orb: move SmartLock into global space and use it also for NuttX

src/drivers/device/device_nuttx.h

@@ -188,6 +188,8 @@ protected:
 	 * Each driver instance has its own lock/semaphore.
 	 *
 	 * Note that we must loop as the wait may be interrupted by a signal.
+	 *
+	 * Careful: lock() calls cannot be nested!
 	 */
 	void		lock()
 	{
@@ -202,10 +204,11 @@ protected:
 		sem_post(&_lock);
 	}
 
+	sem_t		_lock; /**< lock to protect access to all class members (also for derived classes) */
+
 private:
 	int		_irq;
 	bool		_irq_attached;
-	sem_t		_lock;
 
 	/** disable copy construction for this and all subclasses */
 	Device(const Device &);

src/drivers/device/vdev.h

@@ -196,29 +196,9 @@ protected:
 		px4_sem_post(&_lock);
 	}
 
-	/**
-	 * @class Smart locking object that uses the same lock as lock(), but automatically
-	 * takes the lock when created and releases the lock when the object goes out of
-	 * scope. Use like this:
-	 *   {
-	 *       SmartLock smart_lock(*this);
-	 *       //critical section start
-	 *       ...
-	 *       //critical section end
-	 *   }
-	 */
-	class SmartLock
-	{
-	public:
-		SmartLock(Device &device) : _device(device) { _device.lock(); }
-		~SmartLock() { _device.unlock(); }
-	private:
-		Device &_device;
-	};
-
-private:
 	px4_sem_t		_lock; /**< lock to protect access to all class members (also for derived classes) */
 
+private:
 	/** disable copy construction for this and all subclasses */
 	Device(const Device &);