TODO.md

• Stop epoll'ing edges if no one is polling on /value.

• Examine what the default state of lines is. This tool always sets the line direction to input after 'export'.

• Make sure reading and writing from the individual gpio files is the same as the original sysfs interface:

  • Writing:

    • Kernel seems to accept writes to any offset within the file.
    • All data must be within a single write call.
    • Can optionally end with a '\n'

  • Reading:

    • A seek to 0 seems to switch to the next output buffer.

    • Reading individual bytes reads out potentially stale data:

      import os
      fd = os.open("/sys/class/gpio/gpio520/edge", os.O_RDWR)
      os.lseek(fd, 0, 0)
      os.write(fd, b"falling")
      os.lseek(fd, 0, 0)
      print(os.read(fd, 2))  # "fa"
      os.lseek(fd, 0, 0)
      os.write(fd, b"rising")
      os.lseek(fd, 2, 0)
      print(os.read(fd, 2))  # "ll"
      os.lseek(fd, 2, 0)
      print(os.read(fd, 2))  # "ll"
      os.lseek(fd, 0, 0)
      print(os.read(fd, 10)) # "rising"
      

• Chown or similar are not supported at the moment. You can only set permissions using the -o uid=XXX and -o gid=XXX parameters when starting the tool. Using -o default_permissions,allow_other seems useful for that.