1 | @c |
---|
2 | @c COPYRIGHT (c) 1988-1998. |
---|
3 | @c On-Line Applications Research Corporation (OAR). |
---|
4 | @c All rights reserved. |
---|
5 | @c |
---|
6 | @c $Id$ |
---|
7 | @c |
---|
8 | |
---|
9 | @chapter Dual-Ported Memory Manager |
---|
10 | |
---|
11 | @cindex ports |
---|
12 | @cindex dual ported memory |
---|
13 | |
---|
14 | @section Introduction |
---|
15 | |
---|
16 | The dual-ported memory manager provides a mechanism |
---|
17 | for converting addresses between internal and external |
---|
18 | representations for multiple dual-ported memory areas (DPMA). |
---|
19 | The directives provided by the dual-ported memory manager are: |
---|
20 | |
---|
21 | @itemize @bullet |
---|
22 | @item @code{@value{DIRPREFIX}port_create} - Create a port |
---|
23 | @item @code{@value{DIRPREFIX}port_ident} - Get ID of a port |
---|
24 | @item @code{@value{DIRPREFIX}port_delete} - Delete a port |
---|
25 | @item @code{@value{DIRPREFIX}port_external_to_internal} - Convert external to internal address |
---|
26 | @item @code{@value{DIRPREFIX}port_internal_to_external} - Convert internal to external address |
---|
27 | @end itemize |
---|
28 | |
---|
29 | @section Background |
---|
30 | |
---|
31 | @cindex dual ported memory, definition |
---|
32 | @cindex external addresses, definition |
---|
33 | @cindex internal addresses, definition |
---|
34 | |
---|
35 | A dual-ported memory area (DPMA) is an contiguous |
---|
36 | block of RAM owned by a particular processor but which can be |
---|
37 | accessed by other processors in the system. The owner accesses |
---|
38 | the memory using internal addresses, while other processors must |
---|
39 | use external addresses. RTEMS defines a port as a particular |
---|
40 | mapping of internal and external addresses. |
---|
41 | |
---|
42 | There are two system configurations in which |
---|
43 | dual-ported memory is commonly found. The first is |
---|
44 | tightly-coupled multiprocessor computer systems where the |
---|
45 | dual-ported memory is shared between all nodes and is used for |
---|
46 | inter-node communication. The second configuration is computer |
---|
47 | systems with intelligent peripheral controllers. These |
---|
48 | controllers typically utilize the DPMA for high-performance data |
---|
49 | transfers. |
---|
50 | |
---|
51 | @section Operations |
---|
52 | |
---|
53 | @subsection Creating a Port |
---|
54 | |
---|
55 | The @code{@value{DIRPREFIX}port_create} directive creates a port into a DPMA |
---|
56 | with the user-defined name. The user specifies the association |
---|
57 | between internal and external representations for the port being |
---|
58 | created. RTEMS allocates a Dual-Ported Memory Control Block |
---|
59 | (DPCB) from the DPCB free list to maintain the newly created |
---|
60 | DPMA. RTEMS also generates a unique dual-ported memory port ID |
---|
61 | which is returned to the calling task. RTEMS does not |
---|
62 | initialize the dual-ported memory area or access any memory |
---|
63 | within it. |
---|
64 | |
---|
65 | @subsection Obtaining Port IDs |
---|
66 | |
---|
67 | When a port is created, RTEMS generates a unique port |
---|
68 | ID and assigns it to the created port until it is deleted. The |
---|
69 | port ID may be obtained by either of two methods. First, as the |
---|
70 | result of an invocation of the |
---|
71 | @code{@value{DIRPREFIX}port_create} directive, the task |
---|
