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2008-08-22 Joel Sherrill <joel.sherrill@oarcorp.com>

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* bsp_howto/Makefile.am, bsp_howto/init.t, bsp_howto/intro.t,
	bsp_howto/makefiles.t, bsp_howto/support.t: Update initialization
	sequence. Add another figure.
	* bsp_howto/BSPInitFlowchart-49.eps, bsp_howto/BSPInitFlowchart-49.png: New files.
This commit is contained in:
Joel Sherrill
2008-08-22 16:38:00 +00:00
parent a78df7ba0c
commit 0eb595a839
8 changed files with 258 additions and 142 deletions
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7
doc/ChangeLog
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@@ -1,3 +1,10 @@
2008-08-22 Joel Sherrill <joel.sherrill@oarcorp.com>
* bsp_howto/Makefile.am, bsp_howto/init.t, bsp_howto/intro.t,
bsp_howto/makefiles.t, bsp_howto/support.t: Update initialization
sequence. Add another figure.
* bsp_howto/BSPInitFlowchart-49.eps, bsp_howto/BSPInitFlowchart-49.png: New files.
2008-08-21 Joel Sherrill <joel.sherrill@oarcorp.com> 2008-08-21 Joel Sherrill <joel.sherrill@oarcorp.com>
* index.html.in: Reorder manuals. * index.html.in: Reorder manuals.

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2
doc/bsp_howto/Makefile.am
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@@ -19,7 +19,7 @@ GENERATED_FILES = intro.texi target.texi makefiles.texi linkcmds.texi \
COMMON_FILES += $(top_srcdir)/common/cpright.texi COMMON_FILES += $(top_srcdir)/common/cpright.texi
PNG_FILES = Developer-User-Timeline.png PNG_FILES = Developer-User-Timeline.png BSPInitFlowchart-49.png
if USE_HTML if USE_HTML
html_project_DATA += $(PNG_FILES) html_project_DATA += $(PNG_FILES)

224
doc/bsp_howto/init.t
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@@ -1,5 +1,5 @@
@c @c
@c COPYRIGHT (c) 1988-2002. @c COPYRIGHT (c) 1988-2008.
@c On-Line Applications Research Corporation (OAR). @c On-Line Applications Research Corporation (OAR).
@c All rights reserved. @c All rights reserved.
@c @c
@@ -18,62 +18,97 @@ commonly found in the BSP related to initialization. The remainder of
this chapter covers special issues which require attention such this chapter covers special issues which require attention such
as interrupt vector table and chip select initialization. as interrupt vector table and chip select initialization.
Most of the examples in this chapter will be based on the gen68340 BSP Most of the examples in this chapter will be based on the SPARC/ERC32 and
initialization code. Like most BSPs, the initialization for this m68k/gen68340 BSP initialization code. Like most BSPs, the initialization
BSP is divided into two subdirectories under the BSP source directory. for these BSP is divided into two subdirectories under the BSP source
The gen68340 BSP source code is in the following directory: directory. The BSP source code for these BSPs is in the following
directories:
@example @example
c/src/lib/libbsp/m68k/gen68340 c/src/lib/libbsp/m68k/gen68340
c/src/lib/libbsp/sparc/erc32
@end example @end example
The following source code files are in this subdirectory. Both BSPs contain startup code written in assembly language and C.
The gen68340 BSP has its early initialization start code in the
@itemize @bullet @code{start340} subdirectory and its C startup code in the @code{startup}
directory. In the @code{start340} directory are two source files.
@item @code{start340}: assembly language code which contains early The file @code{startfor340only.s} is the simpler of these files as it only
initialization routines has initialization code for a MC68340 board. The file @code{start340.s}
@item @code{startup}: C code with higher level routines (RTEMS
initialization related)
@end itemize
@b{NOTE:} The directory @code{start340} is simply named @code{start} or
start followed by a BSP designation.
In the @code{start340} directory are two source files. The file
@code{startfor340only.s} is the simpler of these files as it only has
initialization code for a MC68340 board. The file @code{start340.s}
contains initialization for a 68349 based board as well. contains initialization for a 68349 based board as well.
Similarly, the ERC32 BSP has startup code written in assembly language
and C. However, this BSP shares this code with other SPARC BSPs.
Thus the @code{Makefile.am} explicitly references the following files
for this functionality.
