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

[Oleksandr Andrushchenko <andr2000@xxxxxxxxx>]

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>

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@xxxxxxxx>
---
 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


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