On Fri, 14 Feb 2014, Stanislaw Gruszka wrote: > On Thu, Feb 13, 2014 at 11:45:16AM -0500, Alan Stern wrote: > > @@ -1074,6 +1089,7 @@ static int proc_clearhalt(struct dev_sta > > ret = checkintf(ps, ret); > > if (ret) > > return ret; > > + check_reset_of_active_ep(ps->dev, ep, "CLEAR_HALT"); > > if (ep & USB_DIR_IN) > > pipe = usb_rcvbulkpipe(ps->dev, ep & 0x7f); > > else > > In documentation is written:
What documentation? Where? Maybe the documentation should be updated. > USBDEVFS_CLEAR_HALT > Clears endpoint halt (stall) and > resets the endpoint toggle. This is only > meaningful for bulk or interrupt endpoints. > The ioctl parameter is an integer endpoint number > (1 to 15, as identified in an endpoint descriptor), > masked with USB_DIR_IN when referring to an endpoint which > sends data to the host from the device. > > Use this on bulk or interrupt endpoints which have > stalled, returning <emphasis>-EPIPE</emphasis> status > to a data transfer request. > Do not issue the control request directly, since > that could invalidate the host's record of the > data toggle. > > Is possible that user space driver can issue dozen of URBs , then get > -EPIPE for last of them, and then call CLEAR_HALT ? Certainly that is possible. It wouldn't trigger the warning, because after the last URB terminates with -EPIPE there won't be any more URBs in the queue. > According > documentation, this behaviour should be correct. And indeed, it is correct. What would be incorrect is if userspace issues dozens of URBs, gets -EPIPE for the third URB, and then does CLEAR_HALT without first cancelling all the remaining URBs. > Or peraps can not issue > more than one URB for USB_DIR_IN endpoint and should not do CLEAR_HALT > for USB_DIR_OUT endpoints ? Userspace definitely _should_ issue more than one URB for IN endpoints. Using only one URB at a time is very inefficient for streaming. Also, userspace _has_ to issue CLEAR_HALT for OUT endpoints. Otherwise the endpoint will become unusable when it halts. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
