NAME

       rtapi_parport - portable access to PC-style parallel ports

SYNTAX

       #include "rtapi_parport.h"

       int rtapi_parport_get(const char *module_name, rtapi_parport_t *port, unsigned short base, unsigned short
              base_hi, unsigned int modes)

       void rtapi_parport_release(rtapi_parport_t *port)

ARGUMENTS

       module_name
              By convention, the name of the RTAPI module or HAL component using the parport.

       port   A pointer to a rtapi_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

       rtapi_parport_get allocates a parallel port for exclusive use of the named hal component.  If successful,
       access  the port with I/O calls such as rtapi_inb at address based at the base or base_hi addresses.  The
       port must be released with rtapi_parport_release before the component exits with rtapi_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
           } rtapi_parport_t;

RETURN VALUE

       rtapi_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 rtapi_parport_release.

       rtapi_parport_release does not return a value.  It always succeeds.

NOTES

       In new code, prefer use of rtapi_parport to rtapi_parport.

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