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.