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->µITRON Configuration FAQ</TITLE
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->Chapter 32. µITRON API</TD
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-><DIV
-CLASS="SECT1"
-><H1
-CLASS="SECT1"
-><A
-NAME="COMPAT-UITRON-CONFIGURATION-FAQ">µITRON Configuration FAQ</H1
-><P
-><SPAN
-CLASS="emphasis"
-><I
-CLASS="EMPHASIS"
->Q: How are µITRON objects created?</I
-></SPAN
-></P
-><P
->For each type of uITRON object (tasks, semaphores, flags, mboxes, mpf, mpl)
-these two quantities are controlled by configuration:</P
-><P
-></P
-><UL
-><LI
-><P
->The <SPAN
-CLASS="emphasis"
-><I
-CLASS="EMPHASIS"
->maximum</I
-></SPAN
-> number of this type of object.</P
-></LI
-><LI
-><P
->The number of these objects which exist <SPAN
-CLASS="emphasis"
-><I
-CLASS="EMPHASIS"
->initially</I
-></SPAN
->.</P
-></LI
-></UL
-><P
->This is assuming that for the relevant object type,
-<SPAN
-CLASS="emphasis"
-><I
-CLASS="EMPHASIS"
->create</I
-></SPAN
-> and <SPAN
-CLASS="emphasis"
-><I
-CLASS="EMPHASIS"
->delete</I
-></SPAN
->
-operations are enabled; enabled is the default. For example, the option
-<TT
-CLASS="LITERAL"
->CYGPKG_UITRON_MBOXES_CREATE_DELETE</TT
->
-controls whether the functions
-<TT
-CLASS="FUNCTION"
->cre_mbx()</TT
->
-and
-<TT
-CLASS="FUNCTION"
->del_mbx()</TT
->
-exist in the API. If not, then the maximum number of
-mboxes is the same as the initial number of mboxes, and so on for all
-µITRON object types.</P
-><P
->Mboxes have no initialization, so there are only a few, simple
-configuration options:</P
-><P
-></P
-><UL
-><LI
-><P
-><TT
-CLASS="LITERAL"
->CYGNUM_UITRON_MBOXES</TT
->
-is the total number of mboxes that you can have in the
-system. By default this is 4, so you can use mboxes 1,2,3 and 4. You
-cannot create mboxes outside this range; trying to
-<TT
-CLASS="FUNCTION"
->cre_mbx(5,...)</TT
->
-will return an error.</P
-></LI
-><LI
-><P
-><TT
-CLASS="LITERAL"
->CYGNUM_UITRON_MBOXES_INITIALLY</TT
->
-is the number of mboxes created
-automatically for you, during startup. By default this is 4, so all 4
-mboxes exist already, and an attempt to create one of these
-eg. <TT
-CLASS="FUNCTION"
->cre_mbx(3,...)</TT
->
-will return an error because the mbox in quesion already
-exists. You can delete a pre-existing mbox, and then re-create it.</P
-></LI
-></UL
-><P
->If you change
-<TT
-CLASS="LITERAL"
->CYGNUM_UITRON_MBOXES_INITIALLY</TT
->,
-for example to 0, no mboxes
-are created automatically for you during startup. Any attempt to use an
-mbox without creating it will return E_NOEXS because the mbox does not
-exist. You can create an mbox, say <TT
-CLASS="FUNCTION"
->cre_mbx(3,...)</TT
->
-and then use it, say
-<TT
-CLASS="FUNCTION"
->snd_msg(3,&foo)</TT
->, and all will be well.</P
-><P
-><SPAN
-CLASS="emphasis"
-><I
-CLASS="EMPHASIS"
->Q: How are µITRON objects initialized?</I
-></SPAN
-></P
-><P
->Some object types have optional initialization. Semaphores are an
-example. You could have
-<TT
-CLASS="LITERAL"
->CYGNUM_UITRON_SEMAS</TT
->=10 and
-<TT
-CLASS="LITERAL"
->CYGNUM_UITRON_SEMAS_INITIALLY</TT
->=5
-which means you can use semaphores 1-5
-straight off, but you must create semaphores 6-10 before you can use them.
