if_el.c revision 1.86 1 /* $NetBSD: if_el.c,v 1.86 2010/04/05 07:20:24 joerg Exp $ */
2
3 /*
4 * Copyright (c) 1994, Matthew E. Kimmel. Permission is hereby granted
5 * to use, copy, modify and distribute this software provided that both
6 * the copyright notice and this permission notice appear in all copies
7 * of the software, derivative works or modified versions, and any
8 * portions thereof.
9 */
10
11 /*
12 * 3COM Etherlink 3C501 device driver
13 */
14
15 /*
16 * Bugs/possible improvements:
17 * - Does not currently support DMA
18 * - Does not currently support multicasts
19 */
20
21 #include <sys/cdefs.h>
22 __KERNEL_RCSID(0, "$NetBSD: if_el.c,v 1.86 2010/04/05 07:20:24 joerg Exp $");
23
24 #include "opt_inet.h"
25 #include "rnd.h"
26
27 #include <sys/param.h>
28 #include <sys/systm.h>
29 #include <sys/errno.h>
30 #include <sys/ioctl.h>
31 #include <sys/mbuf.h>
32 #include <sys/socket.h>
33 #include <sys/syslog.h>
34 #include <sys/device.h>
35 #if NRND > 0
36 #include <sys/rnd.h>
37 #endif
38
39 #include <net/if.h>
40 #include <net/if_dl.h>
41 #include <net/if_types.h>
42
43 #include <net/if_ether.h>
44
45 #ifdef INET
46 #include <netinet/in.h>
47 #include <netinet/in_systm.h>
48 #include <netinet/in_var.h>
49 #include <netinet/ip.h>
50 #include <netinet/if_inarp.h>
51 #endif
52
53
54 #include <net/bpf.h>
55 #include <net/bpfdesc.h>
56
57 #include <sys/cpu.h>
58 #include <sys/intr.h>
59 #include <sys/bus.h>
60
61 #include <dev/isa/isavar.h>
62 #include <dev/isa/if_elreg.h>
63
64 /* for debugging convenience */
65 #ifdef EL_DEBUG
66 #define DPRINTF(x) printf x
67 #else
68 #define DPRINTF(x)
69 #endif
70
71 /*
72 * per-line info and status
73 */
74 struct el_softc {
75 struct device sc_dev;
76 void *sc_ih;
77
78 struct ethercom sc_ethercom; /* ethernet common */
79 bus_space_tag_t sc_iot; /* bus space identifier */
80 bus_space_handle_t sc_ioh; /* i/o handle */
81
82 #if NRND > 0
83 rndsource_element_t rnd_source;
84 #endif
85 };
86
87 /*
88 * prototypes
89 */
90 int elintr(void *);
91 void elinit(struct el_softc *);
92 int elioctl(struct ifnet *, u_long, void *);
93 void elstart(struct ifnet *);
94 void elwatchdog(struct ifnet *);
95 void elreset(struct el_softc *);
96 void elstop(struct el_softc *);
97 static int el_xmit(struct el_softc *);
98 void elread(struct el_softc *, int);
99 struct mbuf *elget(struct el_softc *sc, int);
100 static inline void el_hardreset(struct el_softc *);
101
102 int elprobe(device_t, cfdata_t, void *);
103 void elattach(device_t, device_t, void *);
104
105 CFATTACH_DECL(el, sizeof(struct el_softc),
106 elprobe, elattach, NULL, NULL);
107
108 /*
109 * Probe routine.
110 *
111 * See if the card is there and at the right place.
112 * (XXX - cgd -- needs help)
113 */
114 int
115 elprobe(device_t parent, cfdata_t match, void *aux)
116 {
117 struct isa_attach_args *ia = aux;
118 bus_space_tag_t iot = ia->ia_iot;
119 bus_space_handle_t ioh;
120 int iobase;
121 u_int8_t station_addr[ETHER_ADDR_LEN];
122 u_int8_t i;
123 int rval;
124
125 rval = 0;
126
127 if (ia->ia_nio < 1)
128 return (0);
129 if (ia->ia_nirq < 1)
130 return (0);
131
132 if (ISA_DIRECT_CONFIG(ia))
133 return (0);
134
135 iobase = ia->ia_io[0].ir_addr;
136
137 if (ia->ia_io[0].ir_addr == ISA_UNKNOWN_PORT)
138 return (0);
139 if (ia->ia_irq[0].ir_irq == ISA_UNKNOWN_IRQ)
140 return (0);
141
142 /* First check the base. */
143 if (iobase < 0x200 || iobase > 0x3f0)
144 return 0;
145
146 /* Map i/o space. */
147 if (bus_space_map(iot, iobase, 16, 0, &ioh))
148 return 0;
149
150 /*
151 * Now attempt to grab the station address from the PROM and see if it
152 * contains the 3com vendor code.
