Introduction

The following readme are cuts from the linux-hotplug-devel mailing list announcement.
http://marc.theaimsgroup.com/?l=linux-hotplug-devel&m=115720744227751&w=2

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Hotplug2 is aimed at early Linux user space, that is, initramfs or initrd,
possibly also at embedded devices (such as WRT-like routers) or very weak
machines, such as 386/486 (some still use them as workstations).

Hotplug2 connects to the uevent netlink socket and read events. The
application generally operates in two modes, dumb and smart.

In dumb mode, when event arrives, we generally only check if it has MODALIAS
set; if yes, we spawn modprobe and carry on.

In smart mode, simple form of rules are applied. Those rules allow matching of
the variables obtained by the uevent socket and allows execution of
applications, with those variables set as their environmental variables.
Further documentation of rules syntax is available at the homepage of the
project.

Hotplug2 supports cold plugging simply by calling the 'udevtrigger' binary
internally. As udevtrigger is fairly independent on the rest of udev, it can be
easily embedded along with Hotplug2. Given that Hotplug2 is in it's infancy,
this can be considered a minor detail and replaced some time later.

The advantages over udev are, as I believe:
 * Faster (way faster!) processing of events, because far less actions are
performed. 
 * The size is (obviously) also way smaller, which is a generic advantage;)

The disadvantages would be:
 * Far less actions are performed and far less actions _can_ be performed.
 
Therefore, as said earlier, Hotplug2 definitely is not aimed as replacement
for udev on desktop, with the exception of initramfs / initrd.
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To enable debugging, compile with -DDEBUG.