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QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running the QNX OS 8.0.
Programming
Getting Started with the QNX OS
Getting Started with the QNX OS: A Guide for Realtime Programmers is intended to introduce you to the QNX OS and help you develop applications and resource managers for it.
Resource Managers
In this chapter, we'll take a look at what you need to understand in order to write a resource manager. Resource managers are another distintive feature of QNX OS that allow you to access services through standard POSIX calls.
Alphabetical listing of connect and I/O functions
This section gives an alphabetical listing of the connect and I/O function entry points that you can fill in (the two tables passed to resmgr_attach()). Remember that if you simply call iofunc_func_init(), all these entries will be filled in with the appropriate defaults; you'd want to modify a particular entry only if you wish to handle that particular message. In the Examples section, below, you'll see some examples of the common functions.
Unblock I/O function handler

QNX Momentics IDE User's Guide
This User's Guide describes version 8.0 of the Integrated Development Environment (IDE) that's part of the QNX Tool Suite.
QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running the QNX OS 8.0.
- Quickstart Guide
- System Architecture
  The System Architecture guide accompanies the QNX OS and is intended for both application developers and end-users.
- OS Components & Operations
- Graphics
- Programming
  - Getting Started with the QNX OS
    Getting Started with the QNX OS: A Guide for Realtime Programmers is intended to introduce you to the QNX OS and help you develop applications and resource managers for it.
    - Processes and Threads
      This chapter explains the concepts behind processes and threads, and the challenges of synchronization and scheduling. A thread is a flow of execution, and a process is a collection of threads. In the QNX OS, the schedulable entity is a thread, not a process.
    - Message Passing
      In this chapter, we'll look at the most distinctive feature of QNX OS, message passing. Message passing lies at the heart of the operating system's microkernel architecture, giving the OS its modularity.
    - Interrupts
      In this chapter, we'll take a look at interrupts, how we deal with them under QNX OS, their impact on scheduling and realtime, and some interrupt-management strategies.
    - Resource Managers
      In this chapter, we'll take a look at what you need to understand in order to write a resource manager. Resource managers are another distintive feature of QNX OS that allow you to access services through standard POSIX calls.
      - What is a resource manager?
        A resource manager is simply a program with some well-defined characteristics.
      - The client's view
        We've already seen a hint of what the client expects. It expects a file-descriptor-based interface, using standard POSIX functions.
      - The resource manager's view
        Let's look at things from the resource manager's perspective.
      - The resource manager library
        Before we get too far into all the issues surrounding resource managers, we have to get acquainted with the QNX OS resource manager library.
      - Writing a resource manager
        Now that we've introduced the basics—how the client looks at the world, how the resource manager looks at the world, and an overview of the two cooperating layers in the library, it's time to focus on the details.
      - Handler routines
        Not all outcalls correspond to client messages—some are synthesized by the kernel, and some by the library.
      - Alphabetical listing of connect and I/O functions
        This section gives an alphabetical listing of the connect and I/O function entry points that you can fill in (the two tables passed to resmgr_attach()). Remember that if you simply call iofunc_func_init(), all these entries will be filled in with the appropriate defaults; you'd want to modify a particular entry only if you wish to handle that particular message. In the Examples section, below, you'll see some examples of the common functions.
        Access control list I/O function handler
        Change file mode I/O function handler
        Change ownership I/O function handler
        Change timestamps I/O function handler
        Close duplicate OCB I/O function handler
        Close OCB I/O function handler
        Create file link connect function handler
        Device control I/O function handler
        Duplicate a file descriptor I/O function handler
        File descriptor information I/O function handler
        File locking I/O function handler
        Flush data I/O function handler
        Lock OCB I/O function handler
        Make filesystem node connect function handler
        Map memory I/O function handler
        Mount connect function handler
        Open connect function handler
        Open file descriptor I/O function handler
        pathconf I/O function handler
        Power I/O function handler
        Read I/O function handler
        Read link connect function handler
        Register for notification I/O function handler
        Rename connect function handler
        Resize file I/O function handler
        Set file position I/O function handler
        Shutdown I/O function handler
        stat I/O function handler
        Unblock connect function handler
        Unblock I/O function handler
        Unlink connect function handler
        Unlock OCB I/O function handler
        User-defined message I/O function handler
        Write I/O function handler
      - Examples
        I'm now going to show you a number of cookbook examples you can cut and paste into your code, to use as a basis for your projects. These aren't complete resource managers—you'll need to add the thread pool and dispatch skeleton shown immediately below, and ensure that your versions of the I/O functions are placed into the I/O functions table after you've done the iofunc_func_init(), in order to override the defaults!
      - Advanced topics
        Now that we've covered the basics of resource managers, it's time to look at some more complicated aspects.
      - Summary
        Writing a resource manager is by far the most complicated task that we've discussed in this book.
    - Sample Programs
      This appendix contains the complete versions of some of the sample programs discussed in this book.
    - Glossary
  - Programmer's Guide
    The QNX OS Programmer's Guide covers a variety of topics that might interest developers who are building applications that will run under the QNX OS.
  - Writing a Resource Manager
- System Security Guide
  The QNX System Security Guide is intended for both system integrators who are responsible for the security of a QNX OS system and developers who want to create a QNX OS resource manager free from vulnerabilities.
- Utilities & Libraries
- Migrating to QNX OS 8.0
QNX Software in the Cloud
QNX Software in the Cloud enables developers to use the QNX OS in the Amazon cloud environment.
QNX Toolkit for Visual Studio Code
This User's Guide describes the QNX^® Toolkit for Visual Studio Code. The guide introduces you to the QNX Toolkit by explaining the QNX development environment and how to build, run, and debug your QNX^® Operating System (OS) applications and systems.
QNX Hypervisor User's Guide
This User's Guide explains the QNX hypervisor architecture and provides instructions for installing and running a QNX Hypervisor system, changing system components and configuration, and using hypervisor features such as virtual devices (vdevs).
Typographical Conventions, Support, and Licensing
This section describes the typographical conventions used throughout the documentation, explains how to obtain technical support, and provides some information about licensing.

Unblock I/O function handler

QNX SDP8.0Getting Started with the QNX OSDeveloperUser

Prototype:

int (*unblock) ( resmgr_context_t *ctp,
                io_pulse_t *msg,
                RESMGR_OCB_T *ocb )

Classification:

I/O (synthesized by kernel, synthesized by library)

Default handler:

iofunc_unblock_default()

Helper functions:

iofunc_unblock()

Client function:

none—kernel action due to signal or timeout

Messages:

none—synthesized by library

Data structure:

pointer to message structure being interrupted

Description:

This is the I/O message version of the unblock outcall, synthesized by the library as a result of a kernel pulse due to the client's attempt to unblock during the I/O message phase. The unblock connect function handler is substantially the same (see the preceding section).

Common to both unblock handlers (connect and I/O) is the characteristic that the client wishes to unblock, but is at the mercy of the resource manager. The resource manager must reply to the client's message in order to unblock the client. (This is discussed in the Message Passing chapter when we looked at the ChannelCreate() flags, particularly the _NTO_CHF_UNBLOCK flag).

Returns:

The status via the helper macro _RESMGR_STATUS().

See the section in the Message Passing chapter, titled Using the _NTO_MI_UNBLOCK_REQ for a detailed discussion of unblocking strategies.

Referenced by:

resmgr_io_funcs_t I/O table

Permission checking:

The default implementation iofunc_unblock_default() does not perform any permission checking.

Page updated: March 05, 2025