patch-2.1.47 linux/drivers/misc/parport_ieee1284.c

• Lines: 90
• Date: Wed Jul 23 11:07:59 1997
• Orig file: v2.1.46/linux/drivers/misc/parport_ieee1284.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.1.46/linux/drivers/misc/parport_ieee1284.c linux/drivers/misc/parport_ieee1284.c
@@ -0,0 +1,89 @@
+/* $Id$ 
+ * IEEE-1284 implementation for parport.
+ *
+ * Authors: Philip Blundell <pjb27@cam.ac.uk>
+ *          Carsten Gross <carsten@sol.wohnheim.uni-ulm.de>
+ *	    Jose Renau <renau@acm.org>
+ */
+
+#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
+ * 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.
+ */ 
+
+int parport_wait_peripheral(struct parport *port, unsigned char mask, 
+	unsigned char result)
+{
+	int counter=0;
+	unsigned char status; 
+	
+	do {
+		status = parport_read_status(port);
+		udelay(25);
+		counter++;
+		if (need_resched)
+			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 */
+}		
+
+/* 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.
+ */
+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 
+                           */ 
+	}
+	parport_write_control(port, parport_read_control(port) | 1);      /* Strobe  high */
+	udelay(5);				     /* Strobe wait */
+	parport_write_control(port, parport_read_control(port) & ~1);     /* Strobe  low */
+	udelay(5);
+	parport_write_control(port, parport_read_control(port) & ~2);     /*  AutoFeed low */
+	return (parport_wait_peripheral(port, 0x20, 0))?2:1;
+}