linux

619 Articles

Linux Fu: The Browser Emacs Fusion

July 6, 2022 by 20 Comments

It is no secret that I have a few things permanently burned into my neurons: the 1802 instruction set, the commands for WordStar, and the commands for emacs. There was a time when emacs was almost my operating system. With no X11, emacs gave you a way to have a shell in one window, check your mail, and keep your work open.

I still use emacs a lot (although I’ve been getting more and more pleased with vscode with an emacs keybinding extension). But I also spend a lot of time — like right now — writing in a Web browser. Especially if I’m writing about code, it gets hard to remember which set of keys you have to use and I’ve wanted to do something about it for a long time. The answer is a very cool program called Autokey. (You can download my files for it, but you probably want to read more first.) It probably doesn’t work if you have switched to Wayland, but it can do a lot for you ranging from saving you some typing to reprogramming your favorite program to have different keystrokes. However, it isn’t without its problems, and I’ll tell you what I know about it.

The Value Proposition

Autokey sits in your system tray and it watches what you type. In its most simple usage, you can set up different phrases to substitute what you type.

For example, I might reprogram HaD to show up as Hackaday to save myself some typing. I usually use some odd character at the start or end so I don’t accidentally trigger things. So maybe I’m tired of typing or mistyping http://www.hackaday.com. I could set up ~had to automatically type the correct URL for me.

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Need A Linux Kernel Module? Scratch That

July 4, 2022 by 15 Comments

If you have been for (or against) Rust in the Linux kernel, get ready for a Linux kernel module written in… Scratch. That’s right. Scratch, the MIT-developed language with blocks popular for teaching kids to code. We didn’t mean “from scratch.” We meant IN Scratch. The bootstrap code and Makefile is out there on GitHub.

Of course, it is a simple module and the reason it is possible is because of the scratchnative system that lets you compile Scratch into C code. If you want to look at the decidedly simple code, you can open it in your browser.

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Linux Fu: Docking Made Easy

June 21, 2022 by 20 Comments

Most computer operating systems suffer from some version of “DLL hell” — a decidedly Windows term, but the concept applies across the board. Consider doing embedded development which usually takes a few specialized tools. You write your embedded system code, ship it off, and forget about it for a few years. Then, the end-user wants a change. Too bad the compiler you used requires some library that has changed so it no longer works. Oh, and the device programmer needs an older version of the USB library. The Python build tools use Python 2 but your system has moved on. If the tools you need aren’t on the computer anymore, you may have trouble finding the install media and getting it to work. Worse still if you don’t even have the right kind of computer for it anymore.

One way to address this is to encapsulate all of your development projects in a virtual machine. Then you can save the virtual machine and it includes an operating system, all the right libraries, and basically is a snapshot of how the project was that you can reconstitute at any time and on nearly any computer.

In theory, that’s great, but it is a lot of work and a lot of storage. You need to install an operating system and all the tools. Sure, you can get an appliance image, but if you work on many projects, you will have a bunch of copies of the very same thing cluttering things up. You’ll also need to keep all those copies up-to-date if you need to update things which — granted — is sort of what you are probably trying to avoid, but sometimes you must.

Docker is a bit lighter weight than a virtual machine. You still run your system’s normal kernel, but essentially you can have a virtual environment running in an instant on top of that kernel. What’s more, Docker only stores the differences between things. So if you have ten copies of an operating system, you’ll only store it once plus small differences for each instance.

The downside is that it is a bit tough to configure. You need to map storage and set up networking, among other things. I recently ran into a project called Dock that tries to make the common cases easier so you can quickly just spin up a docker instance to do some work without any real configuration. I made a few minor changes to it and forked the project, but, for now, the origin has synced up with my fork so you can stick with the original link.

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iPhone 6 with Linux boot log on its screen

Boot Mainline Linux On Apple A7, A8 And A8X Devices

June 12, 2022 by 10 Comments

[Konrad Dybcio] tells about his journey booting Linux on A7/8/8X processors, playing around with an old iPhone 5 he’s got in a drawer. It’s been a two-year “revisit every now and then” journey, motivationally fueled by the things like Linux on M1 Macs announcement. In the end, what we have here is a way to boot mainline Linux on a few less-than-modern but still very usable iPhones, and a fun story about getting there.

