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