Greetings linux-usb,
I've been having problems for about a month with a driver I wrote for
a USB device, first in Windows using UMDF, and now as a Linux kernel
module. In short, at certain points in the driver, usb_bulk_msg(),
usb_submit_urb(), etc. return -75, (-EOVERFLOW) which has been
associated with unexpected extra data. ('babble')
In order to address these problems I need a good way to 'clear' all
data sent by the device through the input bulk endpoint. Currently I
have a function that basically calls usb_bulk_msg(), reading in
wMaxPacketSize bytes at a time until the length of the read reported
does not match this maximum packet size. (typically 512) This fixes
some problems, but usage of the input endpoint immediately following
this 'flush' function (for data that's requested after the flush takes
place) fails with -75.
In UMDF, there's a method called IWDFUsbTargetPipe::Flush() that wipes
data from the fifo buffer associated with the USB endpoint:
http://msdn.microsoft.com/en-us/library/dd184035.aspx
I'm not sure if usbcore performs buffering, or if the USB host
controller does this, or what is going on, but does the Linux USB
subsystem include similar functionality, allowing a bulk input to be
'wiped' of data, or 'reset'?
- Lucas
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