Claude review: drm/atomic: only add colorop state from active color pipeline

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

Patch Review

**Purpose:** Changes `drm_atomic_add_affected_colorops()` to walk only the active pipeline's linked list (`colorop->next`) instead of iterating all colorops on the device and filtering by plane.

**Review:**

The core logic change is good — walking the linked list via `plane_state->color_pipeline` / `colorop->next` is both more efficient and semantically correct:

```c
for (colorop = plane_state->color_pipeline;
     colorop;
     colorop = colorop->next) {
    colorop_state = drm_atomic_get_colorop_state(plane_state->state, colorop);
```

However, the function signature change is a notable API change:

```c
-drm_atomic_add_affected_colorops(struct drm_atomic_state *state,
+drm_atomic_add_affected_colorops(struct drm_plane_state *plane_state,
                                  struct drm_plane *plane)
```

**Concern:** The `plane` parameter is now redundant since it can be derived from `plane_state->plane`. Keeping both parameters is mildly inconsistent — consider whether `plane` should be dropped from the signature entirely to avoid callers passing a mismatched plane. That said, it mirrors the pattern of other DRM helpers that take both state and object, so this is acceptable as-is.

The null-guard at the top is a good addition:
```c
if (!plane_state || !plane_state->color_pipeline)
    return 0;
```

The removal of the `WARN_ON` for missing plane state is correct since the plane_state is now passed directly.

The callers in `drm_atomic_add_affected_planes` and `drm_atomic_helper_duplicate_state` are updated cleanly — the redundant `if (plane_state->color_pipeline)` checks are moved inside the function itself.

**Minor nit:** The `@state` parameter documentation says "DRM plane state" but the parameter is named `plane_state` — this is fine but slightly unusual for kerneldoc since `@state` doesn't match the parameter name `plane_state`. Looking at the header, the declaration parameter name is `state`, so the mismatch is between the .c and .h files. The declaration in `drm_atomic.h` uses `state` as the parameter name:

```c
drm_atomic_add_affected_colorops(struct drm_plane_state *state,
                                 struct drm_plane *plane);
```

This is acceptable, but ideally the parameter name in the header and implementation should match (`plane_state` in both places would be clearer).

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