Claude review: drm/vblank: Extract get_vblank_counter_and_timestamp()

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

Patch Review

**Correctness:**

The three original do/while loops are identical in structure:
```c
do {
    cur_vblank = __get_vblank_counter(dev, pipe);
    rc = drm_get_last_vbltimestamp(dev, pipe, &t_vblank, in_vblank_irq);
} while (cur_vblank != __get_vblank_counter(dev, pipe) && --count > 0);
```

The new helper faithfully reproduces this pattern. Two of the three call sites (`drm_reset_vblank_timestamp` and `drm_update_vblank_count`) used the return value (`rc`) — the refactored code preserves this.

**Minor observation:** In `drm_vblank_restore()` (line 1563 in the original), the return value of `drm_get_last_vbltimestamp()` was **not** captured:
```c
drm_get_last_vbltimestamp(dev, pipe, &t_vblank, false);
```
The new code now captures it via the helper's `rc` return, but the caller discards the return value:
```c
get_vblank_counter_and_timestamp(dev, pipe, &cur_vblank,
                                 &t_vblank, false);
```
This is harmless — the return value is simply ignored — but it does mean the refactoring subtly changes the code from "never captured" to "captured then discarded." No functional impact.

**Style:** The helper is well-placed (right after `__get_vblank_counter()`), the naming is descriptive, and the parameter list matches the existing patterns in the file.

**Reviewed-by worthy:** Yes, this is a clean extraction with no behavioral changes.

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Generated by Claude Code Patch Reviewer