Hacker News Reader

brontitallon Show HN: Interactive systemd – a better way to work with systemd units

Doing it the way it does allows specifying multiple services.

systemctl status myapp mydb

brontitallon Matt Mullenweg describes building a business around WordPress.org as a "gamble"

Taken down by legal threat? Has he gone full Billy Mitchell?

OMG yes! That appeared in the somewhat recent UI revamp and I’m so tired of mashing at that button. Not only is it unavailable for what feels like more than a second, but now it’s in a different place

brontitallon Tetris shows promise in reducing PTSD symptoms

This is a newer application of an existing approach

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2607539/

brontitallon Windows NT vs. Unix: A design comparison

> (Windows also has a stable driver API and I have yet to see a Unix with that, but that's another tangent)

Solaris has (or at least had) DDI (Device Driver Interface) and DLPI (Data Link Provider Interface)

brontitallon My new favourite AArch64 CPU instruction: RMIF – rotate then merge in to flags

While we are on funny real instructions, I remember years ago thinking that the VAX MOVTUC instruction was the hilarious pinnacle of CISC instructions

http://odl.sysworks.biz/disk$axpdocdec011/opsys/vmsos73/vmso...

brontitallon My new favourite AArch64 CPU instruction: RMIF – rotate then merge in to flags

Not sure if this is it

https://web.archive.org/web/20170908154113/https://www.physi...

brontitallon Hello world in C inline assembly (2018)

Not inline, but this was linked in a comment on HN a few days ago

https://github.com/below/HelloSilicon

brontitallon Biscuit authorization

I think the RFC pronunciation guide

> the same as the English word "jot".

Only makes sense if your dialect has the cot-caught merger[0]

[0] https://en.wikipedia.org/wiki/Cot%E2%80%93caught_merger

brontitallon The Timer in WatchOS 10

You can save, err, time here

“Hey, Siri, 10 minutes” works fine

brontitallon Assembler on Raspberry Pi

I wrote a longer answer in response to your other comment. It has a lot of explanation that I see from this comment is likely not needed for you. I’m pasting it here, anyway. I’m no expert in ARM assembler but it appears that SWI 0, later renamed SVC[1], is how you make system calls in ARM Linux[2]. That would make it equivalent to x86 syscall. In other words, it’s the underlying mechanism that libc uses to ask the kernel to output some data. In this case you are calling the write[3] system call (selected by r7=4) with the arguments (r0:fd=1 - file descriptor 1 – i.e. stdout, r1:buf - the address of the data to write, r2:count=14). The kernel then does whatever is necessary to accomplish that write. It could be talking to the video core to update the text console or the contents of a window. It could be passing it to its lower networking layers for sending over an existing network connection for an ssh connection.

It’s pretty fundamental to the Linux kernel that you can’t access any hardware directly unless things have been set up specially to allow it in a limited way. If you really want to deal directly with the hardware, you either have to convince the kernel to allow you to, or run without an operating system. In that latter case, it’s on you to drive all of the hardware. And there’s actually quite a lot of hardware involved in getting stuff displayed on a raspberry pi screen.

[1]: https://developer.arm.com/documentation/qrc0001/latest/ [2]: https://man7.org/linux/man-pages/man2/syscall.2.html [3]: https://man7.org/linux/man-pages/man2/write.2.html