about usb

Chuck Robey chuckr at chuckr.org
Tue Feb 12 20:58:24 UTC 2008


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I am running FreeBSD-current, and I'm trying to learn more about how usb
devices work under FreeBSD.  I guess I better get specific, being that I
know there's many kinds of devices, so I have a UC-Logic WP8060-TAB08,
which is an 8" by 6" Graphic Tablet.  Thanks to Kai Wang, I know about the
USBHID spec, and I'm aboout 1/2 way finished with it, and thanks to some
use  of apropos, I know about the libusbhid, which does actually still seem
to exist.

But, I guess there's been a lot of coding in usb, because the state of usb
docs is, well, mostly missing in action.  I found about a conf file in /etc
called usbd.conf, but I would guess that's a goner too (although this is a
recently installed machine, so it shouldn't be too chock full of ancient
memorabilia.

I know from using Kai Wang's incredible usb dumping tool that it's a hid
device, and I am learning to parse usb's version of ancient greek, but I
wonder, why (if this device shows up in usbdevs, and it does) why isn't
there a /dev/uhid to let me play some (at least generic) games with it,
maybe with usbhidctl?

The handbook, both the regular version AND the developer version, treat usb
only from the direction of masss storage.  Once I get to the point of
understanding this data dump I have (and that won't bee all that long) I
need more into about how to architecturally amke this work.  Questions
like, does this item need to operate alone, or along with my current
trackball?  If I write a device driver for this, what kind of interface
should I present at /dev?  If I get this done, will I just enter some
deathless prose into my xorg.conf's input section, or do I need some
special XInput input module. like those in
/usr/local/lib/xorg/modules/input, and where would I go to find out what
that fella's supposed to look like?

OK, I think I'm running down now, your turn!
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