Claude review: drm: Suppress intentional warning backtraces in scaling unit tests

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

Patch Review

Clean application of the scoped API.

**1. The `expected_warnings` calculation is clever:**

```c
+	int expected_warnings = IS_ENABLED(CONFIG_BUG) ?
+			(params->expected_scaling_factor == -EINVAL) : 0;
```

When `CONFIG_BUG=n`, `WARN_ON()` is a no-op, so no warnings fire and the count stays at 0. This handles the conditional cleanly without `#ifdef`. The expression `(params->expected_scaling_factor == -EINVAL)` evaluates to 0 or 1, matching whether the specific test case triggers a warning or not.

**2. `scaling_factor = INT_MIN` initialization:**

```c
+	int scaling_factor = INT_MIN;
```

Necessary because if `kunit_start_suppress_warning()` fails (returns NULL), the for-loop body doesn't execute, and `scaling_factor` would be uninitialized at the `KUNIT_EXPECT_EQ` check below. `INT_MIN` is a safe sentinel (no test case expects it). Good fix from v10.

**3. The `KUNIT_EXPECT_EQ` for `scaling_factor` is outside the suppression block:**

```c
+	kunit_warning_suppress(test) {
+		scaling_factor = drm_rect_calc_hscale(...);
+		KUNIT_EXPECT_SUPPRESSED_WARNING_COUNT(test, expected_warnings);
+	}
 	KUNIT_EXPECT_EQ(test, scaling_factor, params->expected_scaling_factor);
```

This is the right structure — the warning count must be inside the block, but the functional assertion can (and should) be outside it. Clean.

**4. Nit: the `#include <linux/limits.h>` addition for `INT_MIN`:**

```c
+#include <linux/limits.h>
```

Correct include for `INT_MIN`.

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