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<!-- Copyright (C) 2003 Red Hat, Inc.                                -->
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>Review of the functions</TITLE
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TITLE="Generic Ethernet Device Driver"
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TITLE="Generic Ethernet Device Driver"
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TITLE="Upper Layer Functions"
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><BODY
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SUMMARY="Header navigation table"
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><TR
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><TH
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COLSPAN="3"
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ALIGN="center"
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>eCos Reference Manual</TH
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></TR
51 
><TR
52 
><TD
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WIDTH="10%"
54 
ALIGN="left"
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VALIGN="bottom"
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><A
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HREF="io-eth-drv-generic1.html"
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ACCESSKEY="P"
59 
>Prev</A
60 
></TD
61 
><TD
62 
WIDTH="80%"
63 
ALIGN="center"
64 
VALIGN="bottom"
65 
>Chapter 46. Generic Ethernet Device Driver</TD
66 
><TD
67 
WIDTH="10%"
68 
ALIGN="right"
69 
VALIGN="bottom"
70 
><A
71 
HREF="io-eth-drv-upper-api.html"
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ACCESSKEY="N"
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>Next</A
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></TD
75 
></TR
76 
></TABLE
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><HR
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ALIGN="LEFT"
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WIDTH="100%"></DIV
80 
><DIV
81 
CLASS="SECT1"
82 
><H1
83 
CLASS="SECT1"
84 
><A
85 
NAME="IO-ETH-DRV-API-FUNCS">Review of the functions</H1
86 
><P
87 
>Now a brief review of the functions.  This discussion will use generic
88 
names for the functions &#8212; your driver should use hardware-specific
89 
names to maintain uniqueness against any other drivers.</P
90 
><DIV
91 
CLASS="SECT2"
92 
><H2
93 
CLASS="SECT2"
94 
><A
95 
NAME="IO-ETH-DRV-API-INIT">Init function</H2
96 
><P
97 
><TABLE
98 
BORDER="5"
99 
BGCOLOR="#E0E0F0"
100 
WIDTH="70%"
101 
><TR
102 
><TD
103 
><PRE
104 
CLASS="PROGRAMLISTING"
105 
>static bool <TT
106 
CLASS="REPLACEABLE"
107 
><I
108 
>DRV_HDWR</I
109 
></TT
110 
>_init(struct cyg_netdevtab_entry *tab)</PRE
111 
></TD
112 
></TR
113 
></TABLE
114 
>
115 
This function is called as part of system initialization.  Its primary
116 
function is to decide if the hardware (as indicated via
117 
<SPAN
118 
CLASS="TYPE"
119 
>tab-&gt;device_instance</SPAN
120 
>)
121 
is working and if the interface needs to be made
122 
available in the system.  If this is the case, this function needs to
123 
finish with a call to the ethernet driver function:
124 
<TABLE
125 
BORDER="5"
126 
BGCOLOR="#E0E0F0"
127 
WIDTH="70%"
128 
><TR
129 
><TD
130 
><PRE
131 
CLASS="PROGRAMLISTING"
132 
>    struct eth_drv_sc *sc = (struct eth_drv_sc *)tab-&#62;device_instance;
133 
    <TT
134 
CLASS="REPLACEABLE"
135 
><I
136 
>....initialization code....</I
137 
></TT
138 
>
139 
    // Initialize upper level driver
140 
    (sc-&gt;funs-&gt;eth_drv-&gt;init)( sc, unsigned char *enaddr );</PRE
141 
></TD
142 
></TR
143 
></TABLE
144 
>
145 
where <TT
146 
CLASS="PARAMETER"
147 
><I
148 
>enaddr</I
149 
></TT
150 
>
151 
is a pointer to the ethernet station address for this unit, to inform
152 
the stack of this device's readiness and availability.</P
153 
><DIV
154 
CLASS="NOTE"
155 
><BLOCKQUOTE
156 
CLASS="NOTE"
157 
><P
158 
><B
159 
>Note: </B
160 
>The ethernet station address
161 
(<SPAN
162 
CLASS="ACRONYM"
163 
>ESA</SPAN
164 
>)
165 
is supposed to be a
166 
world-unique, 48 bit address for this particular ethernet interface.
