OpenCores
URL https://opencores.org/ocsvn/openrisc/openrisc/trunk

Subversion Repositories openrisc

[/] [openrisc/] [trunk/] [rtos/] [ecos-2.0/] [doc/] [html/] [ref/] [io-eth-call-graph.html] - Blame information for rev 174

Details | Compare with Previous | View Log

Line No. Rev Author Line
1 28 unneback 
<!-- Copyright (C) 2003 Red Hat, Inc.                                -->
2 
<!-- This material may be distributed only subject to the terms      -->
3 
<!-- and conditions set forth in the Open Publication License, v1.0  -->
4 
<!-- or later (the latest version is presently available at          -->
5 
<!-- http://www.opencontent.org/openpub/).                           -->
6 
<!-- Distribution of the work or derivative of the work in any       -->
7 
<!-- standard (paper) book form is prohibited unless prior           -->
8 
<!-- permission is obtained from the copyright holder.               -->
9 
<HTML
10 
><HEAD
11 
><TITLE
12 
>Calling graph for Transmission and Reception</TITLE
13 
><meta name="MSSmartTagsPreventParsing" content="TRUE">
14 
<META
15 
NAME="GENERATOR"
16 
CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
17 
"><LINK
18 
REL="HOME"
19 
TITLE="eCos Reference Manual"
20 
HREF="ecos-ref.html"><LINK
21 
REL="UP"
22 
TITLE="Generic Ethernet Device Driver"
23 
HREF="io-eth-drv-generic1.html"><LINK
24 
REL="PREVIOUS"
25 
TITLE="Upper Layer Functions"
26 
HREF="io-eth-drv-upper-api.html"><LINK
27 
REL="NEXT"
28 
TITLE="SNMP"
29 
HREF="net-snmp.html"></HEAD
30 
><BODY
31 
CLASS="SECT1"
32 
BGCOLOR="#FFFFFF"
33 
TEXT="#000000"
34 
LINK="#0000FF"
35 
VLINK="#840084"
36 
ALINK="#0000FF"
37 
><DIV
38 
CLASS="NAVHEADER"
39 
><TABLE
40 
SUMMARY="Header navigation table"
41 
WIDTH="100%"
42 
BORDER="0"
43 
CELLPADDING="0"
44 
CELLSPACING="0"
45 
><TR
46 
><TH
47 
COLSPAN="3"
48 
ALIGN="center"
49 
>eCos Reference Manual</TH
50 
></TR
51 
><TR
52 
><TD
53 
WIDTH="10%"
54 
ALIGN="left"
55 
VALIGN="bottom"
56 
><A
57 
HREF="io-eth-drv-upper-api.html"
58 
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="net-snmp.html"
72 
ACCESSKEY="N"
73 
>Next</A
74 
></TD
75 
></TR
76 
></TABLE
77 
><HR
78 
ALIGN="LEFT"
79 
WIDTH="100%"></DIV
80 
><DIV
81 
CLASS="SECT1"
82 
><H1
83 
CLASS="SECT1"
84 
><A
85 
NAME="IO-ETH-CALL-GRAPH">Calling graph for Transmission and Reception</H1
86 
><P
87 
>It may be worth clarifying further the flow of control in the transmit and
88 
receive cases, where the hardware driver does use interrupts and so DSRs to
89 
tell the &#8220;foreground&#8221; when something asynchronous has occurred.</P
90 
><DIV
91 
CLASS="SECT2"
92 
><H2
93 
CLASS="SECT2"
94 
><A
95 
NAME="IO-ETH-CALL-GRAPH-TX">Transmission</H2
96 
><P
97 
></P
98 
><OL
99 
TYPE="1"
100 
><LI
101 
><P
102 
>Some foreground task such as the application, SNMP &#8220;daemon&#8221;,
103 
DHCP management thread or whatever, calls into network stack to send a
104 
packet, or the stack decides to send a packet in response to incoming
105 
traffic such as a &#8220;ping&#8221; or <SPAN
106 
CLASS="ACRONYM"
107 
>ARP</SPAN
108 
> request.</P
109 
></LI
110 
><LI
111 
><P
112 
>The driver calls the
113 
<TT
114 
CLASS="FUNCTION"
115 
><TT
116 
CLASS="REPLACEABLE"
117 
><I
118 
>HRDWR</I
119 
></TT
120 
>_can_send()</TT
121 
>
122 
function in the hardware driver.</P
123 
></LI
124 
