Minix1.5/kernel/printer.c
/* This file contains the printer driver. It is a fairly simple driver,
* supporting only one printer. Characters that are written to the driver
* are written to the printer without any changes at all.
*
* The valid messages and their parameters are:
*
* HARD_INT: interrupt handler has finished current chunk of output
* TTY_WRITE: a process wants to write on a terminal
* CANCEL: terminate a previous incomplete system call immediately
*
* m_type TTY_LINE PROC_NR COUNT ADDRESS
* -------------------------------------------------------
* | HARD_INT | | | | |
* |-------------+---------+---------+---------+---------|
* | TTY_WRITE |minor dev| proc nr | count | buf ptr |
* |-------------+---------+---------+---------+---------|
* | CANCEL |minor dev| proc nr | | |
* -------------------------------------------------------
*
* Note: since only 1 printer is supported, minor dev is not used at present.
*/
#include "kernel.h"
#include <minix/callnr.h>
#include <minix/com.h>
/* Control bits (in port_base + 2). "+" means positive logic and "-" means
* negative logic. Most of the signals are negative logic on the pins but
* many are converted to positive logic in the ports. Some manuals are
* misleading because they only document the pin logic.
*
* +0x01 Pin 1 -Strobe
* +0x02 Pin 14 -Auto Feed
* -0x04 Pin 16 -Initialize Printer
* +0x08 Pin 17 -Select Printer
* +0x10 IRQ7 Enable
*
* Auto Feed and Select Printer are always enabled. Strobe is enabled briefly
* when characters are output. Initialize Printer is enabled briefly when
* the task is started. IRQ7 is enabled when the first character is output
* and left enabled until output is completed (or later after certain
* abnormal completions).
*/
#define ASSERT_STROBE 0x1D /* strobe a character to the interface */
#define NEGATE_STROBE 0x1C /* enable interrupt on interface */
#define SELECT 0x0C /* select printer bit */
#define INIT_PRINTER 0x08 /* init printer bits */
/* Status bits (in port_base + 2).
*
* -0x08 Pin 15 -Error
* +0x10 Pin 13 +Select Status
* +0x20 Pin 12 +Out of Paper
* -0x40 Pin 10 -Acknowledge
* -0x80 Pin 11 +Busy
*/
#define BUSY_STATUS 0x10 /* printer gives this status when busy */
#define NO_PAPER 0x20 /* status bit saying that paper is out */
#define NORMAL_STATUS 0x90 /* printer gives this status when idle */
#define ON_LINE 0x10 /* status bit saying that printer is online */
#define STATUS_MASK 0xB0 /* mask to filter out status bits */
/* Centronics interface timing that must be met by software (in microsec).
*
* Strobe length: 0.5u to 100u (not sure about the upper limit).
* Data set up: 0.5u before strobe.
* Data hold: 0.5u after strobe.
* Init pulse length: over 200u (not sure).
*
* The strobe length is about 50u with the code here and function calls for
* out_byte() - not much to spare. The 0.5u minimums may be violated if
* out_byte() is generated in-line on a fast machine. Some printer boards
* are slower than 0.5u anyway.
