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    SubjectRe: [PATCH 2/9] drm/xen-front: Implement Xen bus state handling
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    On 21/02/18 09:03, Oleksandr Andrushchenko wrote:
    > From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
    >
    > Initial handling for Xen bus states: implement
    > Xen bus state machine for the frontend driver according to
    > the state diagram and recovery flow from display para-virtualized
    > protocol: xen/interface/io/displif.h.
    >
    > Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
    > ---
    > drivers/gpu/drm/xen/xen_drm_front.c | 124 +++++++++++++++++++++++++++++++++++-
    > drivers/gpu/drm/xen/xen_drm_front.h | 26 ++++++++
    > 2 files changed, 149 insertions(+), 1 deletion(-)
    > create mode 100644 drivers/gpu/drm/xen/xen_drm_front.h
    >
    > diff --git a/drivers/gpu/drm/xen/xen_drm_front.c b/drivers/gpu/drm/xen/xen_drm_front.c
    > index fd372fb464a1..d0306f9d660d 100644
    > --- a/drivers/gpu/drm/xen/xen_drm_front.c
    > +++ b/drivers/gpu/drm/xen/xen_drm_front.c
    > @@ -24,19 +24,141 @@
    >
    > #include <xen/interface/io/displif.h>
    >
    > +#include "xen_drm_front.h"
    > +
    > +static void xen_drv_remove_internal(struct xen_drm_front_info *front_info)
    > +{
    > +}
    > +
    > +static int backend_on_initwait(struct xen_drm_front_info *front_info)
    > +{
    > + return 0;
    > +}
    > +
    > +static int backend_on_connected(struct xen_drm_front_info *front_info)
    > +{
    > + return 0;
    > +}
    > +
    > +static void backend_on_disconnected(struct xen_drm_front_info *front_info)
    > +{
    > + xenbus_switch_state(front_info->xb_dev, XenbusStateInitialising);
    > +}
    > +
    > static void backend_on_changed(struct xenbus_device *xb_dev,
    > enum xenbus_state backend_state)
    > {
    > + struct xen_drm_front_info *front_info = dev_get_drvdata(&xb_dev->dev);
    > + int ret;
    > +
    > + DRM_DEBUG("Backend state is %s, front is %s\n",
    > + xenbus_strstate(backend_state),
    > + xenbus_strstate(xb_dev->state));
    > +
    > + switch (backend_state) {
    > + case XenbusStateReconfiguring:
    > + /* fall through */
    > + case XenbusStateReconfigured:
    > + /* fall through */
    > + case XenbusStateInitialised:
    > + break;
    > +
    > + case XenbusStateInitialising:
    > + /* recovering after backend unexpected closure */
    > + backend_on_disconnected(front_info);
    > + break;
    > +
    > + case XenbusStateInitWait:
    > + /* recovering after backend unexpected closure */
    > + backend_on_disconnected(front_info);
    > + if (xb_dev->state != XenbusStateInitialising)
    > + break;
    > +
    > + ret = backend_on_initwait(front_info);
    > + if (ret < 0)
    > + xenbus_dev_fatal(xb_dev, ret, "initializing frontend");
    > + else
    > + xenbus_switch_state(xb_dev, XenbusStateInitialised);
    > + break;
    > +
    > + case XenbusStateConnected:
    > + if (xb_dev->state != XenbusStateInitialised)
    > + break;
    > +
    > + ret = backend_on_connected(front_info);
    > + if (ret < 0)
    > + xenbus_dev_fatal(xb_dev, ret, "initializing DRM driver");
    > + else
    > + xenbus_switch_state(xb_dev, XenbusStateConnected);
    > + break;
    > +
    > + case XenbusStateClosing:
    > + /*
    > + * in this state backend starts freeing resources,
    > + * so let it go into closed state, so we can also
    > + * remove ours
    > + */
    > + break;
    > +
    > + case XenbusStateUnknown:
    > + /* fall through */
    > + case XenbusStateClosed:
    > + if (xb_dev->state == XenbusStateClosed)
    > + break;
    > +
    > + backend_on_disconnected(front_info);
    > + break;
    > + }
    > }
    >
    > static int xen_drv_probe(struct xenbus_device *xb_dev,
    > const struct xenbus_device_id *id)
    > {
    > - return 0;
    > + struct xen_drm_front_info *front_info;
    > +
    > + front_info = devm_kzalloc(&xb_dev->dev,
    > + sizeof(*front_info), GFP_KERNEL);
    > + if (!front_info) {
    > + xenbus_dev_fatal(xb_dev, -ENOMEM, "allocating device memory");

    No need for message in case of allocation failure: this is
    handled in memory allocation already.


    Juergen

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