[Libusb-devel] what does a LIBUSB_TRANSFER_STALL on control transfer mean?

[bob 2. <ica...@29...>]

I'm still very much a USB/libusb-1.0 newbie.

I've been trying to teach myself the libusb-1.0 library against a Phidgets SBC 
board.    This board comes with libusb-0.1 source code,  albeit a tad 
difficult to follow.   The relevant libusb-0.1 call I'm trying to emulate in 
async libusb-1.0 is:

=========  begin Phidget lib snip =============
 BytesWritten = usb_control_msg((usb_dev_handle *)phid->deviceHandle,
                                        USB_ENDPOINT_OUT | USB_TYPE_CLASS |
USB_RECIP_INTERFACE,
                                        USB_REQ_SET_CONFIGURATION,
                                        0x0200, /* value */
                                        phid->deviceDef->pdd_iid, /* index*/
                                        (char *)buffer,
                                        phid->outputReportByteLength, /* size 
*/
                                        500); /* FIXME? timeout */
=========== end Phidget lib snip ===========



Recently I tried programming an async control transfer message by adding some 
modifications to the dpfp.c example (documented at 
http://www.icanprogram.com/opndrs/phidgets/2012Apr13.html).    The relevant 
code is:

========== begin my dpfp.c snip =============

libusb_fill_control_setup(ctrlbuf, 
		LIBUSB_ENDPOINT_OUT | LIBUSB_REQUEST_TYPE_CLASS |
		LIBUSB_RECIPIENT_INTERFACE,
		0x09,
		0x0200,
		0,
		6);

	ctrlbuf[8]=0x1;

printf("go2: ctrlbuf0-7]=0x%X-%X-%X-%X-%X-%X-%X-%X\n",
		ctrlbuf[0],
		ctrlbuf[1],
		ctrlbuf[2],
		ctrlbuf[3],
		ctrlbuf[4],
		ctrlbuf[5],
		ctrlbuf[6],
		ctrlbuf[7]);

printf("go3: ctrlbuf[8-15]=0x%X-%X-%X-%X-%X-%X-%X-%X\n",
		ctrlbuf[8],
		ctrlbuf[9],
		ctrlbuf[10],
		ctrlbuf[11],
		ctrlbuf[12],
		ctrlbuf[13],
		ctrlbuf[14],
		ctrlbuf[15]);


	libusb_fill_control_transfer(ctrl_transfer, devh, ctrlbuf,
		cb_ctrl, NULL, 0);


========== end my dpfp.c snip ==============

    

What does it mean when the control transfer returns a LIBUSB_TRANSFER_STALL?

Thanks in advance for your help.

bob