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authorGedare Bloom <gedare@rtems.org>2013-04-22 13:14:36 -0400
committerGedare Bloom <gedare@rtems.org>2013-04-23 09:06:41 -0400
commit0ced77e947aa09944723c3e4f6312a42446bd3a9 (patch)
tree5205bc7e25b748fd7ceb671a98ccbe0b8ccd1e12 /README
parentdfd15081689328a651ce5323b4aa210e1c861aa2 (diff)
downloadrtems-0ced77e947aa09944723c3e4f6312a42446bd3a9.tar.bz2
README: Rewrite and reduce
Delete old bit-rotting README files and rewrite the README to point readers toward authoritative sources of documentation.
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-Building RTEMS
-==============
-See the file README.configure.
+See the documentation manuals in doc/ with daily builds available online at
+http://rtems.org/onlinedocs/doc-current/share/rtems/html/ and released builds
+at http://www.rtems.org/onlinedocs/releases/
-Directory Overview
-==================
+See the RTEMS Wiki at http://wiki.rtems.org/wiki/index.php/Main_Page
+for community knowledge and tutorials.
-This is the top level of the RTEMS directory structure. The following
-is a description of the files and directories in this directory:
+RTEMS Doxygen available at http://www.rtems.org/onlinedocs/doxygen/cpukit/html
- INSTALL
- Rudimentary installation instructions. For more detailed
- information please see the Release Notes. The Postscript
- version of this manual can be found in the file
- c_or_ada/doc/relnotes.tgz.
+Get help on the mailing lists:
+* For general-purpose questions related to using RTEMS, use the
+ rtems-users ml: http://www.rtems.org/mailman/listinfo/rtems-users
+* For questions and discussion related to development of RTEMS, use the
+ rtems-devel ml: http://www.rtems.org/mailman/listinfo/rtems-devel
- LICENSE
- Required legalese.
-
- README
- This file.
-
- c
- This directory contains the source code for the C
- implementation of RTEMS as well as the test suites, sample
- applications, Board Support Packages, Device Drivers, and
- support libraries.
-
- doc
- This directory contains the PDL for the RTEMS executive.
-
-Ada versus C
-============
-
-There are two implementations of RTEMS in this source tree --
-in Ada and in C. These two implementations are functionally
-and structurally equivalent. The C implementation follows
-the packaging conventions and hierarchical nature of the Ada
-implementation. In addition, a style has been followed which
-allows one to easily find the corresponding Ada and C
-implementations.
-
-File names in C and code placement was carefully designed to insure
-a close mapping to the Ada implementation. The following file name
-extensions are used:
-
- .adb - Ada body
- .ads - Ada specification
- .adp - Ada body requiring preprocessing
- .inc - include file for .adp files
-
- .c - C body (non-inlined routines)
- .inl - C body (inlined routines)
- .h - C specification
-
-In the executive source, XYZ.c and XYZ.inl correspond directly to a
-single XYZ.adb or XYZ.adp file. A .h file corresponds directly to
-the .ads file. There are only a handful of .inc files in the
-Ada source and these are used to insure that the desired simple
-inline textual expansion is performed. This avoids scoping and
-calling convention side-effects in carefully constructed tests
-which usually test context switch behavior.
-
-In addition, in Ada code and data name references are always fully
-qualified as PACKAGE.NAME. In C, this convention is followed
-by having the package name as part of the name itself and using a
-capital letter to indicate the presence of a "." level. So we have
-PACKAGE.NAME in Ada and _Package_Name in C. The leading "_" in C
-is used to avoid naming conflicts between RTEMS and user variables.
-By using these conventions, one can easily compare the C and Ada
-implementations.
-
-The most noticeable difference between the C and Ada83 code is
-the inability to easily obtain a "typed pointer" in Ada83.
-Using the "&" operator in C yields a pointer with a specific type.
-The 'Address attribute is the closest feature in Ada83. This
-returns a System.Address and this must be coerced via Unchecked_Conversion
-into an access type of the desired type. It is easy to view
-System.Address as similar to a "void *" in C, but this is not the case.
-A "void *" can be assigned to any other pointer type without an
-explicit conversion.
-
-The solution adopted to this problem was to provide two routines for
-each access type in the Ada implementation -- one to convert from
-System.Address to the access type and another to go the opposite
-direction. This results in code which accomplishes the same thing
-as the corresponding C but it is easier to get lost in the clutter
-of the apparent subprogram invocations than the "less bulky"
-C equivalent.
-
-A related difference is the types which are only in Ada which are used
-for pointers to arrays. These types do not exist and are not needed
-in the C implementation.