20060303

1 files changed, 1064 insertions, 0 deletions

diff --git a/os/cerf405/devuart.c b/os/cerf405/devuart.c
new file mode 100644
index 00000000..eba92cba
--- /dev/null
+++ b/os/cerf405/devuart.c
@@ -0,0 +1,1064 @@
+#include	"u.h"
+#include	"../port/lib.h"
+#include	"mem.h"
+#include	"dat.h"
+#include	"fns.h"
+#include	"io.h"
+#include	"../port/error.h"
+
+#include	"../port/netif.h"
+
+/*
+ *  Driver for the uart.
+ */
+enum
+{
+	/*
+	 *  register numbers
+	 */
+	Data=	0,		/* xmit/rcv buffer */
+	Iena=	1,		/* interrupt enable */
+	 Ircv=	(1<<0),		/*  for char rcv'd */
+	 Ixmt=	(1<<1),		/*  for xmit buffer empty */
+	 Irstat=(1<<2),		/*  for change in rcv'er status */
+	 Imstat=(1<<3),		/*  for change in modem status */
+	Istat=	2,		/* interrupt flag (read) */
+	 Ipend=	1,		/* interrupt pending (not) */
+	 Fenabd=(3<<6),   		/*  on if fifo's enabled */
+	Fifoctl=2,		/* fifo control (write) */
+	 Fena=	(1<<0),		/*  enable xmit/rcv fifos */
+	 Fdma=	(1<<3),		/* dma on */
+	 Ftrig=	(1<<6),		/*  trigger after 4 input characters */
+	 Fclear=(3<<1),		/*  clear xmit & rcv fifos */
+	Format=	3,		/* byte format */
+	 Bits8=	(3<<0),		/*  8 bits/byte */
+	 Stop2=	(1<<2),		/*  2 stop bits */
+	 Pena=	(1<<3),		/*  generate parity */
+	 Peven=	(1<<4),		/*  even parity */
+	 Pforce=(1<<5),		/*  force parity */
+	 Break=	(1<<6),		/*  generate a break */
+	 Dra=	(1<<7),		/*  address the divisor */
+	Mctl=	4,		/* modem control */
+	 Dtr=	(1<<0),		/*  data terminal ready */
+	 Rts=	(1<<1),		/*  request to send */
+	 Ri=	(1<<2),		/*  ring */
+	 Inton=	(1<<3),		/*  turn on interrupts */
+	 Loop=	(1<<4),		/*  loop back */
+	Lstat=	5,		/* line status */
+	 Inready=(1<<0),	/*  receive buffer full */
+	 Oerror=(1<<1),		/*  receiver overrun */
+	 Perror=(1<<2),		/*  receiver parity error */
+	 Ferror=(1<<3),		/*  rcv framing error */
+	 Berror=(1<<4),		/* break alarm */
+	 Outready=(1<<5),	/*  output buffer full */
+	Mstat=	6,		/* modem status */
+	 Ctsc=	(1<<0),		/*  clear to send changed */
+	 Dsrc=	(1<<1),		/*  data set ready changed */
+	 Rire=	(1<<2),		/*  rising edge of ring indicator */
+	 Dcdc=	(1<<3),		/*  data carrier detect changed */
+	 Cts=	(1<<4),		/*  complement of clear to send line */
+	 Dsr=	(1<<5),		/*  complement of data set ready line */
+	 Ringl=	(1<<6),		/*  complement of ring indicator line */
+	 Dcd=	(1<<7),		/*  complement of data carrier detect line */
+	Scratch=7,		/* scratchpad */
+	Dlsb=	0,		/* divisor lsb */
+	Dmsb=	1,		/* divisor msb */
+
+	CTLS= 023,
+	CTLQ= 021,
+
+	Stagesize= 1024,
+	Nuart=	2,		/* max per machine */
+};
+
+typedef struct Uart Uart;
+struct Uart
+{
+	QLock;
+	int	opens;
+
+	int	enabled;
+	Uart	*elist;			/* next enabled interface */
+	char	name[KNAMELEN];
+
+	uchar	sticky[8];		/* sticky write register values */
+	void*	regs;
+	ulong	port;
+	ulong	freq;			/* clock frequency */
+	uchar	mask;			/* bits/char */
+	int	dev;
