UDEV

udev (userspace /dev) is a device manager for the Linux kernel

Find device info

$ udevadm info -a /dev/ttyUSB0

  looking at device '/devices/pci0000:00/0000:00:14.0/usb3/3-3/3-3:1.0/ttyUSB0/tty/ttyUSB0':
    KERNEL=="ttyUSB0"                                                                       
    SUBSYSTEM=="tty"                                                                        
    DRIVER==""                                                                              
    ATTR{power/async}=="disabled"                                                           
    ATTR{power/control}=="auto"                                                             
    ATTR{power/runtime_active_kids}=="0"                                                    
    ATTR{power/runtime_active_time}=="0"                                                    
    ATTR{power/runtime_enabled}=="disabled"                                                 
    ATTR{power/runtime_status}=="unsupported"                                               
    ATTR{power/runtime_suspended_time}=="0"                                                 
    ATTR{power/runtime_usage}=="0"                                                          
                                                                       
  looking at parent device '/devices/pci0000:00/0000:00:14.0/usb3/3-3/3-3:1.0/ttyUSB0':
    KERNELS=="ttyUSB0"                         
    SUBSYSTEMS=="usb-serial"                                           
    DRIVERS=="ch341-uart"                                                                   
    ATTRS{port_number}=="0"                 
    ATTRS{power/async}=="enabled"  
    ATTRS{power/control}=="auto"         
    ATTRS{power/runtime_active_kids}=="0"
    ATTRS{power/runtime_active_time}=="0"      
    ATTRS{power/runtime_enabled}=="disabled" 
    ATTRS{power/runtime_status}=="unsupported"
    ATTRS{power/runtime_suspended_time}=="0"
    ATTRS{power/runtime_usage}=="0"     
                                                                       
  looking at parent device '/devices/pci0000:00/0000:00:14.0/usb3/3-3/3-3:1.0':
    KERNELS=="3-3:1.0"                                  
    SUBSYSTEMS=="usb"                 
    DRIVERS=="ch341"                        
    ATTRS{authorized}=="1"                             
    ATTRS{bAlternateSetting}==" 0"                        
    ATTRS{bInterfaceClass}=="ff"         
    ATTRS{bInterfaceNumber}=="00"                                      
    ATTRS{bInterfaceProtocol}=="02"                                
    ATTRS{bInterfaceSubClass}=="01"                     
    ATTRS{bNumEndpoints}=="03"                                         
    ATTRS{physical_location/dock}=="no"                                

...
...

udev rule file examples

udev directory

ls /etc/udev/rules.d

example

ATTRS{idVendor}=="10c4", ATTRS{idProduct}=="ea60", MODE:="0666", GROUP:="dialout", SYMLINK+="ttyMCU"

example

KERNEL=="ttyUSB*", ATTRS{idVendor}=="1a86", ATTRS{idProduct}=="7523", MODE:="0777", SYMLINK+="AHRS"

Find all serial device info

$ ls -l /sys/class/tty

...
lrwxrwxrwx 1 root root 0  8월 20 09:30 ttyS27 -> ../../devices/platform/serial8250/tty/ttyS27/
lrwxrwxrwx 1 root root 0  8월 20 09:30 ttyS28 -> ../../devices/platform/serial8250/tty/ttyS28/
lrwxrwxrwx 1 root root 0  8월 20 09:30 ttyS29 -> ../../devices/platform/serial8250/tty/ttyS29/
lrwxrwxrwx 1 root root 0  8월 20 09:30 ttyS3 -> ../../devices/platform/serial8250/tty/ttyS3/
lrwxrwxrwx 1 root root 0  8월 20 09:30 ttyS30 -> ../../devices/platform/serial8250/tty/ttyS30/
lrwxrwxrwx 1 root root 0  8월 20 09:30 ttyS31 -> ../../devices/platform/serial8250/tty/ttyS31/
lrwxrwxrwx 1 root root 0  8월 20 09:30 ttyS4 -> ../../devices/platform/serial8250/tty/ttyS4/
lrwxrwxrwx 1 root root 0  8월 20 09:30 ttyS5 -> ../../devices/platform/serial8250/tty/ttyS5/
lrwxrwxrwx 1 root root 0  8월 20 09:30 ttyS6 -> ../../devices/platform/serial8250/tty/ttyS6/
lrwxrwxrwx 1 root root 0  8월 20 09:30 ttyS7 -> ../../devices/platform/serial8250/tty/ttyS7/
lrwxrwxrwx 1 root root 0  8월 20 09:30 ttyS8 -> ../../devices/platform/serial8250/tty/ttyS8/
lrwxrwxrwx 1 root root 0  8월 20 09:30 ttyS9 -> ../../devices/platform/serial8250/tty/ttyS9/
lrwxrwxrwx 1 root root 0  8월 20 09:30 ttyUSB0 -> ../../devices/pci0000:00/0000:00:14.0/usb3/3-3/3-3:1.0/ttyUSB0/tty/ttyUSB0/
lrwxrwxrwx 1 root root 0  8월 20 09:30 ttyUSB1 -> ../../devices/pci0000:00/0000:00:14.0/usb3/3-1/3-1:1.0/ttyUSB1/tty/ttyUSB1/
...

udev reload

$ udevadm control --reload-rules && udevadm trigger