Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933347AbZJMOof (ORCPT ); Tue, 13 Oct 2009 10:44:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760057AbZJMOod (ORCPT ); Tue, 13 Oct 2009 10:44:33 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:43804 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760056AbZJMOob (ORCPT ); Tue, 13 Oct 2009 10:44:31 -0400 Subject: Re: [LTP] [PATCH] pac_common: redesign function for finding Start Of Frame From: Subrata Modak Reply-To: subrata@linux.vnet.ibm.com To: =?ISO-8859-1?Q?N=E9meth_M=E1rton?= Cc: Jean-Francois Moine , Thomas Kaiser , Kyle Guinn , Theodore Kilgore , ltp-list@lists.sourceforge.net, LKML , V4L Mailing List In-Reply-To: <4AC90C17.70103@freemail.hu> References: <4AC90BBF.9040803@freemail.hu> <4AC90C17.70103@freemail.hu> Content-Type: text/plain; charset=utf-8 Organization: IBM Date: Tue, 13 Oct 2009 20:13:34 +0530 Message-Id: <1255445014.8438.65.camel@subratamodak.linux.ibm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.12.3 (2.12.3-8.el5_2.2) Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6056 Lines: 201 On Sun, 2009-10-04 at 22:56 +0200, Németh Márton wrote: > Hi, > > I wrote a simple test for pac_find_sof(). I implemented a user-space test > which takes the implementation from the source file and calls it directly. > You can find the source code of the test attached. Németh, Can you please add this test to LTP then ? Regards-- Subrata > > The test results for the pac_find_sof() implementation in the Linux kernel > 2.6.32-rc1 is the following: > > Test case 1: exact match > PDEBUG: SOF found, bytes to analyze: 5. Frame starts at byte #5 > PASSED > > Test case 2: offset 1 > PDEBUG: SOF found, bytes to analyze: 6. Frame starts at byte #6 > PASSED > > Test case 3: offset 1, first byte may be misleading > FAILED > > Test case 4: offset 2, first two bytes may be misleading > PDEBUG: SOF found, bytes to analyze: 7. Frame starts at byte #7 > PASSED > > Test case 5: offset 3, first three bytes may be misleading > FAILED > > Test case 6: offset 4, first four bytes may be misleading > FAILED > > Test case 7: pattern starts at end of packet and continues in the next one > PDEBUG: SOF found, bytes to analyze: 1. Frame starts at byte #1 > PASSED > > Test case 8: splited pattern, with misleading first byte > FAILED > > Test case 9: splited pattern, with misleading first three bytes > FAILED > > Test case 10: no match, extra byte at offset 1 > PASSED > > Test case 11: no match, extra byte at offset 2 > PASSED > > Test case 12: no match, extra byte at offset 3 > PASSED > > Test case 13: no match, extra byte at offset 4 > PASSED > > I also executed the test with the patched pac_find_sof() implementation > and that one passes all these test cases. > > Regards, > > Márton Németh > > 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; > > } > > } > > > > ------------------------------------------------------------------------------ > Come build with us! 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