anszom / vtty Goto Github PK

You need to unregister tty driver (tty_unregister_driver) before module exit to prevent kernel panic.

Hello,

I was trying out your driver to use it with a gps using gpsd, and another serial device, so I can choose which data gets sent to a real serial device port. The baudrate of the serial device, in my case called /dev/ttyTHS1 is 9600 baud. So now I mirror the port into ttyV0 and ttyV1. If I let gpsd connect to the "fake" serial port ttyV0, it autodetects that V0 is 38400 baud. The original ttyTHS1 port is 9600 when I start the mirror program. How can I force ttyV0 to return 9600 baud?

Best regards

Seems missing:

#include <linux/sched/signal.h>

Running make successfully builds the module /vtty.ko, but installing via make modules_install fails:

$ sudo make modules_install 
make -C /lib/modules/6.2.0-32-generic/build M= modules
make[1]: Verzeichnis „/usr/src/linux-headers-6.2.0-32-generic“ wird betreten
make[2]: *** Keine Regel vorhanden, um das Ziel „arch/x86/entry/syscalls/syscall_32.tbl“, 
  benötigt von „arch/x86/include/generated/uapi/asm/unistd_32.h“, zu erstellen.  Schluss.
make[1]: *** [arch/x86/Makefile:248: archheaders] Fehler 2
make[1]: Verzeichnis „/usr/src/linux-headers-6.2.0-32-generic“ wird verlassen
make: *** [Makefile:5: modules] Fehler 2

That is more or less saying:

*** No rule exists to create target 'arch/x86/entry/syscalls/syscall_32.tbl' required by 'arch/x86/include/generated/uapi/asm/unistd_32.h'. Ending.

Are there instructions on how to build the module?

I don't recall the exact circumstances, this is just a note to myself to test and fix this one day

First error is

vtty.c:283:24: error: initialization of ‘void (*)(struct tty_struct *, const struct ktermios *)’ from incompatible pointer type ‘void (*)(struct tty_struct *, struct ktermios *)’ [-Werror=incompatible-pointer-types]
  283 |         .set_termios = vtty_set_termios,

Signature of set_termios in struct tty_operations changed since 6.0.0. It can be easily fixed with this PR.

Second error is

vtty.c:449:54: error: implicit declaration of function ‘kernel_termios_to_user_termios’ [-Werror=implicit-function-declaration]
  449 |                                         copystatus = kernel_termios_to_user_termios((struct termios2 __user*)ptr, &port->oob_data.termios);

#include <linux/termios_internal.h> doesn't fix it because the symbol seems no longer exported. Trying to figure out how to solve it.

I created two simple test programs in Python to send and receive data:

Write to master send.py:

#!/usr/bin/env python3
import serial
import time


if __name__ == '__main__':
    # causes: termios.error: (25, 'Inappropriate ioctl for device')
    # serial_port = serial.Serial(
    #    port='/dev/vtmx',
    #    baudrate=100000,
    #    parity=serial.PARITY_EVEN,
    #    stopbits=serial.STOPBITS_TWO,
    #    bytesize=serial.EIGHTBITS)

    serial_port = open('/dev/vtmx', 'w')

    while True:
        try:
            for i in range(10):
                msg = str(i)
                serial_port.write(msg)
                serial_port.flush()
                print(f"sent {msg}")
                time.sleep(0.5)
        except KeyboardInterrupt:
            break

    serial_port.close()

Read from slave recv.py:

#!/usr/bin/env python3
import serial

if __name__ == '__main__':
    serial_port = serial.Serial(
       port='/dev/ttyV0',
       baudrate=100000,
       parity=serial.PARITY_EVEN,
       stopbits=serial.STOPBITS_TWO,
       bytesize=serial.EIGHTBITS)

    print(f"serial port open: {serial_port.is_open}")

    while True:
        byte = serial_port.read()
        print(chr(byte))

    serial_port.close()

However, instantiating the serial port gets stuck somewhere at termios.tcsetattr.

How do I configure the master device such that I can read from the slave like a regular serial device?