*/
PRIVATE int caller; /* process to tell when printing done (FS) */
PRIVATE int done_status; /* status of last output completion */
PRIVATE int oleft; /* bytes of output left in obuf */
PRIVATE char obuf[128]; /* output buffer */
PRIVATE phys_bytes obuf_phys; /* physical address of obuf */
PRIVATE int opending; /* nonzero while expected printing not done */
PRIVATE char *optr; /* ptr to next char in obuf to print */
PRIVATE int orig_count; /* original byte count */
PRIVATE int port_base; /* I/O port for printer */
PRIVATE int proc_nr; /* user requesting the printing */
PRIVATE int user_left; /* bytes of output left in user buf */
PRIVATE phys_bytes user_phys; /* physical address of remainder of user buf */
PRIVATE int writing; /* nonzero while write is in progress */
FORWARD void do_cancel();
FORWARD void do_done();
FORWARD void do_write();
FORWARD void pr_error();
FORWARD void pr_start();
FORWARD void print_init();
FORWARD void reply();
/*===========================================================================*
* printer_task *
*===========================================================================*/
PUBLIC void printer_task()
{
/* Main routine of the printer task. */
message print_mess; /* buffer for all incoming messages */
print_init(); /* initialize */
while (TRUE) {
receive(ANY, &print_mess);
switch(print_mess.m_type) {
case TTY_WRITE: do_write(&print_mess); break;
case CANCEL : do_cancel(&print_mess); break;
case HARD_INT : do_done(); break;
default: reply(TASK_REPLY, print_mess.m_source,
print_mess.PROC_NR, EINVAL);
break;
}
}
}
/*===========================================================================*
* do_write *
*===========================================================================*/
PRIVATE void do_write(m_ptr)
register message *m_ptr; /* pointer to the newly arrived message */
{
/* The printer is used by sending TTY_WRITE messages to it. Process one. */
register int r;
r = SUSPEND; /* if no errors, tell FS to suspend user */
/* Reject command if last write is not finished or count is not positive. */
if (writing) r = EIO;
if (m_ptr->COUNT <= 0) r = EINVAL;
if (r == SUSPEND) {
/* Save information needed later. */
caller = m_ptr->m_source;
proc_nr = m_ptr->PROC_NR;
user_left = m_ptr->COUNT;
orig_count = m_ptr->COUNT;
user_phys = numap(m_ptr->PROC_NR, (vir_bytes) m_ptr->ADDRESS,
(vir_bytes) m_ptr->COUNT);
if (user_phys == 0)
r = E_BAD_ADDR;
else {
pr_start();
writing = TRUE;
}
}
/* Reply to FS, no matter what happened. */
reply(TASK_REPLY, m_ptr->m_source, m_ptr->PROC_NR, r);
}
/*===========================================================================*
* do_done *
*===========================================================================*/
PRIVATE void do_done()
{
/* Previous chunk of printing is finished. Continue if OK and more.
* Otherwise, reply to caller (FS).
*/
register int status;
if (!writing) return; /* interrupt while canceling */
if (done_status != OK) {
oleft = 0; /* cancel output by interrupt handler */
pr_error(done_status);
status = EIO;
} else if (user_left != 0) {
pr_start();
return;
} else {
status = orig_count;
}
reply(REVIVE, caller, proc_nr, status);
writing = FALSE;
}
/*===========================================================================*
* do_cancel *
*===========================================================================*/
PRIVATE void do_cancel(m_ptr)
register message *m_ptr; /* pointer to the newly arrived message */
{
/* Cancel a print request that has already started. Usually this means that
* the process doing the printing has been killed by a signal. It is not
* clear if there are race conditions. Try not to cancel the wrong process,
* but rely on FS to handle the EINTR reply and de-suspension properly.
*/
if (writing && m_ptr->PROC_NR == proc_nr) {
oleft = 0; /* cancel output by interrupt handler */
writing = FALSE;
}
reply(TASK_REPLY, m_ptr->m_source, m_ptr->PROC_NR, EINTR);
}
/*===========================================================================*
* reply *
*===========================================================================*/
PRIVATE void reply(code, replyee, process, status)
int code; /* TASK_REPLY or REVIVE */
int replyee; /* destination for message (normally FS) */
int process; /* which user requested the printing */
int status; /* number of chars printed or error code */
{
/* Send a reply telling FS that printing has started or stopped. */
message pr_mess;
pr_mess.m_type = code; /* TASK_REPLY or REVIVE */
pr_mess.REP_STATUS = status; /* count or EIO */
pr_mess.REP_PROC_NR = process; /* which user does this pertain to */
send(replyee, &pr_mess); /* send the message */
}
/*===========================================================================*
* pr_error *
*===========================================================================*/
PRIVATE void pr_error(status)
int status; /* printer status byte */
{
/* The printer is not ready. Display a message on the console telling why. */
if ((status & ON_LINE) == 0)
printf("Printer is not on line\n");
else {
if (status & NO_PAPER)
printf("Printer is out of paper\n");
else
printf("Printer error, status is 0x%02x\n", status);
}
}
/*===========================================================================*
* print_init *
*===========================================================================*/
PRIVATE void print_init()
{
/* Set global variables. Get the port base for the first printer from the
* BIOS and initialize the printer.
