forked from Imagelibrary/rtems
312 lines
11 KiB
Perl
312 lines
11 KiB
Perl
@c
|
|
@c COPYRIGHT (c) 1988-2008.
|
|
@c On-Line Applications Research Corporation (OAR).
|
|
@c All rights reserved.
|
|
|
|
@chapter Initialization Manager
|
|
|
|
@section Introduction
|
|
|
|
The Initialization Manager is responsible for
|
|
initiating and shutting down RTEMS. Initiating RTEMS involves
|
|
creating and starting all configured initialization tasks, and
|
|
for invoking the initialization routine for each user-supplied
|
|
device driver. In a multiprocessor configuration, this manager
|
|
also initializes the interprocessor communications layer. The
|
|
directives provided by the Initialization Manager are:
|
|
|
|
@itemize @bullet
|
|
@item @code{@value{DIRPREFIX}initialize_executive} - Initialize RTEMS
|
|
@item @code{@value{DIRPREFIX}shutdown_executive} - Shutdown RTEMS
|
|
@end itemize
|
|
|
|
@section Background
|
|
|
|
@subsection Initialization Tasks
|
|
|
|
@cindex initialization tasks
|
|
|
|
Initialization task(s) are the mechanism by which
|
|
RTEMS transfers initial control to the user's application.
|
|
Initialization tasks differ from other application tasks in that
|
|
they are defined in the User Initialization Tasks Table and
|
|
automatically created and started by RTEMS as part of its
|
|
initialization sequence. Since the initialization tasks are
|
|
scheduled using the same algorithm as all other RTEMS tasks,
|
|
they must be configured at a priority and mode which will ensure
|
|
that they will complete execution before other application tasks
|
|
execute. Although there is no upper limit on the number of
|
|
initialization tasks, an application is required to define at
|
|
least one.
|
|
|
|
A typical initialization task will create and start
|
|
the static set of application tasks. It may also create any
|
|
other objects used by the application. Initialization tasks
|
|
which only perform initialization should delete themselves upon
|
|
completion to free resources for other tasks. Initialization
|
|
tasks may transform themselves into a "normal" application task.
|
|
This transformation typically involves changing priority and
|
|
execution mode. RTEMS does not automatically delete the
|
|
initialization tasks.
|
|
|
|
@subsection System Initialization
|
|
|
|
System Initialization begins with board reset and continues
|
|
through RTEMS initialization, initialization of all device
|
|
drivers, and eventually a context switch to the first user
|
|
task. Remember, that interrupts are disabled during
|
|
initialization and the @i{initialization context} is not
|
|
a task in any sense and the user should be very careful
|
|
during initialization.
|
|
|
|
The BSP must ensure that the there is enough stack
|
|
space reserved for the initialization context to
|
|
successfully execute the initialization routines for
|
|
all device drivers and, in multiprocessor configurations, the
|
|
Multiprocessor Communications Interface Layer initialization
|
|
routine.
|
|
|
|
@subsection The Idle Task
|
|
|
|
The Idle Task is the lowest priority task in a system
|
|
and executes only when no other task is ready to execute. This
|
|
default implementation of this task consists of an infinite
|
|
loop. RTEMS allows the Idle Task body to be replaced by a CPU
|
|
specific implementation, a BSP specific implementation or an
|
|
application specific implementation.
|
|
|
|
The Idle Task is preemptible and @b{WILL} be preempted when
|
|
any other task is made ready to execute. This characteristic is
|
|
critical to the overall behavior of any application.
|
|
|
|
@subsection Initialization Manager Failure
|
|
|
|
The @code{@value{DIRPREFIX}fatal_error_occurred} directive will
|
|
be invoked from @code{@value{DIRPREFIX}initialize_executive}
|
|
for any of the following reasons:
|
|
|
|
@itemize @bullet
|
|
@item If either the Configuration Table or the CPU Dependent
|
|
Information Table is not provided.
|
|
|
|
@item If the starting address of the RTEMS RAM Workspace,
|
|
supplied by the application in the Configuration Table, is NULL
|
|
or is not aligned on a four-byte boundary.
|
|
|
|
@item If the size of the RTEMS RAM Workspace is not large
|
|
enough to initialize and configure the system.
|
|
|
|
@item If the interrupt stack size specified is too small.
