From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from youngberry.canonical.com ([91.189.89.112]:48755 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753508AbbH0WMr (ORCPT ); Thu, 27 Aug 2015 18:12:47 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Tilman Schmidt , "David S. Miller" , Kamal Mostafa Subject: [PATCH 3.19.y-ckt 050/130] isdn/gigaset: reset tty->receive_room when attaching ser_gigaset Date: Thu, 27 Aug 2015 15:10:41 -0700 Message-Id: <1440713521-5906-51-git-send-email-kamal@canonical.com> In-Reply-To: <1440713521-5906-1-git-send-email-kamal@canonical.com> References: <1440713521-5906-1-git-send-email-kamal@canonical.com> Sender: stable-owner@vger.kernel.org List-ID: 3.19.8-ckt6 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Tilman Schmidt commit fd98e9419d8d622a4de91f76b306af6aa627aa9c upstream. Commit 79901317ce80 ("n_tty: Don't flush buffer when closing ldisc"), first merged in kernel release 3.10, caused the following regression in the Gigaset M101 driver: Before that commit, when closing the N_TTY line discipline in preparation to switching to N_GIGASET_M101, receive_room would be reset to a non-zero value by the call to n_tty_flush_buffer() in n_tty's close method. With the removal of that call, receive_room might be left at zero, blocking data reception on the serial line. The present patch fixes that regression by setting receive_room to an appropriate value in the ldisc open method. Fixes: 79901317ce80 ("n_tty: Don't flush buffer when closing ldisc") Signed-off-by: Tilman Schmidt Signed-off-by: David S. Miller Signed-off-by: Kamal Mostafa --- drivers/isdn/gigaset/ser-gigaset.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/drivers/isdn/gigaset/ser-gigaset.c b/drivers/isdn/gigaset/ser-gigaset.c index 8c91fd5..3ac9c41 100644 --- a/drivers/isdn/gigaset/ser-gigaset.c +++ b/drivers/isdn/gigaset/ser-gigaset.c @@ -524,9 +524,18 @@ gigaset_tty_open(struct tty_struct *tty) cs->hw.ser->tty = tty; atomic_set(&cs->hw.ser->refcnt, 1); init_completion(&cs->hw.ser->dead_cmp); - tty->disc_data = cs; + /* Set the amount of data we're willing to receive per call + * from the hardware driver to half of the input buffer size + * to leave some reserve. + * Note: We don't do flow control towards the hardware driver. + * If more data is received than will fit into the input buffer, + * it will be dropped and an error will be logged. This should + * never happen as the device is slow and the buffer size ample. + */ + tty->receive_room = RBUFSIZE/2; + /* OK.. Initialization of the datastructures and the HW is done.. Now * startup system and notify the LL that we are ready to run */ -- 1.9.1