167 
Typically it is provided by the board/hardware manufacturer in ROM.</P
168 
><P
169 
>In many packages it is possible for the
170 
<SPAN
171 
CLASS="ACRONYM"
172 
>ESA</SPAN
173 
>
174 
to be set from RedBoot,
175 
(perhaps from 'fconfig' data), hard-coded from
176 
<SPAN
177 
CLASS="ACRONYM"
178 
>CDL</SPAN
179 
>, or from an <SPAN
180 
CLASS="ACRONYM"
181 
>EPROM</SPAN
182 
>.
183 
A driver should choose a run-time specified
184 
<SPAN
185 
CLASS="ACRONYM"
186 
>ESA</SPAN
187 
>
188 
(e.g. from RedBoot)
189 
preferentially, otherwise (in order) it should use a <SPAN
190 
CLASS="ACRONYM"
191 
>CDL</SPAN
192 
> specified
193 
<SPAN
194 
CLASS="ACRONYM"
195 
>ESA</SPAN
196 
>
197 
if one has been set, otherwise an <SPAN
198 
CLASS="ACRONYM"
199 
>EPROM</SPAN
200 
> set
201 
<SPAN
202 
CLASS="ACRONYM"
203 
>ESA</SPAN
204 
>, or otherwise
205 
fail. See the <TT
206 
CLASS="FILENAME"
207 
>cl/cs8900a</TT
208 
>
209 
ethernet driver for an example.</P
210 
></BLOCKQUOTE
211 
></DIV
212 
></DIV
213 
><DIV
214 
CLASS="SECT2"
215 
><H2
216 
CLASS="SECT2"
217 
><A
218 
NAME="IO-ETH-DRV-API-START">Start function</H2
219 
><P
220 
><TABLE
221 
BORDER="5"
222 
BGCOLOR="#E0E0F0"
223 
WIDTH="70%"
224 
><TR
225 
><TD
226 
><PRE
227 
CLASS="PROGRAMLISTING"
228 
>static void
229 
<TT
230 
CLASS="REPLACEABLE"
231 
><I
232 
>HRDWR</I
233 
></TT
234 
>_start(struct eth_drv_sc *sc, unsigned char *enaddr, int flags)</PRE
235 
></TD
236 
></TR
237 
></TABLE
238 
>
239 
This function is called, perhaps much later than system initialization
240 
time, when the system (an application) is ready for the interface to
241 
become active.  The purpose of this function is to set up the hardware
242 
interface to start accepting packets from the network and be able to
243 
send packets out.  The receiver hardware should not be enabled prior to
244 
this call.</P
245 
><DIV
246 
CLASS="NOTE"
247 
><BLOCKQUOTE
248 
CLASS="NOTE"
249 
><P
250 
><B
251 
>Note: </B
252 
>This function will be called whenever the
253 
up/down state of the logical interface changes, e.g. when the IP address
254 
changes, or when promiscuous mode is selected by means of an
255 
<TT
256 
CLASS="FUNCTION"
257 
>ioctl()</TT
258 
> call in the application.
