Re: USB mouse protocol,

[Anssi Hannula <anssi.hannula@gmail.com>]

Vojtech Pavlik wrote:
> On Wed, Apr 30, 2008 at 04:07:06PM +0200, xerces8 wrote:
>> Vojtech Pavlik wrote:
>>
>>> On Wed, Apr 30, 2008 at 11:28:59AM +0200, xerces8 wrote:
>>>> 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