Category: Open Source Infrastructure

  • A V4L2 staging driver for the Raspberry Pi (RPi) was recently merged into the Linux kernel 4.11. While this driver is currently under development, I wanted to test it and to provide help with V4L2-related issues. So, I took some time to build an upstream kernel for the Raspberry Pi 3 with V4L2 enabled. This isn’t a complex process, but it requires some tricks for it to work; this article describes the process. Prepare an Upstream Kernel The first step is to prepare an upstream kernel by cloning a git tree from the kernel repositories. Since the Broadcom 2835 camera driver (bcm2835-v4l2) is currently under staging, it’s best to clone the staging tree because it contains the staging/vc04_services directory with both ALSA and V4L2 drivers:

    There’s an extra patch that it is required for DT to work with the bcm2835-v4l2 driver:

    You need to apply this to the git tree, in order for the vciq […]

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  • January 24, 2017 - Cedric Bail

    Improving the Security of Your SSH Configuration

    Most developers make use of SSH servers on a regular basis and it’s quite common to be a bit lazy when it comes to the admin of some of them. However, this can create significant problems because SSH is usually served over a port that’s remotely accessible. I always spend time securing my own SSH servers according to some best practices, and you should review the steps in this article yourself.  This blog post will expand upon these best practices by offering some improvements. Setup SSH Server Configuration The first step is to make the SSH service accessible via only the local network and Tor. Tor brings a few benefits for an SSH server: Nobody knows where users are connecting to the SSH server from. Remote scans need to know the hidden service address Tor uses, which reduces the risk of automated scan attacks on known login/password and bugs in the ssh server. It’s always […]

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  • October 28, 2016 - Mauro Carvalho Chehab

    Improving Linux Kernel Development Process Documentation

    This article will cover how the Linux kernel community handled the conversion of documentation related to the kernel development process; it’s part of a series on improvements being made to Linux kernel documentation. Introduction It’s not an easy task to properly describe the Linux development process. The kernel community moves at a very fast pace and produces about 6 versions per year. Thousands of people, distributed worldwide, contribute to this collective work; the development process is a live being that constantly adjusts to what best fits the people involved in the process. Additionally, since kernel development is managed per subsystems, each maintainer has their own criteria for what works best for the subsystem they take care of. To address this, the documentation provides a common ground for understanding the best practices all kernel developers should follow. The Documentation/Development-Process Book There are several files inside the kernel that describes the development […]

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  • October 13, 2016 - Mauro Carvalho Chehab

    Finishing the Conversion of Linux Media Documentation to ReST

    This article is part of a series on improvements to Linux Kernel documentation; this article will describe the effort to convert the remaining Linux Media subsystem documentation. The Linux Media Subsystem Documentation Before Kernel 4.8, the Linux Media documentation was splt into the Linux Media Infrastructure userspace API (uAPI), which described the system calls and sysfs devices the media subsystem uses. The conversion of this book was already explained in a previous article from this series, the Media subsystem kernel internal API (kAPI), which described the functions and data structures a media driver should use to implement drivers, some text files describing how to use the kAPI, these are spread inside the Documentation/ directory at the Kernel tree, a set of files that document some V4L drivers under Documentation/video4linux, and a set of files that document some DVB drivers, under Documentation/dvb. Converting the kAPI Book The kAPI book is actually […]

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  • This article is a part of a series that covers improvements that are being made to the Linux Kernel documentation; this article will begin to explain how we handled the conversion of the Linux Media subsystem documentation. The Linux Media Subsystem The Linux Media subsystem is actually a set of subsystems; each subsystem has its own particularities: Video4Linux –  API and core provide functions for video stream capture and output. It also provides support for video codecs, analog TV, AM/FM radio receivers and transmitters and for software digital radio (SDR) receivers and transmitters. Linux DVB – provides support for digital TV. Despite its name, it supports worldwide standards, including DVB, ATSC, ISDB, and CDDB, as well remote controllers and infra-red devices. Media Controller – provides pipeline control and reconfiguration inside the hardware. HDMI CEC – provides support for the HDMI Consumers Electronic Control (CEC): a system to pass remote controller […]

