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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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