><LI
125 
><P
126 
><TT
127 
CLASS="FUNCTION"
128 
><TT
129 
CLASS="REPLACEABLE"
130 
><I
131 
>HRDWR</I
132 
></TT
133 
>_can_send()</TT
134 
>
135 
returns the number of available "slots" in which it
136 
can store a pending transmit packet.
137 
If it cannot send at this time, the packet is queued outside the
138 
hardware driver for later; in this case, the hardware is already busy
139 
transmitting, so expect an interrupt as described below for completion
140 
of the packet currently outgoing.</P
141 
></LI
142 
><LI
143 
><P
144 
>If it can send right now, <TT
145 
CLASS="REPLACEABLE"
146 
><I
147 
>HRDWR</I
148 
></TT
149 
>_send() is called.
150 
<TT
151 
CLASS="FUNCTION"
152 
><TT
153 
CLASS="REPLACEABLE"
154 
><I
155 
>HRDWR</I
156 
></TT
157 
>_send()</TT
158 
> copies the
159 
data into special hardware buffers, or instructs the hardware to
160 
&#8220;send that.&#8221; It also remembers the key that is associated with
161 
this tx request.</P
162 
></LI
163 
><LI
164 
><P
165 
>These calls return &#8230; time passes &#8230;</P
166 
></LI
167 
><LI
168 
><P
169 
>Asynchronously, the hardware makes an interrupt to say
170 
&#8220;transmit is done.&#8221;
171 
The ISR quietens the interrupt source in the hardware and
172 
requests that the associated DSR be run.</P
173 
></LI
174 
><LI
175 
><P
176 
>The DSR calls (or <SPAN
177 
CLASS="emphasis"
178 
><I
179 
CLASS="EMPHASIS"
180 
>is</I
181 
></SPAN
182 
>) the
183 
<TT
184 
CLASS="FUNCTION"
185 
>eth_drv_dsr()</TT
186 
> function in the generic driver.</P
187 
></LI
188 
><LI
189 
><P
190 
><TT
191 
CLASS="FUNCTION"
192 
>eth_drv_dsr()</TT
193 
> in the generic driver awakens the
194 
&#8220;Network Delivery Thread&#8221; which calls the deliver function
195 
<TT
196 
CLASS="REPLACEABLE"
197 
><I
198 
>HRDWR</I
199 
></TT
200 
>_deliver() in the driver.</P
201 
></LI
202 
><LI
203 
><P
204 
>The deliver function realizes that a transmit request has completed,
205 
and calls the callback tx-done function
206 
<TT
207 
CLASS="FUNCTION"
208 
>(sc-&#62;funs-&#62;eth_drv-&#62;tx_done)()</TT
209 
>
210 
with the same key that it remembered for this tx.</P
211 
></LI
212 
><LI
213 
><P
214 
>The callback tx-done function
215 
uses the key to find the resources associated with
216 
this transmit request; thus the stack knows that the transmit has
217 
completed and its resources can be freed.</P
218 
></LI
219 
><LI
220 
><P
221 
>The callback tx-done function
222 
also enquires whether <TT
223 
CLASS="REPLACEABLE"
224 
><I
225 
>HRDWR</I
226 
></TT
227 
>_can_send() now says
228 
&#8220;yes, we can send&#8221;
229 
and if so, dequeues a further transmit request
230 
which may have been queued as described above.  If so, then
231 
<TT
232 
CLASS="REPLACEABLE"
233 
><I
234 
>HRDWR</I
235 
></TT
236 
>_send() copies the data into the hardware buffers, or
237 
instructs the hardware to "send that" and remembers the new key, as above.
238 
These calls then all return to the &#8220;Network Delivery Thread&#8221;
239 
which then sleeps, awaiting the next asynchronous event.</P
240 
></LI
241 
><LI
242 
><P
243 
>All done &#8230;</P
244 
></LI
245 
></OL
246 
></DIV
247 
><DIV
248 
CLASS="SECT2"
249 
><H2
250 
CLASS="SECT2"
251 
><A
252 
NAME="IO-ETH-CALL-GRAPH-RX">Receive</H2
253 
><P
254 
></P
255 
><OL
256 
TYPE="1"
