Here are five possible code completions for the given function:

**Option 1: Null Pointer Check and Free**
```c
void thermal_debug_cdev_remove(struct thermal_cooling_device *cdev)
{
    if (cdev != NULL) {
        kfree(cdev);
        cdev = NULL;
    }
}
```

**Option 2: Device Unregistration and Free**
```c
void thermal_debug_cdev_remove(struct thermal_cooling_device *cdev)
{
    if (cdev != NULL) {
        thermal_cooling_device_unregister(cdev);
        kfree(cdev);
        cdev = NULL;
    }
}
```

**Option 3: Device Cleanup and Free**
```c
void thermal_debug_cdev_remove(struct thermal_cooling_device *cdev)
{
    if (cdev != NULL) {
        thermal_cooling_device_cleanup(cdev);
        kfree(cdev);
        cdev = NULL;
    }
}
```

**Option 4: Device Release and Free**
```c
void thermal_debug_cdev_remove(struct thermal_cooling_device *cdev)
{
    if (cdev != NULL) {
        thermal_cooling_device_release(cdev);
        kfree(cdev);
        cdev = NULL;
    }
}
```

**Option 5: Device Unregister and Cleanup**
```c
void thermal_debug_cdev_remove(struct thermal_cooling_device *cdev)
{
    if (cdev != NULL) {
        thermal_cooling_device_unregister(cdev);
        thermal_cooling_device_cleanup(cdev);
        kfree(cdev);
        cdev = NULL;
    }
}
```

Note: These options assume that the `thermal_cooling_device` struct is dynamically allocated and needs to be freed. The actual implementation may vary depending on the specific requirements of the thermal cooling device driver.