >>>>> + [ ! -f /etc/${MODULES} ] && echo ' OK' && exit 0
> >>>>> +
> >>>>> + while read module args; do
> >>>>> +
> >>>>> + case "$module" in
> >>>>> + ""|"#"*) continue ;;
> >>>>> + esac
> >>>>> +
> >>>>> + if [ "$1" = "load" ]; then
> >>>>> + modprobe -q ${module} ${args} >/dev/null
> >> && \
> >>>>> + printf ' %s success,' "$module"
> >> ||
> >>>>> + printf ' %s failed,' "$module"
> >>>>> + else
> >>>>> + rmmod ${module} >/dev/null
> >>>>> + fi
> >>>>> +
> >>>>> + done < /etc/${MODULES}
> >>>>> +}
> >>>>> +
> >>>>> +start() {
> >>>>> + printf 'Starting %s:' "$MODULES"
> >>>>> +
> >>>>> + load_unload load
> >>>>> +
> >>>>> + echo ' OK'
> >>>>> +}
> >>>>> +
> >>>>> +stop() {
> >>>>> + printf 'Stopping %s: ' "$MODULES"
> >>>>> +
> >>>>> + load_unload unload
> >>>>> +
> >>>>> + echo 'OK'
> >>>>> +}
> >>>>> +
> >>>>> +restart() {
> >>>>> + stop
> >>>>> + sleep 1
> >>>>> + start
> >>>>> +}
> >>>>> +
> >>>>> +case "$1" in
> >>>>> + start|stop|restart)
> >>>>> + "$1";;
> >>>>> + reload)
> >>>>> + # Restart, since there is no true "reload"
> >> feature.
> >>>>> + restart;;
> >>>>> + *)
> >>>>> + echo "Usage: $0 {start|stop|restart|reload}"
> >>>>> + exit 1
> >>>>> +esac
> >>>>> diff --git a/package/busybox/busybox.mk [1]
> >> b/package/busybox/busybox.mk [1]
> >>>>> index 3e49de0a84..40490e866a 100644
> >>>>> --- a/package/busybox/busybox.mk [1]
> >>>>> +++ b/package/busybox/busybox.mk [1]
> >>>>> @@ -382,6 +382,8 @@ define BUSYBOX_INSTALL_TARGET_CMDS
> >>>>> $(BUSYBOX_INSTALL_UDHCPC_SCRIPT)
> >>>>> $(BUSYBOX_INSTALL_ZCIP_SCRIPT)
> >>>>> $(BUSYBOX_INSTALL_MDEV_CONF)
> >>>>> + $(INSTALL) -m 0755 -D package/busybox/S02modules \
> >>>>> + $(TARGET_DIR)/etc/init.d/S02modules;
> >>
> >> Since this is intended for systems without dynamic device handling,
> >> you
> >> might use an optional script, similar to BUSYBOX_INSTALL_*_SCRIPT:
> >>
> >> # Copy S22modules to /etc/init.d if no dynamic device handling is
> >> used
> >> ifeq ($(BR2_ROOTFS_DEVICE_CREATION_STATIC),y)
> >> define BUSYBOX_INSTALL_MODULES_SCRIPT
> >> $(INSTALL) -m 0755 -D package/busybox/S22modules \
> >> $(TARGET_DIR)/etc/init.d/S22modules;
> >> endef # BUSYBOX_INSTALL_MODULES_SCRIPT
> >>
> >> Probably a default /etc/modules could also be installed.
> >
> > Yes, but it is not the only usecase here. A usecase could be a
> > userspace software that needs a special kernel module to be loaded on
> > boot or a hardware which cannot be hotplugged.
>
> Then a Config.in item to select this feature would be appreciated, since
> most configurations will not need it.
>
Not sure if it will be happily accepted ;)
The last word is on the BR maintainers.
Anyway, in systemd we have the service always installed and available, it
prints anything to the console if no module should be loaded.
I can move the check for the modules file at the very beginning of the
script, so it's like it has never been executed.
> My usecase was for a wifi card connected via sdio running only with an
> > out of tree kernel module. The wifi card is soldered and doesn't have
> > a CS to trigger an hotplug event and the only sensible way I found to
> > load the module at boot was to have a proper way to load modules at
> > boot.
>
> I used something similar initially, until switching to udev.
>
Sure I can, but this patch is exactly to cover the cases where a developer
cannot/won't switch to something like that.
>
> > I'm not aware normal distros does so much tinkering about loading a
> > kernel module at boot: /etc/modules or the newly /etc/modules-load.d/
> > for systemd are widely adopted and are usually working out of the box.
> >
>
> Kind regards,
> Andreas
>
> >> Kind regards,
> >> Andreas
> >>
> >>>>
> >>>> This is a sysvinit script, so it should be installed in
> >>>> BUSYBOX_INSTALL_INIT_SYSV.
> >>>>
> >>>>
> >>>>
> >>>> Regards,
> >>>> Arnout
> >>>>
> >>>>> endef
> >>>>>
> >>>>> # Install the sysvinit scripts, for the moment, but not those
> >> that
> >>>> already
> >>>>
> >>>
> >>>
> >>> --
> >>>
> >>> Angelo Compagnucci
> >>>
> >>> Software Engineer
> >>>
> >>> angelo at amarulasolutions.com
> >>> __________________________________
> >>> Amarula Solutions SRL
> >>>
> >>> Via le Canevare 30, 31100 Treviso, Veneto, IT
> >>>
> >>> T. +39 (0)42 243 5310
> >>> info at amarulasolutions.com
> >>>
> >>> www.amarulasolutions.com [2]
> >>> [`as] https://www.amarulasolutions.com|
> >
> > --
> >
> > Angelo Compagnucci
> >
> > Software Engineer
> >
> > angelo at amarulasolutions.com
> > __________________________________
> > Amarula Solutions SRL
> >
> > Via le Canevare 30, 31100 Treviso, Veneto, IT
> >
> > T. +39 (0)42 243 5310
> > info at amarulasolutions.com
> >
> > www.amarulasolutions.com [3]
> >
> > [`as] https://www.amarulasolutions.com|
> >
> > Links:
> > ------
> > [1] http://busybox.mk
> > [2] http://www.amarulasolutions.com
> > [3] http://www.amarulasolutions.com/
>
--
Angelo Compagnucci
Software Engineer
angelo at amarulasolutions.com
__________________________________
Amarula Solutions SRL
Via le Canevare 30, 31100 Treviso, Veneto, IT
T. +39 (0)42 243 5310
info at amarulasolutions.com
www.amarulasolutions.com
[`as] https://www.amarulasolutions.com|
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