From nobody Fri Sep 5 20:12:17 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AE42CC32793 for ; Tue, 23 Aug 2022 11:37:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1357597AbiHWLfs (ORCPT ); Tue, 23 Aug 2022 07:35:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45108 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1357745AbiHWLbx (ORCPT ); Tue, 23 Aug 2022 07:31:53 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D8CB890838; Tue, 23 Aug 2022 02:26:00 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 5835861328; Tue, 23 Aug 2022 09:25:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 50F4AC433D6; Tue, 23 Aug 2022 09:25:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661246758; bh=8fHAmm5kuO8u3fVNM0lsNvv3FgA2v4FB+neb2g6I6+M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=axtYP/YdYeRtDfPOgHpaDBWrU1bIeEDKQKWG6bNfoGHPkHcixEtGJ7thXcxjXzKUs QHnNmHJpEiZPkIOSBVQTSA/2Q5JPD8Y0AVYC9VpeRgaiBKdr2dS1rBD9RbTTrdF9F6 Nqiwr5AEYrNsQbH8c1TdIftoJz846HtirCIlHCrg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Daniel Starke , Sasha Levin Subject: [PATCH 5.4 211/389] tty: n_gsm: fix non flow control frames during mux flow off Date: Tue, 23 Aug 2022 10:24:49 +0200 Message-Id: <20220823080124.428283195@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220823080115.331990024@linuxfoundation.org> References: <20220823080115.331990024@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Daniel Starke [ Upstream commit bec0224816d19abe4fe503586d16d51890540615 ] n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010. See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDeta= ils.aspx?specificationId=3D1516 The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to the newer 27.010 here. Chapter 5.4.6.3.6 states that FCoff stops the transmission on all channels except the control channel. This is already implemented in gsm_data_kick(). However, chapter 5.4.8.1 explains that this shall result in the same behavior as software flow control on the ldisc in advanced option mode. That means only flow control frames shall be sent during flow off. The current implementation does not consider this case. Change gsm_data_kick() to send only flow control frames if constipated to abide the standard. gsm_read_ea_val() and gsm_is_flow_ctrl_msg() are introduced as helper functions for this. It is planned to use gsm_read_ea_val() in later code cleanups for other functions, too. Fixes: c01af4fec2c8 ("n_gsm : Flow control handling in Mux driver") Signed-off-by: Daniel Starke Link: https://lore.kernel.org/r/20220701061652.39604-5-daniel.starke@siemen= s.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/n_gsm.c | 54 ++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 53 insertions(+), 1 deletion(-) diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index 907a4d0784ac..cab30df61196 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -410,6 +410,27 @@ static int gsm_read_ea(unsigned int *val, u8 c) return c & EA; } =20 +/** + * gsm_read_ea_val - read a value until EA + * @val: variable holding value + * @data: buffer of data + * @dlen: length of data + * + * Processes an EA value. Updates the passed variable and + * returns the processed data length. + */ +static unsigned int gsm_read_ea_val(unsigned int *val, const u8 *data, int= dlen) +{ + unsigned int len =3D 0; + + for (; dlen > 0; dlen--) { + len++; + if (gsm_read_ea(val, *data++)) + break; + } + return len; +} + /** * gsm_encode_modem - encode modem data bits * @dlci: DLCI to encode from @@ -657,6 +678,37 @@ static struct gsm_msg *gsm_data_alloc(struct gsm_mux *= gsm, u8 addr, int len, return m; } =20 +/** + * gsm_is_flow_ctrl_msg - checks if flow control message + * @msg: message to check + * + * Returns true if the given message is a flow control command of the + * control channel. False is returned in any other case. + */ +static bool gsm_is_flow_ctrl_msg(struct gsm_msg *msg) +{ + unsigned int cmd; + + if (msg->addr > 0) + return false; + + switch (msg->ctrl & ~PF) { + case UI: + case UIH: + cmd =3D 0; + if (gsm_read_ea_val(&cmd, msg->data + 2, msg->len - 2) < 1) + break; + switch (cmd & ~PF) { + case CMD_FCOFF: + case CMD_FCON: + return true; + } + break; + } + + return false; +} + /** * gsm_data_kick - poke the queue * @gsm: GSM Mux @@ -675,7 +727,7 @@ static void gsm_data_kick(struct gsm_mux *gsm, struct g= sm_dlci *dlci) int len; =20 list_for_each_entry_safe(msg, nmsg, &gsm->tx_list, list) { - if (gsm->constipated && msg->addr) + if (gsm->constipated && !gsm_is_flow_ctrl_msg(msg)) continue; if (gsm->encoding !=3D 0) { gsm->txframe[0] =3D GSM1_SOF; --=20 2.35.1