|
|
|
|
@item If multiprocessing is configured and the node entry in
|
|
the Multiprocessor Configuration Table is not between one and
|
|
the maximum_nodes entry.
|
|
|
|
@item If a multiprocessor system is being configured and no
|
|
Multiprocessor Communications Interface is specified.
|
|
|
|
@item If no user initialization tasks are configured. At
|
|
least one initialization task must be configured to allow RTEMS
|
|
to pass control to the application at the end of the executive
|
|
initialization sequence.
|
|
|
|
@item If any of the user initialization tasks cannot be
|
|
created or started successfully.
|
|
@end itemize
|
|
|
|
A discussion of RTEMS actions when a fatal error occurs
|
|
may be found @ref{Fatal Error Manager Announcing a Fatal Error}.
|
|
|
|
|
|
@section Operations
|
|
|
|
@subsection Initializing RTEMS
|
|
|
|
The Initialization Manager @code{@value{DIRPREFIX}initialize_executive}
|
|
directives is called by the @code{boot_card} routine. The @code{boot_card}
|
|
routine is invoked by the Board Support Package once a basic C run-time
|
|
environment is set up. This consists of
|
|
|
|
@itemize @bullet
|
|
@item a valid and accessible text section, read-only data, read-write data and
|
|
zero-initialized data,
|
|
@item an initialization stack large enough to initialize the rest of the Board
|
|
Support Package, RTEMS and the device drivers,
|
|
@item all registers and components mandated by Application Binary Interface, and
|
|
@item disabled interrupts.
|
|
@end itemize
|
|
|
|
The @code{@value{DIRPREFIX}initialize_executive} directive uses a system
|
|
initialization linker set to initialize only those parts of the overall RTEMS
|
|
feature set that is necessary for a particular application. @xref{Linker
|
|
Sets}. Each RTEMS feature used the application may optionally register an
|
|
initialization handler. The system initialization API is available via
|
|
@code{#included <rtems/sysinit.h>}.
|
|
|
|
A list of all initialization steps follows. Some steps are optional depending
|
|
on the requested feature set of the application. The initialization steps are
|
|
execute in the order presented here.
|
|
|
|
@table @dfn
|
|
|
|
@item RTEMS_SYSINIT_BSP_WORK_AREAS
|
|
The work areas consisting of C Program Heap and the RTEMS Workspace are
|
|
initialized by the Board Support Package. This step is mandatory.
|
|
|
|
@item RTEMS_SYSINIT_BSP_START
|
|
Basic initialization step provided by the Board Support Package. This step is
|
|
mandatory.
|
|
|
|
@item RTEMS_SYSINIT_INITIAL_EXTENSIONS
|
|
Initializes the initial extensions if at least one is configured by the Board
|
|
Support Package or application.
|
|
|
|
@item RTEMS_SYSINIT_DATA_STRUCTURES
|
|
This directive is called when the Board Support Package has completed its basic
|
|
initialization and allows RTEMS to initialize the application environment based
|
|
upon the information in the Configuration Table, User Initialization Tasks
|
|
Table, Device Driver Table, Multiprocessor Configuration Table, and the
|
|
Multiprocessor Communications Interface (MPCI) Table.
|
|
|
|
@item RTEMS_SYSINIT_USER_EXTENSIONS
|
|
Initializes the @ref{User Extensions Manager} in case it is used by the
|
|
application.
|
|
|
|
@item RTEMS_SYSINIT_CPU_SET
|
|
Initializes the global CPU set on SMP configurations in case the application
|
|
uses this information.
|
|
|
|
@item RTEMS_SYSINIT_BSP_LIBC
|
|
Depending on the application configuration the IO library and root filesystem
|
|
is initialized. This step is mandatory.
|
|
|
|
@item RTEMS_SYSINIT_BEFORE_DRIVERS
|
|
This directive performs initialization that must occur between basis RTEMS data
|
|
structure initialization and device driver initialization. In particular, in a
|
|
multiprocessor configuration, this directive will create the MPCI Server Task.
|
|
|
|
@item RTEMS_SYSINIT_BSP_PRE_DRIVERS
|
|
Initialization step performed right before device drivers are initialized
|
|
provided by the Board Support Package. This step is mandatory.