-If you decide not to initialize semaphores, semaphores 1-5 will have an
-initial count of zero. If you decide to initialize them, you must supply
-a dummy initializer for semaphores 6-10 also. For example,
-in terms of the configuration output in
-<TT
-CLASS="FILENAME"
->pkgconf/uitron.h</TT
->:</P
-><TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="PROGRAMLISTING"
-> #define CYGDAT_UITRON_SEMA_INITIALIZERS \
- CYG_UIT_SEMA( 1 ), \
- CYG_UIT_SEMA( 0 ), \
- CYG_UIT_SEMA( 0 ), \
- CYG_UIT_SEMA( 99 ), \
- CYG_UIT_SEMA( 1 ), \
- CYG_UIT_SEMA_NOEXS, \
- CYG_UIT_SEMA_NOEXS, \
- CYG_UIT_SEMA_NOEXS, \
- CYG_UIT_SEMA_NOEXS, \
- CYG_UIT_SEMA_NOEXS</PRE
-></TD
-></TR
-></TABLE
-><P
->Semaphore 1 will have initial count 1, semaphores 2 and 3 will be zero,
-number 4 will be 99 initially, 5 will be one and numbers 6 though 10 do not
-exist initially.</P
-><P
->Aside: this is how the definition of the symbol would appear in the
-configuration header file <TT
-CLASS="FILENAME"
->pkgconf/uitron.h</TT
-> —
-unfortunately editing such a long, multi-line definition is somewhat
-cumbersome in the GUI config tool in current releases. The macros
-<TT
-CLASS="LITERAL"
->CYG_UIT_SEMA()</TT
->
-— to create a semaphore initializer — and
-<TT
-CLASS="LITERAL"
->CYG_UIT_SEMA_NOEXS</TT
->
-— to invoke a dummy initializer —
-are provided in in the environment to help with this. Similar macros are
-provided for other object types. The resulting #define symbol is used in
-the context of a C++ array initializer, such as:
-<TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="PROGRAMLISTING"
->Cyg_Counting_Semaphore2 cyg_uitron_SEMAS[ CYGNUM_UITRON_SEMAS ] = {
- CYGDAT_UITRON_SEMA_INITIALIZERS
-};</PRE
-></TD
-></TR
-></TABLE
->
-which is eventually macro-processed to give
-<TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="PROGRAMLISTING"
->Cyg_Counting_Semaphore2 cyg_uitron_SEMAS[ 10 ] = {
- Cyg_Counting_Semaphore2( ( 1 ) ),
- Cyg_Counting_Semaphore2( ( 0 ) ),
- Cyg_Counting_Semaphore2( ( 0 ) ),
- Cyg_Counting_Semaphore2( ( 99 ) ),
- Cyg_Counting_Semaphore2( ( 1 ) ),
- Cyg_Counting_Semaphore2(0),
- Cyg_Counting_Semaphore2(0),
- Cyg_Counting_Semaphore2(0),
- Cyg_Counting_Semaphore2(0),
- Cyg_Counting_Semaphore2(0),
-};</PRE
-></TD
-></TR
-></TABLE
->
-so you can see how it is necessary to include the dummy entries in that
-definition, otherwise the resulting code will not compile correctly.</P
-><P
->If you choose
-<TT
-CLASS="LITERAL"
->CYGNUM_UITRON_SEMAS_INITIALLY</TT
->=0
-it is meaningless to initialize them, for they must be created and so
-initialized then, before use.</P
-><P
-><SPAN
-CLASS="emphasis"
-><I
-CLASS="EMPHASIS"
->Q: What about µITRON tasks?</I
-></SPAN
-></P
-><P
->Some object types require initialization. Tasks are an example of this.
-You must provide a task with a priority, a function to enter when the task
-starts, a name (for debugging purposes), and some memory to use for the stack.
-For example (again in terms of the resulting
-definitions in <TT
-CLASS="FILENAME"
->pkgconf/uitron.h</TT
->):</P
-><TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="PROGRAMLISTING"
->#define CYGNUM_UITRON_TASKS 4 // valid task ids are 1,2,3,4
-#define CYGNUM_UITRON_TASKS_INITIALLY 4 // they all exist at start
-
-#define CYGDAT_UITRON_TASK_EXTERNS \
-extern "C" void startup( unsigned int ); \
-extern "C" void worktask( unsigned int ); \
-extern "C" void lowtask( unsigned int ); \
-static char stack1[ CYGNUM_UITRON_STACK_SIZE ], \
- stack2[ CYGNUM_UITRON_STACK_SIZE ], \
- stack3[ CYGNUM_UITRON_STACK_SIZE ], \
- stack4[ CYGNUM_UITRON_STACK_SIZE ];
-
-#define CYGDAT_UITRON_TASK_INITIALIZERS \
- CYG_UIT_TASK("main task", 8, startup, &stack1, sizeof( stack1 )), \
- CYG_UIT_TASK("worker 2" , 9, worktask, &stack2, sizeof( stack2 )), \
- CYG_UIT_TASK("worker 3" , 9, worktask, &stack3, sizeof( stack3 )), \
- CYG_UIT_TASK("low task" ,20, lowtask, &stack4, sizeof( stack4 )), \ </PRE
-></TD
-></TR
-></TABLE
-><P
->So this example has all four tasks statically configured to exist, ready to
-run, from the start of time. The “main task” runs a routine
-called <TT
-CLASS="FUNCTION"
->startup()</TT
-> at priority 8. Two
-“worker” tasks run both a priority 9, and a “low
-priority” task runs at priority 20 to do useful non-urgent background
-work.</P
-><TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="SCREEN"
->Task ID | Exists at | Function | Priority | Stack | Stack
- number | startup | entry | | address | size
---------+-----------+----------+----------+---------+----------
- 1 | Yes | startup | 8 | &stack1 | CYGNUM...
