linux udev

udev

• 属性
  KERNEL=="ttyUSB0"、SUBSYSTEM=="tty"、ATTRS{idVendor}=="1a86" 这些都是属性，是用来匹配有这些属性的设备的

• 操作
  SYMLINK+="ttyUSB_A"：再添加一个 /dev/ttyUSB_A 的链接指向这个 ttyusb
  MODE="0666"：权限为 666
  OWNER="abc"：所属用户为 abc

示例：
这个的意思是对于同时有 SUBSYSTEM=="tty" 和 SUBSYSTEMS=="usb" 属性的设备，其所属用户为 abc，这样就不用把用户加到 dialout 用户组也能使用这个设备

cat << EOF | sudo tee /etc/udev/rules.d/50-usb-serial.rules
SUBSYSTEM=="tty", SUBSYSTEMS=="usb", OWNER="abc"
EOF

查看属性信息

先看一个 usb 转串口的设备的信息 udevadm info -a /dev/ttyUSB0：

Udevadm info starts with the device specified by the devpath and then
walks up the chain of parent devices. It prints for every device
found, all possible attributes in the udev rules key format.
A rule to match, can be composed by the attributes of the device
and the attributes from one single parent device.looking at device '/devices/pci0000:00/0000:00:08.1/0000:04:00.3/usb1/1-2/1-2.2/1-2.2:1.0/ttyUSB0/tty/ttyUSB0':KERNEL=="ttyUSB0"SUBSYSTEM=="tty"DRIVER==""ATTR{power/control}=="auto"ATTR{power/runtime_active_time}=="0"ATTR{power/runtime_status}=="unsupported"ATTR{power/runtime_suspended_time}=="0"looking at parent device '/devices/pci0000:00/0000:00:08.1/0000:04:00.3/usb1/1-2/1-2.2/1-2.2:1.0/ttyUSB0':KERNELS=="ttyUSB0"SUBSYSTEMS=="usb-serial"DRIVERS=="ch341-uart"ATTRS{port_number}=="0"ATTRS{power/control}=="auto"ATTRS{power/runtime_active_time}=="0"ATTRS{power/runtime_status}=="unsupported"ATTRS{power/runtime_suspended_time}=="0"looking at parent device '/devices/pci0000:00/0000:00:08.1/0000:04:00.3/usb1/1-2/1-2.2/1-2.2:1.0':KERNELS=="1-2.2:1.0"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{supports_autosuspend}=="1"looking at parent device '/devices/pci0000:00/0000:00:08.1/0000:04:00.3/usb1/1-2/1-2.2':KERNELS=="1-2.2"SUBSYSTEMS=="usb"DRIVERS=="usb"ATTRS{authorized}=="1"ATTRS{avoid_reset_quirk}=="0"ATTRS{bConfigurationValue}=="1"ATTRS{bDeviceClass}=="ff"ATTRS{bDeviceProtocol}=="00"ATTRS{bDeviceSubClass}=="00"ATTRS{bMaxPacketSize0}=="8"ATTRS{bMaxPower}=="104mA"ATTRS{bNumConfigurations}=="1"ATTRS{bNumInterfaces}==" 1"ATTRS{bcdDevice}=="8134"ATTRS{bmAttributes}=="80"ATTRS{busnum}=="1"ATTRS{configuration}==""ATTRS{devnum}=="31"ATTRS{devpath}=="2.2"ATTRS{idProduct}=="7523"ATTRS{idVendor}=="1a86"ATTRS{ltm_capable}=="no"ATTRS{maxchild}=="0"ATTRS{power/active_duration}=="738205"ATTRS{power/autosuspend}=="2"ATTRS{power/autosuspend_delay_ms}=="2000"ATTRS{power/connected_duration}=="738205"ATTRS{power/control}=="on"
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