Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753449Ab1C0Ncy (ORCPT ); Sun, 27 Mar 2011 09:32:54 -0400 Received: from earthlight.etchedpixels.co.uk ([81.2.110.250]:53894 "EHLO www.etchedpixels.co.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751577Ab1C0Ncw (ORCPT ); Sun, 27 Mar 2011 09:32:52 -0400 Date: Sun, 27 Mar 2011 14:30:24 +0100 From: Alan Cox To: Mikhail Kshevetskiy Cc: linux-serial@vger.kernel.org, Greg Kroah-Hartman , stable@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] tty/n_gsm: fix bug in CRC calculation for gsm1 mode Message-ID: <20110327143024.66c1fb0f@lxorguk.ukuu.org.uk> In-Reply-To: <1301184300-9158-1-git-send-email-mikhail.kshevetskiy@gmail.com> References: <1301184300-9158-1-git-send-email-mikhail.kshevetskiy@gmail.com> X-Mailer: Claws Mail 3.7.8 (GTK+ 2.22.0; x86_64-redhat-linux-gnu) Face: iVBORw0KGgoAAAANSUhEUgAAADAAAAAwBAMAAAClLOS0AAAAFVBMVEWysKsSBQMIAwIZCwj///8wIhxoRDXH9QHCAAABeUlEQVQ4jaXTvW7DIBAAYCQTzz2hdq+rdg494ZmBeE5KYHZjm/d/hJ6NfzBJpp5kRb5PHJwvMPMk2L9As5Y9AmYRBL+HAyJKeOU5aHRhsAAvORQ+UEgAvgddj/lwAXndw2laEDqA4x6KEBhjYRCg9tBFCOuJFxg2OKegbWjbsRTk8PPhKPD7HcRxB7cqhgBRp9Dcqs+B8v4CQvFdqeot3Kov6hBUn0AJitrzY+sgUuiA8i0r7+B3AfqKcN6t8M6HtqQ+AOoELCikgQSbgabKaJW3kn5lBs47JSGDhhLKDUh1UMipwwinMYPTBuIBjEclSaGZUk9hDlTb5sUTYN2SFFQuPe4Gox1X0FZOufjgBiV1Vls7b+GvK3SU4wfmcGo9rPPQzgIabfj4TYQo15k3bTHX9RIw/kniir5YbtJF4jkFG+dsDK1IgE413zAthU/vR2HVMmFUPIHTvF6jWCpFaGw/A3qWgnbxpSm9MSmY5b3pM1gvNc/gQfwBsGwF0VCtxZgAAAAASUVORK5CYII= Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1826 Lines: 52 > gsm->received_fcs is not used for GSM1 mode. Thus we put an > additional byte to CRC calculation. As result we get a wrong CRC > and reject incoming frame. That much is true except that it was originally tested with gsm encoding 1 on various modems for a while and not seen the problem. So I am trying to work out why or whether some of the GSM0 patches broke GSM1 somewhere. What hardware was it tested on ? It looks right - probably the code wants pushing into gsm0_receive/gsm1_receive appropriately so no special cases leak into gsm_queue. > > Signed-off-by: Mikhail Kshevetskiy > --- > drivers/tty/n_gsm.c | 8 ++++++-- > 1 files changed, 6 insertions(+), 2 deletions(-) > > diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c > index 176f632..4806276 100644 > --- a/drivers/tty/n_gsm.c > +++ b/drivers/tty/n_gsm.c > @@ -1658,8 +1658,12 @@ static void gsm_queue(struct gsm_mux *gsm) > > if ((gsm->control & ~PF) == UI) > gsm->fcs = gsm_fcs_add_block(gsm->fcs, gsm->buf, gsm->len); > - /* generate final CRC with received FCS */ > - gsm->fcs = gsm_fcs_add(gsm->fcs, gsm->received_fcs); > + if (gsm->encoding == 0){ > + /* WARNING: gsm->received_fcs is used for gsm->encoding = 0 only. > + In this case it contain the last piece of data > + required to generate final CRC */ > + gsm->fcs = gsm_fcs_add(gsm->fcs, gsm->received_fcs); > + } > if (gsm->fcs != GOOD_FCS) { > gsm->bad_fcs++; > if (debug & 4) -- -- "Alan, I'm getting a bit worried about you." -- Linus Torvalds -- 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/