From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-ee0-f42.google.com ([74.125.83.42]:40031 "EHLO mail-ee0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751113Ab2LWOBJ (ORCPT ); Sun, 23 Dec 2012 09:01:09 -0500 Received: by mail-ee0-f42.google.com with SMTP id c41so3130510eek.15 for ; Sun, 23 Dec 2012 06:01:07 -0800 (PST) Message-ID: <50D70EB6.3040409@googlemail.com> Date: Sun, 23 Dec 2012 15:01:26 +0100 From: =?UTF-8?B?RnJhbmsgU2Now6RmZXI=?= MIME-Version: 1.0 To: Mauro Carvalho Chehab CC: Linux Media Mailing List Subject: Re: [PATCH v2 21/21] em28xx: add module parameter for selection of the preferred USB transfer type References: <1352398313-3698-1-git-send-email-fschaefer.oss@googlemail.com> <1352398313-3698-22-git-send-email-fschaefer.oss@googlemail.com> <20121223114413.6d2c7dc1@redhat.com> In-Reply-To: <20121223114413.6d2c7dc1@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-media-owner@vger.kernel.org List-ID: Am 23.12.2012 14:44, schrieb Mauro Carvalho Chehab: > Hi Frank, > > Em Thu, 8 Nov 2012 20:11:53 +0200 > Frank Schäfer escreveu: > >> By default, isoc transfers are used if possible. >> With the new module parameter, bulk can be selected as the >> preferred USB transfer type. > I did some tests yesterday with prefer_bulk. IMHO, webcams should > select bulk mode by default, as this allows more than one camera to > work at the same time (I tested yesterday with 3 Silvercrest ones on > my notebook). With ISOC transfers, the core won't let it to happen, as > a single camera reserves 51% of the max allowed isoc traffic. Ok. I just didn't want to change the current behavior because of potential regressions. Why not change it for all devices ? Frame data processing with bulk transfers has a smaller overhead than with isoc (although not really measurable ;) ). I will send a patch after christmas. > >> Signed-off-by: Frank Schäfer >> --- >> drivers/media/usb/em28xx/em28xx-cards.c | 11 +++++++++-- >> 1 Datei geändert, 9 Zeilen hinzugefügt(+), 2 Zeilen entfernt(-) >> >> diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c >> index a9344f0..7f5b303 100644 >> --- a/drivers/media/usb/em28xx/em28xx-cards.c >> +++ b/drivers/media/usb/em28xx/em28xx-cards.c >> @@ -61,6 +61,11 @@ static unsigned int card[] = {[0 ... (EM28XX_MAXBOARDS - 1)] = UNSET }; >> module_param_array(card, int, NULL, 0444); >> MODULE_PARM_DESC(card, "card type"); >> >> +static unsigned int prefer_bulk; >> +module_param(prefer_bulk, int, 0644); > This needs to be changed to 0444, as prefer_bulk doesn't allow changing > it dynamically, as the test is done during device probe, not at stream on. Good catch ! Can you fix it ? I'm a bit in hurry right now. Otherwise I will try to send a patch tomorrow. Merry Christmas ! Frank > > Regards, > Mauro