Claude review: drm/hyperv: validate resolution_count and fix WIN8 fallback

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

Patch Review

**Status: Good — no issues found.**

The `resolution_count` bounds check is correct. The parse loop at lines 405–410 of the original iterates `resolution_count` times over `supported_resolution[SYNTHVID_MAX_RESOLUTION_COUNT]` (64 entries), so an unchecked count from the host can cause an out-of-bounds read:

```c
+	if (msg->resolution_resp.resolution_count == 0 ||
+	    msg->resolution_resp.resolution_count >
+	    SYNTHVID_MAX_RESOLUTION_COUNT) {
+		drm_err(dev, "Invalid resolution count: %d\n",
+			msg->resolution_resp.resolution_count);
 		return -ENODEV;
```

Folding the upper bound into the existing zero-check is clean. The `%d` format for a `u8` is fine (promoted to `int`).

The fallback refactor is also correct. The original `else` branch only covered pre-WIN10, leaving `screen_width_max` / `screen_height_max` at zero on a failed WIN10 probe, which cascades into `mode_config.max_width = 0` and breaks framebuffer creation. The new guard:

```c
+	if (!hv->screen_width_max) {
 		hv->screen_width_max = SYNTHVID_WIDTH_WIN8;
 		hv->screen_height_max = SYNTHVID_HEIGHT_WIN8;
+		hv->preferred_width = SYNTHVID_WIDTH_WIN8;
+		hv->preferred_height = SYNTHVID_HEIGHT_WIN8;
 	}
```

This works because `screen_width_max` is zero-initialized (the device struct comes from `devm_drm_dev_alloc` → `kzalloc`), and `hyperv_get_supported_resolution()` only sets it to nonzero on success. The pre-WIN10 path also benefits from gaining the `preferred_width`/`preferred_height` defaults that were previously missing. No concerns.

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Generated by Claude Code Patch Reviewer