+	int	baud;			/* baud rate */
+
+	uchar	istat;			/* last istat read */
+	int	frame;			/* framing errors */
+	int	overrun;		/* rcvr overruns */
+
+	/* buffers */
+	int	(*putc)(Queue*, int);
+	Queue	*iq;
+	Queue	*oq;
+
+	Lock	flock;			/* fifo */
+	uchar	fifoon;			/* fifo's enabled */
+	uchar	nofifo;			/* earlier chip version with nofifo */
+
+	Lock	rlock;			/* receive */
+	uchar	istage[Stagesize];
+	uchar	*ip;
+	uchar	*ie;
+
+	int	haveinput;
+
+	Lock	tlock;			/* transmit */
+	uchar	ostage[Stagesize];
+	uchar	*op;
+	uchar	*oe;
+
+	int	modem;			/* hardware flow control on */
+	int	xonoff;			/* software flow control on */
+	int	blocked;
+	int	cts, dsr, dcd;		/* keep track of modem status */ 
+	int	ctsbackoff;
+	int	hup_dsr, hup_dcd;	/* send hangup upstream? */
+	int	dohup;
+
+	Rendez	r;
+};
+
+static Uart *uart[Nuart];
+static int nuart;
+
+struct Uartalloc {
+	Lock;
+	Uart *elist;	/* list of enabled interfaces */
+} uartalloc;
+
+static void uartintr(Uart*);
+
+/*
+ *  pick up architecture specific routines and definitions
+ */
+#include "uart.h"
+
+/*
+ *  set the baud rate by calculating and setting the baudrate
+ *  generator constant.  This will work with fairly non-standard
+ *  baud rates.
+ */
+static void
+uartsetbaud(Uart *p, int rate)
+{
+	ulong brconst;
+
+	if(rate <= 0)
+		return;
+
+	p->freq = archuartclock(p->port, rate);
+	if(p->freq == 0)
+		return;
+
+	brconst = (p->freq+8*rate-1)/(16*rate);
+
+	uartwrreg(p, Format, Dra);
+	uartwr(p, Dmsb, (brconst>>8) & 0xff);
+	uartwr(p, Dlsb, brconst & 0xff);
+	uartwrreg(p, Format, 0);
+
+	p->baud = rate;
+}
+
+/*
+ * decide if we should hangup when dsr or dcd drops.
+ */
+static void
+uartdsrhup(Uart *p, int n)
+{
+	p->hup_dsr = n;
+}
+
+static void
+uartdcdhup(Uart *p, int n)
+{
+	p->hup_dcd = n;
+}
+
+static void
+uartparity(Uart *p, char type)
+{
+	switch(type){
+	case 'e':
+		p->sticky[Format] |= Pena|Peven;
+		break;
+	case 'o':
+		p->sticky[Format] &= ~Peven;
+		p->sticky[Format] |= Pena;
+		break;
+	default:
+		p->sticky[Format] &= ~(Pena|Peven);
+		break;
+	}
+	uartwrreg(p, Format, 0);
+}
+
+/*
+ *  set bits/character, default 8
+ */
+void
+uartbits(Uart *p, int bits)
+{
+	if(bits < 5 || bits > 8)
+		error(Ebadarg);
+
+	p->sticky[Format] &= ~3;
+	p->sticky[Format] |= bits-5;
+
+	uartwrreg(p, Format, 0);
+}
+
+
+/*
+ *  toggle DTR
+ */
+void
+uartdtr(Uart *p, int n)
+{
+	if(n)
+		p->sticky[Mctl] |= Dtr;
+	else
+		p->sticky[Mctl] &= ~Dtr;
+
+	uartwrreg(p, Mctl, 0);
+}
+
+/*
+ *  toggle RTS
+ */
+void
+uartrts(Uart *p, int n)
+{
+	if(n)
+		p->sticky[Mctl] |= Rts;
+	else
+		p->sticky[Mctl] &= ~Rts;
+
+	uartwrreg(p, Mctl, 0);
+}
+
+/*
+ *  send break
+ */
+static void
+uartbreak(Uart *p, int ms)
+{
+	if(ms == 0)
+		ms = 200;
+
+	uartwrreg(p, Format, Break);
+	tsleep(&up->sleep, return0, 0, ms);
+	uartwrreg(p, Format, 0);
+}
+
+static void
+uartfifoon(Uart *p)
+{
+	ulong i, x;
+
+	if(p->nofifo || uartrdreg(p, Istat) & Fenabd)
