Claude review: drm/vmwgfx: Add some checks to vmw_cursor_plane_atomic_update

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

**Coding style issue — declaration after statement:**

```c
+	new_state = drm_atomic_get_new_plane_state(state, plane);
+	if (!new_state)
+		return;
+	old_state = drm_atomic_get_old_plane_state(state, plane);
+	struct drm_crtc *crtc =  new_state->crtc ? new_state->crtc :
+		(old_state ? old_state->crtc : NULL);
+	if (!crtc)
+		return;
+	struct vmw_private *dev_priv = vmw_priv(plane->dev);
```

The `struct drm_crtc *crtc` and `struct vmw_private *dev_priv` declarations are interspersed with code. While C99/GNU extensions allow this, Linux kernel style strongly prefers all declarations at the top of the block. Move `crtc` and `dev_priv` declarations to the top (alongside `new_state`, `old_state`) and assign them after the NULL checks. Also there's a double space (`=  new_state`) on the crtc assignment line.

**Questionable NULL check on new_state:** In the atomic commit path, `drm_atomic_get_new_plane_state()` should always return a valid state for a plane that is part of the commit — this function is called from `atomic_update`, which only runs for planes included in the commit. If `new_state` is NULL here, something has gone seriously wrong at a higher layer. A `WARN_ON(!new_state)` plus return might be more appropriate to flag the unexpected condition rather than silently returning.

**Logic correctness:** The ternary for `crtc` is correct — it safely handles `old_state` being NULL. The original code `new_state->crtc ?: old_state->crtc` would crash if `new_state->crtc` was NULL and `old_state` was also NULL.

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Generated by Claude Code Patch Reviewer