72 | ID is stored in a user provided location. Second, the port ID |
---|
73 | may be obtained later using the |
---|
74 | @code{@value{DIRPREFIX}port_ident} directive. The port |
---|
75 | ID is used by other dual-ported memory manager directives to |
---|
76 | access this port. |
---|
77 | |
---|
78 | @subsection Converting an Address |
---|
79 | |
---|
80 | The @code{@value{DIRPREFIX}port_external_to_internal} directive is used to |
---|
81 | convert an address from external to internal representation for |
---|
82 | the specified port. |
---|
83 | The @code{@value{DIRPREFIX}port_internal_to_external} directive is |
---|
84 | used to convert an address from internal to external |
---|
85 | representation for the specified port. If an attempt is made to |
---|
86 | convert an address which lies outside the specified DPMA, then |
---|
87 | the address to be converted will be returned. |
---|
88 | |
---|
89 | @subsection Deleting a DPMA Port |
---|
90 | |
---|
91 | A port can be removed from the system and returned to |
---|
92 | RTEMS with the @code{@value{DIRPREFIX}port_delete} directive. When a port is deleted, |
---|
93 | its control block is returned to the DPCB free list. |
---|
94 | |
---|
95 | @section Directives |
---|
96 | |
---|
97 | This section details the dual-ported memory manager's |
---|
98 | directives. A subsection is dedicated to each of this manager's |
---|
99 | directives and describes the calling sequence, related |
---|
100 | constants, usage, and status codes. |
---|
101 | |
---|
102 | @c |
---|
103 | @c |
---|
104 | @c |
---|
105 | @page |
---|
106 | @subsection PORT_CREATE - Create a port |
---|
107 | |
---|
108 | @cindex create a port |
---|
109 | |
---|
110 | @subheading CALLING SEQUENCE: |
---|
111 | |
---|
112 | @ifset is-C |
---|
113 | @findex rtems_port_create |
---|
114 | @example |
---|
115 | rtems_status_code rtems_port_create( |
---|
116 | rtems_name name, |
---|
117 | void *internal_start, |
---|
118 | void *external_start, |
---|
119 | rtems_unsigned32 length, |
---|
120 | rtems_id *id |
---|
121 | ); |
---|
122 | @end example |
---|
123 | @end ifset |
---|
124 | |
---|
125 | @ifset is-Ada |
---|
126 | @example |
---|
127 | procedure Port_Create ( |
---|
128 | Name : in RTEMS.Name; |
---|
129 | Internal_Start : in RTEMS.Address; |
---|
130 | External_Start : in RTEMS.Address; |
---|
131 | Length : in RTEMS.Unsigned32; |
---|
132 | ID : out RTEMS.ID; |
---|
133 | Result : out RTEMS.Status_Codes |
---|
134 | ); |
---|
135 | @end example |
---|
136 | @end ifset |
---|
137 | |
---|
138 | @subheading DIRECTIVE STATUS CODES: |
---|
139 | @code{@value{RPREFIX}SUCCESSFUL} - port created successfully@* |
---|
140 | @code{@value{RPREFIX}INVALID_NAME} - invalid task name@* |
---|
141 | @code{@value{RPREFIX}INVALID_ADDRESS} - address not on four byte boundary@* |
---|
142 | @code{@value{RPREFIX}TOO_MANY} - too many DP memory areas created |
---|
143 | |
---|
144 | @subheading DESCRIPTION: |
---|
145 | |
---|
146 | This directive creates a port which resides on the |
---|
147 | local node for the specified DPMA. The assigned port id is |
---|
148 | returned in id. This port id is used as an argument to other |
---|
149 | dual-ported memory manager directives to convert addresses |
---|
150 | within this DPMA. |
---|
151 | |
---|
152 | For control and maintenance of the port, RTEMS |
---|
153 | allocates and initializes an DPCB from the DPCB free pool. Thus |
---|
