Initial GXFP5130 userspace prototype

libfprint-driver/README.md

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+# libfprint GXFP5130 integration skeleton
+
+This driver connects libfprint's `FpImageDevice` state machine to the
+hardware-tested `gxfp_session` API. Blocking sensor operations run in a GLib
+worker thread; all libfprint callbacks run in the main context.
+
+Current discovery is intentionally explicit because the sensor is an ACPI
+platform/character device, while upstream libfprint has no generic ACPI char
+device discovery type. Build the driver as an optional virtual-type driver and
+start libfprint/fprintd with:
+
+```sh
+FP_GXFP5130=/dev/gxfp
+```
+
+The integration must add `gxfp5130` to `drivers_info` and
+`libfprint_drivers_sources` in upstream Meson, include this file, add the GXFP
+headers, and link the PIC-built `libgxfp.a` plus mbedTLS libraries.
+
+The first image path uses the verified 64x80 sample order and the deterministic
+`gxfp_image12_to_u8()` conversion. No transpose, flip, inversion, percentile
+clipping, or unverified `0x21` command is applied.
+
+Before upstreaming, replace the environment-backed discovery with a dedicated
+udev/ACPI character-device discovery mechanism and install permissions for
+`/dev/gxfp`.