259 
This may occur more than once, so this function needs to
260 
be prepared for that case.</P
261 
></BLOCKQUOTE
262 
></DIV
263 
><DIV
264 
CLASS="NOTE"
265 
><BLOCKQUOTE
266 
CLASS="NOTE"
267 
><P
268 
><B
269 
>Note: </B
270 
>In future, the <TT
271 
CLASS="PARAMETER"
272 
><I
273 
>flags</I
274 
></TT
275 
>
276 
field (currently unused) may be used to tell the
277 
function how to start up, e.g. whether interrupts will be used,
278 
alternate means of selecting promiscuous mode etc.</P
279 
></BLOCKQUOTE
280 
></DIV
281 
></DIV
282 
><DIV
283 
CLASS="SECT2"
284 
><H2
285 
CLASS="SECT2"
286 
><A
287 
NAME="IO-ETH-DRV-API-STOP">Stop function</H2
288 
><P
289 
><TABLE
290 
BORDER="5"
291 
BGCOLOR="#E0E0F0"
292 
WIDTH="70%"
293 
><TR
294 
><TD
295 
><PRE
296 
CLASS="PROGRAMLISTING"
297 
>static void <TT
298 
CLASS="REPLACEABLE"
299 
><I
300 
>HRDWR</I
301 
></TT
302 
>_stop(struct eth_drv_sc *sc)</PRE
303 
></TD
304 
></TR
305 
></TABLE
306 
>
307 
This function is the inverse of &#8220;start.&#8221;
308 
It should shut down the hardware, disable the receiver, and keep it from
309 
interacting with the physical network.</P
310 
></DIV
311 
><DIV
312 
CLASS="SECT2"
313 
><H2
314 
CLASS="SECT2"
315 
><A
316 
NAME="IO-ETH-DRV-API-CONTROL">Control function</H2
317 
><P
318 
><TABLE
319 
BORDER="5"
320 
BGCOLOR="#E0E0F0"
321 
WIDTH="70%"
322 
><TR
323 
><TD
324 
><PRE
325 
CLASS="PROGRAMLISTING"
326 
>static int
327 
<TT
328 
CLASS="REPLACEABLE"
329 
><I
330 
>HRDWR</I
331 
></TT
332 
>_control(
333 
        struct eth_drv_sc *sc, unsigned long key,
334 
        void *data, int len)</PRE
335 
></TD
336 
></TR
337 
></TABLE
338 
>
339 
This function is used to perform low-level &#8220;control&#8221;
340 
operations on the
341 
interface.  These operations would typically be initiated via
342 
<TT
343 
CLASS="FUNCTION"
344 
>ioctl()</TT
345 
> calls in the BSD
346 
stack, and would be anything that might require the hardware setup to
347 
change (i.e. cannot be performed totally by the
348 
platform-independent layers).</P
349 
><P
350 
>The <TT
351 
CLASS="PARAMETER"
352 
><I
353 
>key</I
354 
></TT
355 
> parameter selects the operation, and the
356 
<TT
357 
CLASS="PARAMETER"
358 
><I
359 
>data</I
360 
></TT
361 
> and <TT
362 
CLASS="PARAMETER"
363 
><I
364 
>len</I
365 
></TT
366 
> params point describe,
367 
as required, some data for the operation in question.</P
368 
><P
369 
></P
370 
><DIV
371 
CLASS="VARIABLELIST"
372 
><P
373 
><B
374 
>Available Operations:</B
375 
></P
376 
><DL
377 
><DT
378 
>ETH_DRV_SET_MAC_ADDRESS</DT
379 
><DD
380 
><P
381 
>This operation sets the ethernet station address (ESA or MAC) for the
382 
device.  Normally this address is kept in non-volatile memory and is
383 
unique in the world.  This function must at least set the interface to
384 
use the new address.  It may also update the NVM as appropriate.</P
385 
></DD
386 
><DT
387 
>ETH_DRV_GET_IF_STATS_UD, ETH_DRV_GET_IF_STATS</DT
388 
><DD
389 
><P
390 
>These acquire a set of statistical counters from the interface, and write
391 
the information into the memory pointed to by <TT
392 
CLASS="PARAMETER"
393 
><I
394 
>data</I
395 
></TT
396 
>.
