```ruby
module FFI
  module GPhoto2Port
    # libgphoto2_port/gphoto2/gphoto2-port-result.h
    GP_OK = 0
    # ...
    GP_ERROR_IO_USB_CLAIM = -53
  end
end
```

Add all return code constants
user
```ruby
module FFI
  module GPhoto2Port
    # libgphoto2_port/gphoto2/gphoto2-port-result.h
    GP_OK = 0

    GP_ERROR = -1
    GP_ERROR_BAD_PARAMETERS = -2
    GP_ERROR_NO_MEMORY = -3
    GP_ERROR_LIBRARY = -4
    GP_ERROR_UNKNOWN_PORT = -5
    GP_ERROR_NOT_SUPPORTED = -6
    GP_ERROR_IO = -7
    GP_ERROR_FIXED_LIMIT_EXCEEDED = -8

    GP_ERROR_TIMEOUT = -10

    GP_ERROR_IO_SUPPORTED_SERIAL = -20
    GP_ERROR_IO_SUPPORTED_USB = -21

    GP_ERROR_IO_INIT = -31
    GP_ERROR_IO_READ = -34
    GP_ERROR_IO_WRITE = -35
    GP_ERROR_IO_UPDATE = -37

    GP_ERROR_IO_SERIAL_SPEED = -41

    GP_ERROR_IO_USB_CLEAR_HALT = -51
    GP_ERROR_IO_USB_FIND = -52
    GP_ERROR_IO_USB_CLAIM = -53

    GP_ERROR_IO_LOCK = -60

    GP_ERROR_HAL = -70
  end
end
```
assistant