Re: [Xen-devel] [PATCH 2/9] drm/xen-front: Implement Xen bus state handling

[Oleksandr Andrushchenko <Oleksandr_Andrushchenko@xxxxxxxx>]

On 02/21/2018 10:23 AM, Juergen Gross wrote:
> On 21/02/18 09:03, Oleksandr Andrushchenko wrote:
> > From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> >
> > 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@xxxxxxxx>
> > ---
> >   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.
Will remove, thank you
> Juergen

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