397 
The &#8220;UD&#8221; variant explicitly instructs the driver to acquire
398 
up-to-date values.  This is a separate option because doing so may take
399 
some time, depending on the hardware.</P
400 
><P
401 
>The definition of the data structure is in
402 
<TT
403 
CLASS="FILENAME"
404 
>cyg/io/eth/eth_drv_stats.h</TT
405 
>.</P
406 
><P
407 
>This call is typically made by SNMP, see <A
408 
HREF="net-snmp-ecos-port.html"
409 
>Chapter 47</A
410 
>.</P
411 
></DD
412 
><DT
413 
>ETH_DRV_SET_MC_LIST</DT
414 
><DD
415 
><P
416 
>This entry instructs the device to set up multicast packet filtering
417 
to receive only packets addressed to the multicast ESAs in the list pointed
418 
to by <TT
419 
CLASS="PARAMETER"
420 
><I
421 
>data</I
422 
></TT
423 
>.</P
424 
><P
425 
>The format of the data is a 32-bit count of the ESAs in the list, followed
426 
by packed bytes which are the ESAs themselves, thus:
427 
<TABLE
428 
BORDER="5"
429 
BGCOLOR="#E0E0F0"
430 
WIDTH="70%"
431 
><TR
432 
><TD
433 
><PRE
434 
CLASS="PROGRAMLISTING"
435 
>#define ETH_DRV_MAX_MC 8
436 
struct eth_drv_mc_list {
437 
    int len;
438 
    unsigned char addrs[ETH_DRV_MAX_MC][ETHER_ADDR_LEN];
439 
};</PRE
440 
></TD
441 
></TR
442 
></TABLE
443 
></P
444 
></DD
445 
><DT
446 
>ETH_DRV_SET_MC_ALL</DT
447 
><DD
448 
><P
449 
>This entry instructs the device to receive all multicast packets, and
450 
delete any explicit filtering which had been set up.</P
451 
></DD
452 
></DL
453 
></DIV
454 
><P
455 
>This function should return zero if the specified operation was
456 
completed successfully.  It should return non-zero if the operation
457 
could not be performed, for any reason.</P
458 
></DIV
459 
><DIV
460 
CLASS="SECT2"
461 
><H2
462 
CLASS="SECT2"
463 
><A
464 
NAME="IO-ETH-DRV-API-CAN-SEND">Can-send function</H2
465 
><P
466 
><TABLE
467 
BORDER="5"
468 
BGCOLOR="#E0E0F0"
469 
WIDTH="70%"
470 
><TR
471 
><TD
472 
><PRE
473 
CLASS="PROGRAMLISTING"
474 
>static int <TT
475 
CLASS="REPLACEABLE"
476 
><I
477 
>HRDWR</I
478 
></TT
479 
>_can_send(struct eth_drv_sc *sc)</PRE
480 
></TD
481 
></TR
482 
></TABLE
483 
>
484 
This function is called to determine if it is possible to start the
485 
transmission of a packet on the interface.  Some interfaces will allow
486 
multiple packets to be "queued" and this function allows for the highest
487 
possible utilization of that mode.</P
488 
><P
489 
>Return the number of packets which could be accepted at this time, zero
490 
implies that the interface is saturated/busy.</P
491 
></DIV
492 
><DIV
493 
CLASS="SECT2"
494 
><H2
495 
CLASS="SECT2"
496 
><A
497 
NAME="IO-ETH-DRV-API-SEND">Send function</H2
498 
><P
499 
><TABLE
500 
BORDER="5"
501 
BGCOLOR="#E0E0F0"
502 
WIDTH="70%"
503 
><TR
504 
><TD
505 
><PRE
506 
CLASS="PROGRAMLISTING"
507 
>struct eth_drv_sg {
508 
    CYG_ADDRESS  buf;
509 
    CYG_ADDRWORD len;
510 
};
511 
 
512 
static void
513 
<TT
514 
CLASS="REPLACEABLE"
515 
><I
516 
>HRDWR</I
517 
></TT
518 
>_send(
519 
        struct eth_drv_sc *sc,
520 
        struct eth_drv_sg *sg_list, int sg_len,
521 
