NAME

       hal_parport - portable access to PC-style parallel ports

SYNTAX

       #include "hal_parport.h"

       int  hal_parport_get(int  comp_id,  hal_parport_t  *port,  unsigned  short  base, unsigned short base_hi,
              unsigned int modes)

       void hal_parport_release(hal_parport_t *port)

ARGUMENTS

       comp_id
              A HAL component identifier returned by an earlier call to hal_init.

       port   A pointer to a hal_parport_t structure

       base   The base address of the port (if port >= 16) or the linux port number of the port (if port < 16)

       base_hi
              The "high" address of the port (location of the ECP registers), 0 to use a probed high address, or
              -1 to disable the high address

       modes  Advise the driver of the desired port modes, from <linux/parport.h>.   If  a  linux-detected  port
              does  not  provide the requested modes, a warning is printed with rtapi_print_msg.   This does not
              make the port request fail, because unfortunately, many systems that have working EPP parports are
              not detected as such by Linux.

DESCRIPTION

       hal_parport_get allocates a parallel port for exclusive use of the named HAL component.  The port must be
       released with hal_parport_release before the component exits with hal_exit.

HIGH ADDRESS PROBING

       If the port is a parallel port known to Linux, and Linux detected a high I/O address, this value is used.
       Otherwise, if base+0x400 is not registered to any device, it is used.  Otherwise, no address is used.  If
       no high address is detected, port->base_hi is 0.

PARPORT STRUCTURE

           typedef struct
           {
               unsigned short base;
               unsigned short base_hi;
               .... // and further unspecified fields
           } hal_parport_t;

RETURN VALUE

       hal_parport_get returns a HAL status code.  On success, port is filled out  with  information  about  the
       allocated port.  On failure, the contents of port are undefined except that it is safe (but not required)
       to pass this port to hal_parport_release.

       hal_parport_release does not return a value.  It always succeeds.

NOTES

       In new code, prefer use of rtapi_parport to hal_parport.

LinuxCNC Documentation                             2006-10-12                                      parport(3hal)