Path: utzoo!attcan!uunet!mcvax!hp4nl!botter!star.cs.vu.nl!ast@cs.vu.nl
From: ast@cs.vu.nl (Andy Tanenbaum)
Newsgroups: comp.os.minix
Subject: Fix to printer.c
Message-ID: <1785@ast.cs.vu.nl>
Date: 8 Dec 88 21:38:09 GMT
Sender: ast@cs.vu.nl
Reply-To: ast@cs.vu.nl (Andy Tanenbaum)
Organization: VU Informatica, Amsterdam
Lines: 54

There have been lots of reports about printers not working, giving printer
busy or out of paper and refusing to work.  A few weeks ago, somebody (I forget
who, sorry) posted a message saying these were caused by using the wrong 
printer port.  I have now changed printer.c to make a dynamic test to discover
the printer port.  The fix below to printer.c should end this problem forever.
If it doesn't, let me know.

Andy Tanenbaum (ast@cs.vu.nl)

*** printer.old	Thu Dec  8 21:18:44 1988
--- printer.c	Thu Dec  8 21:56:54 1988
***************
*** 221,230 ****
  {
  /* Color display uses 0x378 for printer; mono display uses 0x3BC. */
  
!   int i;
!   extern int color;
! 
!   port_base = (color ? PR_COLOR_BASE : PR_MONO_BASE);
    pr_busy = FALSE;
    port_out(port_base + 2, INIT_PRINTER);
    for (i = 0; i < DELAY_COUNT; i++) ;	/* delay loop */
--- 221,233 ----
  {
  /* Color display uses 0x378 for printer; mono display uses 0x3BC. */
  
!   int i = 0, testval = 0xAA;
!   extern int color;
! 
!   /* See if PR_COLOR_BASE installed by writing to it and reading it back. */
!   port_out(PR_COLOR_BASE, testval);	/* output random bit pattern */
!   port_in(PR_COLOR_BASE, &i);		/* read it back */
!   port_base = (i == testval ? PR_COLOR_BASE : PR_MONO_BASE);
    pr_busy = FALSE;
    port_out(port_base + 2, INIT_PRINTER);
    for (i = 0; i < DELAY_COUNT; i++) ;	/* delay loop */
***************
*** 233,239 ****
  
  
  /*===========================================================================*
!  *				pr_char				     *
   *===========================================================================*/
  PUBLIC pr_char()
  {
--- 236,242 ----
  
  
  /*===========================================================================*
!  *				pr_char					     *
   *===========================================================================*/
  PUBLIC pr_char()
  {