问答主题 WordPress深圳网站优化培训

有时候会插入两个一模一样的usb相机，担心每次启动他们所对应的设备节点 /dev/video* 会变化，所以需要绑定usb口，区分两个相机。把两个相机都插入后，查看usb信息

root@rk3588:/# udevadm info --attribute-walk --name=/dev/video0Udevadm 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/platform/fc800000.usb/usb1/1-1/1-1:1.0/video4linux/video0':KERNEL=="video0"SUBSYSTEM=="video4linux"DRIVER==""ATTR{dev_debug}=="0"ATTR{index}=="0"ATTR{name}=="USB Camera: USB Camera"looking at parent device '/devices/platform/fc800000.usb/usb1/1-1/1-1:1.0':KERNELS=="1-1:1.0"SUBSYSTEMS=="usb"DRIVERS=="uvcvideo"ATTRS{bAlternateSetting}==" 0"ATTRS{authorized}=="1"ATTRS{iad_bFunctionClass}=="0e"ATTRS{iad_bInterfaceCount}=="02"ATTRS{bInterfaceSubClass}=="01"ATTRS{iad_bFunctionSubClass}=="03"ATTRS{bInterfaceNumber}=="00"ATTRS{iad_bFirstInterface}=="00"ATTRS{bInterfaceProtocol}=="00"ATTRS{iad_bFunctionProtocol}=="00"ATTRS{bInterfaceClass}=="0e"ATTRS{bNumEndpoints}=="01"ATTRS{supports_autosuspend}=="1"ATTRS{interface}=="USB Camera"looking at parent device '/devices/platform/fc800000.usb/usb1/1-1':KERNELS=="1-1"SUBSYSTEMS=="usb"DRIVERS=="usb"ATTRS{configuration}==""ATTRS{bMaxPacketSize0}=="64"ATTRS{bDeviceClass}=="ef"ATTRS{bcdDevice}=="1001"ATTRS{bNumInterfaces}==" 2"ATTRS{bConfigurationValue}=="1"ATTRS{manufacturer}=="VNV"ATTRS{bNumConfigurations}=="1"ATTRS{authorized}=="1"ATTRS{speed}=="480"ATTRS{idProduct}=="c001"ATTRS{urbnum}=="32"ATTRS{devnum}=="2"ATTRS{product}=="USB Camera"ATTRS{maxchild}=="0"ATTRS{bmAttributes}=="80"ATTRS{bDeviceSubClass}=="02"ATTRS{bMaxPower}=="500mA"ATTRS{rx_lanes}=="1"ATTRS{removable}=="unknown"ATTRS{idVendor}=="1bcf"ATTRS{version}==" 2.00"ATTRS{avoid_reset_quirk}=="0"ATTRS{bDeviceProtocol}=="01"ATTRS{tx_lanes}=="1"ATTRS{devspec}=="(null)"ATTRS{ltm_capable}=="no"ATTRS{devpath}=="1"ATTRS{busnum}=="1"ATTRS{quirks}=="0x0"looking at parent device '/devices/platform/fc800000.usb/usb1':KERNELS=="usb1"SUBSYSTEMS=="usb"DRIVERS=="usb"ATTRS{configuration}==""ATTRS{bMaxPacketSize0}=="64"ATTRS{bDeviceClass}=="09"ATTRS{bcdDevice}=="0510"ATTRS{bNumInterfaces}==" 1"ATTRS{bConfigurationValue}=="1"ATTRS{manufacturer}=="Linux 5.10.110 ehci_hcd"ATTRS{bNumConfigurations}=="1"ATTRS{authorized}=="1"ATTRS{speed}=="480"ATTRS{idProduct}=="0002"ATTRS{urbnum}=="23"ATTRS{devnum}=="1"ATTRS{product}=="EHCI Host Controller"ATTRS{maxchild}=="1"ATTRS{bmAttributes}=="e0"ATTRS{bDeviceSubClass}=="00"ATTRS{bMaxPower}=="0mA"ATTRS{rx_lanes}=="1"ATTRS{removable}=="unknown"ATTRS{idVendor}=="1d6b"ATTRS{interface_authorized_default}=="1"ATTRS{authorized_default}=="1"ATTRS{version}==" 2.00"ATTRS{avoid_reset_quirk}=="0"ATTRS{serial}=="fc800000.usb"ATTRS{bDeviceProtocol}=="00"ATTRS{tx_lanes}=="1"ATTRS{ltm_capable}=="no"ATTRS{devpath}=="0"ATTRS{busnum}=="1"ATTRS{quirks}=="0x0"looking at parent device '/devices/platform/fc800000.usb':KERNELS=="fc800000.usb"SUBSYSTEMS=="platform"DRIVERS=="ehci-platform"ATTRS{companion}==""ATTRS{driver_override}=="(null)"ATTRS{uframe_periodic_max}=="100"looking at parent device '/devices/platform':KERNELS=="platform"SUBSYSTEMS==""DRIVERS==""

通过 KERNELS=="1-1" (应该可以加更多信息来区分，没深入研究)可以区分usb相机对应的usb口，udev可以绑定usb相机到对应的usb口

root@rk3588:/# cat /etc/udev/rules.d/50-video.rules 
KERNEL =="video*",ATTR{index}=="0",KERNELS=="1-1",MODE:="0777",SYMLINK+="my_video0"
KERNEL =="video*",ATTR{index}=="0",KERNELS=="2-1",MODE:="0777",SYMLINK+="my_video1"

这样不管usb 0口插入的是哪个usb相机，它都对应 /dev/my_video0 节点，应用层访问该节点即可获取数据。