V4L/DVB (9516): cx18: Move DVB buffer transfer handling from irq handler to work_queue

cx18: Move DVB buffer transfer handling from irq handler to work_queue thread.
In order to properly lock the epu2cpu mailbox for driver to CX23418 commands,
the DVB/TS buffer handling needs to be moved from the IRQ handler and IRQ
context to a work queue.  This work_queue implmentation is strikingly similar
to the ivtv implementation - for better or worse.

Signed-off-by: Andy Walls <awalls@radix.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/video/cx18/cx18-driver.c b/drivers/media/video/cx18/cx18-driver.c
index 2befa38..7874d97 100644
--- a/drivers/media/video/cx18/cx18-driver.c
+++ b/drivers/media/video/cx18/cx18-driver.c
@@ -449,6 +449,14 @@
 
 	spin_lock_init(&cx->lock);
 
+	cx->work_queue = create_singlethread_workqueue(cx->name);
+	if (cx->work_queue == NULL) {
+		CX18_ERR("Could not create work queue\n");
+		return -1;
+	}
+
+	INIT_WORK(&cx->work, cx18_work_handler);
+
 	/* start counting open_id at 1 */
 	cx->open_id = 1;
 
@@ -831,6 +839,7 @@
 free_mem:
 	release_mem_region(cx->base_addr, CX18_MEM_SIZE);
 free_workqueue:
+	destroy_workqueue(cx->work_queue);
 err:
 	if (retval == 0)
 		retval = -ENODEV;
@@ -931,6 +940,9 @@
 
 	cx18_halt_firmware(cx);
 
+	flush_workqueue(cx->work_queue);
+	destroy_workqueue(cx->work_queue);
+
 	cx18_streams_cleanup(cx, 1);
 
 	exit_cx18_i2c(cx);