VXWORKS 7编程指南

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"VxWorks 7程序员指南" VxWorks 7是Wind River Systems公司推出的一款先进的实时操作系统（RTOS），专为嵌入式系统设计，适用于各种关键任务应用，如航空、医疗、通信和工业自动化等领域。《VxWorks 7程序员指南》是开发者进行系统开发、应用程序编写和调试的重要参考资料。本指南主要涵盖了以下关键知识点： 1. **系统架构**：VxWorks 7基于微内核设计，提供了一个高效、可扩展的平台。它包括了任务管理、内存管理、中断处理、设备驱动、网络协议栈等核心组件。 2. **任务管理**：VxWorks 7支持抢占式和非抢占式任务，提供了丰富的任务创建、调度、同步和通信机制，如信号量、消息队列、事件标志组等。 3. **内存管理**：系统支持动态内存分配和释放，以及内存池管理，确保高效地使用有限的内存资源。 4. **设备驱动**：VxWorks 7的设备驱动模型允许开发者编写和管理设备驱动程序，以实现硬件与操作系统的交互。 5. **文件系统**：支持多种文件系统类型，如VFAT、LittleFS等，提供对磁盘、闪存等存储设备的操作接口。 6. **网络支持**：内建TCP/IP协议栈，支持IPv4和IPv6，包括HTTP、FTP、UDP、TCP等多种网络服务，满足现代网络应用需求。 7. **编程工具**：VxWorks 7集成了Tornado开发环境或Wind River Workbench，提供IDE、编译器、调试器等工具，简化开发流程。 8. **安全性和认证**：VxWorks 7遵循多个安全标准，如DO-178C（航空电子软件）、IEC 61508（工业安全）等，确保产品在关键领域的可靠性。 9. **移植与升级**：VxWorks 7提供了向后兼容性，方便从旧版本进行迁移，并支持从VxWorks 6.x到VxWorks 7的平滑过渡。 10. **许可证与法律条款**：使用VxWorks 7可能涉及第三方软件的许可，用户需要遵守安装目录下的`legal-notices/`中的相关条款。此外，Wind River可能引用第三方文档或提供指向第三方网站的链接，但不对其内容负责。公司的总部位于美国加利福尼亚州阿尔ameda的500 Wind River Way。对于开发者而言，《VxWorks 7程序员指南》不仅提供了深入的技术细节，还包含了丰富的示例和最佳实践，是理解并充分利用VxWorks 7功能的必备手册。

VxWorks Private Header Files

Some elements of VxWorks are internal details that may change and so should not be referenced

in a kernel application. The only supported uses of a module's facilities are through the public

definitions in the header file, and through the module's function interfaces. Your adherence

ensures that your application code is not affected by internal changes in the implementation of a

VxWorks module.-

Some header files mark internal details using HIDDEN comments:

/* HIDDEN */

...

/* END HIDDEN */

Internal details are also hidden with private header files, which are located in directories named

private. The names of the private header files have the same root as the public ones, but with a P

added. For example, the private header file for semLib is semLibP.h.

Header Files and extern "C" Statements

Do not include system header files within extern "C" statement brackets. All VxWorks system

header files are already configured for use with C and C++ compilers. You may invalidate

declarations in the VxWorks headers if you force a C linkage on the entire header file's content.

The following is incorrect:

#ifdef _cplusplus

extern "C" {

#endif

#include <stdio.h>

But the following is correct:

#include <stdio.h>

#ifdef _cplusplus

extern "C" {

#endif

In addition, do not include a VxWorks header file within an extern "C" statement in C++ files.

The following is incorrect:

extern "C" {

#include <stdio.h>

}

But this example is correct:

#include <stdio.h>

VxWorks

Programmer's Guide

Static Instantiation of Kernel Objects

VxWorks kernel objects, such as tasks and semaphores, can be instantiated statically as well as

dynamically. Static instantiation provides advantages in terms of performance and determinism.

Special VxWorks C macros are provided for static instantiation.

Static instantiation of a kernel object means that the object is declared as a compile-time variable

(using a special VxWorks macro), which is usually global in scope. The compiler therefore

allocates storage for the object in the application, and no run-time memory allocation is required.

The object is therefore immediately available for initialization at startup.

In contrast to static instantiation, dynamic instantiation of kernel objects involves run-time

allocation of system memory and then initialization of the object before it can be used. Object

deletion, in turn, involves invalidation of the object, and then return of the memory to the system.

Object creation and deletion are both dependent on dynamic memory allocation, usually with the

malloc( ) andfree( ) functions.

Applications using dynamic instantiation must therefore account for the possibility that the

system may run out of memory and that it may not be able to create the object (and resort to

some suitable error recovery process or abort). In addition, dynamic allocation is a relatively slow

operation that may block the calling task, and make system performance less deterministic.

