[Xgl/Xegl] Input Devices

[Dane Rushton]

Hi All,

I'm going to have ago at developing the input subsystem for Xegl, and
possible for other X's.
I'm in the early research/requirements gathering stage, so I'm after
some input from the experts and your thoughts on the likely direction of
input drivers in Linux and other Unix-like OS's.
I know Jon Smirl has put together a basic system using EVDEV for Xegl.
The Event Interface (EVDEV) is quite new to Linux, and may not be
available in other OS's, so is it worth using? Or should it be one of
several options?

Xegl is aimed at a Free Desktop that is user friendly and feature rich,
so most things should "Just Work (tm)" without any configuration except
when the user is trying to do something advanced.

The core requirements, as I see them are:
1)	Auto-detect devices attached prior to X server initialisation.
	No config files for basic stuff!
2)	Auto-detect devices added or removed during X server run-time.
	The HAL system available on Linux would be excellent for this,
	but again it isn't available for other systems yet.
	What are people's thoughts on utilizing technologies such as
	HAL?
3)	Most workstations and home PC's will want all pointing devices
	to be combined into a common input. For example a laptop with an
	integrated touchpad and an attached USB mouse.
	The default setting should be to detect all pointing devices at
	startup (and any changes during execution) and just use them.
	Linux currently has a /dev/input/mice node which combines
	/dev/input/mouse* devices, but that isn't available in EVDEV
	(as far as I know) if we go that way.
4)	The same should occur for keyboards or other similar devices.
	Examples are laptops with external keyboards, barcode scanners,
	left-handed number pads etc.
5)	For advanced situations the user may have multiple X server
	instances running, each with their own screen, keyboard and
	mouse. This situation is less likely, and would be okay to
	require manual configuration. In that situation the server will
	take a list of which devices it can use. I don't know what
	should happen when devices are added at runtime, i.e. which
	server should get it etc.

Additions, corrections, comments and general discussion welcome.

Cheers
Dane Rushton