+		return;
+
+	x = splhi();
+
+	/* reset fifos */
+	p->sticky[Fifoctl] = 0;
+	uartwrreg(p, Fifoctl, Fclear);
+
+	/* empty buffer and interrupt conditions */
+	for(i = 0; i < 16; i++){
+		if(uartrdreg(p, Istat)){
+			/* nothing to do */
+		}
+		if(uartrdreg(p, Data)){
+			/* nothing to do */
+		}
+	}
+
+	/* turn on fifo */
+	p->fifoon = 1;
+	p->sticky[Fifoctl] = Fena|Ftrig;
+	uartwrreg(p, Fifoctl, 0);
+	p->istat = uartrdreg(p, Istat);
+	if((p->istat & Fenabd) == 0) {
+		/* didn't work, must be an earlier chip type */
+		p->nofifo = 1;
+	}
+
+	splx(x);
+}
+
+/*
+ *  modem flow control on/off (rts/cts)
+ */
+static void
+uartmflow(Uart *p, int n)
+{
+	ilock(&p->tlock);
+	if(n){
+		p->sticky[Iena] |= Imstat;
+		uartwrreg(p, Iena, 0);
+		p->modem = 1;
+		p->cts = uartrdreg(p, Mstat) & Cts;
+	} else {
+		p->sticky[Iena] &= ~Imstat;
+		uartwrreg(p, Iena, 0);
+		p->modem = 0;
+		p->cts = 1;
+	}
+	iunlock(&p->tlock);
+
+//	ilock(&p->flock);
+//	if(1)
+//		/* turn on fifo's */
+//		uartfifoon(p);
+//	else {
+//		/* turn off fifo's */
+//		p->fifoon = 0;
+//		p->sticky[Fifoctl] = 0;
+//		uartwrreg(p, Fifoctl, Fclear);
+//	}
+//	iunlock(&p->flock);
+}
+
+/*
+ *  turn on a port's interrupts.  set DTR and RTS
+ */
+static void
+uartenable(Uart *p)
+{
+	Uart **l;
+
+	if(p->enabled)
+		return;
+
+	uartportpower(p, 1);
+
+	p->hup_dsr = p->hup_dcd = 0;
+	p->cts = p->dsr = p->dcd = 0;
+
+	/*
+ 	 *  turn on interrupts
+	 */
+	p->sticky[Iena] = Ircv | Ixmt | Irstat;
+	uartwrreg(p, Iena, 0);
+
+	/*
+	 *  turn on DTR and RTS
+	 */
+	uartdtr(p, 1);
+	uartrts(p, 1);
+
+	uartfifoon(p);
+
+	/*
+	 *  assume we can send
+	 */
+	ilock(&p->tlock);
+	p->cts = 1;
+	p->blocked = 0;
+	iunlock(&p->tlock);
+
+	/*
+	 *  set baud rate to the last used
+	 */
+	uartsetbaud(p, p->baud);
+
+	lock(&uartalloc);
+	for(l = &uartalloc.elist; *l; l = &(*l)->elist){
+		if(*l == p)
+			break;
+	}
+	if(*l == 0){
+		p->elist = uartalloc.elist;
+		uartalloc.elist = p;
+	}
+	p->enabled = 1;
+	unlock(&uartalloc);
+}
+
+/*
+ *  turn off a port's interrupts.  reset DTR and RTS
+ */
+static void
+uartdisable(Uart *p)
+{
+	Uart **l;
+
+	/*
+ 	 *  turn off interrupts
+	 */
+	p->sticky[Iena] = 0;
+	uartwrreg(p, Iena, 0);
+
+	/*
+	 *  revert to default settings
+	 */
+	p->sticky[Format] = Bits8;
+	uartwrreg(p, Format, 0);
+
+	/*
+	 *  turn off DTR, RTS, hardware flow control & fifo's
+	 */
+	uartdtr(p, 0);
+	uartrts(p, 0);
+	uartmflow(p, 0);
+	ilock(&p->tlock);
+	p->xonoff = p->blocked = 0;
+	iunlock(&p->tlock);
+
+	uartportpower(p, 0);
+
+	lock(&uartalloc);
+	for(l = &uartalloc.elist; *l; l = &(*l)->elist){
+		if(*l == p){
+			*l = p->elist;
+			break;
+		}
+	}
+	p->enabled = 0;
+	unlock(&uartalloc);
+}
+
+/*
+ *  put some bytes into the local queue to avoid calling
+ *  qconsume for every character
+ */
+static int
+stageoutput(Uart *p)
+{
+	int n;
+
+	n = qconsume(p->oq, p->ostage, Stagesize);
+	if(n <= 0)
