Vojtech Pavlik wrote:

On Wed, Apr 30, 2008 at 04:07:06PM +0200, xerces8 wrote:

quoted

Vojtech Pavlik wrote:

quoted

On Wed, Apr 30, 2008 at 11:28:59AM +0200, xerces8 wrote:

quoted

Hi!

I'm curious about some details in the protocol used by USB mice.
A cursory look at the "Device Class Definition for HID 1.11" documents
tells me (note this is the first USB technical document I ever read)
that a mouse can tell the host the format (the protocol) used to report
data (movement, button state etc.).

Also a quick look into linuxv2.6.25/drivers/hid/usbhid/usbmouse.c suggests
that 8 bits are used for position.

So my questions are:
 - is the position data always 8 bits wide ?

No. The driver you need to look at is usbhid.ko, not usbmouse - that
only works for the static "HID Boot Protocol", and is only useful in
embedded devices.

Pretty hard to read there... Can I activate some debug output, to see what
my mouse is sending ?

Yes, #define DEBUG and possibly also DEBUG_DATA will do the trick.

Not true anymore on recent kernels. You need to enable CONFIG_HID_DEBUG
and use the debug module parameter (/sys/module/hid/parameters/debug).

-- 
Anssi Hannula