- 2 | Yes | worktask | 9 | &stack2 | CYGNUM...
- 3 | Yes | worktask | 9 | &stack3 | CYGNUM...
- 4 | Yes | lowtask | 20 | &stack4 | CYGNUM...
---------+-----------+----------+----------+---------+----------</PRE
-></TD
-></TR
-></TABLE
-><P
-><SPAN
-CLASS="emphasis"
-><I
-CLASS="EMPHASIS"
->Q: How can I create µITRON tasks in the program?</I
-></SPAN
-></P
-><P
->You must provide free slots in the task table in which to create new tasks,
-by configuring the number of tasks existing initially to be smaller than
-the total.
-For a task ID which does not initially exist, it will be told what routine
-to call, and what priority it is, when the task is created. But you must
-still set aside memory for the task to use for its stack, and give it a
-name during initialization. For example:</P
-><TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="PROGRAMLISTING"
->#define CYGNUM_UITRON_TASKS 4 // valid task ids are 1-4
-#define CYGNUM_UITRON_TASKS_INITIALLY 1 // only task #1 exists
-
-#define CYGDAT_UITRON_TASK_EXTERNS \
-extern "C" void startup( unsigned int ); \
-static char stack1[ CYGNUM_UITRON_STACK_SIZE ], \
- stack2[ CYGNUM_UITRON_STACK_SIZE ], \
- stack3[ CYGNUM_UITRON_STACK_SIZE ], \
- stack4[ CYGNUM_UITRON_STACK_SIZE ];
-
-#define CYGDAT_UITRON_TASK_INITIALIZERS \
- CYG_UIT_TASK( "main", 8, startup, &stack1, sizeof( stack1 ) ), \
- CYG_UIT_TASK_NOEXS( "slave", &stack2, sizeof( stack2 ) ), \
- CYG_UIT_TASK_NOEXS( "slave2", &stack3, sizeof( stack3 ) ), \
- CYG_UIT_TASK_NOEXS( "slave3", &stack4, sizeof( stack4 ) ), \ </PRE
-></TD
-></TR
-></TABLE
-><P
->So tasks numbered 2,3 and 4 have been given their stacks during startup,
-though they do not yet exist in terms of <TT
-CLASS="FUNCTION"
->cre_tsk()</TT
-> and
-<TT
-CLASS="FUNCTION"
->del_tsk()</TT
-> so you can create tasks 2–4 at
-runtime.</P
-><TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="SCREEN"
->Task ID | Exists at | Function | Priority | Stack | Stack
- number | startup | entry | | address | size
---------+-----------+----------+----------+---------+----------
- 1 | Yes | startup | 8 | &stack1 | CYGNUM...
- 2 | No | N/A | N/A | &stack2 | CYGNUM...
- 3 | No | N/A | N/A | &stack3 | CYGNUM...
- 4 | No | N/A | N/A | &stack4 | CYGNUM...