@example
../../sparc/shared/start.S
../../sparc/shared/bspclean.c
@end example
@b{NOTE:} In most BSPs, the directory named @code{start340} in the
gen68340 BSP would be simply named @code{start} or start followed by a
BSP designation.
@section Required Global Variables @section Required Global Variables
Although not strictly part of initialization, there are a few global Although not strictly part of initialization, there are a few global
variables assumed to exist by many support components. These variables assumed to exist by reusable device drivers. These global
global variables are normally not defined by the BSP since the RTEMS variables should only defined by the BSP when using one of these device
Project strives to avoid duplication as much as possible. drivers.
The following is a list of these global variables:
@itemize @bullet The BSP author probably should be aware of the @code{Configuration}
@item @code{Configuration} is the RTEMS Configuration Table generated Table structure generated by @code{<rtems/confdefs.h>} during debug but
by @code{<rtems/confdefs.h>}. should not explicitly reference it in the source code. There are helper
routines provided by RTEMS to access individual fields.
@end itemize In older RTEMS versions, the BSP included a number of required global
variables. We have made every attempt to eliminate these in the interest
of simplicity.
@section Board Initialization @section Board Initialization
This section describes the steps an application goes through from the This section describes the steps an application goes through from the
time the first BSP code is executed until the first application task time the first BSP code is executed until the first application task
executes. The routines invoked during this will be discussed and executes. The following figure illustrates the program flow during
their location in the RTEMS source tree pointed out. this sequence:
@ifset use-ascii
IMAGE NOT AVAILABLE IN ASCII VERSION
@end ifset
@ifset use-tex
@image{BSPInitFlowchart-49,6in,,Initialization Sequence,.png}
@c @image{FILENAME[, WIDTH[, HEIGHT[, ALTTEXT[, EXTENSION]]]]}
@end ifset
@ifset use-html
@html
<center>
<IMG SRC="BSPInitFlowchart-49.png" WIDTH=800 ALT="Initialization Sequence">
</center>
@end html
@end ifset
The above figure illustrates the flow from assembly language start code
to the shared @code{bootcard.c} framework then through the C Library,
RTEMS, device driver initialization phases, and the context switch
to the first application task. After this, the application executes
until it calls @code{exit}, @code{rtems_shutdown_executive}, or some
other normal termination initiating routine and control is returned
to @code{bootcard.c} which allows the BSP to perform some clanup in C
(@code{bsp_cleanup}) and then @code{boot_card} returns to the assembly
language which initially invoked it.
The routines invoked during this will be discussed and their location
in the RTEMS source tree pointed out as we discuss each.
@subsection Start Code - Assembly Language Initialization @subsection Start Code - Assembly Language Initialization
The assembly language code in the directory @code{start} is The assembly language code in the directory @code{start} is the first part
the first part of the application to execute. It is of the application to execute. It is responsible for initializing the
responsible for initializing the processor and board enough to execute processor and board enough to execute the rest of the BSP. This includes:
the rest of the BSP. This includes:
@itemize @bullet @itemize @bullet
@item initializing the stack @item initializing the stack
@@ -82,26 +117,28 @@ the rest of the BSP. This includes:
@item copy the initialized data from ROM to RAM @item copy the initialized data from ROM to RAM
@end itemize @end itemize
The general rule of thumb is that the The general rule of thumb is that the start code in assembly should
start code in assembly should do the minimum necessary to allow C code do the minimum necessary to allow C code to execute to complete the
to execute to complete the initialization sequence. initialization sequence.
The initial assembly language start code completes its execution by The initial assembly language start code completes its execution by
invoking the shared routine @code{boot_card()}. invoking the shared routine @code{boot_card()}.
The label (symbolic name) associated with the starting address of the The label (symbolic name) associated with the starting address of the
program is typically called @code{start}. The start object file program is typically called @code{start}. The start object file is the
is the first object file linked into the program image so it is insured first object file linked into the program image so it is ensured that
that the start code is at offset 0 in the @code{.text} section. It is the start code is at offset 0 in the @code{.text} section. It is the
the responsibility of the linker script in conjunction with the responsibility of the linker script in conjunction with the compiler
compiler specifications file to put the start code in the correct location specifications file to put the start code in the correct location in
in the application image. the application image.
