EOVERFLOW problem with usb_control_msg

Hallo!

I am trying to develop a kernel module for the CH341 USB-to-serial 
adaptor. I have working libusb code which sets up the device, but am 
having problems repeating this in the kernel.

The first control message that reads data from the device returns with 
-EOVERFLOW, which the documentation describes as the USB device 
babbling. There is no data on the bus, however.

I have tried tracing through the code in usb_control_msg (down to 
wait_for_completion_timeout) but don't see this error value being
generated.

My kernel code goes something like this (heavily snipped):

static struct usb_driver ch341_driver = {
	.name		= "ch341",
	.probe		= usb_serial_probe,
	.disconnect	= usb_serial_disconnect,
	.id_table	= id_table,
	.no_dynamic_id	= 1,
};

static struct usb_serial_driver ch341_device = {
   ...snip...
	.open             = ch341_open,
	.attach           = ch341_attach,
};

static int ch341_attach(struct usb_serial *serial)
{	...snip...

	r = ch341_configure(serial->dev, priv);
	if (r)
		return r;

	usb_set_serial_port_data(serial->port[0], priv);
	return 0;
}

int ch341_configure(struct usb_device *dev, struct ch341_private *priv)
{	...snip buffer allocation (1KB for testing)...
	/* expect two bytes 0x27 0x00 */
	r=ch341_control_in(dev, 0x5f, 0, 0, buffer, size);
	...snip...
}

static int ch341_control_in(struct usb_device *dev,
			    u8 request, u16 value, u16 index,
			    char *buf, unsigned bufsize)
{
	int r;
	r = usb_control_msg(dev, usb_sndctrlpipe(dev, 0),
			request,
			USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
			value, index, buf, bufsize, 10000);
	return r;
}

If anyone can give me pointers where to look that would be much appreciated.

Regards,

Frank Kingswood


-------------------------------------------------------------------------
This SF.net email is sponsored by: Splunk Inc.
Still grepping through log files to find problems?  Stop.
Now Search log events and configuration files using AJAX and a browser.
Download your FREE copy of Splunk now >>  http://get.splunk.com/
_______________________________________________
[email protected]
To unsubscribe, use the last form field at:
https://lists.sourceforge.net/lists/listinfo/linux-usb-devel