# fprint-asus: libfprint patches for ASUS 04f3:0c6e fingerprint sensor

Patches for the Elan fingerprint sensor found in ASUS laptops (`04f3:0c6e`, FW 0x0161, 150x52 swipe sensor).

## Problem

The device does not implement the blocking behavior of `pre_scan_cmd` (command `0x40 0x3f`).
Instead of holding the USB response open until a finger is placed, it returns immediately with
a non-0x55 value when no finger is present. The upstream `elan` driver treats this as a fatal
protocol error (`FP_DEVICE_ERROR_PROTO`), causing every enrollment attempt to immediately fail
with `enroll-disconnected`.

## Patches applied to `libfprint/drivers/elan.c` and `elan.h`

| Change | Reason |
|---|---|
| `CAPTURE_READ_DATA`: retry instead of PROTO error | Device returns immediately with non-0x55 when no finger; retry until 0x55 |
| `ELAN_CALIBRATION_ATTEMPTS`: 10 → 30 | Give device more time to recalibrate between swipe stages |
| Calibration poll delay: 50ms → 100ms | Device needs ~100ms per calibration cycle |
| `bz3_threshold`: 24 → 10 | Accommodate smaller single-press images |
| `ELAN_MIN_FRAMES`: 7 → 4 | Allow short press/tap captures |

## Building and installing

```bash
# Dependencies (Rocky/RHEL 10)
sudo dnf install git meson ninja-build gcc gcc-c++ glib2-devel libgusb-devel nss-devel pixman-devel gobject-introspection-devel

# Clone upstream libfprint and apply patches
git clone --depth=1 https://gitlab.freedesktop.org/libfprint/libfprint.git
cp libfprint/drivers/elan.c libfprint/drivers/elan.h libfprint/libfprint/drivers/
cd libfprint
meson setup _build --prefix=/usr --buildtype=release
ninja -C _build
sudo systemctl stop fprintd
sudo ninja -C _build install
sudo systemctl start fprintd
```

## Usage

```bash
fprintd-enroll        # enroll a finger (slow press/swipe)
fprintd-verify $USER  # test verification
```

Tested on Rocky Linux 10.1 with ASUS laptop.