This is the device driver for serial port 1: /dev/ttyS1.

Is there a device driver for a USB port, or does USB works in a much complicated way that a USB port can't be represented using a single file?

  • USB in general is complicated and uses multiple modules ("drivers"), while there is a single module ("driver") for USB serial port devices that follow the standard.
    – dirkt
    Jun 6, 2017 at 6:20

1 Answer 1


/dev/ttyS1 is a device node for the second serial port.

USB serial ports also get device nodes, they’re usually called /dev/ttyUSB0 and so on. Some USB devices will allocate two nodes (e.g. /dev/ttyUSB0 and /dev/ttyUSB1; old USB Palm devices do this). Some USB serial devices which act more like a modem will have a /dev/ttyACM0 device node instead.

The actual device drivers are in the kernel, often provided as kernel modules. On PCs using 8250-style serial ports, the driver is tty/serial/8250/serial_cs.ko. For USB serial ports, it will be one of the drivers in usb/serial. (Both paths are relative to /lib/modules/$(uname -r)/kernel/drivers.)

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