@subsection boot_card() - Boot the Card @subsection boot_card() - Boot the Card
The @code{boot_card()} is the first C code invoked. Most of the BSPs The @code{boot_card()} is the first C code invoked. This file is the
use the same shared version of @code{boot_card()} which is located in core component in the RTEMS BSP Initialization Framework and provides
the following file: the proper sequencing of initialization steps for the BSP, RTEMS and
device drivers. All BSPs use the same shared version of @code{boot_card()}
which is located in the following file:
@example @example
c/src/lib/libbsp/shared/bootcard.c c/src/lib/libbsp/shared/bootcard.c
@@ -111,23 +148,88 @@ The @code{boot_card()} routine performs the following functions:
@itemize @bullet @itemize @bullet
@item invokes the BSP specific routine @code{bsp_start()}, @item It disables processor interrupts.
@item invokes the RTEMS directive @code{rtems_initialize_executive_early()} @item It sets the global program name and command line argument variables
to initialize the executive, C Library, and all device drivers but for later use by the application.
return without initiating multitasking or enabling interrupts,
@item invokes the shared @code{main()} in the same file as @item If the macro is BSP_BOOTCARD_HANDLES_RAM_ALLOCATION is defined, it
@code{boot_card()} which does not return until the will invoke the BSP specific @code{bsp_get_work_area} function to obtain
@code{rtems_shutdown_executive} directive is called, and information on the amount and location of BSP RAM that is available to
be allocated to the C Program Heap and RTEMS Workspace. If the amount
of memory available for the RTEMS Workspace is less than that required
by the application (e.g. @code{rtems_configuration_get_work_space_size()},
then a message is printed using @code{printk}, @code{bsp_cleanup} is
invoked, and -1 is return to the assembly language start code. BSPs which
use this memory allocation functionality in @code{bootcard.c}
must invoke the RTEMS specific autoconf macro
@code{RTEMS_BSP_BOOTCARD_HANDLES_RAM_ALLOCATION} in the BSP's
@code{configure.ac} file.
@item invokes the BSP specific routine @code{bsp_cleanup()} to perform @item It invokes the BSP specific routine @code{bsp_start()} which is
any necessary board specific shutdown actions. written in C and thus able to perform more advanced initialization.
Often MMU and bus initialization occurs here.
@item It invokes the RTEMS directive
@code{rtems_initialize_data_structures()} to initialize the RTEMS
executive to a state where objects can be created but tasking is not
enabled.
@item If the macro is BSP_BOOTCARD_HANDLES_RAM_ALLOCATION is defined,
it will calculate the memory available for the C Program Heap and invoke
the initialization routine for the C Library with this information.
@item It invokes the BSP specific routine @code{bsp_pretasking_hook}. On
most BSPs which utilize the framework, this routine does nothing.
@item If @code{RTEMS_DEBUG} is enabled, then the RTEMS debug mask level
is inialized appropriately.
@item It invokes the RTEMS directive
@code{rtems_initialize_before_drivers()} to initialize the MPCI Server
thread in a multiprocessor configuration and execute API specific
extensions.
@item It invokes the BSP specific routine @code{bsp_predriver_hook}. For
most BSPs, the implementation of this routine does nothing. However,
on some BSPs, required subsystems which utilize the C Library
(e.g. @code{malloc} in particular) may be initialized at this point.
@item It invokes the RTEMS directive
@code{rtems_initialize_device_drivers()} to initialize the statically
configured set of device drivers in the order they were specified in
the Configuration Table.
@item It invokes the BSP specific routine @code{bsp_postdriver_hook}. For
most BSPs, the implementation of this routine does nothing. However, some
BSPs use this hook and perform some initialization which must be done at
this point in the initialization sequence. This is the last opportunity
for the BSP to insert BSP specific code into the initialization sequence.
@item It invokes the RTEMS directive
@code{rtems_initialize_start_multitasking()} which starts multitasking and context switches to the first task. @code{boot_card()} will not return until the application is shutdown. As part of this sequence the following actions occur:
@itemize @bullet
@item RTEMS will context switch to the first application task. As a
side-effect of this context switch, processor interrupts will be enabled.
This is often the source of a fatal error during BSP development because
the BSP did not clear and/or disable all interrupt sources and a spurious
interrupt will occur .
@item When in the context of the first task but before its body has been
entered, any C++ Global Constructors will be invoked.
@end itemize @end itemize
It is important to note that the executive and much of the @item Finally after the application shutsdown RTEMS and control is
support environment must be initialized before invoking @code{main()}. return to @code{boot_card()} from RTEMS, it invokes the BSP specific
routine @code{bsp_cleanup()} to perform any necessary board specific
shutdown actions.
