Some low-level Comedi drivers no longer support manual configuration of
devices with the COMEDI_DEVCONFIG ioctl (used by the comedi_config
program). For those drivers, the 'attach_pci' or 'attach_usb' handler
will be set in the struct comedi_driver to configure devices
automatically (via comedi_pci_auto_config() or
comedi_usb_auto_config()). Their 'attach' handlers are redundant but
the the comedi core module currently requires it to be set.
Make the 'attach' handler optional and issue a warning if something
wants to call it.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>