Claude review: drm/vblank: Add drm_crtc_vblank_is_off() helper

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

Patch Review

**Generally clean.** The refactoring correctly replaces the `drm_crtc_vblank_get()` + check return value pattern with a direct state query, removing the need for a balancing `drm_crtc_vblank_put()`.

The condition in `drm_crtc_vblank_is_off()`:
```c
guard(spinlock_irqsave)(&crtc->dev->vbl_lock);
return vblank->inmodeset && !vblank->enabled;
```
correctly captures the "vblank_off was called" state — `inmodeset` is set in `drm_crtc_vblank_off()` when it bumps the refcount, and `enabled` is cleared by `drm_vblank_disable_and_save()`. This is semantically what the original code was checking.

**Minor issues:**

1. The function is declared in `drm_internal.h` but uses `EXPORT_SYMBOL`. This is needed because `drm_atomic_helper.c` compiles into a separate module (`drm_kms_helper`), but it's a slightly awkward pattern — an exported symbol with no public header declaration. Consider whether a public header (e.g., `drm_vblank.h`) would be more appropriate if other drivers/helpers might eventually need this.

2. The kdoc says "Return False otherwise" with a capital 'F' — should be lowercase "false" for consistency.

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Generated by Claude Code Patch Reviewer