libudev-zero

Drop-in replacement for libudev enables you to use whatever device manager you like without worrying about udev dependency at all!

What Works

• xorg-server
• dosfstools - need implement udev_enumerate_add_match_parent()
• libinput
• usbutils
• wlroots
• weston
• libusb
• kwin - fix
• ???

Dependencies

• C99 compiler (build time)
• POSIX make (build time)
• POSIX & XSI libc
• epoll & inotify
• Linux >= 2.6.39

Installation

make
make PREFIX=/usr install # will overwrite existing udev libraries if any
# rebuild all packages which depends on udev
# here we go !

Hotplugging

There is no complicated or overengineered way to use hotplugging. Everything is portable as much as possible. To use hotplugging the only thing you need is uevent's receiver (device manager, busybox uevent, CONFIG_UEVENT_HELPER, ...). I will describe only mdev and CONFIG_UEVENT_HELPER because their usage is very basic. For busybox uevent you need to write your own parser which is kinda ... complex.

UDEV_MONITOR_DIR is arbitrary directory where uevent files stored. Default is /tmp/.libudev-zero. You can change it at build time by appending -DUDEV_MONITOR_DIR=<dir> to CFLAGS. I don't recommend setting UDEV_MONITOR_DIR to regular fs (i.e non-tmpfs) because unneeded files aren't automatically discarded after reboot or termination (yet).

• mdev

  • merge mdev.conf with your mdev.conf
  • restart mdev daemon

• CONFIG_UEVENT_HELPER

  • ensure that CONFIG_UEVENT_HELPER enabled in kernel

  • add full path of helper.sh (must be executable) or helper.c (compile it first) to /proc/sys/kernel/hotplug

    example:

    echo /full/path/to/helper > /proc/sys/kernel/hotplug # will use default UDEV_MONITOR_DIR
    OR
    echo "/full/path/to/helper <dir>" > /proc/sys/kernel/hotplug # change <dir> to your UDEV_MONITOR_DIR
    

• run application which uses hotplugging (e.g xorg-server)

• unplug and plug something to test working capacity

That's all! If you realized that this doesn't work for you, you can always open an issue and describe your bug.

TODO

• speed up performance
• extend devices support
• implement hotplugging support

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