[PATCH v2 1/3] drm/atomic-helper: Implement drm_atomic_helper_duplicate_state()

[Daniel Vetter]

On Wed, Aug 12, 2015 at 04:37:28PM +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.
> 
> v2: move locking to caller, be more explicit about prerequisites
> 
> Signed-off-by: Thierry Reding <treding at nvidia.com>
> ---
>  drivers/gpu/drm/drm_atomic_helper.c | 80 +++++++++++++++++++++++++++++++++++++
>  include/drm/drm_atomic_helper.h     |  2 +
>  2 files changed, 82 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index fd06595c2ee5..1f84df3b0a5d 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -2358,6 +2358,86 @@ 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 is used for example by suspend/
> + * resume support code to save the state prior to suspend such that it can
> + * be restored upon resume.
> + *
> + * Note that this treats atomic state as persistent between save and restore.
> + * Drivers must make sure that this is guaranteed.

s/guaranteed/is possible and won't result in confusion/ maybe?

> + *
> + * Calls to this function must be guarded by drm_modeset_lock_all() and
> + * drm_modeset_unlock_all().

If you pass in the acquire ctx explicitly this isn't strictly true since
you're using the get_*_state functions, which might return -EDEADLK. So
maybe instead:

"Note that if callers haven't already acquired all modeset locks this
might return -EDEADLK, which must be handled by the caller using
rm_modeset_backoff()."

> + *
> + * 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_atomic_state *state;
> +	struct drm_connector *conn;
> +	struct drm_plane *plane;
> +	struct drm_crtc *crtc;
> +	int err = 0;
> +
> +	if (WARN_ON(!dev->mode_config.acquire_ctx))
> +		return ERR_PTR(-EINVAL);
> +
> +	state = drm_atomic_state_alloc(dev);
> +	if (!state)
> +		return ERR_PTR(-ENOMEM);
> +
> +	state->acquire_ctx = dev->mode_config.acquire_ctx;

The hidden acquire_ctx was just a hack to avoid needing to redo _all_
driver entry points by adding a ctx parameter. I want to remove this
long-term, so please don't spread it and instead just add a ctx parameter
to this function.

Didn't spot anything else.
-Daniel

> +
> +	drm_for_each_crtc(crtc, dev) {
> +		struct drm_crtc_state *crtc_state;
> +
> +		crtc_state = drm_atomic_get_crtc_state(state, crtc);
> +		if (IS_ERR(crtc_state)) {
> +			err = PTR_ERR(crtc_state);
> +			goto free;
> +		}
> +	}
> +
> +	drm_for_each_plane(plane, dev) {
> +		struct drm_plane_state *plane_state;
> +
> +		plane_state = drm_atomic_get_plane_state(state, plane);
> +		if (IS_ERR(plane_state)) {
> +			err = PTR_ERR(plane_state);
> +			goto free;
> +		}
> +	}
> +
> +	drm_for_each_connector(conn, dev) {
> +		struct drm_connector_state *conn_state;
> +
> +		conn_state = drm_atomic_get_connector_state(state, conn);
> +		if (IS_ERR(conn_state)) {
> +			err = PTR_ERR(conn_state);
> +			goto free;
> +		}
> +	}
> +
> +	/* clear the acquire context so that it isn't accidentally reused */
> +	state->acquire_ctx = NULL;
> +
> +free:
> +	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