+		return 0;
+	p->op = p->ostage;
+	p->oe = p->ostage + n;
+	return n;
+}
+
+/*
+ *  (re)start output
+ */
+static void
+uartkick0(Uart *p)
+{
+	int i;
+	if((p->modem && (p->cts == 0)) || p->blocked)
+		return;
+
+	/*
+	 *  128 here is an arbitrary limit to make sure
+	 *  we don't stay in this loop too long.  If the
+	 *  chips output queue is longer than 128, too
+	 *  bad -- presotto
+	 */
+	for(i = 0; i < 128; i++){
+		if(!(uartrdreg(p, Lstat) & Outready))
+			break;
+		if(p->op >= p->oe && stageoutput(p) == 0)
+			break;
+		uartwr(p, Data, *p->op++);
+	}
+}
+
+static void
+uartkick(void *v)
+{
+	Uart *p;
+
+	p = v;
+	ilock(&p->tlock);
+	uartkick0(p);
+	iunlock(&p->tlock);
+}
+
+/*
+ *  restart input if it's off
+ */
+static void
+uartflow(void *v)
+{
+	Uart *p;
+
+	p = v;
+	if(p->modem)
+		uartrts(p, 1);
+	ilock(&p->rlock);
+	p->haveinput = 1;
+	iunlock(&p->rlock);
+}
+
+/*
+ *  default is 9600 baud, 1 stop bit, 8 bit chars, no interrupts,
+ *  transmit and receive enabled, interrupts disabled.
+ */
+static void
+uartsetup0(Uart *p)
+{
+	memset(p->sticky, 0, sizeof(p->sticky));
+	/*
+	 *  set rate to 9600 baud.
+	 *  8 bits/character.
+	 *  1 stop bit.
+	 *  interrupts enabled.
+	 */
+	p->sticky[Format] = Bits8;
+	uartwrreg(p, Format, 0);
+	p->sticky[Mctl] |= Inton;
+	uartwrreg(p, Mctl, 0x0);
+
+	uartsetbaud(p, 9600);
+
+	p->iq = qopen(4*1024, 0, uartflow, p);
+	p->oq = qopen(4*1024, 0, uartkick, p);
+	if(p->iq == nil || p->oq == nil)
+		panic("uartsetup0");
+
+	p->ip = p->istage;
+	p->ie = &p->istage[Stagesize];
+	p->op = p->ostage;
+	p->oe = p->ostage;
+}
+
+/*
+ *  called by uartinstall() to create a new duart
+ */
+void
+uartsetup(ulong port, void *regs, ulong freq, char *name)
+{
+	Uart *p;
+
+	if(nuart >= Nuart)
+		return;
+
+	p = xalloc(sizeof(Uart));
+	uart[nuart] = p;
+	strcpy(p->name, name);
+	p->dev = nuart;
+	nuart++;
+	p->port = port;
+	p->regs = regs;
+	p->freq = freq;
+	uartsetup0(p);
+}
+
+/*
+ *  called by main() to configure a duart port as a console or a mouse
+ */
+void
+uartspecial(int port, int baud, Queue **in, Queue **out, int (*putc)(Queue*, int))
+{
+	Uart *p = uart[port];
+	uartenable(p);
+	if(baud)
+		uartsetbaud(p, baud);
+	p->putc = putc;
+	if(in)
+		*in = p->iq;
+	if(out)
+		*out = p->oq;
+	p->opens++;
+}
+
+/*
+ *  handle an interrupt to a single uart
+ */
+static void
+uartintr(Uart *p)
+{
+	uchar ch;
+	int s, l;
+
+	for (s = uartrdreg(p, Istat); !(s&Ipend); s = uartrdreg(p, Istat)) {
+		switch(s&0x3f){
+		case 4:	/* received data available */
+		case 6:	/* receiver line status (alarm or error) */
+		case 12:	/* character timeout indication */
+			while ((l = uartrdreg(p, Lstat)) & Inready) {
+				if(l & Ferror)
+					p->frame++;
+				if(l & Oerror)
+					p->overrun++;
+				ch = uartrdreg(p, Data) & 0xff;
+				if (l & (Berror|Perror|Ferror)) {
+					/* ch came with break, parity or framing error - consume */
+					continue;
