Embedded Linux System Development Embedded Linu...
Today, Linux systems are used throughout computing, from embedded systems to virtually all supercomputers, and have secured a place in server installations such as the popular LAMP application stack. Use of Linux distributions in home and enterprise desktops has been growing. Linux distributions have also become popular in the netbook market, with many devices shipping with customized Linux distributions installed, and Google releasing their own ChromeOS designed for netbooks.
Embedded Linux system development Embedded Linu...
The user interface, also known as the shell, is either a command-line interface (CLI), a graphical user interface (GUI), or controls attached to the associated hardware, which is common for embedded systems. For desktop systems, the default user interface is usually graphical, although the CLI is commonly available through terminal emulator windows or on a separate virtual console.
A common feature of Unix-like systems, Linux includes traditional specific-purpose programming languages targeted at scripting, text processing and system configuration and management in general. Linux distributions support shell scripts, awk, sed and make. Many programs also have an embedded programming language to support configuring or programming themselves. For example, regular expressions are supported in programs like grep and locate, the traditional Unix MTA Sendmail contains its own Turing complete scripting system, and the advanced text editor GNU Emacs is built around a general purpose Lisp interpreter.
Note: The restriction of one single fullscreen window per screen still applies. Changing screens after making the QWindow visible isn't supported either. Therefore, it's essential that embedded applications make all the necessary QWindow::setScreen() calls before calling QWindow::show().
When you start developing on a given embedded device, often it's necessary to verify the behavior of the device and drivers, and that the connected displays are working as they should. One easy way is to use the hellowindow example. Launching it with the -platform eglfs --multiscreen --timeout arguments shows a rotating Qt logo on each connected screen for a few seconds.
Note: In an embedded environment, virtual desktops are more limited compared to a full windowing system. Windows overlapping multiple screens, non-fullscreen windows, and moving windows between screens, should be avoided and may not function as expected.
Other backends, that are typically based on targeting the framebuffer or a composition API directly via the vendor's EGL implementation, usually provide limited or no support for multiple displays. On i.MX6-based boards with Vivante GPUs the QT_QPA_EGLFS_FB environment variable can be used to specify the framebuffer to target, similarly to linuxfb. On the Raspberry Pi the QT_QPA_EGLFS_DISPMANX_ID environment variable can be used to specify the screen to output to. The value corresponds to one of the DISPMANX_ID_ constants, refer to the Dispmanx documentation. Note that these approaches, unlike KMS/DRM, will not typically allow to output to multiple screens from the same application. Alternatively, driver-specific environment variables or kernel parameters may also be available as well to control the used framebuffer. Refer to the embedded board's documentation.
This is the X11 plugin used on regular desktop Linux platforms. In some embedded environments, that provide X and the necessary development files for xcb, this plugin functions just like it does on a regular PC desktop.
With Qt Quick, it's possible to use either hardware-accelerated or software-rendered backends. For complex Uls, using Qt Widgets on embedded targets is not recommended, as it will always use a software backend.
We have already given two sessions of our Embedded Linux system development training with the IGEPv2, and all our future sessions of this training will use this hardware platform, so the participants will benefit from a more modern platform, with far more capabilities than our previous AT91-based training hardware. This is also the board we are now giving to the participants to our public training sessions, so those participants come back home with a very nice and powerful platform which allows countless experiments around embedded Linux. Note that we also intend to port our Embedded Linux kernel and driver development training session to the IGEPv2 platform in the near future.
In your embedded projects, if you are using a compressed kernel, make sure it is loaded far enough from the beginning of RAM, leaving enough space for the decompressed kernel to fit in between. Otherwise, your system will still be able to boot, but depending on the speed of your CPU and storage, it will be slower, from a few tens to a few hundreds of milliseconds.
Linux 6.2 was released a few days ago, and as usual we point our readers to the LWN coverage of the merge window (part 1 and part 2), or the traditional KernelNewbies page or alternatively the embedded focused CNX Software coverage.
For many years, we have been offering our training courses in both English and French. We are happy to announce that we are now expanding our offering towards our Italian customers: we are now able to deliver our very popular Embedded Linux system development and Yocto Project and OpenEmbedded development training courses in Italian. Those courses are delivered by a native Italian speaker, Bootlin engineer Luca Ceresoli. Luca has 20 years of experience working with embedded systems, including 15 years on embedded Linux.
Developers of embedded systems must ensure their products are secure, or they place their customers at risk Developers of embedded systems must ensure their products are secure, or they place their customers at risk massive commitment of time and resources because of the flood of vulnerabilities. With Vigiles, Timesys is delivering a breakthrough in the automation of vulnerability identification, tracking, analysis and mitigation.
libinput is a library to handle input devices. It offers an alternative to the Qt's own evdev input support. To enable using libinput, make sure the development files for libudev and libinput are available when configuring and building Qt. xkbcommon is also necessary if keyboard support is desired. With eglfs and linuxfb no further actions are necessary as these plugins use libinput by default. If libinput support is not available or the environment variable QT_QPA_EGLFS_NO_LIBINPUT is set, Qt's own evdev handlers come in to play.
eglfs comes with its own set of 32x32 sized mouse cursor images. If these are not sufficient, a custom cursor atlas can be provided by setting the QT_QPA_EGLFS_CURSOR environment variable to the name of a JSON file. The file can also be embedded into the application via Qt's resource system.
Note: The restriction of one single fullscreen window per screen still applies. Changing screens after making the QWindow visible is not supported either. Therefore, it is essential that embedded applications make all the necessary QWindow::setScreen() calls before calling QWindow::show().
When getting started with developing on a given embedded device, it is often necessary to verify the behavior of the device and drivers, and that the connected displays are working as they should. One easy way is to use the hellowindow example. Launching it with -platform eglfs --multiscreen --timeout arguments shows a rotating Qt logo on each connected screen for a few seconds.
The KMS/DRM backend also supports custom configurations via a JSON file. Set the environment variable QT_QPA_EGLFS_KMS_CONFIG to the name of the file to enable this. The file can also be embedded into the application via the Qt resource system. An example configuration is below:
Note: In an embedded environment virtual desktops are more limited than with a full windowing system. Windows overlapping multiple screens, non-fullscreen windows and moving windows between screens should be avoided and may not function as expected.
Linux is a Unix-like, open source and community-developed operating system (OS) for computers, servers, mainframes, mobile devices and embedded devices. It is supported on almost every major computer platform, including x86, ARM and SPARC, making it one of the most widely supported operating systems.
There are distributions tailored for specific target functions, such as servers, desktops, gaming, security, or embedded devices including Raspberry Pi systems. Most modern distributions are precompiled and ready to use, while others like Gentoo Linux consist of source code that a user can compile locally during initial installation to optimize their system configuration. Knoppix Linux is one of many distros used to recover damaged hard drives and perform other technical support tasks. Information security professionals use Kali Linux for penetration testing and other security-related tasks. 041b061a72