10-blackberry.rules

	These udev rules run bcharge on matching Blackberry devices
	in order to enable 500mA battery charging mode.

99-blackberry-perms.rules

	These udev rules set the resulting device mode to the
	group 'plugdev' and mode '0660' so that Barry can access
	the device without being root.

69-blackberry.rules

	This is for Fedora 12 and friends who have updated to a different
	udev rules directory layout.


Commentary:
-----------

Yes, I tried to keep this in one file, but the prevailing winds of Linux
keep this very hard to do.

When you run 'udevadm monitor --env' (udevmonitor on some systems)
you will see UEVENT entries and UDEV entries.  The UEVENT entries
represent kernel level events, generated when you plugin your device
or remove it.  These kernel events are what udev daemons watch for.

Udev then works on these events and generates "events" of its own.
The results of these events are displayed in the monitor output
as UDEV entries.

It seems that the rules in the above rules files only match against
the UEVENT kernel events.

Therefore, the common idiom of:

	SUBSYSTEM=="usb", ENV{DEVTYPE}=="usb_device"

is used to select a newly plugged in device.  Unfortunately, it doesn't
seem that the /dev/bus/* device node exists yet at this point, since
that appears to happen in /etc/udev/rules.d/50-udev.rules, and on some
systems, *that* rule depends on SUBSYSTEM=="usb_device" to work.  This is
not guaranteed to exist on all systems.

Plus, if the kernel event SUBSYSTEM=="usb_device" does exist, it comes
after the one above.

So we have the following behaviour:

	SUBSYSTEM=="usb", ENV{DEVTYPE}=="usb_device" (always happens first)
	SUBSYSTEM=="usb_device" (sometimes happens, and if so, happens last)
	/dev/bus/* created (happens based on udev rules, which differ on
				each system)

So... for fans of cross-platform behaviour, and fans of the KISS method,
this behaviour rules out SUBSYSTEM=="usb_device" as a valid keyword.  And
since the /dev/bus/* (or /proc or whatevever) device node does not yet exist
at the very beginning of this udev process, that means we have to do the
power adjustment and the permissions in two udev steps.

And now you know the rest of the story.

- Chris

Sept 2009