+				}
+				if (ch == CTLS || ch == CTLQ) {
+					ilock(&p->tlock);
+					if(p->xonoff){
+						if(ch == CTLS)
+							p->blocked = 1;
+						else
+							p->blocked = 0;	/* clock gets output going again */
+					}
+					iunlock(&p->tlock);
+				}
+				if(p->putc)
+					p->putc(p->iq, ch);
+				else {
+					ilock(&p->rlock);
+					if(p->ip < p->ie)
+						*p->ip++ = ch;
+					else
+						p->overrun++;
+					p->haveinput = 1;
+					iunlock(&p->rlock);
+				}
+			}
+			break;
+
+		case 2:	/* transmitter not full */
+			uartkick(p);
+			break;
+
+		case 0:	/* modem status */
+			ch = uartrdreg(p, Mstat);
+			if(ch & Ctsc){
+				ilock(&p->tlock);
+				l = p->cts;
+				p->cts = ch & Cts;
+				if(l == 0 && p->cts)
+					p->ctsbackoff = 2; /* clock gets output going again */
+				iunlock(&p->tlock);
+			}
+	 		if (ch & Dsrc) {
+				l = ch & Dsr;
+				if(p->hup_dsr && p->dsr && !l){
+					ilock(&p->rlock);
+					p->dohup = 1;
+					iunlock(&p->rlock);
+				}
+				p->dsr = l;
+			}
+	 		if (ch & Dcdc) {
+				l = ch & Dcd;
+				if(p->hup_dcd && p->dcd && !l){
+					ilock(&p->rlock);
+					p->dohup = 1;
+					iunlock(&p->rlock);
+				}
+				p->dcd = l;
+			}
+			break;
+
+		default:
+			iprint("weird uart interrupt #%2.2ux\n", s);
+			break;
+		}
+	}
+	p->istat = s;
+}
+
+/*
+ *  we save up input characters till clock time
+ *
+ *  There's also a bit of code to get a stalled print going.
+ *  It shouldn't happen, but it does.  Obviously I don't
+ *  understand something.  Since it was there, I bundled a
+ *  restart after flow control with it to give some hysteresis
+ *  to the hardware flow control.  This makes compressing
+ *  modems happier but will probably bother something else.
+ *	 -- presotto
+ */
+void
+uartclock(void)
+{
+	int n;
+	Uart *p;
+
+	for(p = uartalloc.elist; p; p = p->elist){
+
+		/* this amortizes cost of qproduce to many chars */
+		if(p->haveinput){
+			ilock(&p->rlock);
+			if(p->haveinput){
+				n = p->ip - p->istage;
+				if(n > 0 && p->iq){
+					if(n > Stagesize)
+						panic("uartclock");
+					if(qproduce(p->iq, p->istage, n) < 0)
+						uartrts(p, 0);
+					else
+						p->ip = p->istage;
+				}
+				p->haveinput = 0;
+			}
+			iunlock(&p->rlock);
+		}
+		if(p->dohup){
+			ilock(&p->rlock);
+			if(p->dohup){
+				qhangup(p->iq, 0);
+				qhangup(p->oq, 0);
+			}
+			p->dohup = 0;
+			iunlock(&p->rlock);
+		}
+
+		/* this adds hysteresis to hardware flow control */
+		if(p->ctsbackoff){
+			ilock(&p->tlock);
+			if(p->ctsbackoff){
+				if(--(p->ctsbackoff) == 0)
+					uartkick0(p);
+			}
+			iunlock(&p->tlock);
+		}
+	}
+}
+
+Dirtab *uartdir;
+int ndir;
+
+static void
+setlength(int i)
+{
+	Uart *p;
+
+	if(i >= 0){
+		p = uart[i];
+		if(p && p->opens && p->iq)
+			uartdir[1+3*i].length = qlen(p->iq);
+	} else for(i = 0; i < nuart; i++){
+		p = uart[i];
+		if(p && p->opens && p->iq)
+			uartdir[1+3*i].length = qlen(p->iq);
+	}
+}
+
+/*