[Konrad]’s work is based on the Sandcastle project research, but he couldn’t quite figure out how to make their code work, and had to make sense of it as he went. At some point, he got stuck on enabling the MMU, which was the main roadblock for a while. Joined by another developer intrigued by Apple hardware, they were hacking away at it, developing tools and neat tricks on their way, but to no avail. With the framebuffer accessible and no other decent debugging methods in sight, he tells about a code snippet they wrote that printed register values as valid barcodes Continue reading “Boot Mainline Linux On Apple A7, A8 And A8X Devices” →

A Linux Distribution For DOOM

June 9, 2022 by 40 Comments

If you’ve gone further into the Linux world than the standard desktop distributions like Ubuntu or Fedora, you have undoubtedly come across some more purpose-built distributions. Some examples are Kali for security testing, DragonOS for software-defined radio, or Hannah Montana Linux for certain music fans. Anyone can roll their own Linux distribution with the right tools, including [Shadly], who recently created one which only loads enough software to launch the 1993 classic DOOM.

The distribution is as simple as possible and loads no bloat other than what’s needed to launch the game. It loads the Linux kernel and the standard utilities via BusyBox, then runs fbDOOM, which is a port of the game specifically designed to run on the Linux framebuffer with minimal dependencies. After most of that, the only thing left is to use GRUB to boot the distribution, and in just a moment, Doomguy can start slaying demons. The entire distribution is placed into a bootable ISO file that can be placed on any bootable drive.

As far as DOOM hacks go, we’re used to seeing the game running on hardware it was never intended for like the NES  or on an office phone. This one, on the other hand, gives us a little more insight into just how little is needed for a full-fledged Linux distribution, as long as what you need to do is relatively straightforward.

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The SoM on an evaluation board, with two LEDs shining, one USB-C cable connected for power and another plugged into the OTG port

New Part Day: X1501 Makes For A Tiny And Open Linux SoM

June 5, 2022 by 26 Comments

Ever wanted to run Linux in an exceptionally small footprint? Then [Reimu NotMoe] from [SudoMaker] has something for you! She’s found an unbelievably small Linux-able chip in BGA, and designed a self-contained tiny SoM (System on Module) breakout with power management and castellated pads. This breakout contains everything you need to have Linux in a 16x16x2mm footprint. For the reference, a 16mm square is the size of the CPU on a Raspberry Pi.

This board isn’t just tiny, it’s also well-thought-out, helping you put the BGA-packaged Ingenic X1501 anywhere with minimal effort. With castellated pads, it’s easy to hand-solder this SoM for development and reflow for production. An onboard switching regulator works from 6V down to as low as 3V, making this a viable battery-powered Linux option. It can even give you up to 3.3V/1A for all your external devices.

The coolest part yet – the X1501 is surprisingly friendly and NDA-free. The datasheets are up for grabs, there are no “CONFIDENTIAL” watermarks – you get a proper 730-page PDF. Thanks to this openness, the X1501 can run mainline Linux with minimal changes, with most of the peripherals already supported. Plus, there’s Efuse-based Secure Boot if your software needs to be protected from cloning.

More after the break…

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Optimizing Linux Pipes

June 3, 2022 by 28 Comments

In CPU design, there is Ahmdal’s law. Simply put, it means that if some process is contributing to 10% of your execution, optimizing it can’t improve things by more than 10%. Common sense, really, but it illustrates the importance of knowing how fast or slow various parts of your system are. So how fast are Linux pipes? That’s a good question and one that [Mazzo] sets out to answer.

The inspiration was a highly-optimized fizzbuzz program that clocked in at over 36GB/s on his laptop. Is that a common speed? Nope. A simple program using pipes on the same machine turned in not quite 4 GB/s. What accounts for the difference?

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