Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753844Ab3HEOkq (ORCPT ); Mon, 5 Aug 2013 10:40:46 -0400 Received: from mail-la0-f48.google.com ([209.85.215.48]:59937 "EHLO mail-la0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753286Ab3HEOko (ORCPT ); Mon, 5 Aug 2013 10:40:44 -0400 MIME-Version: 1.0 In-Reply-To: References: <1374153691-25100-1-git-send-email-nlopezcasad@logitech.com> <1374153691-25100-2-git-send-email-nlopezcasad@logitech.com> Date: Mon, 5 Aug 2013 16:40:42 +0200 Message-ID: Subject: Re: [PATCH 2/2] HID: hid-logitech-dj, querying_devices was never set From: Benjamin Tissoires To: Jiri Kosina Cc: Nestor Lopez Casado , Andrew de los Reyes , joseph.salisbury@canonical.com, linux-input , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2632 Lines: 62 On Mon, Aug 5, 2013 at 3:22 PM, Jiri Kosina wrote: > On Fri, 2 Aug 2013, Benjamin Tissoires wrote: > >> > Could you please elaborate? (and put an elaborate description to revert >> > commit log perhaps?) >> >> Sure, so here is the revert commit log: >> >> -- >> >> Commit "HID: hid-logitech-dj, querying_devices was never set" activate >> a flag which guarantees that we do not ask the receiver for too many >> enumeration. When the flag is set, each following enumeration call is >> discarded (the usb request is not forwarded to the receiver). The flag >> is then released when the driver receive a pairing information event, >> which normally follows the enumeration request. >> However, the USB3 bug makes the driver think the enumeration request >> has been forwarded to the receiver. However, it is actually not the >> case because the USB stack returns -EPIPE. So, when a new unknown >> device appears, the workaround consisting in asking for a new >> enumeration is not working anymore: this new enumeration is discarded >> because of the flag, which is never reset. >> >> A solution could be to trigger a timeout before releasing it, but for >> now, let's just revert the patch. >> >> -- > > Thanks Benjamin. > > I'd like to have a bit more clarification about the USB3 bug, as this > whole issue is not completely clear to me. > > To be more specific -- when exactly do we receive -EPIPE, why do we > receive it and why do we not handle it properly? Sure, I'll try (though the more I think of it, the more it seems blurry to me :( ). So the initial probe function in hid-logitech-dj was implemented by using a direct call to hid_output_raw_report(). This call was synchronous, so we did get the -EPIPE return code. Then, the probe() function returns the -EPIPE error, cleaning the receiver and unregister it from the hid bus. However, now, we use hid_hw_request(), which is asynchronous (from what I can read). At least, this code returns "void" as the set_report command seems to be scheduled for later handling. In usbhid, when the queue is flushed, I did not found a way to retrieve the error code... So basically, the -EPIPE is received in usbhid_restart_ctrl_queue(), but nothing notifies hid-logitech-dj from the error. In the end, the probe() function returns without error code, but the receiver never received the notification. Cheers, Benjamin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/