Override endpoint attributes (was: RE: [PATCH] zd1211rw: change endpoint types of EP_REGS_OUT and EP_INT_IN from interrupt to bulk)

["Martin Schleier" <drahemmaps@gmx.net>]

Sujith <m.sujith@...> writes:
> Jussi Kivilinna wrote:
> > +static int usb_endpoint_int_to_bulk(struct usb_device *udev, unsigned int pipe)
> > +{
> > +	struct usb_host_endpoint *ep;
> > +
> > +	ep = usb_pipe_endpoint(udev, pipe);
> > +	if (!ep)
> > +		return -EPIPE;
> > +
> > +	switch (ep->desc.bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) {
> > +	case USB_ENDPOINT_XFER_INT:
> > +		ep->desc.bmAttributes &= ~USB_ENDPOINT_XFERTYPE_MASK;
> > +		ep->desc.bmAttributes |= USB_ENDPOINT_XFER_BULK;
> > +		ep->desc.bInterval = 0;
> > +		/* passthru */

Interesting, I know that interrupt and bulk endpoints share a lot of
common logic so I can see how this should work. But is it really
possible [and more to the point: sane?!] to override the endpoint
descriptors?

I know that usb_submit_urb checks [when config_usb_debug is enabled]
if the xfertype of the submitted urb matches the one of the endpoint,
so I wonder I started to wonder if we are fooling "just" the code
here, or ourselves in the process?
 
> ath9k_htc does the same thing (see ath/ath9k/hif_usb.c).
> It does seem to be working properly but I am wondering if the
> USB subsystem has to be updated after the driver messes around with bmAttributes.
> (lsusb would still show the endpoint type as INT).
> 
> You have a usb_reset_configuration() call before changing
> the endpoint type, why is that necessary ? And would that
> reset the endpoints as well ?
Huh, has this already catched on?
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