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.