[Buildroot] [PATCH v1] package/busybox: Avoid "can't create /proc/sys/kernel/hotplug" error

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Fri, May 24, 2019 at 11:12:17PM +0200, Peter Korsgaard wrote:
> >>>>> "Andy" == Andy Shevchenko <andriy.shevchenko@linux.intel.com> writes:
> 
>  >> > But how can mdev work on such setups?
> 
>  > At least the script is used to initialize modules at the boot time.
>  > What happens afterwards I didn't investigate. I have no such issues.
> 
> You mean the:
> 
>         # coldplug modules
>         find /sys/ -name modalias -print0 | xargs -0 sort -u | tr '\n' '\0' | \
>             xargs -0 modprobe -abq
> 
> That indeed does not depend on mdev working.
> 
> 
>  >> To be clear, if mdev needs CONFIG_UEVENT_HELPER=y for hotplug
>  >> notifications, then we should rather force that in linux/linux.mk and
>  >> mention the dependency in the mdev help text rather than silently not
>  >> having hotplug work.
>  >> 
>  >> I have marked this patch as changes requested in patchwork.
> 
>  > Kernel can be built outside of Buildroot. Still this needs to be fixed.
> 
> And just like all other packages that require specific kernel options
> enabled, if you are not using Buildroot to build the kernel then you
> have to ensure the kernel has the right config options enabled.
> 
> I am not sure what you mean exactly with "Still this needs to be
> fixed". The only fix I can think of is what I mentioned above,
> E.G. document the need for CONFIG_UEVENT_HELPER in the help text and
> automatically enable it in linux.mk.
> 
> Expecting mdev to work sensible on a system without uevent helper
> support isn't sensible, it is similar to having radvd (IPv6 router
> advertising daemon) work on a system without IPv6.

I'm not sure if mdev follows the change in the kernel, but uEvent helper is
obsolete mechanism.

--- 8< --- 8< --- 8< ---

The external binary /sbin/hotplug was used in earlier releases to inform Udev
about device state change. That has been replaced and Udev can now directly
listen to those events through Netlink.

--- 8< --- 8< --- 8< ---

-- 
With Best Regards,
Andy Shevchenko