From 6de9a332d1a870912b7d3353655929265ba2982b Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Wed, 4 Dec 1991 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1991-12-04

---
 pc/devlpt.c  | 214 +++++++++++++++++++++++++++++++++++++++++++++++++++
 port/ipdat.h |   2 +-
 2 files changed, 215 insertions(+), 1 deletion(-)
 create mode 100644 pc/devlpt.c

diff --git a/pc/devlpt.c b/pc/devlpt.c
new file mode 100644
index 0000000000000000000000000000000000000000..9148f3f7f748af592954de787f4cf10ca17cb51b
--- /dev/null
+++ b/pc/devlpt.c
@@ -0,0 +1,214 @@
+#include	"u.h"
+#include	"lib.h"
+#include	"mem.h"
+#include	"dat.h"
+#include	"fns.h"
+#include	"io.h"
+#include	"errno.h"
+
+/* Centronix parallel (printer) port */
+
+/* base addresses */
+int lptbase[] = {
+	0x3bc,	/* lpt1 */
+	0x378,	/* lpt2 (sic) */
+	0x278	/* lpt3 (sic) */
+};
+#define NDEV	(sizeof lptbase/sizeof lptbase[0])
+
+/* offsets, and bits in the registers */
+enum
+{
+	/* data latch register */
+	Qdlr=		0x0,
+	/* printer status register */
+	Qpsr=		0x1,
+	Fnotbusy=	0x80,
+	Fack=		0x40,
+	Fpe=		0x20,
+	Fselect=	0x10,
+	Fnoerror=	0x08,
+	/* printer control register */
+	Qpcr=		0x2,
+	Fie=		0x10,
+	Fselectin=	0x08,
+	Finitbar=	0x04,
+	Faf=		0x02,
+	Fstrobe=	0x01,
+	/* fake `data register' */
+	Qdata=		0x3,
+};
+
+static int	lptready(void*);
+static void	outch(int, int);
+static void	lptintr(Ureg*);
+
+static Rendez	lptrendez;
+
+Dirtab lptdir[]={
+	"dlr",		{Qdlr},		1,		0666,
+	"psr",		{Qpsr},		5,		0444,
+	"pcr",		{Qpcr},		0,		0222,
+	"data",		{Qdata},	0,		0222,
+};
+#define NLPT	(sizeof lptdir/sizeof lptdir[0])
+
+static int
+lptgen(Chan *c, Dirtab *tab, int ntab, int i, Dir *dp)
+{
+	Qid qid;
+	char name[NAMELEN];
+
+	if(tab==0 || i>=ntab)
+		return -1;
+	tab += i;
+	qid = tab->qid;
+	if(qid.path < Qdata)
+		qid.path += lptbase[c->dev];
+	qid.vers = c->dev;
+	sprint(name, "lpt%d%s", c->dev+1, tab->name);
+	devdir(c, qid, name, tab->length, eve, tab->perm, dp);
+	return 1;
+}
+
+void
+lptreset(void)
+{
+	setvec(Parallelvec, lptintr);
+}
+
+void
+lptinit(void)
+{}
+
+Chan*
+lptattach(char *spec)
+{
+	Chan *c;
+	int i  = (spec && *spec) ? strtol(spec, 0, 0) : 1;
+
+	if(i < 1 || i > NDEV)
+		errors("spec out of range");
+	c = devattach('L', spec);
+	c->dev = i-1;
+	return c;
+}
+
+Chan*
+lptclone(Chan *c, Chan *nc)
+{
+	return devclone(c, nc);
+}
+
+int
+lptwalk(Chan *c, char *name)
+{
+	return devwalk(c, name, lptdir, NLPT, lptgen);
+}
+
+void
+lptstat(Chan *c, char *dp)
+{
+	devstat(c, dp, lptdir, NLPT, lptgen);
+}
+
+Chan*
+lptopen(Chan *c, int omode)
+{
+	return devopen(c, omode, lptdir, NLPT, lptgen);
+}
+
+void
+lptcreate(Chan *c, char *name, int omode, ulong perm)
+{
+	error(Eperm);
+}
+
+void
+lptclose(Chan *c)
+{}
+
+void
+lptremove(Chan *c)
+{
+	error(Eperm);
+}
+
+void
+lptwstat(Chan *c, char *dp)
+{
+	error(Eperm);
+}
+
+long
+lptread(Chan *c, void *a, long n)
+{
+	char str[16]; int size;
+
+	if(c->qid.path == CHDIR)
+		return devdirread(c, a, n, lptdir, NLPT, lptgen);
+	size = sprint(str, "0x%2.2ux\n", inb(c->qid.path));
+	if(c->offset >= size)
+		return 0;
+	if(c->offset+n > size)
+		n = size-c->offset;
+	memmove(a, str+c->offset, n);
+	return n;
+}
+
+long
+lptwrite(Chan *c, void *a, long n)
+{
+	char str[16], *p;
+	long base, k;
+
+	if(n <= 0)
+		return 0;
+	if(c->qid.path != Qdata){
+		if(n > sizeof str-1)
+			n = sizeof str-1;
+		memmove(str, a, n);
+		str[n] = 0;
+		outb(c->qid.path, strtoul(str, 0, 0));
+		return n;
+	}
+	p = a;
+	k = n;
+	base = lptbase[c->dev];
+	if(waserror()){
+		outb(base+Qpcr, Finitbar);
+		nexterror();
+	}
+	while(--k >= 0)
+		outch(base, *p++);
+	poperror();
+	return n;
+}
+
+static void
+outch(int base, int c)
+{
+	int status = inb(base+Qpsr);
+
+	if(!(status & Fselect) || !(status & Fnoerror))
+		error(Eio);
+	if(!(status & Fnotbusy)){
+		outb(base+Qpcr, Finitbar|Fie);
+		sleep(&lptrendez, lptready, (void *)base);
+	}
+	outb(base+Qdlr, c);
+	outb(base+Qpcr, Finitbar|Fstrobe);
+	outb(base+Qpcr, Finitbar);
+}
+
+static int
+lptready(void *base)
+{
+	return inb((int)base+Qpsr)&Fnotbusy;
+}
+
+static void
+lptintr(Ureg *ur)
+{
+	wakeup(&lptrendez);
+}
diff --git a/port/ipdat.h b/port/ipdat.h
index 82445d815211835c4be1d2c71b2852e2228c7fa1..96fbc5501aba4c4f81984d4c55648542b839dae3 100644
--- a/port/ipdat.h
+++ b/port/ipdat.h
@@ -309,7 +309,7 @@ struct Ipconv
 #define MSS_LENGTH	4
 #define MSL2		10
 #define MSPTICK		200
-#define DEF_MSS		1024
+#define DEF_MSS		512
 #define DEF_RTT		1000
 #define	TCPOOB_HADDATA	1
 #define	TCPOOB_HAVEDATA 2