Click here to learn
about this Sponsor:
Home  |  News  |  Articles  |  Polls  |  Forum

Keywords: Match:
4th RTL Workshop: Calling Plain Linux Device Drivers Functions from Hard Real Time Tasks
by Walter Fetter Lages

Abstract

Processes running under plain Linux usually access I/O devices through device drivers implemented monolithically in the kernel or as loadable kernel modules. This has the advantage of exposing standard interfaces for all I/O devices and enables processes running without root privileges to access I/O. Unfortunately, hard real time tasks can not use the standard kernel interfaces to I/O devices, since that would force an execution of kernel code, which does not comply with the hard real time requirements. This problem has been dealt with by implementing special device drivers to be used by real time tasks. Nonetheless, those special device drivers adhere more to the concept of a library than to the concept of a device driver. Each special device driver exposes his own set of functions that can be called by real time tasks, but there is not a common set of functions among all special device drivers. In other words, the concept of uniformity is not implemented. Obviously, it is highly desirable to use the same device driver for programs running under plain Linux or under real time. If soft real time is enough for the application, LXRT can be used. LXRT tasks runs in user space but under control of the real time linux scheduler. By running under user space, LXRT tasks can use standard C library calls to access I/O through standard device drivers. However, to access the device driver a portion of the plain Linux kernel code is executed on behalf of the LXRT task. Since the temporal behavior of the kernel code is not deterministic, the real time scheduler is force to switch the LXRT task to soft real time mode while it is executing kernel code. This paper addresses that problem and shows that under some assumptions it is possible to avoid the switch to soft real time mode while accessing device drivers and therefore the hard real time properties of the task are retained. By using the method proposed in this paper, the very same device driver can be used by plain Linux processes, by hard real time tasks running in kernel space, by LXRT tasks running in soft real time mode and by LXRT tasks running in hard real time mode. The effectiveness of the method is demostrated by the implementation of a device driver for a robot controller. Test programs written in C++ as plain Linux programs, as real time kernel modules, as LXRT soft real time tasks and as LXRT hard real time task, all accessing the controller through the device driver have their temporal behavior discussed.

(Paper not available)


(Click here for further information)


FUEL Database on MontaVista Linux
Whether building a mobile handset, a car navigation system, a package tracking device, or a home entertainment console, developers need capable software systems, including an operating system, development tools, and supporting libraries, to gain maximum benefit from their hardware platform and to meet aggressive time-to-market goals.

Breaking New Ground: The Evolution of Linux Clustering
With a platform comprising a complete Linux distribution, enhanced for clustering, and tailored for HPC, Penguin Computing¿s Scyld Software provides the building blocks for organizations from enterprises to workgroups to deploy, manage, and maintain Linux clusters, regardless of their size.

Data Monitoring with NightStar LX
Unlike ordinary debuggers, NightStar LX doesn¿t leave you stranded in the dark. It¿s more than just a debugger, it¿s a whole suite of integrated diagnostic tools designed for time-critical Linux applications to reduce test time, increase productivity and lower costs. You can debug, monitor, analyze and tune with minimal intrusion, so you see real execution behavior. And that¿s positively illuminating.

Virtualizing Service Provider Networks with Vyatta
This paper highlights Vyatta's unique ability to virtualize networking functions using Vyatta's secure routing software in service provider environments.

High Availability Messaging Solution Using AXIGEN, Heartbeat and DRBD
This white paper discusses a high-availability messaging solution relying on the AXIGEN Mail Server, Heartbeat and DRBD. Solution architecture and implementation, as well as benefits of using AXIGEN for this setup are all presented in detail.

Understanding the Financial Benefits of Open Source
Will open source pay off? Open source is becoming standard within enterprises, often because of cost savings. Find out how much of a financial impact it can have on your organization. Get this methodology and calculator now, compliments of JBoss.

