I wrote an introductory article on how the audio subsystem on SBCs work: CODECs, I2S, DTS, whole nine yards. WordPress editor didn’t seem to be a very convenient tool for this kind of write up so I gave asciidoc a try and so far liked it. Link to the article: https://kernelnomicon.org/texts/sbc-audio.html
Some time ago Filippo Valsorda wrote yubikey-agent, seamless SSH agent for YubiKeys. I really like YubiKeys and worked on the FreeBSD support for U2F in Chromium and pyu2f, getting yubikey-agent ported looked like an interesting project. It took some hacking to make it work but overall it wasn’t hard. Following is the roadmap on how to get it set up on FreeBSD. The actual details depend on your system (as you will see) ...
Whenever I sit down to work at the coffee shop I’ve never been before my preparation routine looks more or less like this: ifconfig wlan0 list scan, copy SSID, vim /etc/wpa_supplicant.conf, service netif restart. The WM I use, i3, does not have fancy network managers that nicely offer you to join available WiFi networks. It’s mildly annoying but not annoying enough to actually make me open a browser and go looking for ways to automate this procedure. Implementing such a utility, on the other hand, sounds like a nice weekend project. ...
If you want to jump right into the action check out freebsd-mkova repo. Below are some technical details on what OVA is and its internals. In addition to installation media like DVD or memstick, FreeBSD RE ships FreeBSD releases as a virtual disk image in a number of formats. This is a convenient way when you start your whole VM using bhyve or qemu, as a single CLI command and pass the image location as an argument. It’s less handy if you try to create VM using GUI-based tools like VMWare or VirtualBox. You need to create VM and then configure it to use the image as a drive. Not an awful lot of work but still. ...
If you’re building OVA based on CentOS 7 and your VM is stuck during boot at “tsc: Refined TSC clocksource calibration: NNNN.MMM MHz” message do not despair! It means the kernel can not find the root device and just waits for it to pop up. Which is not going to happen. In my case, it was a lack of required drivers loaded boot-time. Following line in an OVA build script resolved the issue: ...
Last two weeks I’ve been working on audio support for Firefly-RK3399. Full support requires a number of things that are not quite there or not available in the mainline FreeBSD kernel. The main low-level hardware functionality consists of two parts: I2S block in the SoC and RT5640 audiocodec that converts digital audio to an analog signal. They talk to each other using the I2S protocol. A little bit higher is FDT virtual “devices” called simple-audio-card. This part is responsible for coordinating the setup of both hardware components: make sure they agree on a number of channels, a number of bits per sample and clock specifics of the I2S protocol. There is no code for it in the FreeBSD kernel, so I had to just hardcode these things in both hardware drivers. ...
(Not a FreeBSD topic) A long time ago, in my teens, I watched movie Sneakers and was very impressed by it. It was exactly how I imagined hackers at work: bare PCBs, signal probes, de-scrambling encrypted information right on the screen. I was so impressed by the latter part that I went to re-create a bit of “No more secrets” scene using the only technologies I knew back then: Turbo Pascal running on MS-DOS. It wasn’t an exact replica but it was close enough and I was quite happy with the result. The program itself hasn’t survived my numerous moves from one apartment to another and got lost along with all the floppy discs sometime in the early aughts. ...
After long hiatus (because $JOB) I’m trying to find some time to spend on FreeBSD-related projects, looking for small ones that can be done over weekend or a bit more. One of the ideas came from Ed Maste’s twitter: implement FreeBSD support for pyu2f. Since I already spent some time working on FreeBSD U2F support for Chromium it felt like a good small project. The challenging part of the project was not U2F/HID but interfacing ioctl with Python, something I have never done before. It wasn’t super complex and I learned about Python’s ctype module. ...
About a month ago I purchased Inky pHat from Pimoroni, Pi hat with 220x104 red and black eInk screen. The device has an SPI interface with three additional GPIO signals: reset pin, command/data pin, and busy pin. Reset and busy pins are self-explanatory: the former resets device MCU the latter signals to the Pi whether the MCU is busy handling previous command/data. Command/data signals the type of SPI transaction that is about to be sent to Inky: low means command, high - data. It more or less matches interface to SSD1306 OLED display I played with before. ...
I was updating my laptop to the latest HEAD today and noticed that my bash prompt looks ugly in default console color scheme. So what with one thing and another I ended up writing color themes support for vt(4). Just because it was fun thing to do. The idea is that you can redefine any ANSI color in console using variable in /boot/loader.conf, i.e.: kern.vt.color.0.rgb="0,0,0" # color 0 is black # or kern.vt.color.15.rgb="#ffffff" # color 15 is white Here is how my Tomorrow Night theme looks like: ...