ptp: introduce ptp_cancel_worker_sync

In order to effectively use the PTP kernel thread for tasks such as
timestamping packets, allow the user control over stopping it, which is
needed e.g. when the timestamping queues must be drained.

Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/ptp/ptp_clock.c

@@ -371,6 +371,12 @@ int ptp_schedule_worker(struct ptp_clock *ptp, unsigned long delay)
 }
 EXPORT_SYMBOL(ptp_schedule_worker);
 
+void ptp_cancel_worker_sync(struct ptp_clock *ptp)
+{
+	kthread_cancel_delayed_work_sync(&ptp->aux_work);
+}
+EXPORT_SYMBOL(ptp_cancel_worker_sync);
+
 /* module operations */
 
 static void __exit ptp_exit(void)

include/linux/ptp_clock_kernel.h

@@ -243,6 +243,13 @@ int ptp_find_pin(struct ptp_clock *ptp,
 
 int ptp_schedule_worker(struct ptp_clock *ptp, unsigned long delay);
 
+/**
+ * ptp_cancel_worker_sync() - cancel ptp auxiliary clock
+ *
+ * @ptp:     The clock obtained from ptp_clock_register().
+ */
+void ptp_cancel_worker_sync(struct ptp_clock *ptp);
+
 #else
 static inline struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info,
 						   struct device *parent)
@@ -260,6 +267,8 @@ static inline int ptp_find_pin(struct ptp_clock *ptp,
 static inline int ptp_schedule_worker(struct ptp_clock *ptp,
 				      unsigned long delay)
 { return -EOPNOTSUPP; }
+static inline void ptp_cancel_worker_sync(struct ptp_clock *ptp)
+{ }
 
 #endif