Also in contrast to static instantiation, dynamic instantiation can be accomplished with a single

function call (for example, taskSpawn( ), semBCreate( ), and so on).

The code examples that follow illustrate the difference between coding dynamic and static

instantiation (but do not use any VxWorks object instantiation macros).

Dynamic Instantiation Code

struct my_object * pMyObj;

...

pMyObj = (struct my_object *) malloc (sizeof (struct my_object));

if (pMyObj != NULL)

{

fooObjectInit (pMyOjb);

return (OK);

}

else

{

/* failure path */

return (ERROR);

}

Static Instantiation Code

struct my_object myObj;

...

fooObjectInit(&myOjb);

/* myObj now ready for use */

Kernel Objects That can be Instantiated Statically

The following kernel objects can be instantiated statically:

1 Kernel Applications

Static

Instantiation of Kernel Objects

• kernel tasks

• semaphores

• message queues

• watchdog timers

For detailed information, see Task Creation and Activation on page 85, Semaphore Creation and Use

on page 110, Message Creation and Use on page 126, and Watchdog Timers on page 165.

Static Instantiation and Code Size

Compile-time declaration of objects does not occupy any space in an executable file, in a

VxWorks image, or in storage media (such as flash memory). If an object is declared at compile

time but not initialized, the compiler places it in the un-initialized data (bss) section. Un-

initialized data is required by the ANSI C standard to have a value of zero.

While un-initialized data contributes to the run-time memory footprint, so does dynamic

allocation. In either case, the memory footprint would be the same.

Advantages of Static Instantiation

Static instantiation of kernel objects provides several advantages over dynamic instantiation:

• Static instantiation of objects is faster and more deterministic.

• Application logic is simpler because it does not have to account for the possibility that

dynamic allocation may fail.

• Static declaration of objects cannot fail, unless the program itself is too large to fit into system

memory.

Applications and Static Instantiation

Static instantiation of kernel objects provides notable advantages to real-time applications, and

most applications can make use of static instantiation to some degree. Most applications require

that some objects be available for the lifetime of their execution, and that they never be deleted.

These objects can therefore be statically instantiated. Using static instantiation whenever possible

makes applications more robust, deterministic, and fast.

NOTE:

Static instantiation should only be used with kernel applications. It is not designed

for use with RTP (user-mode) applications.

Scope Of Static Declarations

Kernel objects are usually declared as global variables because the objects IDs are usually used

for inter-task communication and synchronization. However, they need not be global. An object

declaration can also be done at function scope provided the object stays in a valid scope for the

duration of its use.

Caveat With Regard to Macro Use

In order to ensure proper macro expansion, the task instantiation macros must use a backslash

character if the declaration or call that they implement is longer than one line. For example, the

VxWorks

Programmer's Guide

following ensures that the static instantiation of a task with the VX_TASK_INSTANTIATE

macro will be handled properly by the compiler:

myTaskId = VX_TASK_INSTANTIATE(myTask, 100, 0, 4096, pEntry, 0,1,2,3,4,5,6,7,8,9);

Macro use is described in detail in Task Creation and Activation on page 85,Semaphore Creation and

Use on page 110, Message Creation and Use on page 126, and Watchdog Timers on page 165.

Boot-Time Hook Function Facility

VxWorks hook function stubs that are called at specific points in the boot process can be used to

add your own boot-time functionality or test code. The stubs allow you to add code without

modifying the boot loader or operating system code itself, or without creating custom

components for your own code.

You can add code that performs time-critical operations before the operating system is fully up

and running, or code that overrides default features of the system. For example, you can use this

hook function functionality to do the following:

• Provide early feedback that the device is booting (print a message to an LCD display).

• Reset a watchdog timer during the boot process.

• Call custom diagnostic or test code.

• Start applications that do not require networking earlier in the initialization process.

• Read a GPIO for hardware version or test device status.

• Configure an FPGA early.

The boot-time hook function stubs are enabled by including stub-specific components in your

VxWorks configuration. The stubs must be called from the usrAppInit.c file (in your VIP project).

For information about using usrAppInit.c to automatically executing code after VxWorks has

booted, see Using userAppInit() to Run Applications Automatically on page 10.

Boot-Time Hook Function Stubs and Components

The boot-time hook function stubs are enabled by including stub-specific components in your

VxWorks configuration.

For detailed information about the boot process, see the VxWorks 7 BSP Developer's Guide.

Hook Function Stub

Description and Required Component

usrPreKernelAppInit( ) Called at the beginning of usrInit( ), right after cacheLibInit( ). That

is, right after the board boots and before kernel initialization starts.

INCLUDE_USER_PRE_KERNEL_APPL_INIT

1 Kernel Applications

Boot-Time

Hook Function Facility

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