153 */
154 DPRINTF(("Probing 3c501 at 0x%x...\n", iobase));
155
156 /* Reset the board. */
157 DPRINTF(("Resetting board...\n"));
158 bus_space_write_1(iot, ioh, EL_AC, EL_AC_RESET);
159 delay(5);
160 bus_space_write_1(iot, ioh, EL_AC, 0);
161
162 /* Now read the address. */
163 DPRINTF(("Reading station address...\n"));
164 for (i = 0; i < ETHER_ADDR_LEN; i++) {
165 bus_space_write_1(iot, ioh, EL_GPBL, i);
166 station_addr[i] = bus_space_read_1(iot, ioh, EL_EAW);
167 }
168 DPRINTF(("Address is %s\n", ether_sprintf(station_addr)));
169
170 /*
171 * If the vendor code is ok, return a 1. We'll assume that whoever
172 * configured this system is right about the IRQ.
173 */
174 if (station_addr[0] != 0x02 || station_addr[1] != 0x60 ||
175 station_addr[2] != 0x8c) {
176 DPRINTF(("Bad vendor code.\n"));
177 goto out;
178 }
179 DPRINTF(("Vendor code ok.\n"));
180
181 ia->ia_nio = 1;
182 ia->ia_io[0].ir_size = 16;
183
184 ia->ia_nirq = 1;
185
186 ia->ia_niomem = 0;
187 ia->ia_ndrq = 0;
188
189 rval = 1;
190
191 out:
192 bus_space_unmap(iot, ioh, 16);
193 return rval;
194 }
195
196 /*
197 * Attach the interface to the kernel data structures. By the time this is
198 * called, we know that the card exists at the given I/O address. We still
199 * assume that the IRQ given is correct.
200 */
201 void
202 elattach(device_t parent, device_t self, void *aux)
203 {
204 struct el_softc *sc = (void *)self;
205 struct isa_attach_args *ia = aux;
206 bus_space_tag_t iot = ia->ia_iot;
207 bus_space_handle_t ioh;
208 struct ifnet *ifp = &sc->sc_ethercom.ec_if;
209 u_int8_t myaddr[ETHER_ADDR_LEN];
210 u_int8_t i;
211
212 printf("\n");
213
214 DPRINTF(("Attaching %s...\n", device_xname(&sc->sc_dev)));
215
216 /* Map i/o space. */
217 if (bus_space_map(iot, ia->ia_io[0].ir_addr, 16, 0, &ioh)) {
218 aprint_error_dev(self, "can't map i/o space\n");
219 return;
220 }
221
222 sc->sc_iot = iot;
223 sc->sc_ioh = ioh;
224
225 /* Reset the board. */
226 bus_space_write_1(iot, ioh, EL_AC, EL_AC_RESET);
227 delay(5);
228 bus_space_write_1(iot, ioh, EL_AC, 0);
229
230 /* Now read the address. */
231 for (i = 0; i < ETHER_ADDR_LEN; i++) {
232 bus_space_write_1(iot, ioh, EL_GPBL, i);
233 myaddr[i] = bus_space_read_1(iot, ioh, EL_EAW);
234 }
235
236 /* Stop the board. */
237 elstop(sc);
238
239 /* Initialize ifnet structure. */
240 strlcpy(ifp->if_xname, device_xname(&sc->sc_dev), IFNAMSIZ);
241 ifp->if_softc = sc;
242 ifp->if_start = elstart;
243 ifp->if_ioctl = elioctl;
244 ifp->if_watchdog = elwatchdog;
245 ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_NOTRAILERS;
246 IFQ_SET_READY(&ifp->if_snd);
247
248 /* Now we can attach the interface. */
249 DPRINTF(("Attaching interface...\n"));
250 if_attach(ifp);
251 ether_ifattach(ifp, myaddr);
252
253 /* Print out some information for the user. */
254 printf("%s: address %s\n", device_xname(self), ether_sprintf(myaddr));
255
256 sc->sc_ih = isa_intr_establish(ia->ia_ic, ia->ia_irq[0].ir_irq,
257 IST_EDGE, IPL_NET, elintr, sc);
258
259 #if NRND > 0
260 DPRINTF(("Attaching to random...\n"));
261 rnd_attach_source(&sc->rnd_source, device_xname(&sc->sc_dev),
262 RND_TYPE_NET, 0);
263 #endif
264
265 DPRINTF(("elattach() finished.\n"));
266 }
267
268 /*
269 * Reset interface.
