udev rules for supported LiteX Build Environment FPGA boards

These directory contains udev rules for HDMI2USB devices. While these devices don't need these rules to operate correctly, they make things significantly nicer.

These udev rules do the following things;

• Generate /dev/hdmi2usb symlinks. Each entry is a directory which groups together the usbdev, tty and video devices. There are three methods for finding the board;

  1. By number, first board == 0, second board == 1, etc.

  /dev/hdmi2usb/by-num/all$N/{usbdev,tty,video}
  /dev/hdmi2usb/by-num/all0/
  
  /dev/hdmi2usb/by-num/$BOARDTYPE$N/{usbdev,tty,video}
  /dev/hdmi2usb/by-num/opsis0/
  

  2. By location on the USB bus;

  /dev/hdmi2usb/by-path/usb.bus$X.port$Y{-hub.port$Z}*/{usbdev,tty,video}
  /dev/hdmi2usb/by-path/usb.bus1.port2/
  /dev/hdmi2usb/by-path/usb.bus3.port4-hub.port3/
  /dev/hdmi2usb/by-path/usb.bus3.port4-hub.port3-hub.port1/
  

  3. By serial number;

  /dev/hdmi2usb/by-serial/$SERIALNO/{usbdev,tty,video}
  /dev/hdmi2usb/by-serial/ffffd8803956c79a/
  

• Grant anyone on the system permission to access the HDMI2USB boards.

• Make modem-manager ignore the serial ports.

They work the following way;

• 98-hdmi2usb-xxx.rules - These files tag the ENV with the HDMI2USB information.

• 98-hdmi2usb-opsis.rules - Rules for the Numato Opsis board.
• 98-hdmi2usb-atlys.rules - Rules for the Digilent Atlys board.

• 99-hdmi2usb-xxx.rules - These files use the tags to do things.

• 99-hdmi2usb-aliases.rules - Creates the extra symlinks
• 99-hdmi2usb-permissions.rules - Sets the permissions
• 99-hdmi2usb-mm-blacklist.rules - Makes modem manager ignore the device

• 99-hdmi2usbaux-xxx.rules - These files are used for HDMI2USB related devices which don't really follow the proper rules.

• 99-hdmi2usbaux-cypress.rules - Rules for an unconfigured Cypress FX2 (such as the Numato Opsis/Digilent Atlys in fail-safe mode).
• 99-hdmi2usbaux-ixo-usb-jtag.rules - Rules for the boards when loaded with ixo-usb-jtag.

• hdmi2usb-human-path-helper.sh is just a simple shell script which converts the kernel naming into something human readable.

Examining udev data

udevadm info --attribute-walk --name=/dev/ttyACM0
udevadm test /sys/class/tty/ttyACM0 2>&1 | less
udevadm test /sys/class/video4linux/video0 2>&1 | less
udevadm test $(udevadm info -q path -n /dev/bus/usb/003/109) 2>&1 | less

Useful docs:

• udev Linux Man Page
• Linux kernel udev docs
• Debian Wiki
• Oracle Docs on Device Management