[PATCH v2 7/8] iio: magnetometer: hid-sensor-magn-3d: Avoid race between callback setup and device exposure

[Sanjay Chitroda]

From: Sanjay Chitroda <sanjayembeddedse@xxxxxxxxx>

The driver currently exposes the IIO device to userspace before
completing sensor hub callback registration, and similarly removes
callbacks while the device can still be accessed during teardown.

This creates a timing window where userspace may enable the buffer
before callbacks are available. In such cases:
- samples can be dropped,
- buffered reads may observe stale or no data.

Reorder probe and remove paths to ensure callbacks are active before
device exposure and are removed after device is no longer accessible.

This avoids a race window leading to data loss.

Signed-off-by: Sanjay Chitroda <sanjayembeddedse@xxxxxxxxx>
---
 drivers/iio/magnetometer/hid-sensor-magn-3d.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/iio/magnetometer/hid-sensor-magn-3d.c b/drivers/iio/magnetometer/hid-sensor-magn-3d.c
index 23884825eb00..acae77273bd5 100644
--- a/drivers/iio/magnetometer/hid-sensor-magn-3d.c
+++ b/drivers/iio/magnetometer/hid-sensor-magn-3d.c
@@ -513,12 +513,6 @@ static int hid_magn_3d_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	ret = iio_device_register(indio_dev);
-	if (ret) {
-		dev_err(&pdev->dev, "device register failed\n");
-		goto error_remove_trigger;
-	}
-
 	magn_state->callbacks.send_event = magn_3d_proc_event;
 	magn_state->callbacks.capture_sample = magn_3d_capture_sample;
 	magn_state->callbacks.pdev = pdev;
@@ -526,13 +520,19 @@ static int hid_magn_3d_probe(struct platform_device *pdev)
 					&magn_state->callbacks);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "callback reg failed\n");
-		goto error_iio_unreg;
+		goto error_remove_trigger;
+	}
+
+	ret = iio_device_register(indio_dev);
+	if (ret) {
+		dev_err(&pdev->dev, "device register failed\n");
+		goto error_remove_callback;
 	}
 
 	return ret;
 
-error_iio_unreg:
-	iio_device_unregister(indio_dev);
+error_remove_callback:
+	sensor_hub_remove_callback(hsdev, HID_USAGE_SENSOR_COMPASS_3D);
 error_remove_trigger:
 	hid_sensor_remove_trigger(indio_dev, &magn_state->magn_flux_attributes);
 	return ret;
@@ -545,8 +545,8 @@ static void hid_magn_3d_remove(struct platform_device *pdev)
 	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
 	struct magn_3d_state *magn_state = iio_priv(indio_dev);
 
-	sensor_hub_remove_callback(hsdev, HID_USAGE_SENSOR_COMPASS_3D);
 	iio_device_unregister(indio_dev);
+	sensor_hub_remove_callback(hsdev, HID_USAGE_SENSOR_COMPASS_3D);
 	hid_sensor_remove_trigger(indio_dev, &magn_state->magn_flux_attributes);
 }
 

-- 
2.34.1