270 */
271 void
272 elreset(struct el_softc *sc)
273 {
274 int s;
275
276 DPRINTF(("elreset()\n"));
277 s = splnet();
278 elstop(sc);
279 elinit(sc);
280 splx(s);
281 }
282
283 /*
284 * Stop interface.
285 */
286 void
287 elstop(struct el_softc *sc)
288 {
289
290 bus_space_write_1(sc->sc_iot, sc->sc_ioh, EL_AC, 0);
291 }
292
293 /*
294 * Do a hardware reset of the board, and upload the ethernet address again in
295 * case the board forgets.
296 */
297 static inline void
298 el_hardreset(struct el_softc *sc)
299 {
300 bus_space_tag_t iot = sc->sc_iot;
301 bus_space_handle_t ioh = sc->sc_ioh;
302 int i;
303
304 bus_space_write_1(iot, ioh, EL_AC, EL_AC_RESET);
305 delay(5);
306 bus_space_write_1(iot, ioh, EL_AC, 0);
307
308 for (i = 0; i < ETHER_ADDR_LEN; i++)
309 bus_space_write_1(iot, ioh, i,
310 CLLADDR(sc->sc_ethercom.ec_if.if_sadl)[i]);
311 }
312
313 /*
314 * Initialize interface.
315 */
316 void
317 elinit(struct el_softc *sc)
318 {
319 struct ifnet *ifp = &sc->sc_ethercom.ec_if;
320 bus_space_tag_t iot = sc->sc_iot;
321 bus_space_handle_t ioh = sc->sc_ioh;
322
323 /* First, reset the board. */
324 el_hardreset(sc);
325
326 /* Configure rx. */
327 DPRINTF(("Configuring rx...\n"));
328 if (ifp->if_flags & IFF_PROMISC)
329 bus_space_write_1(iot, ioh, EL_RXC,
330 EL_RXC_AGF | EL_RXC_DSHORT | EL_RXC_DDRIB |
331 EL_RXC_DOFLOW | EL_RXC_PROMISC);
332 else
333 bus_space_write_1(iot, ioh, EL_RXC,
334 EL_RXC_AGF | EL_RXC_DSHORT | EL_RXC_DDRIB |
335 EL_RXC_DOFLOW | EL_RXC_ABROAD);
336 bus_space_write_1(iot, ioh, EL_RBC, 0);
337
338 /* Configure TX. */
339 DPRINTF(("Configuring tx...\n"));
340 bus_space_write_1(iot, ioh, EL_TXC, 0);
341
342 /* Start reception. */
343 DPRINTF(("Starting reception...\n"));
344 bus_space_write_1(iot, ioh, EL_AC, EL_AC_IRQE | EL_AC_RX);
345
346 /* Set flags appropriately. */
347 ifp->if_flags |= IFF_RUNNING;
348 ifp->if_flags &= ~IFF_OACTIVE;
349
350 /* And start output. */
351 elstart(ifp);
352 }
353
354 /*
355 * Start output on interface. Get datagrams from the queue and output them,
356 * giving the receiver a chance between datagrams. Call only from splnet or
357 * interrupt level!
358 */
359 void
360 elstart(struct ifnet *ifp)
361 {
362 struct el_softc *sc = ifp->if_softc;
363 bus_space_tag_t iot = sc->sc_iot;
364 bus_space_handle_t ioh = sc->sc_ioh;
365 struct mbuf *m, *m0;
366 int s, i, off, retries;
367
368 DPRINTF(("elstart()...\n"));
369 s = splnet();
370
371 /* Don't do anything if output is active. */
372 if ((ifp->if_flags & IFF_OACTIVE) != 0) {
373 splx(s);
374 return;
375 }
376
377 ifp->if_flags |= IFF_OACTIVE;
378
379 /*
380 * The main loop. They warned me against endless loops, but would I
381 * listen? NOOO....
