patch-2.1.68 linux/drivers/misc/parport_ieee1284.c

• Lines: 122
• Date: Sat Nov 29 16:19:40 1997
• Orig file: v2.1.67/linux/drivers/misc/parport_ieee1284.c
• Orig date: Wed Sep 3 20:52:42 1997

diff -u --recursive --new-file v2.1.67/linux/drivers/misc/parport_ieee1284.c linux/drivers/misc/parport_ieee1284.c
@@ -1,4 +1,5 @@
-/* IEEE-1284 implementation for parport.
+/* $Id: parport_ieee1284.c,v 1.4 1997/10/19 21:37:21 philip Exp $
+ * IEEE-1284 implementation for parport.
  *
  * Authors: Phil Blundell <Philip.Blundell@pobox.com>
  *          Carsten Gross <carsten@sol.wohnheim.uni-ulm.de>
@@ -6,83 +7,63 @@
  */
 
 #include <linux/tasks.h>
-
 #include <linux/parport.h>
 #include <linux/delay.h>
-#include <linux/errno.h>
-#include <linux/interrupt.h>
-#include <linux/ioport.h>
 #include <linux/kernel.h>
-#include <linux/malloc.h>
-
-/* The following read functions are an implementation of a status readback
- * and device id request confirming to IEEE1284-1994.
- *
- * These probably ought to go in some seperate file, so people like the SPARC
- * don't have to pull them in.
- */
 
 /* Wait for Status line(s) to change in 35 ms - see IEEE1284-1994 page 24 to
  * 25 for this. After this time we can create a timeout because the
- * peripheral doesn't conform to IEEE1284. We want to save CPU time: we are
- * waiting a maximum time of 500 us busy (this is for speed). If there is
+ * peripheral doesn't conform to IEEE1284.  We want to save CPU time: we are
+ * waiting a maximum time of 500 us busy (this is for speed).  If there is
  * not the right answer in this time, we call schedule and other processes
- * are able "to eat" the time up to 30ms.  So the maximum load avarage can't
- * get above 5% for a read even if the peripheral is really slow. (but your
- * read gets very slow then - only about 10 characters per second. This
- * should be tuneable). Thanks to Andreas who pointed me to this and ordered
- * the documentation.
+ * are able to eat the time up to 40ms.
  */ 
 
 int parport_wait_peripheral(struct parport *port, unsigned char mask, 
 	unsigned char result)
 {
-	int counter=0;
+	int counter;
 	unsigned char status; 
 	
-	do {
+	for (counter = 0; counter < 20; counter++) {
 		status = parport_read_status(port);
+		if ((status & mask) == result)
+			return 0;
 		udelay(25);
-		counter++;
-		if (need_resched)
+		if (resched_needed())
 			schedule();
-	} while ( ((status & mask) != result) && (counter < 20) );
-	if ( (counter == 20) && ((status & mask) != result) ) { 
-		current->state=TASK_INTERRUPTIBLE;
-		current->timeout=jiffies+4;
-		schedule(); /* wait for 4 scheduler runs (40ms) */
-		status = parport_read_status(port);
-		if ((status & mask) != result) return 1; /* timeout */
 	}
-	return 0; /* okay right response from device */
+	current->state = TASK_INTERRUPTIBLE;
+	current->timeout = jiffies+4;
+	schedule();				/* wait for 40ms */
+	status = parport_read_status(port);
+	return ((status & mask) == result)?0:1;
 }		
 
-/* Test if nibble mode for status readback is okay. Returns the value false
- * if the printer doesn't support readback at all. If it supports readbacks
- * and printer data is available the function returns 1, otherwise 2. The
- * only valid values for "mode" are 0 and 4. 0 requests normal nibble mode,
- * 4 is for "request device id using nibble mode". The request for the
- * device id is best done in an ioctl (or at bootup time).  There is no
- * check for an invalid value, the only function using this call at the
- * moment is lp_read and the ioctl LPGETDEVICEID both fixed calls from
- * trusted kernel.
+/* Test if the peripheral is IEEE 1284 compliant.
+ * return values are:
+ *   0 - handshake failed; peripheral is not compliant (or none present)
+ *   1 - handshake OK; IEEE1284 peripheral present but no data available
+ *   2 - handshake OK; IEEE1284 peripheral and data available
  */
 int parport_ieee1284_nibble_mode_ok(struct parport *port, unsigned char mode) 
 {
 	parport_write_data(port, mode);
-	udelay(5);		
-	parport_write_control(port, parport_read_control(port) & ~8);  /* SelectIN  low */
-	parport_write_control(port, parport_read_control(port) | 2); /* AutoFeed  high */
-	if (parport_wait_peripheral(port, 0x78, 0x38)) { /* timeout? */
-		parport_write_control(port, (parport_read_control(port) & ~2) | 8);
-		return 0; /* first stage of negotiation failed, 
-                           * no IEEE1284 compliant device on this port 
-                           */ 
+	udelay(500);
+	/* nSelectIn high, nAutoFd low */
+	parport_write_control(port, (parport_read_control(port) & ~8) | 2);
+	if (parport_wait_peripheral(port, 0x78, 0x38)) {
+		parport_write_control(port, 
+				      (parport_read_control(port) & ~2) | 8);
+		return 0; 
 	}
-	parport_write_control(port, parport_read_control(port) | 1);      /* Strobe  high */
+	/* nStrobe low */
+	parport_write_control(port, parport_read_control(port) | 1);
 	udelay(5);				     /* Strobe wait */
-	parport_write_control(port, parport_read_control(port) & ~1);     /* Strobe  low */
+	/* nStrobe high */
+	parport_write_control(port, parport_read_control(port) & ~1);
 	udelay(5);
-	parport_write_control(port, parport_read_control(port) & ~2);     /*  AutoFeed low */
+	/* nAutoFd low */
+	parport_write_control(port, parport_read_control(port) & ~2);
 	return (parport_wait_peripheral(port, 0x20, 0))?2:1;
 }