IIRC, we clear that file to prevent the kernel from trying to call /sbin/hotplug. A quick look at the kernel sources suggests that this is still required. (Though we could also clear CONFIG_UEVENT_HELPER_PATH at build time, I think.)

TBH, I'd rather get rid of the whole CONFIG_UEVENT_HELPER* legacy in the kernel as well. I've a patch to do just that at home, but it seems to have escaped the PR. Would that be all right?

(It was never a great design to begin with, and really doesn't seem like something that should be enabled by default anymore. From Kconfig:

Before the switch to the netlink-based uevent source, this was used to hook hotplug scripts into kernel device events. [...] This should not be used today)

Yeah, if there is a kernel option to disable uevent helper stuff, that would be great.

To disable it, I need to set UEVENT_HELPER_PATH to the empty string. How can I do that? "" doesn't work.

CONFIG_UEVENT_HELPER disables the uevent helper, and also /proc/sys/kernel/hotplug, I don't know what version it became available in, but it's in 3.19.0

I seem to remember some obscure Dell driver that still requires that option, though...?

Never mind, that was FW_LOADER_USER_HELPER, not this... Pushed as 9f87f3c.