+ *  all uarts must be uartsetup() by this point or inside of uartinstall()
+ */
+static void
+uartreset(void)
+{
+	int i;
+	Dirtab *dp;
+	uartinstall();	/* architecture specific */
+
+	ndir = 1+3*nuart;
+	uartdir = xalloc(ndir * sizeof(Dirtab));
+	dp = uartdir;
+	strcpy(dp->name, ".");
+	mkqid(&dp->qid, 0, 0, QTDIR);
+	dp->length = 0;
+	dp->perm = DMDIR|0555;
+	dp++;
+	for(i = 0; i < nuart; i++){
+		/* 3 directory entries per port */
+		strcpy(dp->name, uart[i]->name);
+		dp->qid.path = NETQID(i, Ndataqid);
+		dp->perm = 0666;
+		dp++;
+		sprint(dp->name, "%sctl", uart[i]->name);
+		dp->qid.path = NETQID(i, Nctlqid);
+		dp->perm = 0666;
+		dp++;
+		sprint(dp->name, "%sstatus", uart[i]->name);
+		dp->qid.path = NETQID(i, Nstatqid);
+		dp->perm = 0444;
+		dp++;
+	}
+}
+
+static Chan*
+uartattach(char *spec)
+{
+	return devattach('t', spec);
+}
+
+static Walkqid*
+uartwalk(Chan *c, Chan *nc, char **name, int nname)
+{
+	return devwalk(c, nc, name, nname, uartdir, ndir, devgen);
+}
+
+static int
+uartstat(Chan *c, uchar *dp, int n)
+{
+	if(NETTYPE(c->qid.path) == Ndataqid)
+		setlength(NETID(c->qid.path));
+	return devstat(c, dp, n, uartdir, ndir, devgen);
+}
+
+static Chan*
+uartopen(Chan *c, int omode)
+{
+	Uart *p;
+
+	c = devopen(c, omode, uartdir, ndir, devgen);
+
+	switch(NETTYPE(c->qid.path)){
+	case Nctlqid:
+	case Ndataqid:
+		p = uart[NETID(c->qid.path)];
+		qlock(p);
+		if(p->opens++ == 0){
+			uartenable(p);
+			qreopen(p->iq);
+			qreopen(p->oq);
+		}
+		qunlock(p);
+		break;
+	}
+
+	return c;
+}
+
+static void
+uartclose(Chan *c)
+{
+	Uart *p;
+
+	if(c->qid.type & QTDIR)
+		return;
+	if((c->flag & COPEN) == 0)
+		return;
+	switch(NETTYPE(c->qid.path)){
+	case Ndataqid:
+	case Nctlqid:
+		p = uart[NETID(c->qid.path)];
+		qlock(p);
+		if(--(p->opens) == 0){
+			uartdisable(p);
+			qclose(p->iq);
+			qclose(p->oq);
+			p->ip = p->istage;
+			p->dcd = p->dsr = p->dohup = 0;
+		}
+		qunlock(p);
+		break;
+	}
+}
+
+static long
+uartstatus(Chan*, Uart *p, void *buf, long n, long offset)
+{
+	uchar mstat, fstat, istat, tstat;
+	char str[256];
+
+	str[0] = 0;
+	tstat = p->sticky[Mctl];
+	mstat = uartrdreg(p, Mstat);
+	istat = p->sticky[Iena];
+	fstat = p->sticky[Format];
+	snprint(str, sizeof str,
+		"b%d c%d d%d e%d l%d m%d p%c r%d s%d\n"
+		"%d %d %d%s%s%s%s%s\n",
+
+		p->baud,
+		p->hup_dcd, 
+		(tstat & Dtr) != 0,
+		p->hup_dsr,
+		(fstat & Bits8) + 5,
+		(istat & Imstat) != 0, 
+		(fstat & Pena) ? ((fstat & Peven) ? 'e' : 'o') : 'n',
+		(tstat & Rts) != 0,
+		(fstat & Stop2) ? 2 : 1,
+
+		p->dev,
+		p->frame,
+		p->overrun, 
+		uartrdreg(p, Istat) & Fenabd       ? " fifo" : "",
+		(mstat & Cts)    ? " cts"  : "",
+		(mstat & Dsr)    ? " dsr"  : "",
+		(mstat & Dcd)    ? " dcd"  : "",
+		(mstat & Ringl)   ? " ring" : ""
+	);
+	return readstr(offset, buf, n, str);
+}
+
+static long
+uartread(Chan *c, void *buf, long n, vlong off)
+{
+	Uart *p;
