Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758555AbZJEH2q (ORCPT ); Mon, 5 Oct 2009 03:28:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758492AbZJEH2p (ORCPT ); Mon, 5 Oct 2009 03:28:45 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59053 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758441AbZJEH2o (ORCPT ); Mon, 5 Oct 2009 03:28:44 -0400 Message-ID: <4AC9A108.8040504@redhat.com> Date: Mon, 05 Oct 2009 09:32:24 +0200 From: Hans de Goede User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.4pre) Gecko/20090922 Fedora/3.0-3.9.b4.fc12 Thunderbird/3.0b4 MIME-Version: 1.0 To: =?UTF-8?B?TsOpbWV0aCBNw6FydG9u?= CC: Jean-Francois Moine , Thomas Kaiser , Kyle Guinn , Theodore Kilgore , V4L Mailing List , LKML , ltp-list@lists.sourceforge.net Subject: Re: [PATCH] pac_common: redesign function for finding Start Of Frame References: <4AC90BBF.9040803@freemail.hu> In-Reply-To: <4AC90BBF.9040803@freemail.hu> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3894 Lines: 140 Hi, Good one, Acked-by: Hans de Goede Jean-Francois, can you please add this patch to your tree? Thanks, Hans On 10/04/2009 10:55 PM, Németh Márton wrote: > From: Márton Németh > > The original implementation of pac_find_sof() does not always find > the Start Of Frame (SOF) marker. Replace it with a state machine > based design. > > The change was tested with Labtec Webcam 2200. > > Signed-off-by: Márton Németh > --- > --- linux-2.6.32-rc1.orig/drivers/media/video/gspca/pac_common.h 2009-09-10 00:13:59.000000000 +0200 > +++ linux-2.6.32-rc1/drivers/media/video/gspca/pac_common.h 2009-10-04 21:49:19.000000000 +0200 > @@ -33,6 +33,45 @@ > static const unsigned char pac_sof_marker[5] = > { 0xff, 0xff, 0x00, 0xff, 0x96 }; > > +/* > + The following state machine finds the SOF marker sequence > + 0xff, 0xff, 0x00, 0xff, 0x96 in a byte stream. > + > + +----------+ > + | 0: START |<---------------\ > + +----------+<-\ | > + | \---/otherwise | > + v 0xff | > + +----------+ otherwise | > + | 1 |--------------->* > + | | ^ > + +----------+ | > + | | > + v 0xff | > + +----------+<-\0xff | > + /->| |--/ | > + | | 2 |--------------->* > + | | | otherwise ^ > + | +----------+ | > + | | | > + | v 0x00 | > + | +----------+ | > + | | 3 | | > + | | |--------------->* > + | +----------+ otherwise ^ > + | | | > + 0xff | v 0xff | > + | +----------+ | > + \--| 4 | | > + | |----------------/ > + +----------+ otherwise > + | > + v 0x96 > + +----------+ > + | FOUND | > + +----------+ > +*/ > + > static unsigned char *pac_find_sof(struct gspca_dev *gspca_dev, > unsigned char *m, int len) > { > @@ -41,17 +80,54 @@ static unsigned char *pac_find_sof(struc > > /* Search for the SOF marker (fixed part) in the header */ > for (i = 0; i< len; i++) { > - if (m[i] == pac_sof_marker[sd->sof_read]) { > - sd->sof_read++; > - if (sd->sof_read == sizeof(pac_sof_marker)) { > + switch (sd->sof_read) { > + case 0: > + if (m[i] == 0xff) > + sd->sof_read = 1; > + break; > + case 1: > + if (m[i] == 0xff) > + sd->sof_read = 2; > + else > + sd->sof_read = 0; > + break; > + case 2: > + switch (m[i]) { > + case 0x00: > + sd->sof_read = 3; > + break; > + case 0xff: > + /* stay in this state */ > + break; > + default: > + sd->sof_read = 0; > + } > + break; > + case 3: > + if (m[i] == 0xff) > + sd->sof_read = 4; > + else > + sd->sof_read = 0; > + break; > + case 4: > + switch (m[i]) { > + case 0x96: > + /* Pattern found */ > PDEBUG(D_FRAM, > "SOF found, bytes to analyze: %u." > " Frame starts at byte #%u", > len, i + 1); > sd->sof_read = 0; > return m + i + 1; > + break; > + case 0xff: > + sd->sof_read = 2; > + break; > + default: > + sd->sof_read = 0; > } > - } else { > + break; > + default: > sd->sof_read = 0; > } > } > -- > To unsubscribe from this list: send the line "unsubscribe linux-media" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- 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/