parport_yield — relinquish a parallel port temporarily
| int parport_yield ( | struct pardevice * dev ); | 
   This function relinquishes the port if it would be helpful to other
   drivers to do so.  Afterwards it tries to reclaim the port using
   parport_claim, and the return value is the same as for
   parport_claim.  If it fails, the port is left unclaimed and it is
   the driver's responsibility to reclaim the port.
   
   The parport_yield and parport_yield_blocking functions are for
   marking points in the driver at which other drivers may claim the
   port and use their devices.  Yielding the port is similar to
   releasing it and reclaiming it, but is more efficient because no
   action is taken if there are no other devices needing the port.  In
   fact, nothing is done even if there are other devices waiting but
   the current device is still within its “timeslice”.  The default
   timeslice is half a second, but it can be adjusted via the /proc
   interface.