SM8750: AYN Odin 3 Snapdragon Sensor Core accel+gyro (gyro in games)

[aanze]

Summary

• What is the goal of this PR? Bring up the AYN Odin 3 (SM8750) built-in IMU (QST QMI8658) so gyro works in games and Steam (motion aim, tilt, gyro-to-mouse) through the emulated DualSense.

The QMI8658 sits on the ADSP-owned Snapdragon Sensor Core (SSC) island bus — unreachable from the AP directly. Android reads it through the sensor DSP; this PR does the same:

• odin3-sensors package (sysutils/, SM8750-gated via ADDITIONAL_PACKAGES): adsprpcd — built from qualcomm/fastrpc for glibc — spawns the ADSP sensorspd static PD (mainline fastrpc, no kernel changes) and runs the reverse-RPC listener; snsfeed reads accel+gyro over QRTR (sns_client) with gyro bias auto-calibration; ships the Hexagon sensor registry (qcom-hexagon-fs) + a boot service.
• sns_iio kernel module (patch 0514, CONFIG_SNS_IIO=m): exposes accel+gyro as a standard IIO device, fed from userspace via /dev/sns_iio_feed.
• InputPlumber composite gains an imu source → motion routes to the DualSense (ds5-edge) target. Works with stock InputPlumber (no fork).

Credit: the sensor registry data comes from Gio's ROCKNIX/sensor-firmware — all credit for collecting the Odin 3 SSC registry/calibration data goes there.

Note (transparency): Gio is also adding SSC support inside InputPlumber via libssc. This PR takes a different last-mile — a userspace-fed standard IIO device consumed by stock InputPlumber, so the sensors are also usable by anything reading /sys/bus/iio and there's no InputPlumber fork to maintain. Trade-off: the IIO bridge is poll-based vs Gio's event-driven path (his is better for very precise aiming). Flagging so the two efforts don't collide — happy to align/merge approaches.

Testing

• How was this tested? Full SM8750 build, flashed on an AYN Odin 3, tested end-to-end: sensors register at boot, InputPlumber picks up the IMU, gyro works in Steam and in-game via the emulated DualSense.
• Test results: In-game motion aim confirmed, smooth camera control. Steam Input reads the DualSense gyro from hidraw; accel reads gravity correctly; gyro bias auto-calibrated at rest.

Additional Context

• Self-contained: on a clean upstream build ds5-edge is the default target, so gyro is active by default — no extra config needed, no dependency on other changes.
• The IIO device is userspace-fed (a bridge, named bmi323-imu so InputPlumber's iio_imu driver binds via its glob). Suggested review focus: the fastrpc build recipe in the package, and the composite imu source.

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AI Usage

Did you use AI tools to help write this code? YES