        int total_len, unsigned long key)</PRE
522 
></TD
523 
></TR
524 
></TABLE
525 
>
526 
This function is used to send a packet of data to the network.  It is
527 
the responsibility of this function to somehow hand the data over to the
528 
hardware interface.  This will most likely require copying, but just the
529 
address/length values could be used by smart hardware.</P
530 
><DIV
531 
CLASS="NOTE"
532 
><BLOCKQUOTE
533 
CLASS="NOTE"
534 
><P
535 
><B
536 
>Note: </B
537 
>All data in/out of the driver is specified via a
538 
&#8220;scatter-gather&#8221;
539 
list.  This is just an array of address/length pairs which describe
540 
sections of data to move (in the order given by the array), as in the
541 
<SPAN
542 
CLASS="TYPE"
543 
>struct eth_drv_sg</SPAN
544 
> defined above and pointed to by
545 
<TT
546 
CLASS="PARAMETER"
547 
><I
548 
>sg_list</I
549 
></TT
550 
>.</P
551 
></BLOCKQUOTE
552 
></DIV
553 
><P
554 
>Once the data has been successfully sent by the interface (or if an
555 
error occurs), the driver should call
556 
<TT
557 
CLASS="FUNCTION"
558 
>(sc-&#62;funs-&#62;eth_drv-&#62;tx_done)()</TT
559 
>
560 
(see <A
561 
HREF="io-eth-drv-upper-api.html#IO-ETH-DRV-TX-DONE"
562 
>the Section called <I
563 
>Callback Tx-Done function</I
564 
></A
565 
>)
566 
using the specified <TT
567 
CLASS="PARAMETER"
568 
><I
569 
>key</I
570 
></TT
571 
>.
572 
Only then will the upper layers release the resources
573 
for that packet and start another transmission.</P
574 
><DIV
575 
CLASS="NOTE"
576 
><BLOCKQUOTE
577 
CLASS="NOTE"
578 
><P
579 
><B
580 
>Note: </B
581 
>In future, this function may be extended so that the data need not be
582 
copied by having the function return a &#8220;disposition&#8221; code
583 
(done, send pending, etc).  At this point, you should move the data to some
584 
&#8220;safe&#8221; location before returning.</P
585 
></BLOCKQUOTE
586 
></DIV
587 
></DIV
588 
><DIV
589 
CLASS="SECT2"
590 
><H2
591 
CLASS="SECT2"
592 
><A
593 
NAME="IO-ETH-DRV-API-DELIVER">Deliver function</H2
594 
><P
595 
><TABLE
596 
BORDER="5"
597 
BGCOLOR="#E0E0F0"
598 
WIDTH="70%"
599 
><TR
600 
><TD
601 
><PRE
602 
CLASS="PROGRAMLISTING"
603 
>static void
604 
<TT
605 
CLASS="REPLACEABLE"
606 
><I
607 
>HRDWR</I
608 
></TT
609 
>_deliver(struct eth_drv_sc *sc)</PRE
610 
></TD
611 
></TR
612 
></TABLE
613 
>
614 
This function is called from the &#8220;Network Delivery Thread&#8221; in
615 
order to let the device driver do the time-consuming work associated with
616 
receiving a packet &#8212; usually copying the entire packet from the
617 
hardware or a special memory location into the network stack's memory.</P
618 
><P
619 
>After handling any outstanding incoming packets or pending transmission
620 
status, it can unmask the device's interrupts, and free any relevant
621 
resources so it can process further packets.</P
622 
><P
623 
>It will be called when the interrupt handler for the network device
624 
has called
625 
<TABLE
626 
BORDER="5"
627 
BGCOLOR="#E0E0F0"
628 
WIDTH="70%"
629 
><TR
630 
><TD
631 
><PRE