382 */
383 for (;;) {
384 /* Dequeue the next datagram. */
385 IFQ_DEQUEUE(&ifp->if_snd, m0);
386
387 /* If there's nothing to send, return. */
388 if (m0 == 0)
389 break;
390
391 /* Give the packet to the bpf, if any. */
392 bpf_mtap(ifp, m0);
393
394 /* Disable the receiver. */
395 bus_space_write_1(iot, ioh, EL_AC, EL_AC_HOST);
396 bus_space_write_1(iot, ioh, EL_RBC, 0);
397
398 /* Transfer datagram to board. */
399 DPRINTF(("el: xfr pkt length=%d...\n", m0->m_pkthdr.len));
400 off = EL_BUFSIZ - max(m0->m_pkthdr.len,
401 ETHER_MIN_LEN - ETHER_CRC_LEN);
402 #ifdef DIAGNOSTIC
403 if ((off & 0xffff) != off)
404 printf("%s: bogus off 0x%x\n",
405 device_xname(&sc->sc_dev), off);
406 #endif
407 bus_space_write_1(iot, ioh, EL_GPBL, off & 0xff);
408 bus_space_write_1(iot, ioh, EL_GPBH, (off >> 8) & 0xff);
409
410 /* Copy the datagram to the buffer. */
411 for (m = m0; m != 0; m = m->m_next)
412 bus_space_write_multi_1(iot, ioh, EL_BUF,
413 mtod(m, u_int8_t *), m->m_len);
414 for (i = 0;
415 i < ETHER_MIN_LEN - ETHER_CRC_LEN - m0->m_pkthdr.len; i++)
416 bus_space_write_1(iot, ioh, EL_BUF, 0);
417
418 m_freem(m0);
419
420 /* Now transmit the datagram. */
421 retries = 0;
422 for (;;) {
423 bus_space_write_1(iot, ioh, EL_GPBL, off & 0xff);
424 bus_space_write_1(iot, ioh, EL_GPBH, (off >> 8) & 0xff);
425 if (el_xmit(sc)) {
426 ifp->if_oerrors++;
427 break;
428 }
429 /* Check out status. */
430 i = bus_space_read_1(iot, ioh, EL_TXS);
431 DPRINTF(("tx status=0x%x\n", i));
432 if ((i & EL_TXS_READY) == 0) {
433 DPRINTF(("el: err txs=%x\n", i));
434 if (i & (EL_TXS_COLL | EL_TXS_COLL16)) {
435 ifp->if_collisions++;
436 if ((i & EL_TXC_DCOLL16) == 0 &&
437 retries < 15) {
438 retries++;
439 bus_space_write_1(iot, ioh,
440 EL_AC, EL_AC_HOST);
441 }
442 } else {
443 ifp->if_oerrors++;
444 break;
445 }
446 } else {
447 ifp->if_opackets++;
448 break;
449 }
450 }
451
452 /*
453 * Now give the card a chance to receive.
454 * Gotta love 3c501s...
455 */
456 (void)bus_space_read_1(iot, ioh, EL_AS);
457 bus_space_write_1(iot, ioh, EL_AC, EL_AC_IRQE | EL_AC_RX);
458 splx(s);
459 /* Interrupt here. */
460 s = splnet();
461 }
462
463 (void)bus_space_read_1(iot, ioh, EL_AS);
464 bus_space_write_1(iot, ioh, EL_AC, EL_AC_IRQE | EL_AC_RX);
465 ifp->if_flags &= ~IFF_OACTIVE;
466 splx(s);
467 }
468
469 /*
470 * This function actually attempts to transmit a datagram downloaded to the
471 * board. Call at splnet or interrupt, after downloading data! Returns 0 on
472 * success, non-0 on failure.
473 */
474 static int
475 el_xmit(struct el_softc *sc)
476 {
477 bus_space_tag_t iot = sc->sc_iot;
478 bus_space_handle_t ioh = sc->sc_ioh;
479 int i;
480
481 /*
482 * XXX
483 * This busy-waits for the tx completion. Can we get an interrupt
484 * instead?
