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A comment on A note on the USB-to-PS/2 mouse adapter that came with Microsoft mouse devices. Parent comment

Re:A note on the USB-to-PS/2 mouse adapter that came with Mi... by fbrozovic on Friday March 28, 2025 @02:59AM (#43502351)
To add to this: the keyboard matrix scan controller on laptops is usually located inside the Super I/O chip and connected to the CPU/southbridge via LPC or eSPI. Since LPC/eSPI peripherals are mapped to I/O ports, implementing an 8042 controller means that the keyboard can work even without setting up a much more complicated USB host stack.
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Re:A note on the USB-to-PS/2 mouse adapter that came with Mi... by p_l on Friday March 28, 2025 @08:02AM (#43504303)
On laptops it's usually not SuperIO, but EC (Embedded Controller), the same chip that handles battery, power, etc. and is usually connected over LPC to "present" the keyboard as PS/2 compatible input (some new ones are pure USB though, like my current laptop)

Some devices have SPI interfaces for HID though

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