@end itemize
That's it. We just went through the entire sequence.
@subsection bsp_start() - BSP Specific Initialization @subsection bsp_start() - BSP Specific Initialization
@@ -180,7 +282,7 @@ support library and, most importantly, invokes the C++ global
constructors. constructors.
The precise placement of when @code{main()} is invoked in the The precise placement of when @code{main()} is invoked in the
RTEMS initialization sequence insures that C Library and non-blocking RTEMS initialization sequence ensures that C Library and non-blocking
calls can be made in global C++ constructors. calls can be made in global C++ constructors.
The shared implementation of this routine is located in the following file: The shared implementation of this routine is located in the following file:

19
doc/bsp_howto/intro.t
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@@ -55,3 +55,22 @@ this manual as the result of his experiences. At that time, this
document was viewed internally as the most important "missing manual" document was viewed internally as the most important "missing manual"
in the RTEMS documentation set. in the RTEMS documentation set.
The gen68340 BSP is a good example of the life of an RTEMS BSP. It is
based upon a part not recommended for new designs and none of the core RTEMS
Project team members have one of these boards. Thus we are unlikely to
perform major updates on this BSP. So as long as it compiles and links all
tests, it will be available.
The RTEMS Project team members are always trying to identify common
code across BSPs and refactoring the code into shared routines.
As part of this effort, the we will enhance the common BSP Framework.
Not surprisingly, not every BSP takes advantage of every feature in
the framework. The gen68340 does not take advantage of as many features
as the ERC32 BSP does. So in many ways, the ERC32 is a better example
BSP at this point. But even the ERC32 BSP does not include examples
of every driver template and framework available to the BSP author.
So in this guide we will try to point out good examples from other BSPs.
Our goal is for you to be able to reuse as much code as possible and
write as little board specific code as possible.

4
doc/bsp_howto/makefiles.t
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@@ -1,5 +1,5 @@
@c @c
@c COPYRIGHT (c) 1988-2002. @c COPYRIGHT (c) 1988-2008.
@c On-Line Applications Research Corporation (OAR). @c On-Line Applications Research Corporation (OAR).
@c All rights reserved. @c All rights reserved.
@c @c
@@ -27,11 +27,9 @@ of four phases as shown here:
@end example @end example
@end ifset @end ifset
@ifset use-tex @ifset use-tex
@image{Developer-User-Timeline,6in,,Developer User Timeline,.png} @image{Developer-User-Timeline,6in,,Developer User Timeline,.png}
@c @image{FILENAME[, WIDTH[, HEIGHT[, ALTTEXT[, EXTENSION]]]]} @c @image{FILENAME[, WIDTH[, HEIGHT[, ALTTEXT[, EXTENSION]]]]}
@end ifset @end ifset
@ifset use-html @ifset use-html

144
doc/bsp_howto/support.t
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@@ -18,29 +18,19 @@ file from the PowerPC psim BSP:
@example @example
@group @group
%rename cpp old_cpp
%rename lib old_lib
%rename endfile old_endfile %rename endfile old_endfile
%rename startfile old_startfile %rename startfile old_startfile
%rename link old_link %rename link old_link
*cpp:
%(old_cpp) %@{qrtems: -D__embedded__@} -Asystem(embedded)
*lib:
%@{!qrtems: %(old_lib)@} %@{qrtems: --start-group \
%@{!qrtems_debug: -lrtemsall@} %@{qrtems_debug: -lrtemsall_g@} \
-lc -lgcc --end-group ecrtn%O%s \
%@{!qnolinkcmds: -T linkcmds%s@}@}
*startfile: *startfile:
%@{!qrtems: %(old_startfile)@} %@{qrtems: ecrti%O%s \ %@{!qrtems: %(old_startfile)@} \
%@{!qrtems_debug: startsim.o%s@} \ %@{!nostdlib: %@{qrtems: ecrti%O%s rtems_crti%O%s crtbegin.o%s start.o%s@}@}
%@{qrtems_debug: startsim_g.o%s@}@}
*link: *link:
%@{!qrtems: %(old_link)@} %@{qrtems: -Qy -dp -Bstatic \ %@{!qrtems: %(old_link)@} %@{qrtems: -Qy -dp -Bstatic -e _start -u __vectors@}
-T linkcmds%s -e _start -u __vectors@}
*endfile:
%@{!qrtems: %(old_endfile)@} %@{qrtems: crtend.o%s ecrtn.o%s@}
@end group @end group
@end example @end example
@@ -50,26 +40,19 @@ embedded their original definition. The subsequent sections
specify what behavior is expected when the @code{-qrtems} or specify what behavior is expected when the @code{-qrtems} or
@code{-qrtems_debug} option is specified. @code{-qrtems_debug} option is specified.
