Do what other drivers like ftdi_sio do, and ensure that termios are
written to the device when the port is first opened.
Signed-off-by: Jim Paris <j...@jtan.com>
---
Tested on v3.16.5.
I've seen a problem on two CDC-ACM systems based on a Segger J-Link
where the port does not get initialized at the correct baudrate when
opening (using e.g. python-serial). I think this occurs when the tty
device was previously opened at the same baudrate, then the device was
unplugged and replugged. While the port is open, manually switching
to a different baudrate and back fixes it.
Debug output in the failing case is e.g.:
Oct 28 18:37:45 pilot kernel: [1214446.586460] tty ttyACM0: acm_tty_install
Oct 28 18:37:45 pilot kernel: [1214446.586474] tty ttyACM0: acm_tty_open
Oct 28 18:37:45 pilot kernel: [1214446.586477] cdc_acm 1-2.7:1.0:
acm_port_activate
Oct 28 18:37:45 pilot kernel: [1214446.586670] cdc_acm 1-2.7:1.0:
acm_ctrl_msg - rq 0x22, val 0x3, len 0x0, result 0
which is missing the important:
Oct 28 19:03:18 pilot kernel: [1215981.178020] cdc_acm 1-2.7:1.0:
acm_tty_set_termios - set line: 38400 0 0 8
Oct 28 19:03:18 pilot kernel: [1215981.178135] cdc_acm 1-2.7:1.0:
acm_ctrl_msg - rq 0x20, val 0x0, len 0x7, result 7
that I get when changing settings to something different than they
previously were.
I don't really follow all of the termios and tty stuff, so I don't
know if this is the right fix or the real cause. I suspect it
have to do with cached values associated with the particular TTY
("lazy saved data" in tty-io.c); this patch just does what I see in
ftdi_sio and ensures that the termios settings are written to the
device when the port is opened.
---
drivers/usb/class/cdc-acm.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)
diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index e934e19f49f5..144bf43c9190 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -495,15 +495,6 @@ error_init_termios:
return retval;
}
-static int acm_tty_open(struct tty_struct *tty, struct file *filp)
-{
- struct acm *acm = tty->driver_data;
-
- dev_dbg(tty->dev, "%s\n", __func__);
-
- return tty_port_open(&acm->port, tty, filp);
-}
-
static void acm_port_dtr_rts(struct tty_port *port, int raise)
{
struct acm *acm = container_of(port, struct acm, port);
@@ -1000,6 +991,18 @@ static void acm_tty_set_termios(struct tty_struct *tty,
}
}
+static int acm_tty_open(struct tty_struct *tty, struct file *filp)
+{
+ struct acm *acm = tty->driver_data;
+
+ dev_dbg(tty->dev, "%s\n", __func__);
+
+ if (tty)
+ acm_tty_set_termios(tty, NULL);
+
+ return tty_port_open(&acm->port, tty, filp);
+}
+
static const struct tty_port_operations acm_port_ops = {
.dtr_rts = acm_port_dtr_rts,
.shutdown = acm_port_shutdown,
--
2.1.0
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