input devices

[T.C. Hollingsworth]

On Sat, May 24, 2014 at 9:18 AM, lee <lee at yun.yagibdah.de> wrote:
> what would be the device for a Kensington Slimblade which is connected
> to a PS/2 port with an USB-->PS/2 adapter?  The device doesn`t seem to
> appear anywhere when connected like that.

It should appear like any other PS/2 mouse.  If it does not appear,
your mouse does not support the PS/2 protocol.

Most USB-to-PS/2 adapters are passive converters, and require the
device itself to speak the PS/2 protocol.  Many keyboards and mice
were (and some still are) designed to speak both the PS/2 and USB HID
protocols so they can be used with such passive converters.  Most new
ones (e.g. this decade) only speak USB.

If you really must use the PS/2 port, they do make _active_ adapters
that work with any sort of device.

> And what are virtual keyboards for, and why do I supposedly have two
> power buttons?

The XTEST devices allow for the X server to be tested/used without
real hardware:
http://www.x.org/releases/X11R7.7/doc/libXtst/xtestlib.html
(While the interface may have been built for testing purposes, I
wouldn't be surprised if it is used for other reasons these days, like
virtual desktop software.)

Power buttons are implemented as "keyboards" because X has no better
way to let your desktop environment know you've pressed it, seeing as
how it dates back to the days where most computers had actual switches
that really cut power immediately.

As for why you have two, some motherboards have two plugs for them, or
a special little internal power buttons on the motherboards
themselves, or are just poorly engineered and say they have two when
they really have one.  :-)

-T.C.