The @code{*cpp} definition specifies that when @code{-qrtems}
is specified, predefine the preprocessor symbol @code{__embedded__}.
The @code{*lib} section insures that the RTEMS library, BSP specific
linker script, gcc support library, and the EABI specific @code{ecrtn}
file are used.
The @code{*startfile} section specifies that the BSP specific file The @code{*startfile} section specifies that the BSP specific file
@code{startsim.o} will be used instead of @code{crt0.o}. In addition, @code{start.o} will be used instead of @code{crt0.o}. In addition,
the EABI specific file @code{ecrti.o} will be linked in with the various EABI support files (@code{ecrti.o} etc.) will be linked in with
executable. the executable.
The @code{*link} section specifies the arguments that will be passed to The @code{*link} section adds some arguments to the linker when it is
the linker. invoked by GCC to link an application for this BSP.
The format of this file is specific to the GNU Compiler Suite. The The format of this file is specific to the GNU Compiler Suite. The
argument used to override and extend the compiler built-in specifications argument used to override and extend the compiler built-in specifications
is relatively new to the toolset. The @code{-specs} option is present is available in all recent GCC versions. The @code{-specs} option is
in all @code{egcs} distributions and @code{gcc} distributions starting present in all @code{egcs} distributions and @code{gcc} distributions
with version 2.8.0. starting with version 2.8.0.
@section README Files @section README Files
@@ -126,16 +109,11 @@ as a starting point.
Many @code{bsp.h} files provide prototypes of variables defined Many @code{bsp.h} files provide prototypes of variables defined
in the linker script (@code{linkcmds}). in the linker script (@code{linkcmds}).
There are a number of fields in this file that are used only by the @section tm27.h Include File
RTEMS Test Suites. The following is a list of these:
The @code{tm27} test from the RTEMS Timing Test Suite is designed to measure the length of time required to vector to and return from an interrupt handler. This test requires some help from the BSP to know how to cause and manipulate the interrupt source used for this measurement. The following is a list of these:
@itemize @bullet @itemize @bullet
@item @code{MAX_LONG_TEST_DURATION} - the longest length of time a
"long running" test should run.
@item @code{MAX_SHORT_TEST_DURATION} - the longest length of time a
"short running" test should run.
@item @code{MUST_WAIT_FOR_INTERRUPT} - modifies behavior of @code{tm27}. @item @code{MUST_WAIT_FOR_INTERRUPT} - modifies behavior of @code{tm27}.
@item @code{Install_tm27_vector} - installs the interrupt service @item @code{Install_tm27_vector} - installs the interrupt service
@@ -153,6 +131,14 @@ can generate a nested interrupt.
@end itemize @end itemize
All members of the Timing Test Suite are designed to run @b{WITHOUT}
the Clock Device Driver installed. This increases the predictability
of the tests' execution as well as avoids occassionally including the
overhead of a clock tick interrupt in the time reported. Because of
this it is sometimes possible to use the clock tick interrupt source
as the source of this test interrupt. On other architectures, it is
possible to directly force an interrupt to occur.
@section Calling Overhead File @section Calling Overhead File
The file @code{include/coverhd.h} contains the overhead associated The file @code{include/coverhd.h} contains the overhead associated
@@ -168,40 +154,35 @@ The numbers in this file are obtained by running the "Timer Overhead"
overhead is subtracted from the directive execution times reported by overhead is subtracted from the directive execution times reported by
the Timing Suite. the Timing Suite.
There is a shared implementation of @code{coverhd.h} which sets all of
the overhead constants to 0. On faster processors, this is usually the
best alternative for the BSP as the calling overhead is extremely small.
