Re: [Libusb-devel] libusb-1.0 Windows and Lakeview Research WinUSB demo

[Xiaofan C. <xia...@gm...>]

On Sun, Feb 20, 2011 at 7:11 PM, Xiaofan Chen <xia...@gm...> wrote:
> On Sun, Feb 20, 2011 at 5:17 PM, Xiaofan Chen <xia...@gm...> wrote:
>> On Thu, Jan 20, 2011 at 8:20 PM, Pete Batard <pb...@gm...> wrote:
>>>> By the way, what if you run the application twice? I seem to get
>>>> similar issues under Linux where the 2nd run will cause problems.
>>>> Resetting the device will get it to work again.
>>>
>>> Same story on my side (from cygwin). Second run times out on read.
>>>
>>>> On the other hand, running Jan Axelson's test program will
>>>> not have this issue. Strange.
>>>
>>> Hmmm, OK. I'll make on note of this and take a look when I have a chance.
>>>
>>
>> Today I also tried the libusb-win32 based application (using libusb-win32
>> device driver or using libusb-win32 filter driver on top of WinUSB.sys),
>> everything works fine, no reset is necessary. So it seems to be relate
>> to libusb-1.0 behavior which may trigger potential firmware bug.
>
> Then I tested under Ubuntu Linux 10.10 with both libusb-0.1 and
> libusb-1.0, the programs both work without calling
> usb_reset_device()/libusb_reset_device() or resetting the
> device.
>
> So the problem is now unique to libusb-1.0 Windows backend.
>

After some testing, it seems to me the issue is with
libusb_set_configuration(devh, 1), after removing this call,
the issue is gone.

>From the known limitation, it is mentioned that
"Neither WinUSB or HID can be used to set a device configuration that
is different from the default one. This is a limitation of the
Microsoft drivers."

Therefore I have some doubts about the following codes in windows_usb.c.
Apparently the Control Transfer may have some side effect on some
device. Maybe a simple method is to try to get the active configuration
(probably 1) and then if it is equal to the configuration the user wants
to set, then just return success.

/*
 * from http://msdn.microsoft.com/en-us/library/ms793522.aspx: "The port driver
 * does not currently expose a service that allows higher-level drivers to set
 * the configuration."
 */
static int windows_set_configuration(struct libusb_device_handle
*dev_handle, int config)
{
	struct windows_device_priv *priv = __device_priv(dev_handle->dev);
	int r = LIBUSB_SUCCESS;

	if (config >= USB_MAXCONFIG)
		return LIBUSB_ERROR_INVALID_PARAM;

	r = libusb_control_transfer(dev_handle, LIBUSB_ENDPOINT_OUT |
		LIBUSB_REQUEST_TYPE_STANDARD | LIBUSB_RECIPIENT_DEVICE,
		LIBUSB_REQUEST_SET_CONFIGURATION, (uint16_t)config,
		0, NULL, 0, 1000);

	if (r == LIBUSB_SUCCESS) {
		priv->active_config = (uint8_t)config;
	}
	return r;
}


-- 
Xiaofan