*/
obuf_phys = umap(proc_ptr, D, obuf, sizeof obuf);
phys_copy(0x408L, umap(proc_ptr, D, &port_base, 2), 2L);
out_byte(port_base + 2, INIT_PRINTER);
milli_delay(2); /* easily satisfies Centronics minimum */
out_byte(port_base + 2, SELECT);
cim_printer(); /* ready for printer interrupts */
}
/*==========================================================================*
* pr_start *
*==========================================================================*/
PRIVATE void pr_start()
{
/* Start next chunk of printer output. */
register int chunk;
if ( (chunk = user_left) > sizeof obuf) chunk = sizeof obuf;
phys_copy(user_phys, obuf_phys, (phys_bytes) chunk);
user_phys += chunk;
user_left -= chunk;
optr = obuf;
opending = TRUE;
oleft = chunk; /* now interrupt handler is enabled */
}
/*===========================================================================*
* pr_char *
*===========================================================================*/
PUBLIC void pr_char()
{
/* This is the interrupt handler. When a character has been printed, an
* interrupt occurs, and the assembly code routine trapped to calls pr_char().
*
* One problem is that the 8259A controller generates spurious interrupts to
* IRQ7 when it gets confused by mistimed interrupts on any line. (IRQ7 for
* the first controller happens to be the printer IRQ.) Such an interrupt is
* ignored as a side-affect of the method of checking the busy status. This
* is harmless for the printer task but probably fatal to the task that missed
* the interrupt. It may be possible to recover by doing more work here.
*/
register int status;
if (oleft == 0) {
/* Nothing more to print. Turn off printer interrupts in case they
* are level-sensitive as on the PS/2. This should be safe even
* when the printer is busy with a previous character, because the
* interrupt status does not affect the printer.
*/
out_byte(port_base + 2, SELECT);
return;
}
do {
/* Loop to handle fast (buffered) printers. It is important that
* processor interrupts are not disabled here, just printer interrupts.
*/
status = in_byte(port_base + 1);
if ((status & STATUS_MASK) == BUSY_STATUS) {
/* Still busy with last output. This normally happens
* immediately after doing output to an unbuffered or slow
* printer. It may happen after a call from pr_start or
* pr_restart, since they are not synchronized with printer
* interrupts. It may happen after a spurious interrupt.
*/
return;
}
if ((status & STATUS_MASK) == NORMAL_STATUS) {
/* Everything is all right. Output another character. */
out_byte(port_base, *optr++); /* output character */
lock(); /* ensure strobe is not too long */
out_byte(port_base + 2, ASSERT_STROBE);
out_byte(port_base + 2, NEGATE_STROBE);
unlock();
opending = FALSE; /* show interrupt is working */
} else {
/* Error. This would be better ignored (treat as busy). */
done_status = status;
interrupt(PRINTER);
return;
}
}
while (--oleft != 0);
/* Finished printing chunk OK. */
done_status = OK;
interrupt(PRINTER);
}
/*==========================================================================*
* pr_restart *
*==========================================================================*/
PUBLIC void pr_restart()
{
/* Check if printer is hung up, and if so, restart it.
* Test-and-set done by tasim_printer() stops pr_char() being reentered.
*/
if (oleft != 0) {
if (opending && !tasim_printer()) {
pr_char();
cim_printer(); /* ready for printer interrupts again */
}
opending = TRUE; /* expect some printing before next call */
}
}