[PD] [hid] users poll

Christian Klippel ck at mamalala.de
Wed Jun 29 16:34:21 CEST 2005

hi all,

(sorry, was off the net for two weeks, just got back online....)

> Is it sufficient that it respect the USB-HID protocol for it to qualify
> as Human Interface, or does it have to name axes?
> > so I haven't tested a "Multi-Axis Controller" with [hid] yet, that might
> > change my perspective.
> That's another thing I wonder about. How many axes does it take before
> something becomes "Multi-Axis" ?

these names are hid-names as specified by the usb hid spec.
you can find a list of the names in the kernel hid/event sources, for example. 
but of course you can find them also in the hid spec's.....

the device does _not_ define these names as strings, that comes automatically.
in the descriptor, the usage-id (that is what gives name) is represented 
numerical. depending on the type hid device (the so-called usage-page, here 
the multi-axis-controller page) you have a different set of names for those 

multi-axis is just a device that can specify that go beyond x/y/z abs/rel, and 
just some buttons/keys.....

i choosed the multi-axis controller page because it is at nearest to the stuff 
like mouse/keyboard events. i could make the usage-id's (each in/out channel 
has its own id) starting at a lower number. the side-effect would be that 
certain analogoue inputs would control your mouse then, and certain digital 
inputs the keys of your keyboard.

using a different usage page would result in _completely_ unrelated names like 
"batt low" (as in the ups usage page of the section power-devices, also set 
forth in the hid spec's), etc.....

also, because of a limit in the linux event system, you cant use all the 
available i/o (as in a maximum config like 88 adc inputs).
first, there are not that many events defined in the spec, but allowed to be 
used, and second there are limits like "ABS_MAX" in the linux event system 
module which impose that restriction.... to really use it fully, one would 
have to change the sources of the event sytsem (easy, as example on my site), 
or use the second, non-hid configuration of the device.

im open to any suggestions about the right-now used usage tables and id's, to 
find something that fits better maybe...

so, now keeping up with the more mails & stuff,


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