257 
><LI
258 
><P
259 
>Asynchronously, the hardware makes an interrupt to say
260 
&#8220;there is ready data in a receive buffer.&#8221;
261 
The ISR quietens the interrupt source in the hardware and
262 
requests that the associated DSR be run.</P
263 
></LI
264 
><LI
265 
><P
266 
>The DSR calls (or <SPAN
267 
CLASS="emphasis"
268 
><I
269 
CLASS="EMPHASIS"
270 
>is</I
271 
></SPAN
272 
>) the
273 
<TT
274 
CLASS="FUNCTION"
275 
>eth_drv_dsr()</TT
276 
> function in the generic driver.</P
277 
></LI
278 
><LI
279 
><P
280 
><TT
281 
CLASS="FUNCTION"
282 
>eth_drv_dsr()</TT
283 
> in the generic driver awakens the
284 
&#8220;Network Delivery Thread&#8221; which calls the deliver function
285 
<TT
286 
CLASS="REPLACEABLE"
287 
><I
288 
>HRDWR</I
289 
></TT
290 
>_deliver() in the driver.</P
291 
></LI
292 
><LI
293 
><P
294 
>The deliver function realizes that there is data ready and calls
295 
the callback receive function
296 
<TT
297 
CLASS="FUNCTION"
298 
>(sc-&#62;funs-&#62;eth_drv-&#62;recv)()</TT
299 
>
300 
to tell it how many bytes to prepare for.</P
301 
></LI
302 
><LI
303 
><P
304 
>The callback receive function allocates memory within the stack
305 
(eg. <SPAN
306 
CLASS="TYPE"
307 
>MBUFs</SPAN
308 
> in BSD/Unix style stacks) and prepares
309 
a set of scatter-gather buffers that can
310 
accommodate the packet.</P
311 
></LI
312 
><LI
313 
><P
314 
>It then calls back into the hardware driver routine
315 
<TT
316 
CLASS="REPLACEABLE"
317 
><I
318 
>HRDWR</I
319 
></TT
320 
>_recv().
321 
<TT
322 
CLASS="REPLACEABLE"
323 
><I
324 
>HRDWR</I
325 
></TT
326 
>_recv() must copy the data from the
327 
hardware's buffers into the scatter-gather buffers provided, and return.</P
328 
></LI
329 
><LI
330 
><P
331 
>The network stack now has the data in-hand, and does with it what it will.
332 
This might include recursive calls to transmit a response packet.
333 
When this all is done, these calls return, and the
334 
&#8220;Network Delivery Thread&#8221;
335 
sleeps once more, awaiting the next asynchronous event.</P
336 
></LI
337 
></OL
338 
></DIV
339 
></DIV
340 
><DIV
341 
CLASS="NAVFOOTER"
342 
><HR
343 
ALIGN="LEFT"
344 
WIDTH="100%"><TABLE
345 
SUMMARY="Footer navigation table"
346 
WIDTH="100%"
347 
BORDER="0"
348 
CELLPADDING="0"
349 
CELLSPACING="0"
350 
><TR
351 
><TD
352 
WIDTH="33%"
353 
ALIGN="left"
354 
VALIGN="top"
355 
><A
356 
HREF="io-eth-drv-upper-api.html"
357 
ACCESSKEY="P"
358 
>Prev</A
359 
></TD
360 
><TD
361 
WIDTH="34%"
362 
ALIGN="center"
363 
VALIGN="top"
364 
><A
365 
HREF="ecos-ref.html"
366 
ACCESSKEY="H"
367 
>Home</A
368 
></TD
369 
><TD
370 
WIDTH="33%"
371 
ALIGN="right"
372 
VALIGN="top"
373 
><A
374 
HREF="net-snmp.html"
375 
ACCESSKEY="N"
376 
>Next</A
377 
></TD
378 
></TR
379 
><TR
380 
><TD
381 
WIDTH="33%"
382 
ALIGN="left"
383 
VALIGN="top"
384 
>Upper Layer Functions</TD
385 
><TD
386 
WIDTH="34%"
387 
ALIGN="center"
388 
VALIGN="top"
389 
><A
390 
HREF="io-eth-drv-generic1.html"
391 
ACCESSKEY="U"
392 
>Up</A
393 
></TD
394 
><TD
395 
WIDTH="33%"
396 
ALIGN="right"
397 
VALIGN="top"
398 
>SNMP</TD
399 
></TR
400 
></TABLE
401 
></DIV
402 
></BODY
403 
></HTML
404 
>

powered by: WebSVN 2.1.0

© copyright 1999-2024 OpenCores.org, equivalent to Oliscience, all rights reserved. OpenCores®, registered trademark.