This file is located at:
@example
c/src/lib/libbsp/shared/include/coverhd.h
@end example
@section sbrk() Implementation @section sbrk() Implementation
If the BSP wants to dynamically extend the heap used by the Although nearly all BSPs give all possible memory to the C Program Heap
C Library memory allocation routines (i.e. @code{malloc} family), at initialization, it is possible for a BSP to configure the initial
then this routine must be functional. The following is the size of the heap small and let it grow on demand. If the BSP wants
prototype for this routine: to dynamically extend the heap used by the C Library memory allocation
routines (i.e. @code{malloc} family), then the@code{sbrk} routine must
be functional. The following is the prototype for this routine:
@example @example
void * sbrk(size_t increment) void * sbrk(size_t increment)
@end example @end example
The @code{increment} amount is based upon the @code{sbrk_amount} The @code{increment} amount is based upon the @code{sbrk_amount}
parameter passed to the @code{RTEMS_Malloc_Initialize} during system parameter passed to the @code{bsp_libc_init} during system initialization.
initialization. Historically initialization of the C Library was done as part of the
See @ref{Initialization Code RTEMS Pretasking Callback} for more BSP's Pretasking Hook but now the BSP Boot Card Framework can perform
information. this operation.
There is a default implementation which returns an error to indicate If your BSP does not want to support dynamic heap extension, then you do not have to do anything special. However, if you want to support @code{sbrk}, you must provide an implementation of this method and define @code{CONFIGURE_MALLOC_BSP_SUPPORTS_SBRK} in @code{bsp.h}. This informs @code{rtems/confdefs.h} to configure the Malloc Family Extensions which support @code{sbrk}.
that the heap can not be extended. This implementation can be
found in @code{c/src/lib/libbsp/shared/sbrk.c}. Many of the BSPs
use this shared implementation. In order to use this implementation,
the file @code{Makefile.am} in the BSP's @code{startup} directory
must be modified so that the @code{$VPATH} variable searches
both the @code{startup} directory and the shared directory. The following
illustates the @code{VPATH} setting in the PowerPC psim BSP's
@code{startup/Makefile.am}:
@example
VPATH = @@srcdir@@:@@srcdir@@/../../../shared
@end example
This instructs make to look in all of the directories in the @code{VPATH}
for the source files. The directories will be examined in the order
they are specified.
@section bsp_cleanup() - Cleanup the Hardware @section bsp_cleanup() - Cleanup the Hardware
@@ -215,20 +196,28 @@ c/src/lib/libbsp/shared/bspclean.c
The @code{bsp_cleanup()} routine can be used to return to a ROM monitor, The @code{bsp_cleanup()} routine can be used to return to a ROM monitor,
insure that interrupt sources are disabled, etc.. This routine is the insure that interrupt sources are disabled, etc.. This routine is the
last place to insure a clean shutdown of the hardware. last place to insure a clean shutdown of the hardware. On some BSPs,
it prints a message indicating that the application completed execution
and waits for the user to press a key before resetting the board.
The PowerPC/gen83xx and PowerPC/gen5200 BSPs do this when they are built
to support the FreeScale evaluation boards. This is convenient when
using the boards in a development environment and may be disabled for
production use.
@section set_vector() - Install an Interrupt Vector @section set_vector() - Install an Interrupt Vector
The @code{set_vector} routine is responsible for installing an interrupt On targets with Simple Vectored Interrupts, the BSP must provide
vector. It invokes the support routines necessary to install an an implementation of the @code{set_vector} routine. This routine is
interrupt handler as either a "raw" or an RTEMS interrupt handler. Raw responsible for installing an interrupt vector. It invokes the support
handlers bypass the RTEMS interrupt structure and are responsible for routines necessary to install an interrupt handler as either a "raw"
saving and restoring all their own registers. Raw handlers are useful or an RTEMS interrupt handler. Raw handlers bypass the RTEMS interrupt
for handling traps, debug vectors, etc.. structure and are responsible for saving and restoring all their own
registers. Raw handlers are useful for handling traps, debug vectors,
etc..
The @code{set_vector} routine is a central place to perform The @code{set_vector} routine is a central place to perform interrupt
interrupt controller manipulation and encapsulate that information. controller manipulation and encapsulate that information. It is usually
It is usually implemented as follows: implemented as follows:
@example @example
@group @group
@@ -251,7 +240,8 @@ rtems_isr_entry set_vector( /* returns old vector */
@end group @end group
@end example @end example
@b{NOTE:} The i386, PowerPC and ARM ports use a Programmable
@b{NOTE:} @code{set_vector} is provided by the majority of BSPs but Interrupt Controller model which does not require the BSP to implement
not all. In particular, the i386 BSPs use a different scheme. @code{set_vector}. BSPs for these architectures must provide a different
set of support routines.