Re: [Libff-devel] Sidewinder FF driver

[Johann D. <jo...@do...>]

Fabien Brachere wrote:
> Hello,

Hi,

> I'm new to the list, and I'm working on a Microsoft Sidewinder Force
> Feedback 2 driver (Product ID=0x001b, Vendor ID=0x045e).
> I started to study USB, HID and PID protocols and the joystick seems to
> follow PID specification.
> I implemented a skeleton driver (with latest development kernel 2.5.7)
> which do the following things:
> when insmod'ed : reset device, adjust gain, upload an arbitrary effect
> (sort of machine-gun effect sniffed from the Windows test of the
> joystick) and play it, and it works !
> when rmmod'ed : stop effect, reset device.

That sounds really interesting.

> For the moment, no IOCTL and no relation with evdev except for position
> of joystick and buttons.
> 
> The theory of operations:
> the driver uses 4 flow of data with the device: control in (for "block
> load report" and "pid pool report": see pid spec.), control out (for
> "create new effect report") , interrupt in (for joystick state (axes,
> buttons, power, optical switch)) and interrupt out for all other
> commands (set effect report, set envelope report, device gain report,
> pid device control , ....)
> 
> I've not release yet any file, because it's in early alpha stage and
> it's very dirty code, must clean up before all, implement correct data
> structures to follow PID spec...

There really is no reason to be ashamed of dirty code. I don't think any 
hacker really cares about dirtyness at such early development stages.
Several people already started to work on this subject, and I believe 
the amount of code we have seen does not reflect the total amount of 
time spent on it.
Furthermore, if you have an heart attack today, what I don't wish you, 
we lose all your work.

> I think in a few weeks (depend on the time I have), I put all of that on
> a Web site.
> 
> I've a problem with this driver: I can't insert it without rmmod hid, I
> think it's the fault of hid-input who register the device, so I can't
> register it twice. Any idea ? (without modify hid code).
> 

This is how I did for the Logitech WingMan Cordless Rumble Pad: I 
slightly modified hid.h, hid-core.c and hid-input.c to add new function 
entries.
Then I added a file called hid-ff.c where the code for force feedback 
goes. It's available in linuxconsole's CVS on sourceforge. I designed 
the framework so that other protocols could be added.
Please have a look. If you like the way it's done, please use the existing
framework. If you don't, please explain why so that we can improve it ;)

By the way, I think we should have discussions about drivers on the 
linuxconsole mailing list, and discussions about the userland force 
feedback library on libff-devel.

-- 
Johann Deneux