Both sticks on a virtual Switch Pro sat in the top-right corner under
Steam, reaching centre only at full down-left. Buttons and motion were
fine, and the kernel's own evdev node read correctly throughout.
The SPI-flash handler matched an exact (address, length) pair, and those
pairs came from hid-nintendo. Steam does not use the kernel driver here;
it uses SDL's HIDAPI Switch driver, which reads the same calibration as
18 bytes at 0x603D and 22 at 0x8010. Neither matched, so both fell to
the zero-fill path — which echoes the requested address, so SDL accepted
the reply and parsed a zeroed calibration. A zero centre is never
subtracted, leaving every raw axis value positive.
Serve reads by range from a modelled flash image, so every consumer gets
the same bytes whatever shape it asks for. What hid-nintendo receives is
byte-identical, and the IMU block already used SDL's length, so motion is
untouched. The caller loses its zero-fill fallback.
enricobuehler