485 */
486
487 DPRINTF(("el: xmit..."));
488 bus_space_write_1(iot, ioh, EL_AC, EL_AC_TXFRX);
489 i = 20000;
490 while ((bus_space_read_1(iot, ioh, EL_AS) & EL_AS_TXBUSY) && (i > 0))
491 i--;
492 if (i == 0) {
493 DPRINTF(("tx not ready\n"));
494 return -1;
495 }
496 DPRINTF(("%d cycles.\n", 20000 - i));
497 return 0;
498 }
499
500 /*
501 * Controller interrupt.
502 */
503 int
504 elintr(void *arg)
505 {
506 struct el_softc *sc = arg;
507 bus_space_tag_t iot = sc->sc_iot;
508 bus_space_handle_t ioh = sc->sc_ioh;
509 u_int8_t rxstat;
510 int len;
511
512 DPRINTF(("elintr: "));
513
514 /* Check board status. */
515 if ((bus_space_read_1(iot, ioh, EL_AS) & EL_AS_RXBUSY) != 0) {
516 (void)bus_space_read_1(iot, ioh, EL_RXC);
517 bus_space_write_1(iot, ioh, EL_AC, EL_AC_IRQE | EL_AC_RX);
518 return 0;
519 }
520
521 for (;;) {
522 rxstat = bus_space_read_1(iot, ioh, EL_RXS);
523 if (rxstat & EL_RXS_STALE)
524 break;
525
526 /* If there's an overflow, reinit the board. */
527 if ((rxstat & EL_RXS_NOFLOW) == 0) {
528 DPRINTF(("overflow.\n"));
529 el_hardreset(sc);
530 /* Put board back into receive mode. */
531 if (sc->sc_ethercom.ec_if.if_flags & IFF_PROMISC)
532 bus_space_write_1(iot, ioh, EL_RXC,
533 EL_RXC_AGF | EL_RXC_DSHORT | EL_RXC_DDRIB |
534 EL_RXC_DOFLOW | EL_RXC_PROMISC);
535 else
536 bus_space_write_1(iot, ioh, EL_RXC,
537 EL_RXC_AGF | EL_RXC_DSHORT | EL_RXC_DDRIB |
538 EL_RXC_DOFLOW | EL_RXC_ABROAD);
539 (void)bus_space_read_1(iot, ioh, EL_AS);
540 bus_space_write_1(iot, ioh, EL_RBC, 0);
541 break;
542 }
543
544 /* Incoming packet. */
545 len = bus_space_read_1(iot, ioh, EL_RBL);
546 len |= bus_space_read_1(iot, ioh, EL_RBH) << 8;
547 DPRINTF(("receive len=%d rxstat=%x ", len, rxstat));
548 bus_space_write_1(iot, ioh, EL_AC, EL_AC_HOST);
549
550 /* Pass data up to upper levels. */
551 elread(sc, len);
552
553 /* Is there another packet? */
554 if ((bus_space_read_1(iot, ioh, EL_AS) & EL_AS_RXBUSY) != 0)
555 break;
556
557 #if NRND > 0
558 rnd_add_uint32(&sc->rnd_source, rxstat);
559 #endif
560
561 DPRINTF(("<rescan> "));
562 }
563
564 (void)bus_space_read_1(iot, ioh, EL_RXC);
565 bus_space_write_1(iot, ioh, EL_AC, EL_AC_IRQE | EL_AC_RX);
566 return 1;
567 }
568
569 /*
570 * Pass a packet to the higher levels.
571 */
572 void
573 elread(struct el_softc *sc, int len)
574 {
575 struct ifnet *ifp = &sc->sc_ethercom.ec_if;
576 struct mbuf *m;
577
578 if (len <= sizeof(struct ether_header) ||
579 len > ETHER_MAX_LEN) {
580 printf("%s: invalid packet size %d; dropping\n",
581 device_xname(&sc->sc_dev), len);
582 ifp->if_ierrors++;
583 return;
584 }
585
586 /* Pull packet off interface. */
587 m = elget(sc, len);
588 if (m == 0) {
589 ifp->if_ierrors++;
590 return;
591 }
592
593 ifp->if_ipackets++;
594
595 /*
596 * Check if there's a BPF listener on this interface.
