Alan Stern wrote:
An easier approach is for libusb to cancel the URBs in reverse order.
Then any partial data will all be lined up nicely at the start of the
buffer, where it belongs. Libusb won't have to do any special
rearranging.
Good point.
Anybody who cancels a transfer before it has completed is then
obligated to resynchronize with the device. There are lots of ways
this could be done; which to use will depend on how the device works.
Regardless, this is the sort of thing which has to be handled at the
application level -- not by libusb or the kernel.
That sounds reasonable for user-requested cancellations, and I can see
the holes in my ideas. It's less desirable for cancellations due to
timeouts (which feels like it should be a less dangerous operation) but
I guess we have no other option.
It looks like that usb_bulk_msg() within the kernel also comes with some
of the same caveats e.g. the timeout might be hit after some packets
have been transferred, meaning that the caller then has to deal with a
bit of inconvenience with resynchronization or stowing that partial data
away for later.
Thanks,
Daniel
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
