From fd98e9419d8d622a4de91f76b306af6aa627aa9c Mon Sep 17 00:00:00 2001 From: Tilman Schmidt Date: Tue, 14 Jul 2015 00:37:13 +0200 Subject: [PATCH] isdn/gigaset: reset tty->receive_room when attaching ser_gigaset 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 --- 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 8c91fd5eb6fd..3ac9c4194814 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 */