632 
CLASS="PROGRAMLISTING"
633 
>    eth_drv_dsr( vector, count, (cyg_addrword_t)sc );</PRE
634 
></TD
635 
></TR
636 
></TABLE
637 
>
638 
to alert the system that &#8220;something requires attention.&#8221;
639 
This <TT
640 
CLASS="FUNCTION"
641 
>eth_drv_dsr()</TT
642 
> call must occur from within the
643 
interrupt handler's DSR (not the ISR) or actually <SPAN
644 
CLASS="emphasis"
645 
><I
646 
CLASS="EMPHASIS"
647 
>be</I
648 
></SPAN
649 
>
650 
the DSR, whenever it is determined that
651 
the device needs attention from the foreground.  The third parameter
652 
(<TT
653 
CLASS="PARAMETER"
654 
><I
655 
>data</I
656 
></TT
657 
> in the prototype of
658 
<TT
659 
CLASS="FUNCTION"
660 
>eth_drv_dsr()</TT
661 
> <SPAN
662 
CLASS="emphasis"
663 
><I
664 
CLASS="EMPHASIS"
665 
>must</I
666 
></SPAN
667 
>
668 
be a valid <SPAN
669 
CLASS="TYPE"
670 
>struct eth_drv_sc</SPAN
671 
> pointer <TT
672 
CLASS="VARNAME"
673 
>sc</TT
674 
>.</P
675 
><P
676 
>The reason for this slightly convoluted train of events is to keep the DSR
677 
(and ISR) execution time as short as possible, so that other activities of
678 
higher priority than network servicing are not denied the CPU by network
679 
traffic.</P
680 
><P
681 
>To deliver a newly-received packet into the network stack, the deliver
682 
routine must call
683 
<TABLE
684 
BORDER="5"
685 
BGCOLOR="#E0E0F0"
686 
WIDTH="70%"
687 
><TR
688 
><TD
689 
><PRE
690 
CLASS="PROGRAMLISTING"
691 
>(sc-&#62;funs-&#62;eth_drv-&#62;recv)(sc, len);</PRE
692 
></TD
693 
></TR
694 
></TABLE
695 
>
696 
which will in turn call the receive function, which we talk about next.
697 
See also <A
698 
HREF="io-eth-drv-upper-api.html#IO-ETH-DRV-UPPER-RECV"
699 
>the Section called <I
700 
>Callback Receive function</I
701 
></A
702 
> below.</P
703 
></DIV
704 
><DIV
705 
CLASS="SECT2"
706 
><H2
707 
CLASS="SECT2"
708 
><A
709 
NAME="IO-ETH-DRV-API-RECV">Receive function</H2
710 
><P
711 
><TABLE
712 
BORDER="5"
713 
BGCOLOR="#E0E0F0"
714 
WIDTH="70%"
715 
><TR
716 
><TD
717 
><PRE
718 
CLASS="PROGRAMLISTING"
719 
>static void
720 
<TT
721 
CLASS="REPLACEABLE"
722 
><I
723 
>HRDWR</I
724 
></TT
725 
>_recv(
726 
        struct eth_drv_sc *sc,
727 
        struct eth_drv_sg *sg_list, int sg_len)</PRE
728 
></TD
729 
></TR
730 
></TABLE
731 
>
732 
This function is a call back, only invoked after the
733 
upper-level function
734 
<TABLE
735 
BORDER="5"
736 
BGCOLOR="#E0E0F0"
737 
WIDTH="70%"
738 
><TR
739 
><TD
740 
><PRE
741 
CLASS="PROGRAMLISTING"
742 
>(sc-&#62;funs-&#62;eth_drv-&#62;recv)(struct eth_drv_sc *sc, int total_len)</PRE
743 
></TD
744 
></TR
745 
></TABLE
746 
>
747 
has been called itself from your deliver function when it knows that a
748 
packet of data is available on the
749 
interface.  The <TT
750 
CLASS="FUNCTION"
751 
>(sc-&#62;funs-&#62;eth_drv-&#62;recv)()</TT
752 
>
753 
function then arranges network buffers
754 
and structures for the data and then calls
755 
<TT
756 
CLASS="FUNCTION"
757 
><TT
758 
CLASS="REPLACEABLE"
759 
><I
760 
>HRDWR</I
761 
></TT
762 
>_recv()</TT
763 
