Re: [PATCH 06/17] drm: Global atomic state handling

On Sun, Nov 02, 2014 at 02:19:19PM +0100, Daniel Vetter wrote: ...

+/**

• • drm_atomic_get_plane_state - get plane state
• • @state: global atomic state object
• • @plane: plane to get state object for
• • This functions returns the plane state for the given plane, allocating it if
• • needed. It will also grab the relevant plane lock to make sure that the state
• • is consistent.
• • Returns:
• • Either the allocated state or the error code encoded into the pointer. When
• • the error is EDEADLK then the w/w mutex code has detected a deadlock and the
• • entire atomic sequence must be restarted. All other errors are fatal.
• */

+struct drm_plane_state * +drm_atomic_get_plane_state(struct drm_atomic_state *state,

• 	  struct drm_plane *plane)
  

+{

• int ret, index;
• struct drm_plane_state *plane_state;
• index = drm_plane_index(plane);
• if (state->plane_states[index])

• return state->plane_states[index];
  

• /*

• * TODO: We currently don't have per-plane mutexes. So instead of trying
  

• * crazy tricks with deferring plane->crtc and hoping for the best just
  

• * grab all crtc locks. Once we have per-plane locks we must update this
  

• * to only take the plane mutex.
  

• */
  

• ret = drm_modeset_lock_all_crtcs(state->dev, state->acquire_ctx);
• if (ret)

• return ERR_PTR(ret);
  

• plane_state = plane->funcs->atomic_duplicate_state(plane);
• if (!plane_state)

• return ERR_PTR(-ENOMEM);
  

• state->plane_states[index] = plane_state;
• state->planes[index] = plane;
• plane_state->state = state;
• DRM_DEBUG_KMS("Added [PLANE:%d] %p state to %p\n",

•       plane->base.id, plane_state, state);
  

• if (plane_state->crtc) {

• struct drm_crtc_state *crtc_state;
  

• crtc_state = drm_atomic_get_crtc_state(state,
  

• 				       plane_state->crtc);
  

• if (IS_ERR(crtc_state))
  

• 	return ERR_CAST(crtc_state);
  

• }

It's not immediately clear to me why we need to get (create) the crtc state here. Is this just so that we know to do an atomic_begin()/atomic_flush() on this crtc later or do we actually use the state itself somewhere that I'm overlooking?

Matt