154 | memory from the dual-ported memory area is not used to store the |
---|
155 | DPCB. |
---|
156 | |
---|
157 | @subheading NOTES: |
---|
158 | |
---|
159 | The internal_address and external_address parameters |
---|
160 | must be on a four byte boundary. |
---|
161 | |
---|
162 | This directive will not cause the calling task to be |
---|
163 | preempted. |
---|
164 | |
---|
165 | @c |
---|
166 | @c |
---|
167 | @c |
---|
168 | @page |
---|
169 | @subsection PORT_IDENT - Get ID of a port |
---|
170 | |
---|
171 | @cindex get ID of a port |
---|
172 | @cindex obtain ID of a port |
---|
173 | |
---|
174 | @subheading CALLING SEQUENCE: |
---|
175 | |
---|
176 | @ifset is-C |
---|
177 | @findex rtems_port_ident |
---|
178 | @example |
---|
179 | rtems_status_code rtems_port_ident( |
---|
180 | rtems_name name, |
---|
181 | rtems_id *id |
---|
182 | ); |
---|
183 | @end example |
---|
184 | @end ifset |
---|
185 | |
---|
186 | @ifset is-Ada |
---|
187 | @example |
---|
188 | procedure Port_Ident ( |
---|
189 | Name : in RTEMS.Name; |
---|
190 | ID : out RTEMS.ID; |
---|
191 | Result : out RTEMS.Status_Codes |
---|
192 | ); |
---|
193 | @end example |
---|
194 | @end ifset |
---|
195 | |
---|
196 | @subheading DIRECTIVE STATUS CODES: |
---|
197 | @code{@value{RPREFIX}SUCCESSFUL} - port identified successfully@* |
---|
198 | @code{@value{RPREFIX}INVALID_NAME} - port name not found |
---|
199 | |
---|
200 | @subheading DESCRIPTION: |
---|
201 | |
---|
202 | This directive obtains the port id associated with |
---|
203 | the specified name to be acquired. If the port name is not |
---|
204 | unique, then the port id will match one of the DPMAs with that |
---|
205 | name. However, this port id is not guaranteed to correspond to |
---|
206 | the desired DPMA. The port id is used to access this DPMA in |
---|
207 | other dual-ported memory area related directives. |
---|
208 | |
---|
209 | @subheading NOTES: |
---|
210 | |
---|
211 | This directive will not cause the running task to be |
---|
212 | preempted. |
---|
213 | |
---|
214 | @c |
---|
215 | @c |
---|
216 | @c |
---|
217 | @page |
---|
218 | @subsection PORT_DELETE - Delete a port |
---|
219 | |
---|
220 | @cindex delete a port |
---|
221 | |
---|
222 | @subheading CALLING SEQUENCE: |
---|
223 | |
---|
224 | @ifset is-C |
---|
225 | @findex rtems_port_delete |
---|
226 | @example |
---|
227 | rtems_status_code rtems_port_delete( |
---|
228 | rtems_id id |
---|
229 | ); |
---|
230 | @end example |
---|
231 | @end ifset |
---|
232 | |
---|
233 | @ifset is-Ada |
---|
234 | @example |
---|
235 | procedure Port_Delete ( |
---|
236 | ID : in RTEMS.ID; |
---|
237 | Result : out RTEMS.Status_Codes |
---|
238 | ); |
---|
239 | @end example |
---|
240 | @end ifset |
---|
241 | |
---|
242 | @subheading DIRECTIVE STATUS CODES: |
---|
243 | @code{@value{RPREFIX}SUCCESSFUL} - port deleted successfully@* |
---|
244 | @code{@value{RPREFIX}INVALID_ID} - invalid port id |
---|
245 | |
---|
246 | @subheading DESCRIPTION: |
---|
247 | |
---|
248 | This directive deletes the dual-ported memory area |
---|
249 | specified by id. The DPCB for the deleted dual-ported memory |
---|
250 | area is reclaimed by RTEMS. |
---|
251 | |
---|
252 | @subheading NOTES: |
---|
253 | |
---|
254 | This directive will not cause the calling task to be |
---|
255 | preempted. |
---|
256 | |
---|
257 | The calling task does not have to be the task that |
---|
258 | created the port. Any local task that knows the port id can |