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  • This article is the first in a series on improvements to Linux Kernel documentation. The Linux Kernel has one of the biggest communities in the open source world; the numbers are impressive: over 4,000 contributors per year, resulting in about 8 changes per hour. That results in 4,600 lines of code added every day and a major release every 9-10 weeks. With these impressive numbers, it’s impossible for a traditional printed book to follow the changes because by the time the book is finally written, reviewed and published, a lot of changes have already merged upstream. So, the best way to maintain updated documentation is to keep it close to the source code. This way, when some changes happen, the developer that wrote such changes can also update the corresponding documents. That works great in theory, but it is not as effective as one might think. The Old Methods of […]

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  • Consistency is everything. If launching open source projects is part of your job, it is incredibly helpful to have a clear, consistent, and repeatable process for open sourcing code and building a project. Why? There are a few reasons. For one, it increases your odds of success if you can identify the parts of the process that worked well before, and repeat them. Project launches are about people as much as technology. There are actions that attract others, and actions that drive others away; it’s beneficial to remember which is which. If you can’t convince others to join and use your project, you may as well just post the code and be done with it. Another major reason is time. I seriously doubt I’m alone in observing that the typical “We’re launching an OSS project next month! Um, where do we start?” emails usually come with little warning. Most of the time […]

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  • September 6, 2016 - Reynaldo Verdejo

    Wayland Uninstalled, the Easy Way

    I recently had to start looking at some GStreamer & Wayland integration issues and, as everyone would, commenced by trying to setup a Wayland development environment. Before getting my feet wet though, I decided to have a chat about this with Derek Foreman: our resident Wayland expert. This isn’t surprising because on our team, pretty much every task starts by having a conversation (virtual or not) with one of the field specialists in the group. The idea is to save time, as you might have guessed. This time around I was looking for a fairly trivial piece of info: Me – “Hey Derek, I have Wayland installed on my distro for some reason – I don’t really want to take a look at now – and I would like to setup an upstream (development) Wayland environment without messing it up. Do you have some script like GStreamer’s gst-uninstalled so I can perform […]

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  • I have recently moved to a new flat and I love it, though unfortunately not all is perfect. One might expect central London (literally 500m away from the actual geographical centre) to have the best internet connection London has to offer. Well, one would be wrong; I am no longer able to get anything better than lousy ADSL2+, and this amazing offering comes with a high price, a long contract, and a month’s wait for the installation. This has led me to choose a 4G internet provider; the connection is usually better than what I would have expected to get with any of the landline providers, is much cheaper, and I had it up and running less than 24hrs after I joined. However, there is a problem with this: the 4G provider uses a carrier-grade NAT, that made impossible to access my home server from outside my home network. Luckily, […]

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  • Kaffeine version 2.0.4 has been released today, substantially improving its already excellent Digital TV (DTV) support! Update: tarball is now available at: http://download.kde.org/stable/kaffeine/2.0.4/src/kaffeine-2.0.4.tar.xz While version 2.0.4 was meant to solve several bugs reported via the project’s bug tracker, it offers a lot more: DVB-S/S2 Kaffeine improvements Kaffeine now supports the ability to select the Low Noise Blockdown feedhorn (LNBf) among a list of other LNB features used on Digital TV. This list comes from libdvbv5, which provides the backend to setup a satellite configuration. Other Network Information Table Scans Digital TV relies on physical transponders to transmit a signal, and each transponder can carry multiple channels. There’s a special table in the MPEG transport stream that’s responsible for listing the other transponders associated with a given transmission that belong to the same network provider. This table is called the Network Information Table (NIT). Sometimes, there are multiple tables on an […]

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