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sectionioctl (Devices) [7aa79a42]

Part of linux
  • Devices are special file
  • /dev is devices
  • When we need to do IO on a device, just go out and access it!

  • Block special files and character special files

    • ls -l -> c for character file, b for block file

    • major and minor numbers, represents type of the device, and reprsents the instance

      • 4k major numbers, 2^20 minor numbers
    • mknod is used to make a device special file
    • Nothing special about these files! You can make them anywhere

    • udev is a program that sits there and creates files in the /dev directory

      • devices can register themselves or get a number assigned to them
    • much effort has gone into making devices work together

    • traditional device operations

      • open()
      • close()
      • read()
      • write()
      • seek()

      • ioctl

        • lets you do particular things to particular device
        • usually takes some integers (like everything in unix world)

    • block devices

      • tend to do I/O in terms of blocks
      • like disk drives
      • usually more random access
      • disks for example

    • character devices

      • operate in bytes
      • usually more seequential
      • mouse/audio card/printer/tape/terminal for example