[Techtalk] understanding udev

[Akkana Peck]

I've been fighting with a new Ubuntu Edgy install on my laptop --
I'm having trouble getting my PCMCIA wi-fi card to be configured
automatically (yes, I already added "allow-hotplug eth0" in
/etc/network/interfaces), and getting /dev/sda1 to be created so
that I can read cards in the built-in memory stick reader. 

This all boils down to Edgy's elimination of the hotplug and
pcmcia-cs systems in favor of doing everything through udev and
a udev helper called pccardctl. In previous Ubuntu releases it was
pretty easy to tweak the udev and hotplug systems to work together:
/etc/hotplug was all scripts so I could put in debugging lines
to figure out how control passed from one script to another,
but /lib/udev is all binaries so that's no longer an option.

I've done lots of googling and reading man pages, but the udev man
pages are pretty minimal, and everything I've found on the web
describes older versions of the system and references programs that
no longer exist, or udev configuration lines that no longer work.
Questions like: How is a device supposed to get recognized as it
passes through the various udev layers? How do pcmcia devices work,
and at what point is a network suppose to get configured? How does a
program like hal tell udev to create a new device node, and how
could I do that myself?

Anybody have a clue how to find more information about udev, or how
to debug udev problems?  I'm getting a bit tired of having to run
"ifdown eth0; ifup eth0" every time I resume from suspend, or having
to stop and start udev any time I need to read a memory stick.

	...Akkana