> to actually
764 
move the data from the interface.</P
765 
><P
766 
>A scatter-gather list (<SPAN
767 
CLASS="TYPE"
768 
>struct eth_drv_sg</SPAN
769 
>) is used once more,
770 
just like in the send case.</P
771 
></DIV
772 
><DIV
773 
CLASS="SECT2"
774 
><H2
775 
CLASS="SECT2"
776 
><A
777 
NAME="IO-ETH-DRV-API-POLL">Poll function</H2
778 
><P
779 
><TABLE
780 
BORDER="5"
781 
BGCOLOR="#E0E0F0"
782 
WIDTH="70%"
783 
><TR
784 
><TD
785 
><PRE
786 
CLASS="PROGRAMLISTING"
787 
>static void
788 
<TT
789 
CLASS="REPLACEABLE"
790 
><I
791 
>HRDWR</I
792 
></TT
793 
>_poll(struct eth_drv_sc *sc)</PRE
794 
></TD
795 
></TR
796 
></TABLE
797 
>
798 
This function is used when in a non-interrupt driven system, e.g. when
799 
interrupts are completely disabled. This allows the driver time to check
800 
whether anything needs doing either for transmission, or to check if
801 
anything has been received, or if any other processing needs doing.</P
802 
><P
803 
>It is perfectly correct and acceptable for the poll function to look like
804 
this:
805 
<TABLE
806 
BORDER="5"
807 
BGCOLOR="#E0E0F0"
808 
WIDTH="70%"
809 
><TR
810 
><TD
811 
><PRE
812 
CLASS="PROGRAMLISTING"
813 
>static void
814 
<TT
815 
CLASS="REPLACEABLE"
816 
><I
817 
>HRDWR</I
818 
></TT
819 
>_poll(struct eth_drv_sc *sc)
820 
{
821 
   <TT
822 
CLASS="REPLACEABLE"
823 
><I
824 
>my_interrupt_ISR</I
825 
></TT
826 
>(sc);
827 
   <TT
828 
CLASS="REPLACEABLE"
829 
><I
830 
>HRDWR</I
831 
></TT
832 
>_deliver(struct eth_drv_sc *sc);
833 
}</PRE
834 
></TD
835 
></TR
836 
></TABLE
837 
>
838 
provided that both the ISR and the deliver functions are idempotent and
839 
harmless if called when there is no attention needed by the hardware.  Some
840 
devices might not need a call to the ISR here if the deliver function
841 
contains all the &#8220;intelligence.&#8221;</P
842 
></DIV
843 
><DIV
844 
CLASS="SECT2"
845 
><H2
846 
CLASS="SECT2"
847 
><A
848 
NAME="IO-ETH-DRV-API-INT-VECTOR">Interrupt-vector function</H2
849 
><P
850 
><TABLE
851 
BORDER="5"
852 
BGCOLOR="#E0E0F0"
853 
WIDTH="70%"
854 
><TR
855 
><TD
856 
><PRE
857 
CLASS="PROGRAMLISTING"
858 
>static int
859 
<TT
860 
CLASS="REPLACEABLE"
861 
><I
862 
>HRDWR</I
863 
></TT
864 
>_int_vector(struct eth_drv_sc *sc)</PRE
865 
></TD
866 
></TR
867 
></TABLE
868 
>
869 
This function returns the interrupt vector number used for receive
870 
interrupts.
871 
This is so that the common GDB stubs can detect when to check
872 
for incoming &#8220;CTRL-C&#8221; packets (used to asynchronously
873 
halt the application) when debugging over ethernet.
874 
The GDB stubs need to know which interrupt the ethernet device uses
875 
so that they can mask or unmask that interrupt as required.</P
876 
></DIV
877 
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892 
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893 
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894 
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895 
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896 
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