Care And Feeding Of Interrupt Handlers 2026 New

Today I decided to give my embryonic operating system a voice. Not literally—that would be terrifying—but an interactive shell so it could at least complain about its existence in real time. What started as an innocent afternoon project turned into another reminder that hardware and I have what therapists might call "trust issues."

The plan seemed reasonable enough: create a simple command prompt that could poke around the system hardware. You know, basic things like "what PCI devices do we have" and "where did all my memory go." The sort of diagnostic tools that separate a proper OS kernel from what is essentially a very expensive screensaver.

I'd already conquered the Herculean task of drawing pixels to the screen—my proudest achievement to date—so surely adding keyboard input couldn't be that much harder. The UEFI specification even provides nice abstractions for this sort of thing. Just read from ConIn, echo characters back, handle a few special keys. How hard could it be?

Narrator: It was exactly as hard as he expected, which somehow made it worse.

The shell implementation started promisingly. I created a neat little input loop that waits for keyboard events, echoes printable characters, and handles backspace with the sort of careful buffer management that would make my CS professors weep with pride. The command parser splits input on spaces and dispatches to handler functions. Clean, simple, maintainable code.

The first command I implemented was 'help', because I am fundamentally unoriginal. Then 'clear' to wipe the screen, because watching text scroll off into the void makes me existentially uncomfortable. Then 'reboot' and 'halt', because sometimes you need an escape hatch when your creation develops delusions of grandeur.

But the real meat was going to be hardware inspection. I wanted my OS to survey its domain like a new homeowner checking what's actually in the basement. This meant implementing PCI bus scanning—the digital equivalent of opening every cabinet and drawer to see what's inside.

PCI scanning is one of those things that sounds impressive but is really just systematic brute force. You iterate through every possible bus, device, and function combination, poking at I/O ports 0xCF8 and 0xCFC to see if anything responds. It's like knocking on doors in a very large, mostly empty apartment building, except some of the residents are graphics cards with anger management issues.

The beautiful thing about PCI is that it's completely stan

Source: Dev.to