What is scrollwheel?

This is a small personal hardware project by Linus Torvalds that turns an RP2350 microcontroller and a magnetic angle sensor into a physical scroll wheel or volume control knob. The RP2350 is a chip made by Raspberry Pi used in tiny programmable boards. The magnetic sensor (an AS5600) detects rotation, and up to four pushbutton switches can be wired in to act as additional controls. The README names a couple of specific boards it has been tested with, including the Pimoroni Tiny 2350 and the Waveshare RP2350 Zero, but notes that pin assignments and LED types differ between boards. Some boards have a smart RGB LED that needs a special communication protocol, others use three separate GPIO pins for color control, some have no LED at all. The project includes code for a WS2812-style LED but you may need to adjust things depending on what hardware you have. The author is straightforward that this is a toy project and an early experiment with the RP2350 platform, not polished or production-ready. The README explicitly says not to expect it to work out of the box without some adjustment to pin numbers and LED configuration. The intent is for someone to use it as a starting point and adapt it to their own setup. The codebase is written in C and is minimal in scope. The README is brief and the project is framed as a personal tinkering exercise rather than a general-purpose library.