|
|
|
|
@item RTEMS_SYSINIT_DEVICE_DRIVERS
|
|
This step initializes all statically configured device drivers and performs all
|
|
RTEMS initialization which requires device drivers to be initialized. This
|
|
step is mandatory.
|
|
|
|
In a multiprocessor configuration, this service will initialize the
|
|
Multiprocessor Communications Interface (MPCI) and synchronize with the other
|
|
nodes in the system.
|
|
|
|
@item RTEMS_SYSINIT_BSP_POST_DRIVERS
|
|
Initialization step performed right after device drivers are initialized
|
|
provided by the Board Support Package. This step is mandatory.
|
|
|
|
@end table
|
|
|
|
The final action of the @code{@value{DIRPREFIX}initialize_executive} directive
|
|
is to start multitasking. RTEMS does not return to the initialization context
|
|
and the initialization stack may be re-used for interrupt processing.
|
|
|
|
Many of RTEMS actions during initialization are based upon
|
|
the contents of the Configuration Table. For more information
|
|
regarding the format and contents of this table, please refer
|
|
to the chapter @ref{Configuring a System}.
|
|
|
|
The final action in the initialization sequence is the
|
|
initiation of multitasking. When the scheduler and dispatcher
|
|
are enabled, the highest priority, ready task will be dispatched
|
|
to run. Control will not be returned to the Board Support
|
|
Package after multitasking is enabled. The initialization stack may be re-used
|
|
for interrupt processing.
|
|
|
|
@subsection Shutting Down RTEMS
|
|
|
|
The @code{@value{DIRPREFIX}shutdown_executive} directive is invoked by the
|
|
application to end multitasking and terminate the system.
|
|
|
|
@section Directives
|
|
|
|
This section details the Initialization Manager's
|
|
directives. A subsection is dedicated to each of this manager's
|
|
directives and describes the calling sequence, related
|
|
constants, usage, and status codes.
|
|
|
|
@page
|
|
@subsection INITIALIZE_EXECUTIVE - Initialize RTEMS
|
|
|
|
@cindex initialize RTEMS
|
|
@cindex start multitasking
|
|
|
|
@subheading CALLING SEQUENCE:
|
|
|
|
@ifset is-C
|
|
@findex rtems_initialize_executive
|
|
@example
|
|
void rtems_initialize_executive(void);
|
|
@end example
|
|
@end ifset
|
|
|
|
@ifset is-Ada
|
|
@example
|
|
NOT SUPPORTED FROM Ada BINDING
|
|
@end example
|
|
@end ifset
|
|
|
|
@subheading DIRECTIVE STATUS CODES:
|
|
|
|
NONE
|
|
|
|
@subheading DESCRIPTION:
|
|
|
|
Iterates through the system initialization linker set and invokes the
|
|
registered handlers. The final step is to start multitasking.
|
|
|
|
@subheading NOTES:
|
|
|
|
This directive should be called by @code{boot_card} only.
|
|
|
|
This directive @b{does not return} to the caller. Errors in the initialization
|
|
sequence are usually fatal and lead to a system termination.
|
|
|
|
@page
|
|
@subsection SHUTDOWN_EXECUTIVE - Shutdown RTEMS
|
|
|
|
@cindex shutdown RTEMS
|
|
|
|
@subheading CALLING SEQUENCE:
|
|
|
|
@ifset is-C
|
|
@findex rtems_shutdown_executive
|
|
@example
|
|
void rtems_shutdown_executive(
|
|
uint32_t result
|
|
);
|
|
@end example
|
|
@end ifset
|
|
|
|
@ifset is-Ada
|
|
@example
|
|
procedure Shutdown_Executive(
|
|
Status : in RTEMS.Unsigned32
|
|
);
|
|
@end example
|
|
@end ifset
|
|
|
|
@subheading DIRECTIVE STATUS CODES:
|
|
|
|
NONE
|
|
|
|
@subheading DESCRIPTION:
|
|
|
|
This directive is called when the application wishes to shutdown RTEMS. The
|
|
system is terminated with a fatal source of @code{RTEMS_FATAL_SOURCE_EXIT} and
|
|
the specified @code{result} code.
|
|
|
|
@subheading NOTES:
|
|
|
|
This directive @b{must} be the last RTEMS directive
|
|
invoked by an application and it @b{does not return} to the caller.
|
|
|
|
This directive may be called any time.
|