* Linux Keyspan USB serial driver ignoring XOFF
[not found] <87woe37prw.fsf@complete.org>
@ 2019-09-20 19:49 ` John Goerzen
2019-09-23 10:20 ` Johan Hovold
0 siblings, 1 reply; 3+ messages in thread
From: John Goerzen @ 2019-09-20 19:49 UTC (permalink / raw)
To: linux-usb
Hello,
I have narrowed down the issue I'm about to describe to keyspan.c; a
Digi Edgeport/1 with identical configuration works fine.
I am configuring a Raspberry Pi running 4.19.66 (though keyspan.c hasn't
changed since 2017) to talk to a real-live vt420. Configuring agetty
with systemd worked easy enough, but I found that XON/XOFF wasn't
working. stty -a shows ixon and ixoff as appropriate, but sending
Ctrl-S (tested from multiple ways of sending) had no effect on output in
bash, or scrolling output. (Emacs, though, recognized it as the start
of a search, so I knew it was getting down the line.)
After a great deal of head-scratching on this, I went to look at the
kernel source and found that keyspan.c does not appear to be honoring
XOFF. I also have a Digi Edgeport/1 on hand (which uses io_ti.c), and
when I swapped to that, everything worked fine - Ctrl-S caused the
expected pause.
As far as I can tell, keyspan.c simply never implemented handling of
XOFF, but you guys are the experts there.
I twiddled many, many settings with stty but could not find anything
that would make it honor xoff/Ctrl-S with the Keyspan. Even as a
regular user that would use that trick to pause scrolling, it had no
effect. Different TERM settings also had no effect.
Output of stty -a:
speed 19200 baud; rows 24; columns 80; line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>;
eol2 = <undef>; swtch = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R;
werase = ^W; lnext = ^V; discard = ^O; min = 1; time = 0;
-parenb -parodd -cmspar cs8 hupcl -cstopb cread clocal -crtscts
-ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon ixoff
-iuclc -ixany -imaxbel -iutf8
opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
isig icanon -iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt
echoctl echoke -flusho -extproc
Thanks,
John
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Linux Keyspan USB serial driver ignoring XOFF
2019-09-20 19:49 ` Linux Keyspan USB serial driver ignoring XOFF John Goerzen
@ 2019-09-23 10:20 ` Johan Hovold
2019-09-23 15:59 ` John Goerzen
0 siblings, 1 reply; 3+ messages in thread
From: Johan Hovold @ 2019-09-23 10:20 UTC (permalink / raw)
To: John Goerzen; +Cc: linux-usb
On Fri, Sep 20, 2019 at 02:49:51PM -0500, John Goerzen wrote:
> Hello,
>
> I have narrowed down the issue I'm about to describe to keyspan.c; a
> Digi Edgeport/1 with identical configuration works fine.
>
> I am configuring a Raspberry Pi running 4.19.66 (though keyspan.c hasn't
> changed since 2017) to talk to a real-live vt420. Configuring agetty
> with systemd worked easy enough, but I found that XON/XOFF wasn't
> working. stty -a shows ixon and ixoff as appropriate, but sending
> Ctrl-S (tested from multiple ways of sending) had no effect on output in
> bash, or scrolling output. (Emacs, though, recognized it as the start
> of a search, so I knew it was getting down the line.)
>
>
> After a great deal of head-scratching on this, I went to look at the
> kernel source and found that keyspan.c does not appear to be honoring
> XOFF. I also have a Digi Edgeport/1 on hand (which uses io_ti.c), and
> when I swapped to that, everything worked fine - Ctrl-S caused the
> expected pause.
>
> As far as I can tell, keyspan.c simply never implemented handling of
> XOFF, but you guys are the experts there.
That's correct, the driver does not support software flow control even
if the hardware seems to have some support for assisted XON/XOFF.
Would you mind testing the below patch which may be enough to turn
sw-flow control always on. If that works, I can probably find time to
cook up a proper patch to make this configurable later this week.
Johan
From 55b46d78fe63f182923e4674659fa18f4624d6b8 Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan@kernel.org>
Date: Mon, 23 Sep 2019 12:14:56 +0200
Subject: [PATCH] USB: serial: keyspan: enable XON flow control
Signed-off-by: Johan Hovold <johan@kernel.org>
---
drivers/usb/serial/keyspan.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/usb/serial/keyspan.c b/drivers/usb/serial/keyspan.c
index d34779fe4a8d..934430cbdfc4 100644
--- a/drivers/usb/serial/keyspan.c
+++ b/drivers/usb/serial/keyspan.c
@@ -2118,7 +2118,7 @@ static int keyspan_usa26_send_setup(struct usb_serial *serial,
msg.setLcr = 0xff;
msg.ctsFlowControl = (p_priv->flow_control == flow_cts);
- msg.xonFlowControl = 0;
+ msg.xonFlowControl = 1;
msg.setFlowControl = 0xff;
msg.forwardingLength = 16;
msg.xonChar = 17;
@@ -2234,7 +2234,7 @@ static int keyspan_usa28_send_setup(struct usb_serial *serial,
msg.parity = 0; /* XXX for now */
msg.ctsFlowControl = (p_priv->flow_control == flow_cts);
- msg.xonFlowControl = 0;
+ msg.xonFlowControl = 1;
/* Do handshaking outputs, DTR is inverted relative to RTS */
msg.rts = p_priv->rts_state;
@@ -2388,7 +2388,7 @@ static int keyspan_usa49_send_setup(struct usb_serial *serial,
msg.setLcr = 0xff;
msg.ctsFlowControl = (p_priv->flow_control == flow_cts);
- msg.xonFlowControl = 0;
+ msg.xonFlowControl = 1;
msg.setFlowControl = 0xff;
msg.forwardingLength = 16;
@@ -2690,7 +2690,7 @@ static int keyspan_usa67_send_setup(struct usb_serial *serial,
msg.setLcr = 0xff;
msg.ctsFlowControl = (p_priv->flow_control == flow_cts);
- msg.xonFlowControl = 0;
+ msg.xonFlowControl = 1;
msg.setFlowControl = 0xff;
msg.forwardingLength = 16;
msg.xonChar = 17;
--
2.23.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: Linux Keyspan USB serial driver ignoring XOFF
2019-09-23 10:20 ` Johan Hovold
@ 2019-09-23 15:59 ` John Goerzen
0 siblings, 0 replies; 3+ messages in thread
From: John Goerzen @ 2019-09-23 15:59 UTC (permalink / raw)
To: Johan Hovold; +Cc: linux-usb
On Mon, Sep 23 2019, Johan Hovold wrote:
> That's correct, the driver does not support software flow control even
> if the hardware seems to have some support for assisted XON/XOFF.
>
> Would you mind testing the below patch which may be enough to turn
> sw-flow control always on. If that works, I can probably find time to
> cook up a proper patch to make this configurable later this week.
Hi Johan,
I gave it a try, but unfortunately that patch made no difference to the
behavior I was seeing. I'm happy to do whatever debugging may be
helpful.
Thanks!
- John
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2019-09-23 15:59 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
[not found] <87woe37prw.fsf@complete.org>
2019-09-20 19:49 ` Linux Keyspan USB serial driver ignoring XOFF John Goerzen
2019-09-23 10:20 ` Johan Hovold
2019-09-23 15:59 ` John Goerzen
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.