---------+-----------+----------+----------+---------+----------</PRE
-></TD
-></TR
-></TABLE
-><P
->(you must have at least one task at startup in order that the system can
- actually run; this is not so for other uITRON object types)</P
-><P
-><SPAN
-CLASS="emphasis"
-><I
-CLASS="EMPHASIS"
->Q: Can I have different stack sizes for µITRON tasks?</I
-></SPAN
-></P
-><P
->Simply set aside different amounts of memory for each task to use for its
-stack. Going back to a typical default setting for the µITRON tasks,
-the definitions in <TT
-CLASS="FILENAME"
->pkgconf/uitron.h</TT
-> might look like this:</P
-><TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="PROGRAMLISTING"
->#define CYGDAT_UITRON_TASK_EXTERNS \
-extern "C" void task1( unsigned int ); \
-extern "C" void task2( unsigned int ); \
-extern "C" void task3( unsigned int ); \
-extern "C" void task4( unsigned int ); \
-static char stack1[ CYGNUM_UITRON_STACK_SIZE ], \
- stack2[ CYGNUM_UITRON_STACK_SIZE ], \
- stack3[ CYGNUM_UITRON_STACK_SIZE ], \
- stack4[ CYGNUM_UITRON_STACK_SIZE ];
-
-#define CYGDAT_UITRON_TASK_INITIALIZERS \
- CYG_UIT_TASK( "t1", 1, task1, &stack1, CYGNUM_UITRON_STACK_SIZE ), \
- CYG_UIT_TASK( "t2", 2, task2, &stack2, CYGNUM_UITRON_STACK_SIZE ), \
- CYG_UIT_TASK( "t3", 3, task3, &stack3, CYGNUM_UITRON_STACK_SIZE ), \
- CYG_UIT_TASK( "t4", 4, task4, &stack4, CYGNUM_UITRON_STACK_SIZE ) </PRE
-></TD
-></TR
-></TABLE
-><P
->Note that
-<TT
-CLASS="LITERAL"
->CYGNUM_UITRON_STACK_SIZE</TT
->
-is used to control the size of the stack
-objects themselves, and to tell the system what size stack is being provided.</P
-><P
->Suppose instead stack sizes of 2000, 1000, 800 and 800 were required:
-this could be achieved by using the GUI config tool to edit these
-options, or editting the <TT
-CLASS="FILENAME"
->.ecc</TT
-> file to get these
-results in <TT
-CLASS="FILENAME"
->pkgconf/uitron.h</TT
->:</P
-><TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="PROGRAMLISTING"
->#define CYGDAT_UITRON_TASK_EXTERNS \
-extern "C" void task1( unsigned int ); \
-extern "C" void task2( unsigned int ); \
-extern "C" void task3( unsigned int ); \
-extern "C" void task4( unsigned int ); \
-static char stack1[ 2000 ], \
- stack2[ 1000 ], \
- stack3[ 800 ], \
- stack4[ 800 ];
-
-#define CYGDAT_UITRON_TASK_INITIALIZERS \
- CYG_UIT_TASK( "t1", 1, task1, &stack1, sizeof( stack1 ) ), \
- CYG_UIT_TASK( "t2", 2, task2, &stack2, sizeof( stack2 ) ), \
- CYG_UIT_TASK( "t3", 3, task3, &stack3, sizeof( stack3 ) ), \
- CYG_UIT_TASK( "t4", 4, task4, &stack4, sizeof( stack4 ) )</PRE
-></TD
-></TR
-></TABLE
-><P
->Note that the sizeof() operator has been used to tell the system what size
-stacks are provided, rather than quoting a number (which is difficult for
-maintenance) or the symbol
-<TT
-CLASS="LITERAL"
->CYGNUM_UITRON_STACK_SIZE</TT
->
-(which is wrong).</P
-><P
->We recommend using (if available in your release) the stacksize symbols
-provided in the architectural HAL for your target, called
-<TT
-CLASS="LITERAL"
->CYGNUM_HAL_STACK_SIZE_TYPICAL</TT
->
-and
-<TT
-CLASS="LITERAL"
->CYGNUM_HAL_STACK_SIZE_MINIMUM</TT
->.
-So a better (more portable) version of the above might be:</P
-><TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="PROGRAMLISTING"
->#define CYGDAT_UITRON_TASK_EXTERNS \
-extern "C" void task1( unsigned int ); \
-extern "C" void task2( unsigned int ); \
-extern "C" void task3( unsigned int ); \
-extern "C" void task4( unsigned int ); \
-static char stack1[ CYGNUM_HAL_STACK_SIZE_TYPICAL + 1200 ], \
- stack2[ CYGNUM_HAL_STACK_SIZE_TYPICAL + 200 ], \
- stack3[ CYGNUM_HAL_STACK_SIZE_TYPICAL ], \
- stack4[ CYGNUM_HAL_STACK_SIZE_TYPICAL ];
-
-#define CYGDAT_UITRON_TASK_INITIALIZERS \
- CYG_UIT_TASK( "t1", 1, task1, &stack1, sizeof( stack1 ) ), \
- CYG_UIT_TASK( "t2", 2, task2, &stack2, sizeof( stack2 ) ), \
- CYG_UIT_TASK( "t3", 3, task3, &stack3, sizeof( stack3 ) ), \
- CYG_UIT_TASK( "t4", 4, task4, &stack4, sizeof( stack4 ) )</PRE
-></TD
-></TR
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