Embedded Hardware and OS Technology Empower PC-Based Platforms
The modern embedded computer is the jack of all trades appearing in many forms.

Data Management for Real-Time Distributed Systems
This paper provides an overview of the network-centric computing model, data distribution services, and distributed data management. It then describes how the SkyBoard integration and synchronization service, coupled with an implementation of the OMG¿s Data Distribution Service (DDS) standard, can be used to create an efficient data distribution, storage, and retrieval system.

7 Advantages of D2D Backup
For decades, tape has been the backup medium of choice. But, now, disk-to-disk (D2D) backup is gaining in favor. Learn why you should make the move in this whitepaper.

 


Got a HOT tip?   please tell us!
Free weekly newsletter
Enter your email...
Click here for a profile of each sponsor:
PLATINUM SPONSORS
GOLD SPONSORS
(Become a sponsor)

ADVERTISEMENT
(Advertise here)

Check out the latest Linux powered...

mobile phones!

other cool
gadgets



BREAKING NEWS

• Major Mono rev ships
• ETX module targets military apps
• Linux netbook return rates higher?
• Italian carrier ships Linux MID
• 5-second Linux boots on low-powered hardware
• MontaVista "Summit" concludes
• Freescale to jettison cellular chip business
• Open-source server appliance is "free"
• MontaVista Linux drives Dell's quick-boot feature
• "Virtual platform" targets Linux device developers
• Mobile Linux platform supports Cortex-A8 SoC
• Linux design targets 802.11n-enabled homes
• Virtualization design targets wireless base stations
• Linux virtualization tech tapped for telematics
• Linux Foundation spins end-user conference


Most popular stories -- past 90 days:
• Open source phone goes mass-market
• Tinest Linux system, yet?
• Garmin Nav devices run Gnome Linux
• ARM9 board boots Debian in 0.69 seconds
• Low-cost laptop runs Linpus Linux
• Linux-friendly Beagle fetches $150
• Mini Linux PC breaks $100 barrier
• Open source camera records geotagged video to SATA HDD
• Open set-top box ships
• First $100 laptop runs Linux


DesktopLinux headlines:
• Major Mono rev ships
• Intrepid Ibex beta-tests
• Linux netbook returns higher?
• Open-source image editing project launches
• Linux Foundation launches end-user conference
• GNOME 2.24 gains "Empathy" IM
• gOS 3.0 goes gold
• Linux Foundation courts individual members
• Netbook version of Mandriva thinks small
• Mozilla removes EULA from Linux Firefox


Also visit our sister site:


Sign up for LinuxDevices.com's...

news feed

Home  |  News  |  Articles  |  Polls  |  Forum  |  About  |  Contact
 

Ziff Davis Enterprise Home | Contact Us | Advertise | Link to Us | Reprints | Magazine Subscriptions | Newsletters
Tech RSS Feeds | White Papers | ROI Calculators | Tech Podcasts | Tech Video | VARs | Channel News

Baseline | Careers | Channel Insider | CIO Insight | DesktopLinux | DeviceForge | DevSource | eSeminars |
eWEEK | Enterprise Network Security | LinuxDevices | Linux Watch | Microsoft Watch | Mid-market | Networking | PDF Zone |
Publish | Security IT Hub | Strategic Partner | Web Buyer's Guide | Windows for Devices

Developer Shed | Dev Shed | ASP Free | Dev Articles | Dev Hardware | SEO Chat | Tutorialized | Scripts |
Code Walkers | Web Hosters | Dev Mechanic | Dev Archives | igrep

Use of this site is governed by our Terms of Service and Privacy Policy. Except where otherwise specified, the contents of this site are copyright © 1999-2008 Ziff Davis Enterprise Holdings Inc. All Rights Reserved. Reproduction in whole or in part in any form or medium without express written permission of Ziff Davis Enterprise is prohibited. Linux is a registered trademark of Linus Torvalds. All other marks are the property of their respective owners.