[media] dvb_frontend: add "detach" callback

Prepare for making "release" asynchronous (via kref).  Some operations
may need to be run synchronously in dvb_frontend_detach(), and that's
why we need a "detach" callback.
Signed-off-by: Max Kellermann <max.kellermann@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/dvb-core/dvb_frontend.c

@@ -2756,6 +2756,7 @@ void dvb_frontend_detach(struct dvb_frontend* fe)
 	dvb_frontend_invoke_release(fe, fe->ops.release_sec);
 	dvb_frontend_invoke_release(fe, fe->ops.tuner_ops.release);
 	dvb_frontend_invoke_release(fe, fe->ops.analog_ops.release);
+	dvb_frontend_invoke_release(fe, fe->ops.detach);
 	dvb_frontend_invoke_release(fe, fe->ops.release);
 }
 EXPORT_SYMBOL(dvb_frontend_detach);

drivers/media/dvb-core/dvb_frontend.h

@@ -330,7 +330,11 @@ struct dtv_frontend_properties;
  *
  * @info:		embedded struct dvb_tuner_info with tuner properties
  * @delsys:		Delivery systems supported by the frontend
- * @release:		callback function called when frontend is dettached.
+ * @detach:		callback function called when frontend is detached.
+ *			drivers should clean up, but not yet free the struct
+ *			dvb_frontend allocation.
+ * @release:		callback function called when frontend is ready to be
+ *			freed.
  *			drivers should free any allocated memory.
  * @release_sec:	callback function requesting that the Satelite Equipment
  *			Control (SEC) driver to release and free any memory
@@ -415,6 +419,7 @@ struct dvb_frontend_ops {
 
 	u8 delsys[MAX_DELSYS];
 
+	void (*detach)(struct dvb_frontend *fe);
 	void (*release)(struct dvb_frontend* fe);
 	void (*release_sec)(struct dvb_frontend* fe);