On Sun, 14 Dec 2003, Johann Deneux wrote:
> Hi,
>
> I've had bug reports from users trying to use hid with force feed back
> enabled for logitech devices (kernel 2.6.0-test9). The device causing
> trouble is the cordless rumble pad. It is a low-speed device, and
> stubbornly refuses to rumble. It works fine as an input-only device,
> however.
>
> hid-lgff.c, which implements force feedback for this device, needs to
> submit output reports to the device. hid_submit_out submits an output
> bulk urb to the device. ohci-hcd seems fine with that (at least it used
> to, back in 2.4.x times), but uhci-hcd is not.
>
> I commented out two lines in uhci-hcd to force it to accept to submit
> bulk out urbs to low-speed devices:
>
> static inline int uhci_submit_bulk(struct uhci_hcd *uhci, struct urb
> *urb, struc
> t urb *eurb)
> {
> int ret;
>
> /* Can't have low speed bulk transfers */
> /* if (urb->dev->speed == USB_SPEED_LOW)
> return -EINVAL;*/
>
>
> It made by pad rumble, so this quick dirty fix does the job.
> Now, I don't know what the clean fix would be. Maybe change hid to
> submit one-shot-interrupt out urbs when dealing with low-speed devices,
> or just lift the restriction in uhci (I guess there are reasons for this
> restriction, though).
There certainly is an excellent reason for not allowing low-speed bulk
transfers: They are illegal according to the USB specification! Low speed
only supports control and interrupt, not bulk or iso.
I know zero about HID, but it seems likely the problem lies in there.
Alan Stern
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