Re: EOVERFLOW problem with usb_control_msg

On Mon, 20 Aug 2007, Frank A. Kingswood wrote:

> Alan Stern wrote:
>  >> 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.
> 
> USBmon captured this:
> 
> ffff810035075300 1054697874 S Co:3:004:0 s c0 5f 0000 0000 04d2 1234 
> =\ 	00000000 00000000 8000006c 449ba52f 00000000 00000002 000186a3 00000003
> ffff810035075300 1054701674 C Co:3:004:0 -75 1234 >
> ffff810035075780 1067015017 S Co:3:004:0 s 01 0b 0000 0000 0000 0
> ffff810035075780 1067016275 C Co:3:004:0 0 0
> 
> The first two lines correspond to this call in my driver code:
> 	r=ch341_control_in(dev, 0x5f, 0, 0, buffer, size);

It looks like your driver thinks it is performing a control-IN 
transfer, but the usbmon log shows that it is really doing a 
control-OUT.  Could that be your problem?  It stems from the fact that 
ch341_control_in uses usb_sndctrlpipe() instead of usb_rcvctrlpipe().

Alan Stern


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