Claude review: drm/vblank: Add drmm_vblank_init() to indicate managed cleanup

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

Patch Review

This patch renames `drm_vblank_init()` to `drmm_vblank_init()` to follow the DRM managed-resource naming convention, adds a `flags` argument, and keeps the old name as a deprecated inline wrapper.

**Observations:**

- The rename is appropriate — `drm_vblank_init()` already uses `drmm_add_action_or_reset()` internally, so the `drmm_` prefix is the correct convention.

- The new `flags` field is added to `struct drm_vblank_crtc` without documentation:
  ```c
  +	unsigned int flags;
   };
  ```
  Given that every other field in this struct has a kerneldoc `/** @field: ... */` comment, adding one here (even brief) would be consistent. Something like `/** @flags: flags for vblank handling (e.g., DRM_VBLANK_FLAG_SIMULATED) */`.

- The internal release callback rename from `drm_vblank_init_release` to `drmm_vblank_init_release` is a nice consistency touch.

- The inline backward-compat wrapper passing `0` for flags is clean:
  ```c
  +static inline int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs)
  +{
  +	return drmm_vblank_init(dev, num_crtcs, 0);
  +}
  ```
  This avoids a tree-wide conversion in one go.

- Minor: the `flags` parameter is not validated in any way (e.g., rejecting unknown bits). This is fine for an internal kernel API, but if flags grow in the future, you might want a `if (flags & ~DRM_VBLANK_FLAG_SIMULATED) return -EINVAL;` check. Not required now.

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