I, and a growing number of others, have been having trouble with using
touch screen devices in Linux, particularly the motorized ones that fit
into car dashboards.  The problem is that these devices, which have a
USB touchscreen (often the eGalax brand), turn off when the screen is
retracted, causing Linux to remove and/or disconnect the event device
in /dev/input.

Using udev to assign a persistent symlink to the device was the first
thing I tried, but it does not solve the problem, since X windows does
not see the device when it turns back on, even if it's the same name.  I
(and others) have tried hacks like changing virtual terminals, etc. to
get it back, but these are not elegant solutions are are problematic.

Anyway, I finally decided the thing I needed was something like
/dev/input/mice, since it is always there for X to see, even if the
device is off during boot.  But the mousedev devices are not the
right data format for use with the touch screens (you need "event"
ones).  So I hacked evdev.c and added "/dev/input/events", which is a
mixer as well and catches all events from event0, event1, etc.

This works great, and I think it would be a great addition to the Linux
kernel.  I would like to submit this patch, and I hope it can be made a
part of the Linux kernel.  However, I would feel more comfortable if
someone (the maintainer?) could look over my changes and verify that
they are done correctly.  I had a few open questions that resulted from
the fact that evdev is slightly different than mousedev:

For example, in evdev_open, I had to check evdev->handle.dev for
non-zero before making the input call (evdev_mix has a zero in this
pointer), or of course I would get a seg fault.  I also got a lockup
later that I fixed by making other similar checks for a zero
handle.dev, but since these checks were not necessary in mousedev, I
would like to verify that this is the correct way to deal with it.

Another thing is the "grab" concept in evdev.  I check for handle.dev to
be non-zero before I let grab get set, and I do not know every aspect of
the grab mechanism, so I hope this is the right thing to do.

Anyway, I hope my change is valuable.  I (and others) would love to see
it appear in the official kernel source.  I attached the patch.

	Thanks, Joe