[PATCH 1/3] drm: atomic-helper: Implement drm_atomic_helper_duplicate_state()

[Daniel Vetter]

On Tue, Aug 11, 2015 at 01:37:43PM +0200, Thierry Reding wrote:
> From: Thierry Reding <treding at nvidia.com>
> 
> This function can be used to duplicate an atomic state object. This is
> useful for example to implement suspend/resume, where the state before
> suspend can be saved and restored upon resume.
> 
> Signed-off-by: Thierry Reding <treding at nvidia.com>
> ---
>  drivers/gpu/drm/drm_atomic_helper.c | 90 +++++++++++++++++++++++++++++++++++++
>  include/drm/drm_atomic_helper.h     |  2 +
>  2 files changed, 92 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index fd06595c2ee5..f842499ca79e 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -2358,6 +2358,96 @@ drm_atomic_helper_connector_duplicate_state(struct drm_connector *connector)
>  EXPORT_SYMBOL(drm_atomic_helper_connector_duplicate_state);
>  
>  /**
> + * drm_atomic_helper_duplicate_state - duplicate an atomic state object
> + * @dev: DRM device
> + *
> + * Makes a copy of the current atomic state by looping over all objects and
> + * duplicating their respective states.

This needs a big warning that drivers better know what they're doing for
two reasons: It promises that atomic states can be treated as persistent
bits (e.g. if a driver has an update-counter somewhere that won't work).
And it drops locks again so will race if that's not otherwise excluded
(like in suspend/resume where nothing else is allowed to run if you shut
down fbcon with fbdev_set_suspend() before calling this function).

Maybe needs some rewording, but all of the above (including details like
fbdev_set_suspend) must be mentioned.

> + *
> + * Returns: A pointer to the copy of the atomic state object on success or an
> + * ERR_PTR()-encoded error code on failure.
> + */
> +struct drm_atomic_state *
> +drm_atomic_helper_duplicate_state(struct drm_device *dev)
> +{
> +	struct drm_modeset_acquire_ctx ctx;
> +	struct drm_atomic_state *state;
> +	struct drm_connector *conn;
> +	struct drm_plane *plane;
> +	struct drm_crtc *crtc;
> +	int err;
> +
> +	state = drm_atomic_state_alloc(dev);
> +	if (!state)
> +		return ERR_PTR(-ENOMEM);
> +
> +	drm_modeset_acquire_init(&ctx, 0);
> +	state->acquire_ctx = &ctx;
> +
> +	err = drm_modeset_lock(&dev->mode_config.connection_mutex, &ctx);
> +	if (err < 0)
> +		goto free;

Just use drm_modeset_lock_all. You need them all anyway and for
suspend/resume there won't be any contention anyway.

Otherwise lgtm.
-Daniel

> +
> +	drm_for_each_crtc(crtc, dev) {
> +		unsigned int index = drm_crtc_index(crtc);
> +		struct drm_crtc_state *crtc_state;
> +
> +		crtc_state = crtc->funcs->atomic_duplicate_state(crtc);
> +		if (!crtc_state) {
> +			err = -ENOMEM;
> +			goto unlock;
> +		}
> +
> +		state->crtc_states[index] = crtc_state;
> +		state->crtcs[index] = crtc;
> +		crtc_state->state = state;
> +	}
> +
> +	drm_for_each_plane(plane, dev) {
> +		unsigned int index = drm_plane_index(plane);
> +		struct drm_plane_state *plane_state;
> +
> +		plane_state = plane->funcs->atomic_duplicate_state(plane);
> +		if (!plane_state) {
> +			err = -ENOMEM;
> +			goto unlock;
> +		}
> +
> +		state->plane_states[index] = plane_state;
> +		state->planes[index] = plane;
> +		plane_state->state = state;
> +	}
> +
> +	drm_for_each_connector(conn, dev) {
> +		unsigned int index = drm_connector_index(conn);
> +		struct drm_connector_state *conn_state;
> +
> +		conn_state = conn->funcs->atomic_duplicate_state(conn);
> +		if (!conn_state) {
> +			err = -ENOMEM;
> +			goto unlock;
> +		}
> +
> +		state->connector_states[index] = conn_state;
> +		state->connectors[index] = conn;
> +		conn_state->state = state;
> +	}
> +
> +unlock:
> +	drm_modeset_drop_locks(&ctx);
> +free:
> +	drm_modeset_acquire_fini(&ctx);
> +
> +	if (err < 0) {
> +		drm_atomic_state_free(state);
> +		state = ERR_PTR(err);
> +	}
> +
> +	return state;
> +}
> +EXPORT_SYMBOL(drm_atomic_helper_duplicate_state);
> +
> +/**
>   * __drm_atomic_helper_connector_destroy_state - release connector state
>   * @connector: connector object
>   * @state: connector state object to release
> diff --git a/include/drm/drm_atomic_helper.h b/include/drm/drm_atomic_helper.h
> index 4ffe9dca07c4..5d27612997ce 100644
> --- a/include/drm/drm_atomic_helper.h
> +++ b/include/drm/drm_atomic_helper.h
> @@ -118,6 +118,8 @@ __drm_atomic_helper_connector_duplicate_state(struct drm_connector *connector,
>  					   struct drm_connector_state *state);
>  struct drm_connector_state *
>  drm_atomic_helper_connector_duplicate_state(struct drm_connector *connector);
> +struct drm_atomic_state *
> +drm_atomic_helper_duplicate_state(struct drm_device *dev);
>  void
>  __drm_atomic_helper_connector_destroy_state(struct drm_connector *connector,
>  					    struct drm_connector_state *state);
> -- 
> 2.4.5
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch