Re: [PATCH 2/2] usb: gadget serial: Honour termios CLOCAL on disconnect
On 10/27/2014 09:38 AM, Felipe Balbi wrote:
> Hi,
>
> On Sun, Oct 26, 2014 at 08:01:30PM +0200, Kyösti Mälkki wrote:
>> There are applications where it is desirable to not hangup ttyGS* when
>> USB disconnect is detected. USB host side of communication may
>> power-cycle periodically or there may be the actual need to physically
>> disconnect and reconnect USB cable temporarily.
>>
>> USB disconnects on serial gadget are comparable to loss of Carrier Detect
>> of conventional UARTs. With the change, if ttyGS* has termios CLOCAL flag
>> set, disconnect on USB does not hangup the TTY.
>>
>> Signed-off-by: Kyösti Mälkki
>> ---
>> drivers/usb/gadget/function/u_serial.c | 9 +++--
>> 1 file changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/usb/gadget/function/u_serial.c
>> b/drivers/usb/gadget/function/u_serial.c
>> index 491082a..e68ffd7 100644
>> --- a/drivers/usb/gadget/function/u_serial.c
>> +++ b/drivers/usb/gadget/function/u_serial.c
>> @@ -1254,8 +1254,13 @@ void gserial_disconnect(struct gserial *gser)
>> gser->ioport = NULL;
>> if (port->port.count > 0 || port->openclose) {
>> wake_up_interruptible(&port->drain_wait);
>> -if (port->port.tty)
>> -tty_hangup(port->port.tty);
>> +struct tty_struct *tty = port->port.tty;
>
> declare above as Sergei said.
>
>> +if (tty) {
>
> is there any situation where tty would be NULL here ?
>
>> +if (tty->termios.c_cflag & CLOCAL)
>> +stop_tty(tty);
>> +else
>> +tty_hangup(tty);
>
> this I'll defer to Greg who also maintains tty.
I'm curious what happens without stop_tty().
The tty is restartable from userspace with
tcflow(fd, TCOOFF);
tcflow(fd, TCOON);
Regards,
Peter Hurley
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Re: [PATCH 2/2] usb: gadget serial: Honour termios CLOCAL on disconnect
On Mon, Oct 27, 2014 at 05:43:06PM +0200, Kyösti Mälkki wrote:
> On 10/27/2014 03:38 PM, Felipe Balbi wrote:
> >Hi,
> >
> >On Sun, Oct 26, 2014 at 08:01:30PM +0200, Kyösti Mälkki wrote:
> >>There are applications where it is desirable to not hangup ttyGS* when
> >>USB disconnect is detected. USB host side of communication may
> >>power-cycle periodically or there may be the actual need to physically
> >>disconnect and reconnect USB cable temporarily.
> >>
> >>USB disconnects on serial gadget are comparable to loss of Carrier Detect
> >>of conventional UARTs. With the change, if ttyGS* has termios CLOCAL flag
> >>set, disconnect on USB does not hangup the TTY.
> >>
> >>Signed-off-by: Kyösti Mälkki
> >>---
> >> drivers/usb/gadget/function/u_serial.c | 9 +++--
> >> 1 file changed, 7 insertions(+), 2 deletions(-)
> >>
> >>diff --git a/drivers/usb/gadget/function/u_serial.c
> >>b/drivers/usb/gadget/function/u_serial.c
> >>index 491082a..e68ffd7 100644
> >>--- a/drivers/usb/gadget/function/u_serial.c
> >>+++ b/drivers/usb/gadget/function/u_serial.c
> >>@@ -1254,8 +1254,13 @@ void gserial_disconnect(struct gserial *gser)
> >>gser->ioport = NULL;
> >>if (port->port.count > 0 || port->openclose) {
> >>wake_up_interruptible(&port->drain_wait);
> >>- if (port->port.tty)
> >>- tty_hangup(port->port.tty);
> >>+ struct tty_struct *tty = port->port.tty;
> >
> >declare above as Sergei said.
> >
> >>+ if (tty) {
> >
> >is there any situation where tty would be NULL here ?
> >
> >>+ if (tty->termios.c_cflag & CLOCAL)
> >>+ stop_tty(tty);
> >>+ else
> >>+ tty_hangup(tty);
> >
> >this I'll defer to Greg who also maintains tty.