---|
259 | delete the port. |
---|
260 | |
---|
261 | @c |
---|
262 | @c |
---|
263 | @c |
---|
264 | @page |
---|
265 | @subsection PORT_EXTERNAL_TO_INTERNAL - Convert external to internal address |
---|
266 | |
---|
267 | @cindex convert external to internal address |
---|
268 | |
---|
269 | @subheading CALLING SEQUENCE: |
---|
270 | |
---|
271 | @ifset is-C |
---|
272 | @findex rtems_port_external_to_internal |
---|
273 | @example |
---|
274 | rtems_status_code rtems_port_external_to_internal( |
---|
275 | rtems_id id, |
---|
276 | void *external, |
---|
277 | void **internal |
---|
278 | ); |
---|
279 | @end example |
---|
280 | @end ifset |
---|
281 | |
---|
282 | @ifset is-Ada |
---|
283 | @example |
---|
284 | procedure Port_External_To_Internal ( |
---|
285 | ID : in RTEMS.ID; |
---|
286 | External : in RTEMS.Address; |
---|
287 | Internal : out RTEMS.Address; |
---|
288 | Result : out RTEMS.Status_Codes |
---|
289 | ); |
---|
290 | @end example |
---|
291 | @end ifset |
---|
292 | |
---|
293 | @subheading DIRECTIVE STATUS CODES: |
---|
294 | @code{@value{RPREFIX}SUCCESSFUL} - always successful |
---|
295 | |
---|
296 | @subheading DESCRIPTION: |
---|
297 | |
---|
298 | This directive converts a dual-ported memory address |
---|
299 | from external to internal representation for the specified port. |
---|
300 | If the given external address is invalid for the specified |
---|
301 | port, then the internal address is set to the given external |
---|
302 | address. |
---|
303 | |
---|
304 | @subheading NOTES: |
---|
305 | |
---|
306 | This directive is callable from an ISR. |
---|
307 | |
---|
308 | This directive will not cause the calling task to be |
---|
309 | preempted. |
---|
310 | |
---|
311 | @c |
---|
312 | @c |
---|
313 | @c |
---|
314 | @page |
---|
315 | @subsection PORT_INTERNAL_TO_EXTERNAL - Convert internal to external address |
---|
316 | |
---|
317 | @cindex convert internal to external address |
---|
318 | |
---|
319 | @subheading CALLING SEQUENCE: |
---|
320 | |
---|
321 | @ifset is-C |
---|
322 | @findex rtems_port_internal_to_external |
---|
323 | @example |
---|
324 | rtems_status_code rtems_port_internal_to_external( |
---|
325 | rtems_id id, |
---|
326 | void *internal, |
---|
327 | void **external |
---|
328 | ); |
---|
329 | @end example |
---|
330 | @end ifset |
---|
331 | |
---|
332 | @ifset is-Ada |
---|
333 | @example |
---|
334 | procedure Port_Internal_To_External ( |
---|
335 | ID : in RTEMS.ID; |
---|
336 | Internal : in RTEMS.Address; |
---|
337 | External : out RTEMS.Address; |
---|
338 | Result : out RTEMS.Status_Codes |
---|
339 | ); |
---|
340 | @end example |
---|
341 | @end ifset |
---|
342 | |
---|
343 | @subheading DIRECTIVE STATUS CODES: |
---|
344 | @code{@value{RPREFIX}SUCCESSFUL} - always successful |
---|
345 | |
---|
346 | @subheading DESCRIPTION: |
---|
347 | |
---|
348 | This directive converts a dual-ported memory address |
---|
349 | from internal to external representation so that it can be |
---|
350 | passed to owner of the DPMA represented by the specified port. |
---|
351 | If the given internal address is an invalid dual-ported address, |
---|
352 | then the external address is set to the given internal address. |
---|
353 | |
---|
354 | @subheading NOTES: |
---|
355 | |
---|
356 | This directive is callable from an ISR. |
---|
357 | |
---|
358 | This directive will not cause the calling task to be |
---|
359 | preempted. |
---|
360 | |
---|