+	ulong offset = off;
+
+	if(c->qid.type & QTDIR){
+		setlength(-1);
+		return devdirread(c, buf, n, uartdir, ndir, devgen);
+	}
+
+	p = uart[NETID(c->qid.path)];
+	switch(NETTYPE(c->qid.path)){
+	case Ndataqid:
+		return qread(p->iq, buf, n);
+	case Nctlqid:
+		return readnum(offset, buf, n, NETID(c->qid.path), NUMSIZE);
+	case Nstatqid:
+		return uartstatus(c, p, buf, n, offset);
+	}
+
+	return 0;
+}
+
+static void
+uartctl(Uart *p, char *cmd)
+{
+	int i, n;
+
+	/* let output drain for a while */
+	for(i = 0; i < 16 && qlen(p->oq); i++)
+		tsleep(&p->r, (int(*)(void*))qlen, p->oq, 125);
+
+	if(strncmp(cmd, "break", 5) == 0){
+		uartbreak(p, 0);
+		return;
+	}
+
+
+	n = atoi(cmd+1);
+	switch(*cmd){
+	case 'B':
+	case 'b':
+		uartsetbaud(p, n);
+		break;
+	case 'C':
+	case 'c':
+		uartdcdhup(p, n);
+		break;
+	case 'D':
+	case 'd':
+		uartdtr(p, n);
+		break;
+	case 'E':
+	case 'e':
+		uartdsrhup(p, n);
+		break;
+	case 'f':
+	case 'F':
+		qflush(p->oq);
+		break;
+	case 'H':
+	case 'h':
+		qhangup(p->iq, 0);
+		qhangup(p->oq, 0);
+		break;
+	case 'L':
+	case 'l':
+		uartbits(p, n);
+		break;
+	case 'm':
+	case 'M':
+		uartmflow(p, n);
+		break;
+	case 'n':
+	case 'N':
+		qnoblock(p->oq, n);
+		break;
+	case 'P':
+	case 'p':
+		uartparity(p, *(cmd+1));
+		break;
+	case 'K':
+	case 'k':
+		uartbreak(p, n);
+		break;
+	case 'R':
+	case 'r':
+		uartrts(p, n);
+		break;
+	case 'Q':
+	case 'q':
+		qsetlimit(p->iq, n);
+		qsetlimit(p->oq, n);
+		break;
+	case 'W':
+	case 'w':
+		/* obsolete */
+		break;
+	case 'X':
+	case 'x':
+		ilock(&p->tlock);
+		p->xonoff = n;
+		iunlock(&p->tlock);
+		break;
+	}
+}
+
+static long
+uartwrite(Chan *c, void *buf, long n, vlong)
+{
+	Uart *p;
+	char cmd[32];
+
+	if(c->qid.type & QTDIR)
+		error(Eperm);
+
+	p = uart[NETID(c->qid.path)];
+
+	/*
+	 *  The fifo's turn themselves off sometimes.
+	 *  It must be something I don't understand. -- presotto
+	 */
+	lock(&p->flock);
+	if((p->istat & Fenabd) == 0 && p->fifoon && p->nofifo == 0)
+		uartfifoon(p);
+	unlock(&p->flock);
+
+	switch(NETTYPE(c->qid.path)){
+	case Ndataqid:
+		return qwrite(p->oq, buf, n);
+	case Nctlqid:
+		if(n >= sizeof(cmd))
+			n = sizeof(cmd)-1;
+		memmove(cmd, buf, n);
+		cmd[n] = 0;
+		uartctl(p, cmd);
+		return n;
+	}
+}
+
+static int
+uartwstat(Chan *c, uchar *dp, int n)
+{
+	Dir d;
+	Dirtab *dt;
+
+	if(!iseve())
+		error(Eperm);
+	if(c->qid.type & QTDIR)
+		error(Eperm);
+	if(NETTYPE(c->qid.path) == Nstatqid)
+		error(Eperm);
+
+	dt = &uartdir[1+3 * NETID(c->qid.path)];
+	n = convM2D(dp, n, &d, nil);
+	if(n == 0)
+		error(Eshortstat);
+	if(d.mode != ~0UL){
+		d.mode &= 0666;
+		dt[0].perm = dt[1].perm = d.mode;
+	}
+	return n;
+}
+
+Dev uartdevtab = {
+	't',
+	"uart",
+
+	uartreset,
+	devinit,
+	devshutdown,
+	uartattach,
+	uartwalk,
+	uartstat,
+	uartopen,
+	devcreate,
+	uartclose,
+	uartread,
+	devbread,
+	uartwrite,
+	devbwrite,
+	devremove,
+	uartwstat,
+};