Claude review: drm: writeback: Document behaviour for framebuffer size mismatch

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

Patch Review

**Correctness:** The placement of the new text is appropriate — it's inserted into the `WRITEBACK_FB_ID` property description between the "will always read as zero and is not preserved across commits" sentence and the "Userspace must set this property" sentence. Looking at the existing code at line 60-62:

```
 *	and is not preserved across commits.
 *	Userspace must set this property to an output buffer every time it
```

The new text:
```
 *	If the width and height of the framebuffer do not match those of the
 *	attached CRTC, the driver may either fail or scale (not crop) the
 *	content to fit the framebuffer.
```

This reads well in context and is positioned logically.

**Suggestions:**

- Consider making the failure mode more explicit: "the driver may either fail the atomic commit or scale..." — this clarifies that failure should happen at check time, which is important for userspace doing `TEST_ONLY` commits to probe capabilities.

- It may be worth adding a note about aspect ratio behavior being driver-defined, e.g., "the driver may either fail the atomic commit or scale (not crop) the content to fit the framebuffer; the scaling method is driver-defined."

- The commit message mentions "Cropping would make less sense, as the region to crop is underspecified without some other properties to define an origin." This is good reasoning. It might be worth capturing the "not crop" rationale briefly in the doc itself (or at least confirming the commit message is sufficient for future archaeology).

**Nit:** The subject says "Document behaviour" (British English) — this is fine but note the kernel tends toward American English ("behavior") in most documentation, though it's not strictly enforced.

**Overall:** This is a clean, focused documentation patch. The content is correct and fills a real gap in the UAPI specification. It could benefit from slightly more precise wording around failure mode (at atomic check time) and scaling semantics, but as-is it's a reasonable improvement.

**Verdict:** Looks good with optional wording improvements. Reviewed-by worthy.

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Generated by Claude Code Patch Reviewer