[PATCH RESEND 02/11] ALSA: vsnd: Implement Xen bus state handling

[Oleksandr Andrushchenko <andr2000@gmail.com>]

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

Initial handling for Xen bus states: implement
Xen bus state machine for the front driver according to
the state diagram and recovery flow from sound para-virtualized
protocol: xen/interface/io/sndif.h.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
---
 sound/drivers/xen-front.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)

diff --git a/sound/drivers/xen-front.c b/sound/drivers/xen-front.c
index 8c5de7b0e7b5..c4fd21cac3a7 100644
--- a/sound/drivers/xen-front.c
+++ b/sound/drivers/xen-front.c
@@ -36,9 +36,99 @@ static void xdrv_remove_internal(struct xdrv_info *drv_info)
 {
 }
 
+static int xdrv_be_on_initwait(struct xdrv_info *drv_info)
+{
+	return 0;
+}
+
+static inline int xdrv_be_on_connected(struct xdrv_info *drv_info)
+{
+	return 0;
+}
+
+static inline void xdrv_be_on_disconnected(struct xdrv_info *drv_info)
+{
+	xdrv_remove_internal(drv_info);
+}
+
 static void xdrv_be_on_changed(struct xenbus_device *xb_dev,
 	enum xenbus_state backend_state)
 {
+	struct xdrv_info *drv_info = dev_get_drvdata(&xb_dev->dev);
+	int ret;
+
+	switch (backend_state) {
+	case XenbusStateReconfiguring:
+		/* fall through */
+	case XenbusStateReconfigured:
+		/* fall through */
+	case XenbusStateInitialised:
+		/* fall through */
+		break;
+
+	case XenbusStateInitialising:
+		if (xb_dev->state == XenbusStateInitialising)
+			break;
+
+		/* recovering after backend unexpected closure */
+		mutex_lock(&drv_info->mutex);
+		xdrv_be_on_disconnected(drv_info);
+		mutex_unlock(&drv_info->mutex);
+		xenbus_switch_state(xb_dev, XenbusStateInitialising);
+		break;
+
+	case XenbusStateInitWait:
+		if (xb_dev->state != XenbusStateInitialising)
+			break;
+
+		mutex_lock(&drv_info->mutex);
+		ret = xdrv_be_on_initwait(drv_info);
+		mutex_unlock(&drv_info->mutex);
+		if (ret < 0) {
+			xenbus_dev_fatal(xb_dev, ret,
+				"initializing " XENSND_DRIVER_NAME);
+			break;
+		}
+
+		xenbus_switch_state(xb_dev, XenbusStateInitialised);
+		break;
+
+	case XenbusStateConnected:
+		if (xb_dev->state != XenbusStateInitialised)
+			break;
+
+		mutex_lock(&drv_info->mutex);
+		ret = xdrv_be_on_connected(drv_info);
+		mutex_unlock(&drv_info->mutex);
+		if (ret < 0) {
+			xenbus_dev_fatal(xb_dev, ret,
+				"connecting " XENSND_DRIVER_NAME);
+			break;
+		}
+
+		xenbus_switch_state(xb_dev, XenbusStateConnected);
+		break;
+
+	case XenbusStateClosing:
+		/*
+		 * in this state backend starts freeing resources,
+		 * so let it go into closed state first, so we can also
+		 * remove ours
+		 */
+		break;
+
+	case XenbusStateUnknown:
+		/* fall through */
+	case XenbusStateClosed:
+		if (xb_dev->state == XenbusStateClosed)
+			break;
+
+		mutex_lock(&drv_info->mutex);
+		xdrv_be_on_disconnected(drv_info);
+		mutex_unlock(&drv_info->mutex);
+		xenbus_switch_state(xb_dev, XenbusStateInitialising);
+		break;
+	}
 }
 
 static int xdrv_probe(struct xenbus_device *xb_dev,
@@ -56,6 +146,7 @@ static int xdrv_probe(struct xenbus_device *xb_dev,
 	spin_lock_init(&drv_info->io_lock);
 	mutex_init(&drv_info->mutex);
 	dev_set_drvdata(&xb_dev->dev, drv_info);
+	xenbus_switch_state(xb_dev, XenbusStateInitialising);
 	return 0;
 }
 
@@ -63,6 +154,7 @@ static int xdrv_remove(struct xenbus_device *dev)
 {
 	struct xdrv_info *drv_info = dev_get_drvdata(&dev->dev);
 
+	xenbus_switch_state(dev, XenbusStateClosed);
 	mutex_lock(&drv_info->mutex);
 	xdrv_remove_internal(drv_info);
 	mutex_unlock(&drv_info->mutex);
-- 
2.7.4