USB hub 多usb接口重映射：udev 规则
你在开发的过程中是否会出现 USB端口号会发生变化。 例如： 机器人底盘与雷达都是 ttyUSB* .其序号与接入的先后有关。 对于写好的launch每次修改对应接口是不是
很麻法，或者每次得先插入一个再插另外一个。才能保证ttyUSB0 ttyUSB1. 但是如果你重启系统，说不定还是有问题出现。。
==》 不如将端口重映射到新的固定的名字，并且设置其权限为可读。 这样不管你的先后插入，符合对应id的硬件端口自动的映射到新定义的名字。
一. 单一的USB映射说明
参见：http://blog.csdn.net/zyh821351004/article/details/41577105
lsusb 命令查看所有usb端口信息。
yhzhao@yhzhao:~$ lsusb Bus 002 Device 002: ID 0bda:0411 Realtek Semiconductor Corp. Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 001 Device 004: ID 04f2:b48c Chicony Electronics Co., Ltd Bus 001 Device 009: ID 046d:c31c Logitech, Inc. Keyboard K120 Bus 001 Device 010: ID 10c4:ea60 Cygnal Integrated Products, Inc. CP210x UART Bridge / myAVR mySmartUSB light Bus 001 Device 005: ID 0bda:5411 Realtek Semiconductor Corp. Bus 001 Device 008: ID 24ae:1100 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hubudev的规则说明，可以参考博客说明：http://blog.csdn.net/cokewei/article/details/8281239
简单说明:
$kernel, %k：设备的内核设备名称，例如：sda、cdrom。
ID 10c4:ea60 表示usb设备的ID(这个ID由芯片制造商设置，可以唯一表示该设备)
10c4 usb_device_descriptor.idVendor
ea60 usb_device_descriptor.idProduct
依据这些信息，就可以简单的写udev规则了：rplidar.rules
sudo gedit /etc/udev/rules.d/rplidar.rules
# set the udev rule , make the device_port be fixed by rplidar
#
KERNEL=="ttyUSB*", ATTRS{idVendor}=="10c4", ATTRS{idProduct}=="ea60", MODE:="0777", SYMLINK+="rplidar"
创建生效后重新插拔USB。
用下面的命令就可以查看对应的映射结果了。
yhzhao@yhzhao:~$ ls -l /dev |grep ttyUSB lrwxrwxrwx 1 root root 7 Apr 14 13:18 rplidar -> ttyUSB0 crwxrwxrwx 1 root uucp 188, 0 Apr 14 13:18 ttyUSB0 yhzhao@yhzhao:~$
二. USB hub的多端口映射：
同一个hub连接设备base和laser， 将其重映射换名称到 slamtec_base_ 和 slamtec_laser_
yhzhao@yhzhao:~$ lsusb Bus 002 Device 002: ID 0bda:0411 Realtek Semiconductor Corp. Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 001 Device 004: ID 04f2:b48c Chicony Electronics Co., Ltd Bus 001 Device 009: ID 046d:c31c Logitech, Inc. Keyboard K120 Bus 001 Device 011: ID 10c4:ea60 Cygnal Integrated Products, Inc. CP210x UART Bridge / myAVR mySmartUSB light Bus 001 Device 012: ID 10c4:ea60 Cygnal Integrated Products, Inc. CP210x UART Bridge / myAVR mySmartUSB light Bus 001 Device 005: ID 0bda:5411 Realtek Semiconductor Corp. Bus 001 Device 008: ID 24ae:1100 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
现提供固定hub的每个端口的映射。
udevadm info --attribute-walk --path=/sys/bus/usb-serial/devices/ttyUSB0
说明参见： http://askubuntu.com/questions/49910/how-to-distinguish-between-identical-usb-to-serial-adapters
可以找到hub端口的不同：
yhzhao@yhzhao:~$ udevadm info --attribute-walk --path=/sys/bus/usb-serial/devices/ttyUSB1
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/pci0000:00/0000:00:14.0/usb1/1-2/1-2.2/1-2.2:1.0/ttyUSB1':
KERNEL=="ttyUSB1"
SUBSYSTEM=="usb-serial"
DRIVER=="cp210x"
ATTR{port_number}=="0"
looking at parent device '/devices/pci0000:00/0000:00:14.0/usb1/1-2/1-2.2/1-2.2:1.0':
KERNELS=="1-2.2:1.0"
SUBSYSTEMS=="usb"
DRIVERS=="cp210x"
ATTRS{bInterfaceClass}=="ff"
yhzhao@yhzhao:~$ udevadm info --attribute-walk --path=/sys/bus/usb-serial/devices/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/pci0000:00/0000:00:14.0/usb1/1-2/1-2.1/1-2.1:1.0/ttyUSB0':
KERNEL=="ttyUSB0"
SUBSYSTEM=="usb-serial"
DRIVER=="cp210x"
ATTR{port_number}=="0"
looking at parent device '/devices/pci0000:00/0000:00:14.0/usb1/1-2/1-2.1/1-2.1:1.0':
KERNELS=="1-2.1:1.0"
SUBSYSTEMS=="usb"
DRIVERS=="cp210x"
ATTRS{bInterfaceClass}=="ff"
#参考 http://askubuntu.com/questions/49910/how-to-distinguish-between-identical-usb-to-serial-adapters
#lsusb#udevadm info --attribute-walk --path=/sys/bus/usb-serial/devices/ttyUSB0
SUBSYSTEMS=="usb"
DRIVERS=="cp210x"
ATTRS{bInterfaceClass}=="ff"
ATTRS{bInterfaceSubClass}=="00"
ATTRS{bInterfaceProtocol}=="00"
ATTRS{bNumEndpoints}=="02"
ATTRS{supports_autosuspend}=="1"
ATTRS{bAlternateSetting}==" 0"
ATTRS{bInterfaceNumber}=="00"
ATTRS{interface}=="CP2102 USB to UART Bridge Controller"
KERNEL=="ttyUSB*", KERNELS=="1-2.1", MODE:="0777",SYMLINK+="slamtec_base_"
KERNEL=="ttyUSB*", KERNELS=="1-2.2", MODE:="0777",SYMLINK+="slamtec_laser_"
重新拔插。可以看到：
ls -l /dev
yhzhao@yhzhao:~$ ls -l /dev|grep ttyUSB lrwxrwxrwx 1 root root 7 Apr 14 13:45 rplidar -> ttyUSB1 lrwxrwxrwx 1 root root 7 Apr 14 13:45 slamtec_base_ -> ttyUSB0 lrwxrwxrwx 1 root root 7 Apr 14 13:45 slamtec_laser_ -> ttyUSB1 crwxrwxrwx 1 root uucp 188, 0 Apr 14 13:45 ttyUSB0 crwxrwxrwx 1 root dialout 188, 1 Apr 14 13:45 ttyUSB1
参考：http://blog.csdn.net/zyh821351004/article/details/41577105