Revert experimental params to factory defaults

Remove threshold, enrollment stages, frame count, and timing
experiments — none produced reliable security on the 04f3:0c6e
power-button sensor due to bz3's inability to distinguish adjacent
fingers on small dark images from this form factor.

Retained fixes:
- ELAN_CALIBRATION_MAX_DELTA=65535: skip unreliable recalibration loop
- Polling fallback in CAPTURE_READ_DATA: prevent sensor overheating
- Dark frame → fpi_ssm_mark_completed: graceful end-of-swipe

All other values restored to upstream v1.94.10 defaults.

libfprint/drivers/elan.c

@@ -564,18 +564,12 @@ capture_run_state (FpiSsm *ssm, FpDevice *dev)
       r = elan_save_img_frame (self);
       if (r < 0)
         {
-          /* Frame was indistinguishable from background (dark frame / finger lifted
+          /* Frame was indistinguishable from background — treat as end-of-swipe */
-           * mid-capture). Treat as end-of-swipe rather than hard failure — the
-           * frames already accumulated may still be usable. */
           fpi_ssm_mark_completed (ssm);
         }
       else if (self->num_frames < ELAN_MAX_FRAMES)
         {
-          /* Loop back via WAIT_FINGER so the device can re-arm its finger
+          /* quickly stop if finger is removed */
-           * detection. ELAN_FINGER_TIMEOUT controls how long to wait — if
-           * the finger is still pressed the device returns 0x55 again and
-           * we capture another frame; if the finger is lifted it times out
-           * and capture ends. A longer timeout allows tap/hold behaviour. */
           self->cmd_timeout = ELAN_FINGER_TIMEOUT;
           fpi_ssm_jump_to_state (ssm, CAPTURE_WAIT_FINGER);
         }
@@ -770,7 +764,7 @@ calibrate_run_state (FpiSsm *ssm, FpDevice *dev)
           if (self->calib_status == 0x00 &&
               self->last_read[0] == 0x01)
             self->calib_status = 0x01;
-          fpi_ssm_next_state_delayed (ssm, 100);
+          fpi_ssm_next_state_delayed (ssm, 50);
         }
       break;
 
@@ -1016,7 +1010,5 @@ fpi_device_elan_class_init (FpiDeviceElanClass *klass)
   img_class->deactivate = dev_deactivate;
   img_class->change_state = dev_change_state;
 
-  img_class->bz3_threshold = 2;
+  img_class->bz3_threshold = 24;
-
-  dev_class->nr_enroll_stages = 10;
 }

libfprint/drivers/elan.h

@@ -47,10 +47,10 @@
 
 /* times to retry reading calibration status during one session
  * generally prevents calibration from looping indefinitely */
-#define ELAN_CALIBRATION_ATTEMPTS 100
+#define ELAN_CALIBRATION_ATTEMPTS 10
 
 /* min and max frames in a capture */
-#define ELAN_MIN_FRAMES 1
+#define ELAN_MIN_FRAMES 7
 #define ELAN_MAX_FRAMES 30
 
 /* crop frames to this height to improve stitching */
@@ -58,7 +58,7 @@
 
 /* number of frames to drop at the end of capture because frames captured
  * while the finger is being lifted can be bad */
-#define ELAN_SKIP_LAST_FRAMES 0
+#define ELAN_SKIP_LAST_FRAMES 2
 
 #define ELAN_CMD_LEN 0x2
 #define ELAN_EP_CMD_OUT (0x1 | FPI_USB_ENDPOINT_OUT)
@@ -71,7 +71,7 @@
 /* usual command timeout and timeout for when we need to check if the finger is
  * still on the device */
 #define ELAN_CMD_TIMEOUT 10000
-#define ELAN_FINGER_TIMEOUT 350
+#define ELAN_FINGER_TIMEOUT 200
 
 G_DECLARE_FINAL_TYPE (FpiDeviceElan, fpi_device_elan, FPI, DEVICE_ELAN,
                       FpImageDevice);