597 * If so, hand off the raw packet to BPF.
598 */
599 bpf_mtap(ifp, m);
600
601 (*ifp->if_input)(ifp, m);
602 }
603
604 /*
605 * Pull read data off a interface. Len is length of data, with local net
606 * header stripped. We copy the data into mbufs. When full cluster sized
607 * units are present we copy into clusters.
608 */
609 struct mbuf *
610 elget(struct el_softc *sc, int totlen)
611 {
612 struct ifnet *ifp = &sc->sc_ethercom.ec_if;
613 bus_space_tag_t iot = sc->sc_iot;
614 bus_space_handle_t ioh = sc->sc_ioh;
615 struct mbuf *m, *m0, *newm;
616 int len;
617
618 MGETHDR(m0, M_DONTWAIT, MT_DATA);
619 if (m0 == 0)
620 return (0);
621 m0->m_pkthdr.rcvif = ifp;
622 m0->m_pkthdr.len = totlen;
623 len = MHLEN;
624 m = m0;
625
626 bus_space_write_1(iot, ioh, EL_GPBL, 0);
627 bus_space_write_1(iot, ioh, EL_GPBH, 0);
628
629 while (totlen > 0) {
630 if (totlen >= MINCLSIZE) {
631 MCLGET(m, M_DONTWAIT);
632 if ((m->m_flags & M_EXT) == 0)
633 goto bad;
634 len = MCLBYTES;
635 }
636
637 m->m_len = len = min(totlen, len);
638 bus_space_read_multi_1(iot, ioh, EL_BUF, mtod(m, u_int8_t *), len);
639
640 totlen -= len;
641 if (totlen > 0) {
642 MGET(newm, M_DONTWAIT, MT_DATA);
643 if (newm == 0)
644 goto bad;
645 len = MLEN;
646 m = m->m_next = newm;
647 }
648 }
649
650 bus_space_write_1(iot, ioh, EL_RBC, 0);
651 bus_space_write_1(iot, ioh, EL_AC, EL_AC_RX);
652
653 return (m0);
654
655 bad:
656 m_freem(m0);
657 return (0);
658 }
659
660 /*
661 * Process an ioctl request. This code needs some work - it looks pretty ugly.
662 */
663 int
664 elioctl(struct ifnet *ifp, u_long cmd, void *data)
665 {
666 struct el_softc *sc = ifp->if_softc;
667 struct ifaddr *ifa = (struct ifaddr *)data;
668 int s, error = 0;
669
670 s = splnet();
671
672 switch (cmd) {
673
674 case SIOCINITIFADDR:
675 ifp->if_flags |= IFF_UP;
676
677 elinit(sc);
678 switch (ifa->ifa_addr->sa_family) {
679 #ifdef INET
680 case AF_INET:
681 arp_ifinit(ifp, ifa);
682 break;
683 #endif
684 default:
685 break;
686 }
687 break;
688
689 case SIOCSIFFLAGS:
690 if ((error = ifioctl_common(ifp, cmd, data)) != 0)
691 break;
692 /* XXX re-use ether_ioctl() */
693 switch (ifp->if_flags & (IFF_UP|IFF_RUNNING)) {
694 case IFF_RUNNING:
695 /*
696 * If interface is marked down and it is running, then
697 * stop it.
698 */
699 elstop(sc);
700 ifp->if_flags &= ~IFF_RUNNING;
701 break;
702 case IFF_UP:
703 /*
704 * If interface is marked up and it is stopped, then
705 * start it.
706 */
707 elinit(sc);
708 break;
709 default:
710 /*
711 * Some other important flag might have changed, so
712 * reset.
713 */
714 elreset(sc);
715 break;
716 }
717 break;
718
719 default:
720 error = ether_ioctl(ifp, cmd, data);
721 break;
722 }
723
724 splx(s);
725 return error;
726 }
727
728 /*
729 * Device timeout routine.
730 */
731 void
732 elwatchdog(struct ifnet *ifp)
733 {
734 struct el_softc *sc = ifp->if_softc;
735
736 log(LOG_ERR, "%s: device timeout\n", device_xname(&sc->sc_dev));
737 sc->sc_ethercom.ec_if.if_oerrors++;
738
739 elreset(sc);
740 }
741