From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934673AbbJIJXu (ORCPT ); Fri, 9 Oct 2015 05:23:50 -0400 Received: from smtprelay06.ispgateway.de ([80.67.31.103]:39144 "EHLO smtprelay06.ispgateway.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933868AbbJIJXs (ORCPT ); Fri, 9 Oct 2015 05:23:48 -0400 Subject: Re: [PATCH v3 1/4] usb: gadget: f_midi: free usb request when done To: Felipe Tonello , USB list References: <1443528119-31830-1-git-send-email-eu@felipetonello.com> Cc: Kernel development list , Peter Chen , Greg Kroah-Hartman , Felipe Balbi , Andrzej Pietrasiewicz From: Clemens Ladisch Message-ID: <56178799.9000409@ladisch.de> Date: Fri, 9 Oct 2015 11:23:37 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Df-Sender: bGludXgtdXNiQGNsLmRvbWFpbmZhY3Rvcnkta3VuZGUuZGU= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Felipe Tonello wrote: > req->actual == req->length means that there is no data left to enqueue, This condition is not checked in the patch. > so free the request. > > Signed-off-by: Felipe F. Tonello > --- > drivers/usb/gadget/function/f_midi.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > diff --git a/drivers/usb/gadget/function/f_midi.c b/drivers/usb/gadget/function/f_midi.c > index edb84ca..93212ca 100644 > --- a/drivers/usb/gadget/function/f_midi.c > +++ b/drivers/usb/gadget/function/f_midi.c > @@ -256,9 +256,8 @@ f_midi_complete(struct usb_ep *ep, struct usb_request *req) > /* We received stuff. req is queued again, below */ > f_midi_handle_out_data(ep, req); > } else if (ep == midi->in_ep) { > - /* Our transmit completed. See if there's more to go. > - * f_midi_transmit eats req, don't queue it again. */ > - f_midi_transmit(midi, req); > + /* Our transmit completed. Don't queue it again. */ > + free_ep_req(ep, req); > return; > } > break; The ALSA framework will give you a notification _once_. If the resulting data is larger than midi->buflen, then you have to continue sending packets. This is exactly what the call to f_midi_transmit() does. (To decrease latency, it might be a good idea to queue multiple requests, but you wouldn't want to continue piling up requests if the host isn't listening. sound/usb/midi.c just allocates a fixed number of requests, and always reuses them.) Regards, Clemens