> >
>
> My main concern is if someone runs getty on ttyACM without explicitly
> clearing CLOCAL. With the patch here login session would no longer get
> SIGHUP if cable is disconnected. And it is not possible to tell if it is the
> same cable that is plugged back in.
true, but woudln't the same thing happen with a real UART port using
8250.ko ?
--
balbi
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Re: [PATCH 2/2] usb: gadget serial: Honour termios CLOCAL on disconnect
On 10/27/2014 03:38 PM, Felipe Balbi wrote:
Hi,
On Sun, Oct 26, 2014 at 08:01:30PM +0200, Kyösti Mälkki wrote:
There are applications where it is desirable to not hangup ttyGS* when
USB disconnect is detected. USB host side of communication may
power-cycle periodically or there may be the actual need to physically
disconnect and reconnect USB cable temporarily.
USB disconnects on serial gadget are comparable to loss of Carrier Detect
of conventional UARTs. With the change, if ttyGS* has termios CLOCAL flag
set, disconnect on USB does not hangup the TTY.
Signed-off-by: Kyösti Mälkki
---
drivers/usb/gadget/function/u_serial.c | 9 +++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/usb/gadget/function/u_serial.c
b/drivers/usb/gadget/function/u_serial.c
index 491082a..e68ffd7 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -1254,8 +1254,13 @@ void gserial_disconnect(struct gserial *gser)
gser->ioport = NULL;
if (port->port.count > 0 || port->openclose) {
wake_up_interruptible(&port->drain_wait);
- if (port->port.tty)
- tty_hangup(port->port.tty);
+ struct tty_struct *tty = port->port.tty;
declare above as Sergei said.
+ if (tty) {
is there any situation where tty would be NULL here ?
+ if (tty->termios.c_cflag & CLOCAL)
+ stop_tty(tty);
+ else
+ tty_hangup(tty);
this I'll defer to Greg who also maintains tty.
My main concern is if someone runs getty on ttyACM without explicitly
clearing CLOCAL. With the patch here login session would no longer get
SIGHUP if cable is disconnected. And it is not possible to tell if it is
the same cable that is plugged back in.
KM
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Re: [PATCH 2/2] usb: gadget serial: Honour termios CLOCAL on disconnect
Hi,
On Sun, Oct 26, 2014 at 08:01:30PM +0200, Kyösti Mälkki wrote:
> There are applications where it is desirable to not hangup ttyGS* when
> USB disconnect is detected. USB host side of communication may
> power-cycle periodically or there may be the actual need to physically
> disconnect and reconnect USB cable temporarily.
>
> USB disconnects on serial gadget are comparable to loss of Carrier Detect
> of conventional UARTs. With the change, if ttyGS* has termios CLOCAL flag
> set, disconnect on USB does not hangup the TTY.
>
> Signed-off-by: Kyösti Mälkki
> ---
> drivers/usb/gadget/function/u_serial.c | 9 +++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/gadget/function/u_serial.c
> b/drivers/usb/gadget/function/u_serial.c
> index 491082a..e68ffd7 100644
> --- a/drivers/usb/gadget/function/u_serial.c
> +++ b/drivers/usb/gadget/function/u_serial.c
> @@ -1254,8 +1254,13 @@ void gserial_disconnect(struct gserial *gser)
> gser->ioport = NULL;
> if (port->port.count > 0 || port->openclose) {
> wake_up_interruptible(&port->drain_wait);
> - if (port->port.tty)
> - tty_hangup(port->port.tty);
> + struct tty_struct *tty = port->port.tty;
declare above as Sergei said.
> + if (tty) {
is there any situation where tty would be NULL here ?
> + if (tty->termios.c_cflag & CLOCAL)
> + stop_tty(tty);
> + else
> + tty_hangup(tty);
this I'll defer to Greg who also maintains tty.
--
balbi
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Re: [PATCH 2/2] usb: gadget serial: Honour termios CLOCAL on disconnect
On 10/27/2014 02:31 PM, Sergei Shtylyov wrote:
Hello.
