[Bug 208959] New: USB-serial (mct_u232): bit7=1 when tty is set to cs7?

[Bug 208959] New: USB-serial (mct_u232): bit7=1 when tty is set to cs7?

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=208959

            Bug ID: 208959
           Summary: USB-serial (mct_u232): bit7=1 when tty is set to cs7?
           Product: Drivers
           Version: 2.5
    Kernel Version: 5.7.0
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: low
          Priority: P1
         Component: USB
          Assignee: drivers_usb@kernel-bugs.kernel.org
          Reporter: mslade@epic-code.com.au
        Regression: No

I'm not 100% certain this is a bug, please let me know if this is expected
behavior.

I have hooked an old serial mouse up to a USB serial device, USB ID 0711:0230
(part of an circa 2000 Targus port replicator)

when I configure it with the appropriate 1200 baud and 7 bit char width, the
bytes that come through /dev/ttyUSB0 all have bit7 set to 1.

This behavior is in contrast to an old serial port on a box running a 2.4.19
kernel.

Is there a standard for the value that non-data bits should be set to?

-- 
You are receiving this mail because:
You are watching the assignee of the bug.

Re: [Bug 208959] New: USB-serial (mct_u232): bit7=1 when tty is set to cs7?

[Johan Hovold]

On Wed, Aug 19, 2020 at 02:52:47AM +0000, bugzilla-daemon@bugzilla.kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=208959
> 
>             Bug ID: 208959
>            Summary: USB-serial (mct_u232): bit7=1 when tty is set to cs7?
>            Product: Drivers
>            Version: 2.5
>     Kernel Version: 5.7.0
>           Hardware: All
>                 OS: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: low
>           Priority: P1
>          Component: USB
>           Assignee: drivers_usb@kernel-bugs.kernel.org
>           Reporter: mslade@epic-code.com.au
>         Regression: No
> 
> I'm not 100% certain this is a bug, please let me know if this is expected
> behavior.
> 
> I have hooked an old serial mouse up to a USB serial device, USB ID 0711:0230
> (part of an circa 2000 Targus port replicator)
> 
> when I configure it with the appropriate 1200 baud and 7 bit char width, the
> bytes that come through /dev/ttyUSB0 all have bit7 set to 1.
> 
> This behavior is in contrast to an old serial port on a box running a 2.4.19
> kernel.
> 
> Is there a standard for the value that non-data bits should be set to?

This sounds like a configuration issue. If the mouse is indeed using
7n1 and the converter is expecting 8n1 you could end up with bit 7
always set on input.

Can you verify that the converter is configured correctly, for example,
by reading out the termios settings, enabling debugging and/or
connecting it to another serial port configured for 7n1?

Johan

[Bug 208959] USB-serial (mct_u232): bit7=1 when tty is set to cs7?

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=208959

--- Comment #1 from Johan Hovold (johan@kernel.org) ---
On Wed, Aug 19, 2020 at 02:52:47AM +0000, bugzilla-daemon@bugzilla.kernel.org
wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=208959
> 
>             Bug ID: 208959
>            Summary: USB-serial (mct_u232): bit7=1 when tty is set to cs7?
>            Product: Drivers
>            Version: 2.5
>     Kernel Version: 5.7.0
>           Hardware: All
>                 OS: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: low
>           Priority: P1
>          Component: USB
>           Assignee: drivers_usb@kernel-bugs.kernel.org
>           Reporter: mslade@epic-code.com.au
>         Regression: No
> 
> I'm not 100% certain this is a bug, please let me know if this is expected
> behavior.
> 
> I have hooked an old serial mouse up to a USB serial device, USB ID 0711:0230
> (part of an circa 2000 Targus port replicator)
> 
> when I configure it with the appropriate 1200 baud and 7 bit char width, the
> bytes that come through /dev/ttyUSB0 all have bit7 set to 1.
> 
> This behavior is in contrast to an old serial port on a box running a 2.4.19
> kernel.
> 
> Is there a standard for the value that non-data bits should be set to?

This sounds like a configuration issue. If the mouse is indeed using
7n1 and the converter is expecting 8n1 you could end up with bit 7
always set on input.

Can you verify that the converter is configured correctly, for example,
by reading out the termios settings, enabling debugging and/or
connecting it to another serial port configured for 7n1?

Johan

-- 
You are receiving this mail because:
You are watching the assignee of the bug.

[Bug 208959] USB-serial (mct_u232): bit7=1 when tty is set to cs7?

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=208959

--- Comment #2 from mslade@epic-code.com.au (mslade@epic-code.com.au) ---
Please clarify what you mean by "converter" here.

FYI to test I was just doing this:

# stty -F /dev/ttyUSB0 1200 cs7
# dd if=/dev/ttyUSB0 bs=1|hd

-- 
You are receiving this mail because:
You are watching the assignee of the bug.

Re: [Bug 208959] USB-serial (mct_u232): bit7=1 when tty is set to cs7?

[Johan Hovold]

On Tue, Aug 25, 2020 at 03:20:48PM +0000, bugzilla-daemon@bugzilla.kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=208959
> 
> --- Comment #2 from mslade@epic-code.com.au (mslade@epic-code.com.au) ---
> Please clarify what you mean by "converter" here.

I was referring to the USB-serial device.

> FYI to test I was just doing this:
> 
> # stty -F /dev/ttyUSB0 1200 cs7

What is the output of "stty -a -F /dev/ttyUSB0" after this?

> # dd if=/dev/ttyUSB0 bs=1|hd

Try using a terminal program instead and connect the device to another
USB-serial device (e.g. ftdi or pl2303) and see if you can get 7-bit
words to work.

You can also try enabling debugging and provide the relevant bits from
dmesg when you connect, configure and read from the device:

	echo module mct_u232 +p > /sys/kernel/debug/dynamic_debug/control

Johan

[Bug 208959] USB-serial (mct_u232): bit7=1 when tty is set to cs7?

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=208959

--- Comment #3 from Johan Hovold (johan@kernel.org) ---
On Tue, Aug 25, 2020 at 03:20:48PM +0000, bugzilla-daemon@bugzilla.kernel.org
wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=208959
> 
> --- Comment #2 from mslade@epic-code.com.au (mslade@epic-code.com.au) ---
> Please clarify what you mean by "converter" here.

I was referring to the USB-serial device.

> FYI to test I was just doing this:
> 
> # stty -F /dev/ttyUSB0 1200 cs7

What is the output of "stty -a -F /dev/ttyUSB0" after this?

> # dd if=/dev/ttyUSB0 bs=1|hd

Try using a terminal program instead and connect the device to another
USB-serial device (e.g. ftdi or pl2303) and see if you can get 7-bit
words to work.

You can also try enabling debugging and provide the relevant bits from
dmesg when you connect, configure and read from the device:

        echo module mct_u232 +p > /sys/kernel/debug/dynamic_debug/control

Johan

-- 
You are receiving this mail because:
You are watching the assignee of the bug.