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2002-04-12 Chris Johns <ccj@acm.org>

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* doc/user/userext.t: Per PR138, updated the documentation to show
	how to obtain an extension table index. Also provided some extra
	background on the user extension API.
This commit is contained in:
Joel Sherrill
2002-04-13 16:47:23 +00:00
parent 18b6986b89
commit b5c5bbcf07
2 changed files with 34 additions and 2 deletions
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6
doc/user/ChangeLog
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@@ -1,3 +1,9 @@
2002-04-12 Chris Johns <ccj@acm.org>
* doc/user/userext.t: Per PR138, updated the documentation to show
how to obtain an extension table index. Also provided some extra
background on the user extension API.
2002-04-03 Ralf Corsepius <corsepiu@faw.uni-ulm.de>
* io.t: Fix typo @sybsection.

30
doc/user/userext.t
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@@ -119,7 +119,15 @@ of these extension sets could be written and installed
independently of the others.
All user extensions are optional and RTEMS places no
naming restrictions on the user.
naming restrictions on the user. The user extension entry points
are copied into an internal RTEMS structure. This means the user
does not need to keep the table after creating it, and changing the
handler entry points dynamically in a table once created has no
effect. Creating a table local to a function can save space in
space limited applications.
Extension switches do not effect the context switch overhead if
no switch handler is installed.
@subsection TCB Extension Area
@@ -134,7 +142,25 @@ to utilize the notepad locations associated with each task
although this may conflict with application usage of those
particular notepads.
The TCB extension is an array of pointers in the TCB.
The TCB extension is an array of pointers in the TCB. The
index into the table can be obtained from the extension id
returned when the extension is created:
@findex rtems extensions table index
@ifset is-C
@example
@group
index = rtems_get_index(extension_id);
@end group
@end example
@end ifset
@ifset is-Ada
@example
There is currently no example for Ada.
@end example
@end ifset
The number of pointers in the area is the same as the number of
user extension sets configured. This allows an application to
augment the TCB with user-defined information. For example, an