On 10/26/2014 9:01 PM, Kyösti Mälkki wrote:
There are applications where it is desirable to not hangup ttyGS* when
USB disconnect is detected. USB host side of communication may
power-cycle periodically or there may be the actual need to physically
disconnect and reconnect USB cable temporarily.
USB disconnects on serial gadget are comparable to loss of Carrier Detect
of conventional UARTs. With the change, if ttyGS* has termios CLOCAL flag
set, disconnect on USB does not hangup the TTY.
Signed-off-by: Kyösti Mälkki
---
drivers/usb/gadget/function/u_serial.c | 9 +++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/usb/gadget/function/u_serial.c
b/drivers/usb/gadget/function/u_serial.c
index 491082a..e68ffd7 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -1254,8 +1254,13 @@ void gserial_disconnect(struct gserial *gser)
gser->ioport = NULL;
if (port->port.count > 0 || port->openclose) {
wake_up_interruptible(&port->drain_wait);
-if (port->port.tty)
-tty_hangup(port->port.tty);
+struct tty_struct *tty = port->port.tty;
Don't declare variables amidst the code. And please add empty line
after declaration.
Sloppy rebase there from my part :/
I'll update once there is advice on the CLOCAL matter itself.
+if (tty) {
+if (tty->termios.c_cflag & CLOCAL)
+stop_tty(tty);
+else
+tty_hangup(tty);
+}
}
WBR, Sergei
Thanks,
KM
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Re: [PATCH 2/2] usb: gadget serial: Honour termios CLOCAL on disconnect
Hello.
On 10/26/2014 9:01 PM, Kyösti Mälkki wrote:
There are applications where it is desirable to not hangup ttyGS* when
USB disconnect is detected. USB host side of communication may
power-cycle periodically or there may be the actual need to physically
disconnect and reconnect USB cable temporarily.
USB disconnects on serial gadget are comparable to loss of Carrier Detect
of conventional UARTs. With the change, if ttyGS* has termios CLOCAL flag
set, disconnect on USB does not hangup the TTY.
Signed-off-by: Kyösti Mälkki
---
drivers/usb/gadget/function/u_serial.c | 9 +++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/usb/gadget/function/u_serial.c
b/drivers/usb/gadget/function/u_serial.c
index 491082a..e68ffd7 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -1254,8 +1254,13 @@ void gserial_disconnect(struct gserial *gser)
gser->ioport = NULL;
if (port->port.count > 0 || port->openclose) {
wake_up_interruptible(&port->drain_wait);
- if (port->port.tty)
- tty_hangup(port->port.tty);
+ struct tty_struct *tty = port->port.tty;
Don't declare variables amidst the code. And please add empty line after
declaration.
+ if (tty) {
+ if (tty->termios.c_cflag & CLOCAL)
+ stop_tty(tty);
+ else
+ tty_hangup(tty);
+ }
}
WBR, Sergei
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[PATCH 2/2] usb: gadget serial: Honour termios CLOCAL on disconnect
There are applications where it is desirable to not hangup ttyGS* when
USB disconnect is detected. USB host side of communication may
power-cycle periodically or there may be the actual need to physically
disconnect and reconnect USB cable temporarily.
USB disconnects on serial gadget are comparable to loss of Carrier Detect
of conventional UARTs. With the change, if ttyGS* has termios CLOCAL flag
set, disconnect on USB does not hangup the TTY.
Signed-off-by: Kyösti Mälkki
---
drivers/usb/gadget/function/u_serial.c | 9 +++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/usb/gadget/function/u_serial.c
b/drivers/usb/gadget/function/u_serial.c
index 491082a..e68ffd7 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -1254,8 +1254,13 @@ void gserial_disconnect(struct gserial *gser)
gser->ioport = NULL;
if (port->port.count > 0 || port->openclose) {
wake_up_interruptible(&port->drain_wait);
- if (port->port.tty)
- tty_hangup(port->port.tty);
+ struct tty_struct *tty = port->port.tty;
+ if (tty) {
+ if (tty->termios.c_cflag & CLOCAL)
+ stop_tty(tty);
+ else
+ tty_hangup(tty);
+ }
}
spin_unlock_irqrestore(&port->port_lock, flags);
--
1.8.1.1
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